U.S. patent application number 14/659771 was filed with the patent office on 2015-07-09 for titanium sheet covered with protective film superior in high temperature oxidation resistance and high temperature salt damage resistance, automobile exhaust system using same, and methods of production of same.
This patent application is currently assigned to Nippon Steel & Sumitomo Metal Corporation. The applicant listed for this patent is Takashi Domoto, Hideki Fujii, Yoshiaki Itami, Kiyonori Kiyonori, Hiroaki Otsuka. Invention is credited to Takashi Domoto, Hideki Fujii, Yoshiaki Itami, Kiyonori Kiyonori, Hiroaki Otsuka.
Application Number | 20150192056 14/659771 |
Document ID | / |
Family ID | 37942824 |
Filed Date | 2015-07-09 |
United States Patent
Application |
20150192056 |
Kind Code |
A1 |
Otsuka; Hiroaki ; et
al. |
July 9, 2015 |
TITANIUM SHEET COVERED WITH PROTECTIVE FILM SUPERIOR IN HIGH
TEMPERATURE OXIDATION RESISTANCE AND HIGH TEMPERATURE SALT DAMAGE
RESISTANCE, AUTOMOBILE EXHAUST SYSTEM USING SAME, AND METHODS OF
PRODUCTION OF SAME
Abstract
The present invention provides a titanium sheet covered with a
protective film superior in high temperature oxidation resistance
and high temperature salt damage resistance and a method of
production of the same and an automobile exhaust system using the
same. The titanium sheet covered with a protective film is formed
on its surface with a protective film of a thickness of 1 to 100
.mu.m where flake-shaped metal Al with an average thickness of 0.1
to 5 .mu.m and average width or average length of 1 to 50 .mu.m or
grain-shaped metal Al with an average size of 0.1 to 30 .mu.m is
dispersed in 20 to 60 mass % silicone resin or silicone grease and
comprised of Si: 15 to 55 mass % and C: 10 to 45 mass % and having
a balance of unavoidable impurities. Preferably the titanium sheet
of the substrate contains one or both of 0.5 to 2.1 mass % of Cu
and 0.4 to 2.5 mass % of Al. The method of production is to brush
or spray the above composition of a silicone resin on a titanium
sheet to form a protective film and heat it at 150 to 300.degree.
C. for 5 to 60 minutes.
Inventors: |
Otsuka; Hiroaki;
(Futtsu-shi, JP) ; Fujii; Hideki; (Futtsu-shi,
JP) ; Kiyonori; Kiyonori; (Tokyo, JP) ; Itami;
Yoshiaki; (Futtsu-shi, JP) ; Domoto; Takashi;
(Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Otsuka; Hiroaki
Fujii; Hideki
Kiyonori; Kiyonori
Itami; Yoshiaki
Domoto; Takashi |
Futtsu-shi
Futtsu-shi
Tokyo
Futtsu-shi
Tokyo |
|
JP
JP
JP
JP
JP |
|
|
Assignee: |
Nippon Steel & Sumitomo Metal
Corporation
Tokyo
JP
|
Family ID: |
37942824 |
Appl. No.: |
14/659771 |
Filed: |
March 17, 2015 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11992911 |
Mar 31, 2008 |
9011976 |
|
|
PCT/JP2006/320348 |
Oct 5, 2006 |
|
|
|
14659771 |
|
|
|
|
Current U.S.
Class: |
428/328 ;
427/327; 427/350; 427/387; 427/427; 427/427.5; 427/429; 428/334;
428/336 |
Current CPC
Class: |
Y10T 428/259 20150115;
F01N 13/16 20130101; B05D 1/02 20130101; C22C 14/00 20130101; C22F
1/183 20130101; Y10T 428/265 20150115; B05D 3/12 20130101; Y10T
428/25 20150115; C23C 26/00 20130101; Y10T 428/258 20150115; B05D
3/0254 20130101; C09D 5/103 20130101; B05D 5/00 20130101; B05D 1/28
20130101; Y10T 428/256 20150115; C09D 5/18 20130101; Y10T 428/263
20150115 |
International
Class: |
F01N 13/16 20060101
F01N013/16; B05D 1/28 20060101 B05D001/28; B05D 5/00 20060101
B05D005/00; B05D 3/02 20060101 B05D003/02; B05D 3/12 20060101
B05D003/12; C22C 14/00 20060101 C22C014/00; B05D 1/02 20060101
B05D001/02 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 5, 2005 |
JP |
2005-292062 |
Dec 14, 2005 |
JP |
2005-360114 |
Jun 15, 2006 |
JP |
2006-165721 |
Jun 27, 2006 |
JP |
2006-176348 |
Claims
1. A titanium sheet covered with a protective film superior in high
temperature oxidation resistance and high temperature salt damage
resistance characterized by comprising a titanium sheet on the
surface of which is formed a protective film of a thickness of 1
.mu.m to 100 .mu.m comprising Si: 15 to 55 mass % and C: 10 to 45
mass % and having a balance of unavoidable impurities.
2. A titanium sheet covered with a protective film superior in high
temperature oxidation resistance and high temperature salt damage
resistance as set forth in claim 1, characterized in that said
protective film further contains Al: 20 to 60 mass %.
3. A titanium sheet covered with a protective film superior in high
temperature oxidation resistance and high temperature salt damage
resistance as set forth in claim 2, characterized in that said
protective film has said Al of metal Al of a thin flake shape with
an average thickness of 0.1 to 5 .mu.m and an average width or
average length of 1 to 50 .mu.m or of a grain shape with an average
particle size of 0.1 to 30 .mu.m dispersed in a silicone resin or
silicone grease.
4. A titanium sheet covered with a protective film superior in high
temperature oxidation resistance and high temperature salt damage
resistance characterized by comprising a titanium sheet on the
surface of which is formed a protective film of a thickness of 1
.mu.m to 100 .mu.m comprising a metal Al alloy of a thin flake
shape with an average thickness of 0.1 to 5 .mu.m and an average
width or average length of 1 to 50 .mu.m or of a grain shape with
an average particle size of 0.1 to 30 .mu.m dispersed in a silicone
resin in a ratio of 10 to 40 mass %, said Al alloy being one or
more of an Al--Si alloy comprised of Si: 10.5 to 30 mass % and
having a balance of Al and unavoidable impurities, an Al--Mg alloy
comprised of Mg: 0.3 to 13.0 mass % and having a balance of Al and
unavoidable impurities, and an Al--Mg--Si alloy comprised of Mg:
0.3 to 13.0 mass % and Si: 0.3 to 13.0 mass % and having a balance
of Al and unavoidable impurities.
5. A titanium sheet covered with a protective film superior in high
temperature oxidation resistance and high temperature salt damage
resistance as set forth in claim 4, characterized in that said
protective film further has SiO.sub.2 and/or MgO with an average
particle diameter of 0.1 to 30 .mu.m dispersed in it in a total of
0.5 to 20.0 mass %.
6. A titanium sheet covered with a protective film superior in high
temperature oxidation resistance and high temperature salt damage
resistance as set forth in claim 1, characterized in that said
titanium sheet contains one or both of Cu: 0.5 to 2.1 mass % and
Al: 0.4 to 2.5 mass % and has a balance of titanium and unavoidable
impurities.
7. A titanium sheet covered with a protective film superior in high
temperature oxidation resistance and high temperature salt damage
resistance as set forth in claim 6, characterized in that said
titanium sheet further contains Nb: 0.3 to 1.1 mass %.
8. A method of production of a titanium sheet covered with a
protective film superior in high temperature oxidation resistance
and high temperature salt damage resistance characterized by
coating a silicone resin or silicone grease prepared to contain Si:
15 to 55 mass % and C: 10 to 45 mass % on a titanium sheet by
brushing or spraying to form a protective film on the surface of
the titanium sheet.
9. A method of production of a titanium sheet covered with a
protective film superior in high temperature oxidation resistance
and high temperature salt damage resistance as set forth in claim 8
characterized in that said silicone resin or silicone grease
further contains Al: 20 to 60 mass %.
10. A method of production of a titanium sheet covered with a
protective film superior in high temperature oxidation resistance
and high temperature salt damage resistance characterized by
coating a silicone resin or silicone grease, prepared by making
metal Al of a thin flake shape with an average thickness of 0.1 to
5 .mu.m and an average width or average length of 1 to 50 .mu.m or
of a grain shape with an average particle size of 0.1 to 30 .mu.m
disperse in a silicone resin or silicone grease so as to give a
composition of Si: 15 to 55 mass %, C: 10 to 45 mass %, and Al: 20
to 60 mass %, on a titanium sheet by brushing or spraying and
heating at 150.degree. C. to 300.degree. C. for 5 to 60 minutes to
form a protective film on the titanium sheet surface.
11. A method of production of a titanium sheet covered with a
protective film superior in high temperature oxidation resistance
and high temperature salt damage resistance characterized by
coating a silicone resin, containing an Al alloy of a thin flake
shape with an average thickness of 0.1 to 5 .mu.m and an average
width or average length of 1 to 50 .mu.m or of a grain shape with
an average particle size of 0.1 to 30 .mu.m, said Al alloy being
one or more of an Al--Si alloy comprised of Si: 10.5 to 30 mass %
and having a balance of Al and unavoidable impurities, an Al--Mg
alloy comprised of Mg: 0.3 to 13.0 mass % and having a balance of
Al and unavoidable impurities, and an Al--Mg--Si alloy comprised of
Mg: 0.3 to 13.0 mass % and Si: 0.3 to 13.0 mass % and having a
balance of Al and unavoidable impurities, dispersed in a ratio of
10 to 40 mass %, on a titanium sheet by brushing or spraying and
heating at 150.degree. C. to 300.degree. C. for 5 to 60 minutes to
form a protective film on the titanium sheet surface.
12. A method of production of a titanium sheet covered with a
protective film superior in high temperature oxidation resistance
and high temperature salt damage resistance as set forth in claim
11 characterized in that said silicone resin further contains
SiO.sub.2 and/or MgO with an average particle size of 0.1 to 30
.mu.m in a total of 0.5 to 20.0 mass %.
13. A method of production of a titanium sheet covered with a
protective film superior in high temperature oxidation resistance
and high temperature salt damage resistance as set forth in claim
12 characterized in that said titanium sheet before covering by
said protective film is a cold rolled, then vacuum annealed
material.
14. A method of production of a titanium sheet covered with a
protective film superior in high temperature oxidation resistance
and high temperature salt damage resistance as set forth in claim 8
characterized by further heating said titanium sheet covered with a
protective film at 600.degree. C. to 800.degree. C. for 30 minutes
to 10 hours.
15. A method of production of a titanium sheet covered with a
protective film superior in high temperature oxidation resistance
and high temperature salt damage resistance as set forth in claim 8
characterized in that said titanium sheet contains one or both of
Cu: 0.5 to 2.1 mass % and Al: 0.4 to 2.5 mass % and has a balance
of titanium and unavoidable impurities.
16. A method of production of a titanium sheet covered with a
protective film superior in high temperature oxidation resistance
and high temperature salt damage resistance as set forth in claim
15, characterized in that said titanium sheet further contains Nb:
0.3 to 1.1 mass %.
17. An automobile exhaust system made of a titanium sheet covered
with a protective film superior in high temperature oxidation
resistance and high temperature salt damage resistance
characterized by using a titanium sheet covered with a protective
film superior in high temperature oxidation resistance and high
temperature salt damage resistance as set forth in claim 1 or a
titanium member obtained by shaping said titanium sheet covered
with a protective film as a component member.
18. An automobile exhaust system made of a titanium sheet covered
with a protective film superior in high temperature oxidation
resistance and high temperature salt damage resistance
characterized by comprising an automobile exhaust system having a
protective film as set forth in claim 4 on an inside and outside
surface.
19. An automobile exhaust system made of a titanium sheet covered
with a protective film superior in high temperature oxidation
resistance and high temperature salt damage resistance as set forth
in claim 17 characterized by part or all of the composition of
ingredients in the protective film of said titanium substrate
changing to one or two of a Ti--Al intermetallic compound and
Ti--Si intermetallic compound by maintenance at a high temperature
along with use of said automobile exhaust system.
20. An automobile exhaust system made of a titanium sheet covered
with a protective film superior in high temperature oxidation
resistance and high temperature salt damage resistance as set forth
in claim 19 characterized in that said titanium substrate is formed
on its surface with one or more of Al.sub.2O.sub.3, SiO.sub.2, MgO,
and TiC.
21. A method of production of an automobile exhaust system made of
a titanium sheet covered with a protective film superior in high
temperature oxidation resistance and high temperature salt damage
resistance characterized by coating a silicone resin containing an
Al alloy of a thin flake shape or grain shape as set forth in claim
11 on the inside and outside surfaces of an automobile exhaust
system, obtained by shaping a titanium sheet, by brushing or
spraying, then heating at 150.degree. C. to 300.degree. C. for 5 to
60 minutes to form protective film coverings on the inside and
outside surfaces.
Description
TECHNICAL FIELD
[0001] The present invention relates to a titanium material used
for an automobile exhaust system in four-wheeled vehicles and
two-wheeled vehicles and relates as well as to a titanium sheet
covered with a protective film superior in high temperature salt
damage resistance able to be used for a main muffler of course, an
exhaust manifold, exhaust pipe, catalytic muffler, or other
location exposed to a high temperature of 600.degree. C. or more
and where heat resistance and oxidation resistance are particularly
required, a method of production of the same, and an automobile
exhaust system using the same.
BACKGROUND ART
[0002] Titanium materials are light in weight, yet high in strength
and excellent in corrosion resistance, so are being used even for
the exhaust systems of automobiles. The combustion gas discharged
from the engines of automobiles and motorcycles is collected at an
exhaust manifold and discharged by an exhaust pipe from an exhaust
outlet at the rear of a vehicle. An exhaust pipe is formed split
into several segments to enable insertion of a catalyst and muffler
in the middle. In the Description, the entire system from the
exhaust manifold to the exhaust pipe and exhaust outlet will be
called an "exhaust system".
[0003] As the material of such an exhaust system, Japanese
Unexamined Patent Publication No. 2001-234266 discloses an
invention relating to a titanium alloy having both cold workability
and high temperature strength. Further, as methods which form an
oxidation prevention film to increase the oxidation resistance, an
invention relating to coating an antioxidant including aluminum
powder (see Japanese Unexamined Patent Publication No. 1-022404),
an invention relating to coating Al particles, Si particles, or
Al--Si alloy particles (see Japanese Unexamined Patent Publication
No. 2004-115906), an invention relating to Al--Ti-based vapor
deposition plating (see Japanese Unexamined Patent Publication No.
6-088208), an invention relating to a film containing Al and N (see
Japanese Unexamined Patent Publication No. 9-256138), an invention
relating to hot dip plating of a surface layer containing Al or Si
(see Japanese Unexamined Patent Publication No. 2005-036311), and
the like have been disclosed. Further, as a surface-treated
titanium material superior in oxidation resistance, a titanium
material formed with a fired coating layer of 5 .mu.m or more
comprised of particles comprised of pure Al or an Al alloy
containing 10 at % or less of Si between which a compound comprised
of a metal element M (where M is one or more types of Ti, Zr, Cr,
Si, and Al) and C and/or O is filled (see Japanese Unexamined
Patent Publication No. 2006-009115) is disclosed.
DISCLOSURE OF THE INVENTION
[0004] Titanium materials easily oxidize at a high temperature of
600.degree. C. or more. The oxidation weight gain by a continuous
oxidation test at 600 to 800.degree. C. (100 to 200 hour exposure
in the atmosphere at each temperature) is about 2 orders of
magnitude larger compared to the ferritic stainless steel material
which is generally used as an automobile exhaust system, but there
is the problem that oxidation further proceeds when exposed to a
high temperature of 600.degree. C. or more in a state where
chlorine ions are present compared to when there no chlorine ions
are present. That is, the problem to be solved by the present
invention is the problem of the progression of high temperature
oxidation when chlorine ions are present (hereinafter the high
temperature oxidation when there are chlorine ion present also
being referred to as "high temperature salt damage", while the high
temperature oxidation resistance when there are chlorine ions
present also being referred to as "high temperature salt damage
resistance"). Further, when using a titanium material for an
automobile exhaust system, there are the problem of high
temperature oxidation in the atmosphere (hereinafter referred to as
the "high temperature oxidation resistance"), the problem of the
progression of high temperature oxidation in the case when chlorine
ions are present, the problem of whether the adhesion of the
protective film is sufficient when the surface is coated by a
material other than titanium to improve the oxidation resistance,
and the problem of whether the protective film after heating is
resistant to flaws (hereinafter referred to as "flaw
resistance").
[0005] With the titanium alloy described in Japanese Unexamined
Patent Publication No. 2001-234266 not given any surface treatment,
there is the problem that the oxidation in the atmosphere at 600 to
800.degree. C. is remarkable compared to the ferritic stainless
SUS436 J1L (for example, Fe-17Cr-0.5Mo-0.2Ti) and the oxidation
weight gain is two orders of magnitude larger. When heated to
700.degree. C. or more in a state where chlorine ions are present,
the oxidation proceeds remarkably and the high temperature salt
damage resistance is remarkably insufficient. Further, the high
temperature oxidation resistance also cannot be said to be
sufficient.
[0006] Further, with the coating of the antioxidant according to
the invention described in Japanese Unexamined Patent Publication
No. 1-022404, there is the problem that the adhesion of the coated
film is poor and the coated film easily peels off even with a small
impact. On top of this, the high temperature salt damage resistance
at 700.degree. C. or more is insufficient.
[0007] Further, with the invention described in Japanese Unexamined
Patent Publication No. 2004-115906, the Al particles and Si
particles or Al--Si alloy particles have to be mixed with a
fluoride flux, coated on the substrate, then heated in an inert gas
environment at 600.degree. C. or more. There is therefore the
problem that the labor and costs rise.
[0008] Further, with the inventions described in Japanese
Unexamined Patent Publication No. 6-088208 and Japanese Unexamined
Patent Publication No. 09-256138, there are the problems that
equipment for vapor deposition or sputtering or ion plating, ion
implantation, or plasma spraying is necessary and that film
formation after the substrate formation is difficult.
[0009] Further, with the invention described in Japanese Unexamined
Patent Publication No. 2005-036311, an oxidation protective film
containing 90% or more of Al or 90% or more of Al+Si (Si is 1 to
20%) is formed by the hot dip plating method. In this patent
publication, it is described that methods other than the hot dip
plating method, for example, coating an organic based coating
containing Al flakes, are possible. However, when using an organic
resin, it is difficult to make the content of Al flakes or the
total content of Al and Si 90% or more. Ultimately, it can be
presumed that the film formation of the invention described in this
patent publication is basically by the method by hot dip plating as
recommended. From this, the invention described in this patent
publication has the problem that it requires a plating tank and
heating and again the cost rises
[0010] The titanium material formed with a fired coating layer of 5
.mu.m or more comprised of particles comprised of pure Al or an Al
alloy containing 10 at % or less of Si between which a compound
comprised of a metal element M (where M is one or more types of Ti,
Zr, Cr, Si, and Al) and C and/or O is filled described in Japanese
Unexamined Patent Publication No. 2006-009115 had a high
temperature oxidation resistance, but had the problem that the
coated layer easily peeled off.
[0011] Note that the above publications lacked any description
relating to the high temperature salt damage resistance.
[0012] Therefore, the present invention has as its object the
provision of a titanium sheet covered with a protective film
superior in high temperature oxidation resistance (high temperature
salt damage resistance) and adhesion in the atmosphere and in a
state where chlorine ions are present or further resistant to flaws
in the coated film after being heated to a high temperature of
600.degree. C. or more, an automobile exhaust system using this,
and methods of production of the same.
[0013] The present invention intensively surveyed the component
ingredients having an oxidation suppression effect at a high
temperature as the protective film of a titanium material
substrate. As a result, it discovered that by forming a surface
layer containing Si and C on the substrate, a film having an
excellent oxidation suppression effect could be obtained. Further,
it discovered that by adding Al in addition to Si and C, a
protective film superior in oxidation suppression effect could be
further obtained. Further, it intensively surveyed and researched
the component ingredients having a high temperature salt damage
suppression effect as a protective film of a titanium material
substrate. As a result, it discovered that by forming a protective
film containing Si, C, and fine flake-shaped or powder-shaped metal
Al on a substrate, a remarkable high temperature salt damage
suppression effect could be obtained. Still further, it intensively
surveyed and researched component ingredients having high
temperature oxidation and high temperature salt damage suppression
effects and superior in adhesion and flaw resistance as a
protective film of a titanium material substrate. As a result, it
discovered that by forming a protective film comprised of a
silicone resin containing a fine flake-shaped or powder-shaped Al
alloy on a substrate, a remarkable high temperature oxidation
suppression effect, high temperature salt damage suppression
effect, adhesion after formation of the protective film, and flaw
resistance at a high temperature of 600.degree. C. or more were
obtained.
[0014] The present invention is based on such discoveries and has
as its gist the following.
[0015] (1) A titanium sheet covered with a protective film superior
in high temperature oxidation resistance and high temperature salt
damage resistance characterized by comprising a titanium sheet on
the surface of which is formed a protective film of a thickness of
1 .mu.m to 100 .mu.m comprising Si: 15 to 55 mass % and C: 10 to 45
mass % and having a balance of unavoidable impurities.
[0016] (2) A titanium sheet covered with a protective film superior
in high temperature oxidation resistance and high temperature salt
damage resistance as set forth in claim 1, characterized in that
said protective film further contains Al: 20 to 60 mass %.
[0017] (3) A titanium sheet covered with a protective film superior
in high temperature oxidation resistance and high temperature salt
damage resistance as set forth in (2), characterized in that said
protective film has said Al of metal Al of a thin flake shape with
an average thickness of 0.1 to 5 .mu.m and an average width or
average length of 1 to 50 .mu.m or of a grain shape with an average
particle size of 0.1 to 30 .mu.m dispersed in a silicone resin or
silicone grease.
[0018] (4) A titanium sheet covered with a protective film superior
in high temperature oxidation resistance and high temperature salt
damage resistance characterized by comprising a titanium sheet on
the surface of which is formed a protective film of a thickness of
1 .mu.m to 100 .mu.m comprising a metal Al alloy of a thin flake
shape with an average thickness of 0.1 to 5 .mu.m and an average
width or average length of 1 to 50 .mu.m or of a grain shape with
an average particle size of 0.1 to 30 .mu.m dispersed in a silicone
resin in a ratio of 10 to 40 mass %, said Al alloy being one or
more of an Al--Si alloy comprised of Si: 10.5 to 30 mass % and
having a balance of Al and unavoidable impurities, an Al--Mg alloy
comprised of Mg: 0.3 to 13.0 mass % and having a balance of Al and
unavoidable impurities, and an Al--Mg--Si alloy comprised of Mg:
0.3 to 13.0 mass % and Si: 0.3 to 13.0 mass % and having a balance
of Al and unavoidable impurities.
[0019] (5) A titanium sheet covered with a protective film superior
in high temperature oxidation resistance and high temperature salt
damage resistance as set forth in (4), characterized in that said
protective film further has SiO.sub.2 and/or MgO with an average
particle diameter of 0.1 to 30 .mu.m dispersed in it in a total of
0.5 to 20.0 mass %.
[0020] (6) A titanium sheet covered with a protective film superior
in high temperature oxidation resistance and high temperature salt
damage resistance as set forth in any one of (1) to (5),
characterized in that said titanium sheet contains one or both of
Cu: 0.5 to 2.1 mass % and Al: 0.4 to 2.5 mass % and has a balance
of titanium and unavoidable impurities.
[0021] (7) A titanium sheet covered with a protective film superior
in high temperature oxidation resistance and high temperature salt
damage resistance as set forth in (6), characterized in that said
titanium sheet further contains Nb: 0.3 to 1.1 mass %.
[0022] (8) A method of production of a titanium sheet covered with
a protective film superior in high temperature oxidation resistance
and high temperature salt damage resistance characterized by
coating a silicone resin or silicone grease prepared to contain Si:
15 to 55 mass % and C: 10 to 45 mass % on a titanium sheet by
brushing or spraying to form a protective film on the surface of
the titanium sheet.
[0023] (9) A method of production of a titanium sheet covered with
a protective film superior in high temperature oxidation resistance
and high temperature salt damage resistance as set forth in (8)
characterized in that said silicone resin or silicone grease
further contains Al: 20 to 60 mass %.
[0024] (10) A method of production of a titanium sheet covered with
a protective film superior in high temperature oxidation resistance
and high temperature salt damage resistance characterized by
coating a silicone resin or silicone grease, prepared by making
metal Al of a thin flake shape with an average thickness of 0.1 to
5 .mu.m and an average width or average length of 1 to 50 .mu.m or
of a grain shape with an average particle size of 0.1 to 30 .mu.m
disperse in a silicone resin or silicone grease so as to give a
composition of Si: 15 to 55 mass %, C: 10 to 45 mass %, and Al: 20
to 60 mass %, on a titanium sheet by brushing or spraying and
heating at 150.degree. C. to 300.degree. C. for 5 to 60 minutes to
form a protective film on the titanium sheet surface.
[0025] (11) A method of production of a titanium sheet covered with
a protective film superior in high temperature oxidation resistance
and high temperature salt damage resistance characterized by
coating a silicone resin, containing an Al alloy of a thin flake
shape with an average thickness of 0.1 to 5 .mu.m and an average
width or average length of 1 to 50 .mu.m or of a grain shape with
an average particle size of 0.1 to 30 .mu.m, said Al alloy being
one or more of an Al--Si alloy comprised of Si: 10.5 to 30 mass %
and having a balance of Al and unavoidable impurities, an Al--Mg
alloy comprised of Mg: 0.3 to 13.0 mass % and having a balance of
Al and unavoidable impurities, and an Al--Mg--Si alloy comprised of
Mg: 0.3 to 13.0 mass % and Si: 0.3 to 13.0 mass % and having a
balance of Al and unavoidable impurities, dispersed in a ratio of
10 to 40 mass %, on a titanium sheet by brushing or spraying and
heating at 150.degree. C. to 300.degree. C. for 5 to 60 minutes to
form a protective film on the titanium sheet surface.
[0026] (12) A titanium sheet covered with a protective film
superior in high temperature oxidation resistance and high
temperature salt damage resistance as set forth in (11)
characterized in that said silicone resin further contains
SiO.sub.2 and/or MgO with an average particle size of 0.1 to 30
.mu.m in a total of 0.5 to 20.0 mass %.
[0027] (13) A method of production of a titanium sheet covered with
a protective film superior in high temperature oxidation resistance
and high temperature salt damage resistance as set forth in any one
of (8) to (12) characterized in that said titanium sheet before
covering by said protective film is a cold rolled, then vacuum
annealed material.
[0028] (14) A method of production of a titanium sheet covered with
a protective film superior in high temperature oxidation resistance
and high temperature salt damage resistance as set forth in any one
of (8) to (13) characterized by further heating said titanium sheet
covered with a protective film at 600.degree. C. to 800.degree. C.
for 30 minutes to 10 hours.
[0029] (15) A method of production of a titanium sheet covered with
a protective film superior in high temperature oxidation resistance
and high temperature salt damage resistance as set forth in any one
of (8) to (14) characterized in that said titanium sheet contains
one or both of Cu: 0.5 to 2.1 mass % and Al: 0.4 to 2.5 mass % and
has a balance of titanium and unavoidable impurities.
[0030] (16) A method of production of a titanium sheet covered with
a protective film superior in high temperature oxidation resistance
and high temperature salt damage resistance as set forth in (15),
characterized in that said titanium sheet further contains Nb: 0.3
to 1.1 mass %.
[0031] (17) An automobile exhaust system made of a titanium sheet
covered with a protective film superior in high temperature
oxidation resistance and high temperature salt damage resistance
characterized by using a titanium sheet covered with a protective
film superior in high temperature oxidation resistance and high
temperature salt damage resistance as set forth in any one of (1)
to (7) or a titanium member obtained by shaping said titanium sheet
covered with a protective film as a component member.
[0032] (18) An automobile exhaust system made of a titanium sheet
covered with a protective film superior in high temperature
oxidation resistance and high temperature salt damage resistance
characterized by comprising an automobile exhaust system having a
protective film as set forth in (4) or (5) on inside and outside
surfaces.
[0033] (19) An automobile exhaust system made of a titanium sheet
covered with a protective film superior in high temperature
oxidation resistance and high temperature salt damage resistance as
set forth in (17) or (18) characterized by part or all of the
composition of ingredients in the protective film of said titanium
substrate changing to one or two of a Ti--Al intermetallic compound
and Ti--Si intermetallic compound by maintenance at a high
temperature along with use of said automobile exhaust system.
[0034] (20) An automobile exhaust system made of a titanium sheet
covered with a protective film superior in high temperature
oxidation resistance and high temperature salt damage resistance as
set forth in (19) characterized in that said titanium substrate is
formed on its surface with one or more of Al.sub.2O.sub.3,
SiO.sub.2, MgO, and TiC.
[0035] (21) A method of production of an automobile exhaust system
made of a titanium sheet covered with a protective film superior in
high temperature oxidation resistance and high temperature salt
damage resistance characterized by coating a silicone resin
containing an Al alloy of a thin flake shape or grain shape as set
forth in (11) on the inside and outside surfaces of an automobile
exhaust system, obtained by shaping a titanium sheet, by brushing
or spraying, then heating at 150.degree. C. to 300.degree. C. for 5
to 60 minutes to form protective film coverings on the inside and
outside surfaces.
[0036] According to the present invention, it becomes possible to
provide a titanium sheet superior in high temperature oxidation
resistance and high temperature salt damage resistance even at a
high temperature of 600.degree. C. or more, having sufficient
strength at a high temperature, excellent in workability at room
temperature, or further having flaw resistance to flaws introduced
during use. If used for the exhaust system of a four-wheeled
vehicle, two-wheeled vehicle, or other automobile, great advances
may be made in reduction of weight. The industrial contribution is
extremely remarkable.
BEST MODE FOR CARRYING OUT THE INVENTION
[0037] Below, the present invention will be explained in detail.
The present invention includes a titanium sheet and a titanium
member shaped from a titanium sheet. Below, the two will also be
referred to together as a "titanium substrate".
[0038] The titanium sheet covered with a protective film superior
in high temperature oxidation resistance and/or high temperature
salt damage resistance or further superior in flaw resistance of
the present invention is characterized in that a protective film of
a thickness of 1 .mu.m to 100 .mu.m containing Si in 15 to 55 mass
% and C in 10 to 40 mass % is formed on the surface of a titanium
substrate.
[0039] The protective film containing Si and C acts to improve the
heat resistance and oxidation resistance. Si and C are preferably
coated as a silicone resin. A "silicone resin" is a straight chain
polymer comprised of siloxane bonds (--Si--O-- bonds) and indicates
dimethyl silicone, methylphenyl silicone, or methyl hydrogen
silicone. The Si and C in the silicone resin remain on the titanium
sheet in the form of SiO.sub.2 and TiC after being heated to a high
temperature, whereby the oxidation resistance is maintained even
when subsequently repeatedly heated.
[0040] Here, the content of Si contained in the protective film is
15 to 55 mass % and the content of C is 10 to 45 mass %. To form a
protective film of an SiO.sub.2 layer and TiC layer having
sufficient oxidation resistance when heated to a high temperature,
the Si content has to be 15 mass % or more and the C has to be 10
mass % or more. If Si exceeds 55 mass %, the SiO.sub.2 layer
becomes too thick and easily peels off, so the upper limit was made
55 mass %. Further, if C exceeds 45 mass %, the TiC layer becomes
thick and the effect of oxidation resistance is saturated, so the
upper limit of C was made 45 mass %.
[0041] Further, the protective film of the present invention
further preferably contains Al in 20 to 60 mass %. Al is included
in the protective film in the form of flakes or powder. By
including Al the oxidation resistance is further improved. This
remains at the substrate surface as a Ti--Al intermetallic compound
in addition to SiO.sub.2 and TiC when heated to a high temperature.
By these covering the substrate surface, the diffusion of oxygen
into the titanium substrate is remarkably suppressed and the
oxidation is suppressed. Here, the content of Al contained in the
protective film is 20 to 60 mass %. To form a Ti--Al intermetallic
compound, a content of 20 mass % or more is necessary. If over 60
mass %, the effect becomes saturated.
[0042] Further, the titanium sheet covered with a protective film
superior in high temperature oxidation resistance and high
temperature salt damage resistance of the present invention is
characterized by comprising a titanium sheet on the surface of
which is formed a protective film of a thickness of 1 .mu.m to 100
.mu.m comprising flake-shaped metal Al with an average thickness of
0.1 to 5 .mu.m and an average width or average length of 1 to 50
.mu.m or grain-shaped metal Al with an average size of 0.1 to 30
.mu.m dispersed in a silicone resin or silicone grease in a ratio
of 20 to 60 mass %, containing Si: 15 to 55 mass % and C: 10 to 45
mass %, and having a balance of unavoidable impurities.
[0043] The elements of Al, Si, and C contained in the protective
film all act to improve the high temperature oxidation resistance
and high temperature salt damage resistance. The metal Al uniformly
dispersed in the protective film in the form of fine flakes or
grains densely covers the entire surface of the titanium substrate.
When heated to a high temperature of 600.degree. C. or more, the
entire surface of the titanium substrate is covered with a Ti--Al
intermetallic compound and/or Al.sub.2O.sub.3. On the other hand,
Si becomes a Ti--Si intermetallic compound and/or SiO.sub.2 when
heated to a high temperature of 600.degree. C. or more. These cover
the Ti--Al intermetallic compound and/or Al.sub.2O.sub.3 layer. By
the combination of the two, the diffusion of the oxygen in the
protective film into the titanium substrate is reliably suppressed
and the progression of high temperature salt damage is suppressed.
These protective films remain on the titanium substrate even with
subsequent repeated heating in an environment in which chlorine
ions are present, so the high temperature salt damage resistance is
maintained. Further, C is required for maintaining the adhesion of
the protective film. Si and C are preferably coated as a silicone
resin or silicone grease. A "silicone resin" is a straight chain
polymer comprised of siloxane bonds (--Si--O-- bonds) and indicates
dimethyl silicone, methylphenyl silicone, methyl hydrogen silicone,
or another straight silicone and also alkyl silicone, higher fatty
acid ester silicone, and other modified silicones etc., while a
"silicone grease" indicates a silicone resin base into which a
thickener (fine powder of aluminum, lithium, silica, etc.),
oiliness agent (higher fatty acid, ester, etc.), etc. are mixed.
When coating Si and C as a silicone resin, the balance of the
protective film is comprised of O and H and unavoidable
impurities.
[0044] Here, the metal Al contained dispersed in the protective
film is flake shaped with an average thickness of 0.1 to 5 .mu.m
and an average width or average length of 1 to 50 .mu.m or grain
shaped with an average size of 0.1 to 30 .mu.m. The content is 20
to 60 mass %. Further, the Si content of the protective film is 15
to 55 mass %, while the C content is 10 to 45 mass %.
[0045] Metal Al must be included in an amount of 20 mass % or more
in order to form a Ti--Al intermetallic compound and/or
Al.sub.2O.sub.3. If over 60 mass %, the effect becomes saturated,
so the amount was made 60 mass % or less. Further, regarding the
shape of the metal Al, with flake-shaped Al, the dimensions were
made an average thickness of 0.1 to 5 .mu.m and an average width or
average length of 1 to 30 .mu.m, while with grain-shaped Al, the
average size was made 0.1 to 30 .mu.m. These sizes are the upper
and lower limits for the flake-shaped or grain-shaped metal Al to
be uniform in the protective film, the titanium substrate to be
densely covered, and the entire surface of the titanium substrate
to be formed with an Ti--Al intermetallic compound layer and/or
Al.sub.2O.sub.3 when heated to a high temperature. When the average
value of the size of the Al exceeds the upper limit of this range,
locations where the Ti--Al intermetallic compound and/or
Al.sub.2O.sub.3 are not formed occur at the titanium substrate
surface and high temperature salt damage progresses. If fine metal
Al, the entire surface of the titanium substrate is covered and the
entire surface is formed with a Ti--Al intermetallic compound
and/or Al.sub.2O.sub.3, but in practice manufacture of flake shapes
with a thickness of less than an average 0.1 .mu.m or particles
with an average size of less than 0.1 .mu.m is difficult, so the
lower limit of the thickness and diameter of the Al flakes and
grains was made 0.1 .mu.m. To make the metal Al in the protective
film uniformly disperse, it is preferable that 70% or more of the
metal Al in the protective film fall in this range of
dimensions.
[0046] To form an SiO.sub.2 layer and/or Ti--Si intermetallic
compound having sufficient high temperature salt damage resistance
when heated to a high temperature over the entire surface, the Si
content must be 15 mass % or more. On the other hand, if Si is over
55 mass %, the SiO.sub.2 layer and/or layer of Ti--Si intermetallic
compound becomes too thick and easily peels off, so the upper limit
was made 55 mass %.
[0047] C has to be 10 mass % or more to maintain the adhesion of
the protective film. Further, if C exceeds 45 mass %, the effect
becomes saturated, so the upper limit of C was made 45 mass %.
[0048] Further, the titanium sheet covered with a protective film
of the present invention is characterized in that it has a
protective film of a thickness of 1 .mu.m to 100 .mu.m, in which
flake-shaped Al alloy with an average thickness of 0.1 to 5 .mu.m
and an average width or average length of 1 to 50 .mu.m and/or
grain-shaped Al alloy with an average particle size of 0.1 to 30
.mu.m is dispersed in a silicone resin in a ratio of 10 to 40 mass
%, formed on the surface of the titanium sheet, said Al alloy
comprising one or more of an Al--Si alloy containing Si: 10.5 mass
% to 30.0 mass % and having a balance of Al and unavoidable
impurities, an Al--Mg alloy containing Mg: 0.3 to 13.0 mass % and
having a balance of Al and unavoidable impurities, and an
Al--Mg--Si alloy containing Mg: 0.3 to 13.0 mass % and Si: 0.3 to
13.0 mass % and having a balance of Al and unavoidable impurities
and is superior in high temperature oxidation resistance, high
temperature salt damage resistance, adhesion, and flaw
resistance.
[0049] The Al--Si alloy, Al--Mg alloy, and/or Al--Mg--Si alloy
dispersed in the protective film as fine particles densely cover
the surface of the titanium substrate. The particles may be shaped
as grains (spherical) and also flakes or irregular shapes (for
example, shapes after crushing rocks). Note that the average
particle size, in the case of an irregular shape, indicates the
length of the line segment connecting the most prominent locations
sticking out.
[0050] These Al-based alloys are made to disperse in the silicone
resin and cover the titanium sheet surface. Silicone has a suitable
viscosity, so is suitable as a resin for causing dispersion of an
Al alloy and further as a coating material.
[0051] When the titanium sheet covered with a protective film is
heated to a high temperature of 600.degree. C. or more, the Al--Si
alloy, Al--Mg alloy, and/or Al--Mg--Si alloy in the protective film
react with the titanium sheet whereby they cover the surface of the
titanium sheet in the form of one or more of Ti--Al intermetallic
compounds, Al.sub.2O.sub.3, Ti--Si intermetallic compounds,
SiO.sub.2, and MgO. On the other hand, the Si contained in silicone
also becomes a Ti--Si intermetallic compound and/or SiO.sub.2 when
heated to a high temperature of 600.degree. C. or more and covers
the surface of the titanium substrate together with the Ti--Al
intermetallic compounds and Al.sub.2O.sub.3, MgO, etc. By the two
combined, the diffusion of the oxygen in the protective film to the
titanium substrate is reliably suppressed and the progression of
high temperature oxidation and high temperature salt damage is
suppressed. These protective films remain on the titanium substrate
even with subsequent repeated heating in an environment in which
chlorine ions are present, so the high temperature salt damage
resistance is maintained.
[0052] In this invention, the substance dispersed in the protective
film as fine particles is made an Al--Si alloy, Al--Mg alloy, or
Al--Mg--Si alloy containing Si and Mg in predetermined amounts or
more. Due to this, compared with the case where pure Al or an
Al--Si alloy with an Si content of less than 10.5 mass % is
dispersed in the protective film, a protective film more superior
in durability and with a high temperature salt damage resistance is
obtained. That is, even if the protective film becomes flawed after
being heated to a temperature of 600.degree. C. or more, sufficient
high temperature salt damage resistance is obtained. This is
because the Ti--Al and Ti--Si intermetallic compound layer and MgO
formed from the Al--Si alloy or Al--Mg alloy and/or Al--Mg--Si
alloy are denser compared with the intermetallic compound layer
formed from pure Al or an Al--Si alloy with an Si content of less
than 10.5 mass %. The Al alloy dispersed in the silicone is one or
more of an Al-10.5 to 30.0 mass % Si alloy, Al-0.3 to 13.0 mass %
Mg alloy, and Al-0.3 to 13.0 mass % Mg-0.3 to 13.0 mass % Si alloy
dispersed in a total of 10 to 40 mass %.
[0053] If making the Si content 10.5 mass % or more in Al-10.5 to
30.0 mass % Si, a dense intermetallic compound layer superior in
flaw resistance and superior in high temperature oxidation
resistance and high temperature salt damage resistance is formed at
the interface of the protective film and matrix material after high
temperature heating. If Si exceeds 30.0 mass %, the density of the
protective film deteriorates. Along with this, the flaw resistance
of the protective film after heating deteriorates and the high
temperature oxidation characteristic and high temperature salt
damage characteristic deteriorate.
[0054] When the Mg and Si in the Al-0.3 to 13.0 mass % Mg alloy and
Al-0.3 to 13.0 mass % Mg-0.3 to 13.0 mass % Si alloy are also
heated to a high temperature, MgO and SiO.sub.2 are formed and the
high temperature oxidation resistance is improved. Here, the
contents of the Mg and Si of the Al--Mg alloy and Al--Mg--Si alloy
were all made 0.3 to 13.0 mass % because if less than 0.3 mass %,
the MgO or SiO.sub.2 contributing to the high temperature oxidation
resistance are not sufficiently formed, while if over 13.0 mass %,
the effect becomes saturated.
[0055] The Al--Si alloy, Al--Mg alloy, and Al--Mg--Si alloy
contained dispersed in the protective film is of a flake shape with
an average thickness of 0.1 to 5 .mu.m and an average width or
average length of 1 to 50 .mu.m and/or a grain shape with an
average particle size of 0.1 to 30 .mu.m. The average thickness,
average width or average length, and average particle size defined
are the upper and lower limits set so that the flake-shaped or
grain-shaped dispersed substances are uniform in the protective
film, the titanium substrate is densely covered, and, when heated
to a high temperature, the entire titanium substrate is formed with
a Ti--Al intermetallic compound layer, Ti--Si intermetallic
compound, and/or Al.sub.2O.sub.3, SiO.sub.2, and MgO. When the
average value of the size of the dispersed substances exceeds the
upper limit of the range, spottiness easily occurs when sprayed
mixed with a solvent. When extremely large, spraying itself becomes
difficult. On the other hand, manufacturing flakes with an average
thickness of less than 0.1 .mu.m or grains with an average diameter
of 0.1 .mu.m is difficult, so the lower limit of the thickness and
diameter of the dispersed substances was made 0.1 .mu.m. To make
the substances dispersed in the protective film evenly disperse, it
is preferable that 70% or more of the substances dispersed in the
protective film fall in this range of dimensions.
[0056] The ratio of the total content of the Al alloys to the
protective film as a whole was made 10 to 40 mass % because if less
than 10 mass %, the production of the Ti--Al intermetallic
compounds is small and the high temperature salt damage resistance
is not sufficient, while if over 40 mass %, the content of silicone
falls and the adhesion of the protective film drops.
[0057] The silicone used in the protective film of the present
invention is sometimes called a "silicone resin" or "silicone oil",
but here will be referred to as "silicone". A silicone is a
straight chain polymer comprised of siloxane bonds (--Si--O--
bonds) and indicates dimethyl silicone, methylphenyl silicone,
methyl hydrogen silicone, or another straight silicone and also
alkyl silicone, higher fatty acid ester silicone, and other
modified silicones etc.
[0058] By adding SiO.sub.2 and MgO in the protective film as well,
the protective film is improved in high temperature oxidation
resistance, high temperature salt damage resistance, and flaw
resistance. In particular, the high temperature salt damage
resistance at 700.degree. C. or more is improved. The SiO.sub.2 and
MgO added may also be supplied in the form of hydrous magnesium
silicate ((MgO).sub.3(SiO.sub.2).sub.4H.sub.2O). The total of these
contents was made 0.5 to 20.0 mass % because if less than 0.5 mass
%, the effect of high temperature salt damage resistance at
700.degree. C. or more is insufficient, while if over 20.0 mass %,
the effect becomes saturated.
[0059] The average particle size of the SiO.sub.2 and MgO contained
in the protective film is made 0.1 to 30 .mu.m. By this particle
size range, when heated to a high temperature, the entire surface
of the titanium substrate is formed with a Ti--Al intermetallic
compounds layer, Ti--Si intermetallic compound, and/or
Al.sub.2O.sub.3, SiO.sub.2, or MgO and the titanium substrate is
densely covered.
[0060] To obtain a high temperature oxidation resistance and high
temperature salt damage resistance effect, it is sufficient that
the protective film of the present invention, even if small in
amount, be evenly coated on the surface. The thickness was made 1
.mu.m or more because uniformly coating a protective film at a
thickness of less than 1 .mu.m on a surface is difficult. If
coating it over 100 .mu.m, the effect of high temperature oxidation
resistance and prevention of high temperature salt damage becomes
saturated and the coating is not only wasted, but easily peels off,
so the thickness was made 100 .mu.m or less. Note that a
"protective film" means a solid covering formed on a substrate
surface and indicates the covering after the solvent which had been
contained in the coating material at the time of coating completely
evaporates.
[0061] The protective film of the present invention may be formed
by adjusting the amounts of Si, C, or further metal Al in the
silicone resin or silicone grease or adjusting the amount of Al
alloy in the silicone resin to give a predetermined composition,
adding a solvent to this to obtain a coating for a protective film,
coating this on the titanium substrate, and drying or heating this.
Note that the contents of Si and C of the protective film are
adjusted by selecting the type of the silicone resin or adding
additives to the silicone resin. For example, dimethyl silicone
mainly has methyl groups at its side chain, while methylphenyl
silicone mainly has phenyl groups at its side chains, so the amount
of C is large. On the other hand, methyl hydrogen silicone has H at
one side of its side chain, so the ratio of the amount of Si
becomes greater. Further, by adding silica or another thickener or
talc (magnesium silicate containing about 60% of silica) to the
silicone resin, it is possible to adjust the amount of Si.
[0062] The protective film of the present invention is preferably
formed on the titanium substrate by brushing or spraying. By mixing
predetermined ingredients of the protective film and a solvent such
as toluene, xylene, and ethyl benzene, brushing or spraying becomes
possible. These solvents evaporate upon drying after brushing or
spraying (room temperature, several hours) or upon heating, whereby
the silicone resin is cured and the adhesion with the titanium
substrate is raised. The heating after coating is preferably
performed at a temperature of 150 to 300.degree. C. for 5 to 60
minutes. This is because if the heating temperature is less than
150.degree. C., the adhesion of the protective film becomes
insufficient, while even if over 300.degree. C., the adhesion does
not change, so the temperature was made 150 to 300.degree. C.
Further, the heating time was made 5 minutes or more because if
less than 5 minutes, the solvent will not sufficiently evaporate
and the adhesion of the protective film will become insufficient,
while even if over 60 minutes, the adhesion of the protective film
does not change.
[0063] The adhesion of the protective film differs depending on the
surface shape of the substrate. For example, if the surface of the
substrate is pickled skin, the adhesion of the protective film is
poor. Further, the techniques performed in the case of general
steel sheet for increasing the surface area, that is shot blasting
and sandblasting, also conversely cause the adhesion to
deteriorate. On the other hand, the surface of a cold rolled
material has a high adhesion with a protective film. This is
because the surface has streak-like sharp relief shapes. The height
difference of the relief shapes is 2 to 5 .mu.m, and the interval
between projections and depressions is about 20 to 100 .mu.m. These
fine, sharp relief shapes are believed to raise the adhesion of the
protective film. The adhesion of the protective film is
sufficiently obtained with just cold rolling, but a substrate
requires sufficient elongation, so is annealed after cold rolling.
An annealing temperature of 600.degree. C. to 750.degree. C. and a
time of several hours to tens of hours are preferable. Using a
titanium sheet cold rolled, then annealed in this way is preferable
in terms of the adhesion of the protective film and the material
characteristics of the titanium sheet.
[0064] The adhesion of the protective film was evaluated by a cross
cut tape peeling test and a Dupont type impact test (both based on
JIS K 5600).
[0065] To make the high temperature oxidation resistance and high
temperature salt damage resistance by the protective film further
sufficient, it is effective to heat the titanium sheet covered with
a protective film at 600.degree. C. to 800.degree. C. for 30
minutes to 10 hours. Due to this heating, Al.sub.2O.sub.3 and
SiO.sub.2 are densely formed in addition to the Ti--Al
intermetallic compounds and Ti--Si intermetallic compounds at the
interface of the protective film and titanium substrate. By the
titanium substrate being covered by these protective films, the
protective film exhibits a particularly superior high temperature
oxidation resistance and high temperature salt damage resistance.
If heating in an environment where chlorine ions are present to
600.degree. C. or more, these substances are formed at the
interface and a high temperature salt damage resistance is
exhibited, but by forming a dense protective film in advance, a
higher reliability high temperature salt damage resistance is
obtained. To form these substances, heating at 600.degree. C. or
more for 30 minutes or more is necessary. If over 800.degree. C.,
the substrate remarkably softens, so the upper limit of the heating
temperature was made 800.degree. C. Further, if over 10 hours, the
effect is saturated, so the time was made 10 hours or less.
[0066] Note that in the analysis of the composition of the
protective film referred to here, the analysis of the C and the
analysis of the metal elements were performed as follows:
[0067] The content of C is found by the heating and melting
thermoelectric conductivity method instantaneously applying oxygen
gas to a sample to cause it to completely oxidize and form CO.sub.2
gas and detecting the thermal conductivity difference between this
and the carrier gas. The contents of the C, H, and N contained in
the sample are simultaneously detected by this method. For example,
this can be measured by using EA-1108 made by FISONS.
[0068] Further, Si, Al, and other metal elements are analyzed by
fluorescent X-ray analysis (based on JIS K 0119). Specifically, a
protective film was coated on filter paper, allowed to sufficiently
dry at room temperature for 2 days, and analyzed by fluorescent
X-ray analysis. The contents of the metal elements were found by
subtracting the total of the previously found contents of C, H, and
N and the content of O found by the separate inert gas melting
infrared adsorption method (based on JIS H 1620) from 100 mass %
and dividing the remaining percentage by the contents of metal
elements found by fluorescent X-ray analysis.
[0069] The high temperature oxidation resistance and/or high
temperature salt damage resistance are provided by the protective
film, so the substrate can be suitably selected from pure titanium
and a titanium alloy able to be shaped into a sheet, but with pure
titanium, the high temperature strength at 600.degree. C. or more
is insufficient, so from the viewpoint of the high temperature
strength and the workability at room temperature, a titanium alloy
substrate with a 0.2% yield strength at 600 to 800.degree. C. of
1.5 times or more that of pure titanium type 2 (JIS H 4600) and,
since workability at room temperature is also required, with an
elongation (C direction) of 30% or more is preferable. As such a
titanium alloy substrate, in the present invention, a Ti-0.5 to 2.1
mass % Cu alloy, Ti-0.4 to 2.5 mass % Al alloy, and Ti-0.5 to 2.1
mass % Cu-0.4 to 2.5 mass % Al alloy, Ti-0.5 to 2.1 mass % Cu-0.3
to 1.1 mass % Nb alloy, Ti-0.4 to 2.5 mass % Al-0.3 to 1.1 mass %
Nb alloy, and Ti-0.5 to 2.1 mass % Cu-0.4 to 2.5 mass % Al-0.3 to
1.1 mass % Nb alloy can be suitably selected. The lower limits of
the Cu and Al contents in these alloys are 0.5 mass % and 0.4 mass
%, respectively. These contents are necessary so that the 0.2%
yield strength at 600 to 800.degree. C. becomes 1.5 times or more
that of pure titanium type 2.
[0070] Further, the content of Cu was made 2.1 mass % or less
because if included over 2.1 mass %, the Cu easily segregates at
the time of melting. Further, the content of Al was made 2.5 mass %
or less because if included over 2.5 mass %, the strength at room
temperature rises and over 30% elongation can no longer be
obtained.
[0071] Further, Nb was included in 0.3 to 1.1 mass % because the
inclusion of Nb further improves the high temperature salt damage
resistance. To improve the high temperature salt damage resistance,
a content of 0.3 mass % or more is necessary. With a content over
1.1 mass %, the effect relating to the high temperature salt damage
resistance is saturated.
[0072] As the titanium sheet used as the substrate of the present
invention, when used for the titanium material for an automobile
exhaust system, a material with a high strength at a high
temperature and a good workability at room temperature is suitable,
but when only a high temperature salt damage resistance is
requested, even materials other than the titanium substrate
described in the present invention are effective as can be easily
imagined. For example, even a Ti-6Al-4V, Ti-3Al-2.5V,
Ti-15V-3Cr-3Al-3Sn, or other titanium alloy sheet can be given a
high temperature salt damage resistance.
[0073] The titanium sheet covered with a protective film of the
present invention exhibits superior effects if used for an
automobile exhaust system.
[0074] As parts of the automobile exhaust system produced using the
titanium sheet of the present invention, a main muffler, exhaust
manifold, exhaust pipe, etc. of a two-wheeled vehicle, four-wheeled
vehicle, or other automobile may be mentioned. In the present
invention, as explained above, a protective film superior in high
temperature salt damage resistance at a high temperature in the
atmosphere can be formed by an easy method such as brushing or
spraying, so it is possible to perform the coating not only on a
titanium sheet, but also after shaping the titanium sheet into an
automobile exhaust system.
[0075] That is, it is also possible to use a titanium sheet covered
with a protective film or a component member obtained by shaping
this titanium sheet for an automobile exhaust system made of a
titanium sheet covered with protective film. Further, it is
possible to use a titanium sheet formed with protective films on
both of its surfaces or a component member obtained by shaping this
titanium sheet to form an automobile exhaust system made of a
titanium sheet covered with a protective film having protective
films at its inside and outside surfaces.
[0076] Furthermore, it is possible to use a titanium sheet before
coverage by a protective film or a component member obtained by
shaping a titanium sheet to form an automobile exhaust system made
of a titanium sheet, then coat the above protective film covering
coating on the inside and outside surfaces of the titanium sheet or
component member to obtain an automobile exhaust system made from a
titanium sheet covered with a protective film having protective
films on its inside and outside surfaces.
[0077] In this way, the automobile exhaust system made from a
titanium sheet covered with a protective film of the present
invention is characterized by having the protective film of the
present invention at the inside and outside surfaces of the
automobile exhaust system made of a titanium sheet. A titanium
sheet is shaped to form an automobile exhaust system made of a
titanium sheet, then the protective film of the present invention
is formed on the inside and outside surfaces.
[0078] Further, the automobile exhaust system made from a titanium
sheet covered with a protective film of the present invention is
characterized by using the titanium sheet covered with a protective
film of the present invention or a titanium member obtained by
shaping said titanium sheet covered with a protective film as a
component member. A protective film is formed on the titanium sheet
surface to form a titanium sheet covered with a protective film of
the present invention, then this titanium sheet covered with a
protective film is shaped to obtain a component member of an
automobile exhaust system.
[0079] The automobile exhaust system made from a titanium sheet
covered with a protective film of the present invention is
characterized by part or all of the composition of ingredients in
said protective film changing to one or more of Al.sub.2O.sub.3,
SiO.sub.2, MgO, a Ti--Al intermetallic compound, and Ti--Si
intermetallic compound due to maintenance at a high temperature
along with use of the automobile exhaust system. An automobile
exhaust system is exposed to a high temperature over 600.degree. C.
when used placed in an automobile. At this time, the Al--Si alloy,
Al--Mg alloy, and/or Al--Mg--Si alloy in the protective film
covering the surface of automobile exhaust system made of a
titanium sheet and Si contained in the silicone resin react with
the titanium sheet or oxidize to cover the surface of the titanium
sheet in the form of one or more of a Ti--Al intermetallic
compound, Al.sub.2O.sub.3, Ti--Si intermetallic compound,
SiO.sub.2, and MgO. These protective films remain on the titanium
substrate even with repeated heating subsequent to that in an
environment with chlorine ions present, so the high temperature
salt damage resistance is maintained. By making the Si content of
the Al--Si alloy 10.5 mass % or more, a dense intermetallic
compound layer superior in flaw resistance and superior in high
temperature oxidation resistance and high temperature salt damage
resistance is formed between the protective film and matrix
material after high temperature heating. Further, by making the
contents of Mg and Si of the Al--Mg alloy and Al--Mg--Si alloy 0.3
mass % or more, it is possible to sufficiently form MgO or
SiO.sub.2 contributing to the high temperature oxidation
resistance.
EXAMPLES
Example 1
[0080] Each composition of the silicone resin or silicone grease
was prepared or thin flake-shaped or powder-shaped metal Al was
added, then a solvent was added to obtain a coating for protective
film coverings. Each coating was coated on various types of
titanium substrates and dried to form protective films. The
substrates formed with these protective films were subjected to
various types of tests and evaluated for characteristics.
[0081] Table 1 shows the substrate used for the tests, the Si, C,
and Al contents of the surface protective film, and the results of
a continuous oxidation test. The dimensions of the samples used for
the continuous oxidation test were thickness 1.5 mm.times.20
mm.times.20 mm. The continuous oxidation test measured the
oxidation weight gain after heating the same test pieces at 600,
700, and 800.degree. C. for 200 hours in the atmosphere. Further, a
tensile test was performed at room temperature and 700.degree. C.
Further, Table 1 also shows the elongation in the C direction at
room temperature and the 0.2% yield strength at 700.degree. C.
TABLE-US-00001 TABLE 1 Oxidation weight gain Surface protective
after continuous Room 700.degree. C. film layer atmospheric
oxidation test temperature 0.2% yield Test Si, C, Al contents
g/m.sup.2 elongation strength No. Substrate (mass %) 600.degree. C.
700.degree. C. 800.degree. C. (C direction) (L direction) Remarks
1-1 Ti--1Cu Si: 38, C: 33, Al: -- 0.3 0.5 0.9 37% 30 MPa Inv. ex.
1-2 Ti--1Cu Si: 40, C: 35, Al: -- 0.3 0.5 0.9 37% 30 MPa Inv. ex.
1-3 Ti--1Cu Si: 32, C: 28, Al: 25 0.2 0.4 0.8 37% 30 MPa Inv. ex.
1-4 Ti--1Cu Si: 29, C: 25, Al: 25 0.2 0.4 0.8 37% 30 MPa Inv. ex.
1-5 Ti--1.5Al Si: 40, C: 35, Al: -- 0.3 0.5 0.9 30% 28 MPa Inv. ex.
1-6 Ti--1.5Al Si: 38, C: 33, Al: -- 0.3 0.5 0.9 30% 28 MPa Inv. ex.
1-7 Ti--1.5Al Si: 29, C: 25, Al: 25 0.2 0.4 0.8 30% 28 MPa Inv. ex.
1-8 Ti--1.5Al Si: 32, C: 28, Al: 25 0.2 0.4 0.8 30% 28 MPa Inv. ex.
1-9 Ti--1Cu--0.5Nb Si: 42, C: 36, Al: -- 0.1 0.2 0.4 37% 30 MPa
Inv. ex. 1-10 Ti--1Cu--0.5Nb Si: 38, C: 33, Al: -- 0.1 0.2 0.4 37%
30 MPa Inv. ex. 1-11 Ti--1Cu--0.5Nb Si: 24, C: 21, Al: 37 0.05 0.1
0.2 37% 30 MPa Inv. ex. 1-12 Ti--1Cu--0.5Nb Si: 32, C: 28, Al: 25
0.05 0.1 0.2 37% 30 MPa Inv. ex. 1-13 Ti--1Cu--1Al--0.5Nb Si: 38,
C: 33, Al: -- 0.1 0.2 0.4 30% 37 MPa Inv. ex. 1-14
Ti--1Cu--1Al--0.5Nb Si: 42, C: 36, Al: -- 0.1 0.2 0.4 30% 37 MPa
Inv. ex. 1-15 Ti--1Cu--1Al--0.5Nb Si: 24, C: 21, Al: 37 0.05 0.1
0.2 30% 37 MPa Inv. ex. 1-16 Ti--1Cu--1Al--0.5Nb Si: 32, C: 28, Al:
25 0.05 0.1 0.2 30% 37 MPa Inv. ex. 1-17 pure Ti type 2 None 7 28
299 32% 15 MPa Comp. ex. 1-18 Ti--1Cu None 7 27 236 37% 30 MPa
Comp. ex. 1-19 Ti--1.5Al None 7 27 229 30% 28 MPa Comp. ex. 1-23
Fe--17Cr--0.5Mo--0.2Ti None 0.4 0.6 7 34% 50 MPa Comp. ex.
[0082] Test Nos. 1-1 and 1-2 are Ti-1 mass % Cu substrates coated
with coatings of mixtures of a silicone resin and toluene by
brushing and dried at room temperature for 24 hours. The formed
protective films had thicknesses of 20 .mu.m, while the mass %'s of
contents of Si and C were 38% and 33% in No. 1-1 and 40% and 35% in
No. 1-2.
[0083] Test Nos. 1-3 and 1-4 are Ti-1 mass % Cu substrates coated
with coatings of mixtures of a silicone resin, aluminum flakes,
toluene, and xylene by spraying and dried at room temperature for
24 hours. The formed protective films had thicknesses of 15 .mu.m,
while the mass %'s of contents of Si, C, and Al were 32%, 28%, and
25% in No. 1-3 and 29%, 25%, and 25% in No. 1-4.
[0084] Test Nos. 1-5 and 1-6 are Ti-1.5 mass % Al substrates coated
with coatings of mixtures of a silicone resin and toluene by
brushing and dried at room temperature for 24 hours. The formed
protective films had thicknesses of 30 .mu.m, while the mass %'s of
contents of Si and C were 40% and 35% in No. 1-5 and 38% and 33% in
No. 1-6.
[0085] Test Nos. 1-7 and 1-8 are Ti-1.5 mass % Al substrates coated
with coatings of mixtures of a silicone resin, aluminum flakes,
toluene, and xylene by spraying and dried at room temperature for
24 hours. The formed protective films had thicknesses of 25 .mu.m,
while the mass %'s of contents of Si, C, and Al were 29% and 25% in
No. 1-7 and 32%, 28%, and 25% in No. 1-8.
[0086] Test Nos. 1-9 and 1-10 are Ti-1 mass % Cu-0.5 mass % Nb
substrates coated with coatings of mixtures of a silicone resin and
toluene by brushing and dried at room temperature for 24 hours. The
formed protective films had thicknesses of 55 .mu.m, while the mass
%'s of contents of Si and C were 42% and 36% in No. 1-9 and 38% and
33% in No. 1-10.
[0087] Test Nos. 1-11 and 1-12 are Ti-1 mass % Cu-0.5 mass % Nb
substrates coated with coatings of mixtures of a silicone resin,
aluminum flakes, toluene, and xylene by spraying and dried at room
temperature for 24 hours. The formed protective films had
thicknesses of 40 .mu.m, while the mass %'s of contents of Si, C,
and Al were 24%, 21%, and 37% in No. 1-11 and 32%, 28%, and 25% in
No. 1-12.
[0088] Test Nos. 1-13 and 1-14 are Ti-1 mass % Cu-1 mass % Al-0.5
mass % Nb substrates coated with mixtures of a silicone resin and
toluene by brushing and dried at room temperature for 24 hours. The
formed protective films had thicknesses of 65 .mu.m, while the mass
%'s of contents of Si and C were 38% and 33% in No. 1-13 and 42%
and 36% in No. 1-14.
[0089] Test Nos. 1-15 and 1-16 are Ti-1 mass % Cu-1 mass % Al-0.5
mass % Nb substrates coated with coatings of mixtures of a silicone
resin, aluminum flakes, toluene, and xylene by spraying and dried
at room temperature for 24 hours. The formed protective films had
thicknesses of 40 .mu.m, while the mass %'s of contents of Si, C,
and Al were 24%, 21%, and 37% in No. 1-15 and 32%, 28%, and 25% in
No. 1-16.
[0090] The Invention Example Nos. 1-1 to 1-16 had an oxidation
weight gain after heating at 600 to 800.degree. C. for 200 hours in
the atmosphere smaller than Comparative Example No. 1-23, that is,
the ferritic stainless steel SUS436J1L (Fe-17 mass % Cr-0.5 mass %
Mo-0.2 mass % Ti) and therefore a superior oxidation resistance.
The elongation at room temperature (C direction) was in each case,
with the exception of Nos. 1-5 to 1-8, larger than pure titanium
type 2, while the 0.2% yield strength at 700.degree. C. was 2 times
or more of that of pure titanium type 2. No. 1-5 to No. 1-8 had an
elongation at room temperature (C direction) somewhat smaller than
that of pure titanium type 2, but substantially equal, and a 0.2%
yield strength at 700.degree. C. of 1.5 times or more of that of
pure titanium type 2. These can be said to be titanium substrates
superior in oxidation resistance and high temperature salt damage
resistance provided with both high temperature strength and
workability at room temperature.
[0091] On the other hand, in each of Nos. 1-17 to 1-19 not coated
with the protective film of the present invention, the oxidation
weight gain after the continuous atmospheric oxidation test was two
to three orders of magnitude greater than the present invention
materials. Comparative Example 1-23 is the ferritic stainless steel
SUS436J1L (Fe-17Cr-0.5Mo-0.2Ti) not formed with the protective film
of the present invention. This material inherently has little
oxidative weight gain, but even so has a greater oxidative weight
gain compared with substrates formed with the protective film of
the present invention.
Example 2-1
[0092] Thin flake-shaped or grain-shaped metal Al was added to a
silicone resin or silicone grease to prepare each composition, then
a solvent was added to this to obtain a coating. Each coating was
coated on various types of titanium substrates, then heated to form
protective films. The substrates formed with these protective films
were subjected to various types of tests and evaluated for
characteristics.
[0093] Table 2 and Table 3 show the titanium substrates used for
the tests, the Al, Si, Ccontents (mass %) of the surface protective
films, the size of the metal Al, the heating temperature after
coating, the results of the adhesion evaluation test, and the
results of the high temperature salt damage test (atmospheric
heating test after deposition of chlorine ions). The adhesion was
evaluated by a cross cut tape peeling test and a Dupont type impact
test (both based on JIS K 5600).
[0094] The cross cut tape peeling test was performed by making six
parallel cuts in a test piece of a thickness 1 mm.times.50
mm.times.70 mm coated with a surface protective film using equal
distance spacers at intervals of 1 mm and making a further six
parallel cuts at right angles with these cuts to prepare a lattice
pattern of 100 1 mm squares, attaching a tape to this, then
removing it, observing any peeling of the surface protective film
by a jeweler's glass, and evaluating the number of square remaining
without being peeled off.
[0095] The Dupont type impact test was performed by clamping a test
piece of 1 mm.times.50 mm.times.70 mm of a sample coated with a
surface protective film, with the coated surface up, between a
striking die of a radius of 6.35 mm and a receiving table, dropping
a weight of a mass of 500 g from a height of 500 mm on the striking
die, and observing if there were any cracks, peeling, or other
damage on the coated surface.
[0096] The test piece dimensions in the high temperature salt
damage test were made a thickness 1 mm.times.20 mm.times.20 mm. The
conditions for the high temperature salt damage test were immersion
in 5% saline for 1 hour and heating at 700.degree. C. for 23 hours
in the atmosphere repeated 5 times, then observation of the
cross-section of the sample and measurement of the rate of
reduction of thickness at locations where the thickness was reduced
the most. Further, a tensile test was conducted at room temperature
and 700.degree. C. The tables show the elongation in the C
direction at room temperature and the 0.2% yield strength at
700.degree. C.
TABLE-US-00002 TABLE 2 Rate of reduction Typical surface Protective
film of thickness after products after Si, C, Al 700.degree. C.
high 700.degree. C. high Test Average size of Heat contents
temperature salt temperature no. Substrate contained Al temp./time
(mass %) damage test (%) salt damage test 2-1-1 Ti--1Cu Thickness
0.5 .mu.m 180.degree. C. Al: 27, Si: 33, C: 28 2.1 Ti.sub.3Al,
Ti.sub.5Si.sub.3, width/length 7 .mu.m 40 min SiO.sub.2, TiC 2-1-2
Ti--1Cu Diameter 0.4 .mu.m 250.degree. C. Al: 26, Si: 30, C: 25 1.8
Ti.sub.3Al, Ti.sub.5Si.sub.3, 15 min SiO.sub.2, TiC 2-1-3 Ti--1.5Al
Thickness 0.5 .mu.m 200.degree. C. Al: 27, Si: 33, C: 28 1.6
Ti.sub.3Al, Ti.sub.5Si.sub.3, width/length 7 .mu.m 20 min
SiO.sub.2, TiC 2-1-4 Ti--1.5Al Diameter 0.4 .mu.m 180.degree. C.
Al: 26, Si: 30, C: 25 2.3 Ti.sub.3Al, Ti.sub.5Si.sub.3, 40 min
SiO.sub.2, TiC 2-1-5 Ti--1Cu--0.5Nb Thickness 0.3 .mu.m 250.degree.
C. Al: 37, Si: 24, C: 21 1.4 Ti.sub.3Al, Al.sub.2O.sub.3,
width/length 5 .mu.m 15 min Ti.sub.5Si.sub.3, SiO.sub.2 2-1-6
Ti--1Cu--0.5Nb Diameter 0.6 .mu.m 250.degree. C. Al: 25, Si: 32, C:
28 1.5 Ti.sub.3Al, Ti.sub.5Si.sub.3, 30 min SiO.sub.2, TiC 2-1-7
T--1.2Al--1Nb Diameter 0.7 .mu.m 160.degree. C. Al: 26, Si: 29, C:
24 2.5 Ti.sub.3Al, Ti.sub.5Si.sub.3, 50 min SiO.sub.2, TiC 2-1-8
Ti--0.8Cu--1Al Thickness 0.5 .mu.m 250.degree. C. Al: 27, Si: 33,
C: 28 1.3 Ti.sub.3Al, Ti.sub.5Si.sub.3, width/length 7 .mu.m 15 min
SiO.sub.2, TiC 2-1-9 Ti--1Cu--1Al--0.5Nb Thickness 0.3 .mu.m
200.degree. C. Al: 37, Si: 24, C: 21 1.8 Ti.sub.3Al,
Al.sub.2O.sub.3, width/length 5 .mu.m 30 min Ti.sub.5Si.sub.3,
SiO.sub.2 2-1-10 Ti--1Cu--1Al--0.5Nb Diameter 0.6 .mu.m 230.degree.
C. Al: 25, Si: 32, C: 28 1.4 Ti.sub.3Al, Ti.sub.5Si.sub.3, 20 min
SiO.sub.2, TiC 2-1-11 Ti--1Cu Thickness 3 .mu.m 250.degree. C. Al:
25, Si: 33, C: 30 2.1 Ti.sub.3Al, Al.sub.2O.sub.3, width/length 35
.mu.m 20 min Ti.sub.5Si.sub.3, SiO.sub.2 2-1-12 Ti--1.5Al Thickness
4 .mu.m 200.degree. C. Al: 25, Si: 33, C: 30 2.5 Ti.sub.3Al,
Al.sub.2O.sub.3, width/length 25 .mu.m 30 min Ti.sub.5Si.sub.3,
SiO.sub.2 2-1-13 Ti--1Cu--0.5Nb Diameter 25 .mu.m 200.degree. C.
Al: 25, Si: 33, C: 30 2.1 Ti.sub.3Al, Al.sub.2O.sub.3, 30 min
Ti.sub.5Si.sub.3, SiO.sub.2 2-1-14 Ti--1Cu--1Al--0.5Nb Thickness 2
.mu.m 200.degree. C. Al: 25, Si: 33, C: 30 1.9 Ti.sub.3Al,
Al.sub.2O.sub.3, width/length 45 .mu.m 30 min Ti.sub.5Si.sub.3,
SiO.sub.2 No. of squares Room 700.degree. C. remaining after
temperature 0.2% yield Test cross cut tape peeling Dupont type
elongation strength no. test/100 impact test (C direction) (L
direction) Remarks 2-1-1 100/100 No cracks 37% 30 MPa Inv. ex.
2-1-2 100/100 No cracks 37% 30 MPa Inv. ex. 2-1-3 100/100 No cracks
30% 28 MPa Inv. ex. 2-1-4 100/100 No cracks 30% 28 MPa Inv. ex.
2-1-5 100/100 No cracks 37% 30 MPa Inv. ex. 2-1-6 100/100 No cracks
37% 30 MPa Inv. ex. 2-1-7 100/100 No cracks 31% 25 MPa Inv. ex.
2-1-8 100/100 No cracks 32% 27 MPa Inv. ex. 2-1-9 100/100 No cracks
30% 37 MPa Inv. ex. 2-1-10 100/100 No cracks 30% 37 MPa Inv. ex.
2-1-11 100/100 No cracks 37% 30 MPa Inv. ex. 2-1-12 100/100 No
cracks 30% 28 MPa Inv. ex. 2-1-13 100/100 No cracks 37% 30 MPa Inv.
ex. 2-1-14 100/100 No cracks 30% 37 MPa Inv. ex.
TABLE-US-00003 TABLE 3 Rate of reduction Typical surface Protective
film of thickness after products after Si, C, Al 700.degree. C.
high 700.degree. C. high Test Average size of Heating contents
temperature salt temperature no. Substrate contained Al temp./time
(mass %) damage test (%) salt damage test 2-1-15 Pure Ti type 2 No
protective film 28.2 TiO.sub.2 2-1-16 Ti--1Cu No protective film
15.1 TiO.sub.2 2-1-17 Ti--1.5Al No protective film 14.9 TiO.sub.2
2-1-21 Ti--1Cu Diameter 50 .mu.m 200.degree. C. Al: 25, Si: 33, C:
30 6.4 Ti.sub.3Al, Al.sub.2O.sub.3, 30 min Ti.sub.5Si.sub.3,
SiO.sub.2 2-1-22 Ti--1.5Al Thickness 10 .mu.m 200.degree. C. Al:
25, Si: 33, C: 30 7.3 Ti.sub.3Al, Al.sub.2O.sub.3, width/length 25
.mu.m 30 min Ti.sub.5Si.sub.3, SiO.sub.2 2-1-23
Fe--17Cr--0.5Mo--0.2Ti No protective film 27.9 FeO,
Fe.sub.3O.sub.4, Fe.sub.2O.sub.3 Remaining no. Room 700.degree. C.
of squares of temperature 0.2% yield Test cross cut tape Dupont
type elongation strength no. peeling test/100 impact test (C
direction) (L direction) Remarks 2-1-15 -- -- 32% 15 MPa Comp. ex.
2-1-16 -- -- 37% 30 MPa Comp. ex. 2-1-17 -- -- 30% 28 MPa Comp. ex.
2-1-21 45/100 Peeling 37% 30 MPa Comp. ex. 2-1-22 43/100 Peeling
30% 28 MPa Comp. ex. 2-1-23 -- -- 34% 50 MPa Comp. ex.
[0097] Nos. 2-1-1 to 2-1-14 are titanium sheets covered with
protective films of the present invention. These titanium sheets
had a rate of reduction of thickness after a high temperature salt
damage test of a small 3% or less in each case and a sufficient
high temperature salt damage resistance, while the titanium sheets
of Nos. 2-1-15 to 2-1-17 not covered by a protective film had large
reductions of thickness after a high temperature salt damage test.
The elongation at room temperature (C direction) was equal to or
greater than that of pure titanium type 2 in each case, while the
0.2% yield strength at 700.degree. C. was 1.5 times or more that of
pure titanium type 2. These can be said to be titanium sheets
covered with protective films superior in high temperature salt
damage resistance provided with both high temperature strength and
workability at room temperature.
[0098] On the other hand, in each of the titanium sheets of Nos.
2-1-21 and 2-1-22 with average sizes of metal Al contained in the
protective films over the upper limit of the present invention, the
adhesion of the protective film was poor. In the cross-cut peeling
test, over half of the 1 mm squares peeled off. Peeling occurred
even in the Dupont type impact test. Further, the rate of reduction
of thickness after the high temperature salt damage test was larger
than in the present invention, the high temperature salt damage
resistance was insufficient, and the substrate was unsuitable for
use for an automobile exhaust system.
[0099] With the ferritic stainless steel material of No. 2-1-23,
the rate of reduction of thickness after the high temperature salt
damage test was large and the substrate was unsuitable for use for
an automobile exhaust system.
[0100] After the high temperature salt damage test, the substances
formed on the surface were identified by X-ray diffraction. The
main products determined as a result are shown in Table 2 and Table
3. In Nos. 2-1-1 to 2-1-14, one or more of Al.sub.2O.sub.3,
SiO.sub.2, TiC, Ti--Al intermetallic compounds, and Ti--Si
intermetallic compounds were formed. On the other hand, in Nos.
2-1-15 to 2-1-17 formed with protective films, the surface products
were almost all TiO.sub.2 showing the progression of the oxidation.
Further, in No. 2-1-23 where the substrate is a ferritic stainless
steel material, Fe oxides were formed and oxidation progressed.
Note that in Comparative Example Nos. 2-1-21 and 2-1-22, one or
more of Al.sub.2O.sub.3, SiO.sub.2, TiC, Ti--Al intermetallic
compounds, and Ti--Si intermetallic compounds were formed, but the
average size of the metal Al contained was over the upper limit of
the present invention, so peeling of the protective film occurred
in the impact test.
[0101] Note that the substrates of the present invention shown in
Example 2-1 (Table 2 and Table 3) are all cold rolled annealed
materials.
Example 2-2
[0102] Thin flake-shaped or grain-shaped metal Al of the sizes
shown in Table 4 was added to a silicone resin to prepare each
composition, then xylene was added to this to obtain a coating for
a protective film covering. Each coating was coated on various
types of titanium substrates, heated under the conditions shown in
heating I to form a protective film, then further baked on under
the conditions shown in heating II to prepare the test materials of
Nos. 2-2-1 to 2-2-8.
[0103] The substrates formed with these protective films were
subjected to various types of tests and evaluated for
characteristics.
[0104] Table 4 shows the titanium substrates used for the tests,
the treatment conditions of the substrates, the contents of Al, Si,
and C of the surface protective films (mass %), the size of the Al,
the heating conditions I after coating, the heating conditions II
of baking, the results of the adhesion evaluation test, and the
results of the high temperature salt damage test.
[0105] Note that the adhesion evaluation test and high temperature
salt damage test were conducted by the same methods as in Example
2-1.
TABLE-US-00004 TABLE 4 Protective film Test Treatment of Average
size of Heating I Si, C, Al Heating II no. Substrate substrate
contained Al temp./time contents (mass %) temp./time 2-2-1 Ti--1Cu
Cold rolling Thickness 2 .mu.m 180.degree. C. Al: 26, Si: 34, C: 28
700.degree. C. and annealing width/length 20 .mu.m 40 min 20 min
2-2-2 Ti--1Cu--0.5Nb Cold rolling Diameter 20 .mu.m 250.degree. C.
Al: 25, Si: 31, C: 25 650.degree. C. and annealing 15 min 30 min
2-2-3 Ti--1.5Al Cold rolling Thickness 3 .mu.m 200.degree. C. Al:
26, Si: 34, C: 28 750.degree. C. and annealing width/length 30
.mu.m 20 min 10 min 2-2-4 Ti--1Cu--1Al--0.5Nb Cold rolling Diameter
15 .mu.m 180.degree. C. Al: 26, Si: 30, C: 25 600.degree. C. and
annealing 40 min 60 min 2-2-5 Ti--1Cu Pickling Thickness 2 .mu.m
200.degree. C. Al: 26, Si: 34, C: 28 None width/length 20 .mu.m 20
min 2-2-6 Ti--1Cu--0.5Nb Pickling Diameter 20 .mu.m 180.degree. C.
Al: 25, Si: 31, C: 25 700.degree. C. 40 min 20 min 2-2-7 Ti--1Cu
Sandblasting Thickness 2 .mu.m 250.degree. C. Al: 36, Si: 25, C: 21
None width/length 20 .mu.m 15 min 2-2-8 Ti--1Cu--0.5Nb Sandblasting
Diameter 20 .mu.m 250.degree. C. Al: 24, Si: 33, C: 28 650.degree.
C. 30 min 30 min Rate of reduction Typical surface of thickness
products after after 700.degree. C. 700.degree. C. high Remaining
no. of Test high temperature temperature squares in cross-cut
Dupont type no. salt damage test (%) salt damage test peeling
test/100 impact test Remarks 2-2-1 0.2 Ti.sub.3Al, Al.sub.2O.sub.3,
100/100 No cracks Inv. ex. Ti.sub.5Si.sub.3, SiO.sub.2 2-2-2 0.3
Ti.sub.3Al, Al.sub.2O.sub.3, 100/100 No cracks Inv. ex.
Ti.sub.5Si.sub.3, SiO.sub.2 2-2-3 0.2 Ti.sub.3Al, Al.sub.2O.sub.3,
100/100 No cracks Inv. ex. Ti.sub.5Si.sub.3, SiO.sub.2 2-2-4 0.3
Ti.sub.3Al, Al.sub.2O.sub.3, 100/100 No cracks Inv. ex.
Ti.sub.5Si.sub.3, SiO.sub.2 2-2-5 1.6 Ti.sub.3Al, Ti.sub.5Si.sub.3,
48/100 Peeling Comp. ex. SiO.sub.2, TiC 2-2-6 0.4 Ti.sub.3Al,
Al.sub.2O.sub.3, 51/100 Peeling Comp. ex. Ti.sub.5Si.sub.3,
SiO.sub.2 2-2-7 1.4 Ti.sub.3Al, Ti.sub.5Si.sub.3, 63/100 Peeling
Comp. ex. SiO.sub.2, TiC 2-2-8 0.4 Ti.sub.3Al, Al.sub.2O.sub.3,
56/100 Peeling Comp. ex. Ti.sub.5Si.sub.3, SiO.sub.2
[0106] Nos. 2-2-1 to 2-2-4 are substrates treated by cold rolling
and annealing. Specifically, they are substrates cold rolled from
thicknesses of 3.5 mm to 1 mm, then heat treated in vacuum at
680.degree. C. for 5 hours. On the other hand, Nos. 2-2-5 and 2-2-6
are substrates treated by sandblasting, then pickling. The pickling
solution was a mixture of nitric acid and fluoric acid. Further,
Nos. 2-2-7 and 2-2-8 are substrates treated by sandblasting. The
particle size of the silica used for the sandblasting was F30 (JIS
R6001-1998).
[0107] The test items and methods were the same as in Example 1.
The adhesion was evaluated by a cross cut tape peeling test and a
Dupont type impact test (both based on JIS K 5600) conducted after
heating I.
[0108] Nos. 2-2-1 to 2-2-4 are titanium sheets covered with
protective films of the present invention. Before being covered by
the protective films, these titanium substrates were cold rolled
and annealed. On the other hand, the substrates of Comparative
Example Nos. 2-2-5 and 2-2-6 were finally treated by pickling,
while the substrates of Nos. 2-2-7 and 2-2-8 were treated by just
sandblasting. If comparing the adhesion of these, in both the cross
cut tape peeling test and Dupont type impact test, the protective
films of the substrates which were just pickled and were just
sandblasted peeled off. Further, the Invention Nos. 2-2-1 to 2-2-4
with the addition of the heating II had a rate of reduction of
thickness after the high temperature salt damage test of a small
0.3% in each case, that is, a remarkable high temperature salt
damage resistance. On the other hand, No. 2-2-5 and No. 2-2-6
without the addition of the heating II had a somewhat large
reduction of thickness after the high temperature salt damage
test.
Example 3
[0109] Thin flake-shaped or grain-shaped Al alloy was added to a
silicone resin to prepare each composition, then a solvent was
added to this to obtain a coating for a protective film covering.
Each coating was coated on various types of titanium substrates and
heated to form protective films. The substrates formed with these
protective films were subjected to various types of tests and
evaluated for characteristics.
[0110] Table 5 and Table 6 show the substrates used for the tests,
the contents of the ingredients of the Al alloy dispersed in the
silicone resin (mass %) and their sizes, the heating temperature
after coating, the result of the adhesion evaluation test, the
results of the high temperature oxidation test, the results of the
high temperature salt damage test (atmospheric heating test after
deposition of chlorine ions), and the results of flaw resistance.
The adhesion was evaluated by a cross cut tape peeling test and a
Dupont type impact test (both based on JIS K 5600).
[0111] The cross cut tape peeling test was performed by making six
parallel cuts in a test piece of a thickness 1 mm.times.50
mm.times.70 mm coated with a surface protective film using equal
distance spacers at intervals of 1 mm and making a further six
parallel cuts at right angles with these cuts to prepare a lattice
pattern of 100 1 mm squares, attaching a tape to this, then
removing it, observing any peeling of the surface protective film
by a jeweler's glass.
[0112] The Dupont type impact test was performed by clamping a test
piece of 1 mm.times.50 mm.times.70 mm of a sample coated with a
surface protective film, with the coated surface up, between a
striking die of a radius of 6.35 mm and a receiving table, dropping
a weight of a mass of 500 g from a height of 500 mm on the striking
die, and observing if there were any cracks, peeling, or other
damage on the coated surface.
[0113] The high temperature salt damage test was performed by
treating a test piece of a thickness of 1 mm.times.width of 20
mm.times.length of 20 mm coated with a surface protective film by
immersion in 5% saline for 1 hour and heating at 700.degree. C. for
23 hours repeated 5 times, then observing the cross-section of the
sample and measuring the maximum rate of reduction of thickness
where the thickness is reduced the most.
[0114] The flaw resistance test was performed by after the above
high temperature salt damage test by making a cross-shaped flaw to
a depth equal to the coated thickness by a superhard scriber in the
sample surface, performing the 700.degree. C. high temperature salt
damage test again, observing the cross-section of the sample of the
part with the flaw after the test, and measuring the rate of
reduction of thickness at the location where the thickness was
reduced the most.
TABLE-US-00005 TABLE 5 Content of Oxidation Al alloy Al alloy in
weight gain average protective after heating particle film as a
Coating at 700.degree. C., 200 h Sample Al alloy size whole
thickness Heating in atmosphere no. Substrate (numbers: mass %)
(.mu.m) (mass %) (.mu.m) temp./time (mg/cm.sup.2) 3-1 Pure Ti type
2 Al--12Si 2 15 4 180.degree. C. 0.35 40 min 3-2 Ti--1Cu Al--20Si
14 23 15 250.degree. C. 0.31 15 min 3-3 Ti--1.5Cu Al--27Si 28 32 16
200.degree. C. 0.25 20 min 3-4 Ti--1.5Al Al--11Si 3 36 72
180.degree. C. 0.36 40 min 3-5 Ti--1Cu--0.5Nb Al--16Si 15 33 11
250.degree. C. 0.23 15 min 3-6 Ti--1Cu--2Al Al--35Si 26 17 30
250.degree. C. 0.22 30 min 3-7 Ti--1.2Al--1Nb Al--24Si 9 25 57
160.degree. C. 0.39 50 min 3-8 Ti--0.8Cu--1Al Al--12Si 20 37 8
250.degree. C. 0.21 15 min 3-9 Ti--1Cu--1Al--0.5Nb Al--20Si 14 27
12 200.degree. C. 0.29 30 min 3-10 Ti--3Al--2.5V Al--18Si 19 14 44
230.degree. C. 0.24 20 min 3-11 Pure Ti type 2 No protective film
2.95 3-12 Ti--1Cu No protective film 2.81 3-13 Ti--1.5Al No
protective film 2.85 3-14 Ti--1Cu--0.5Nb Al--20Si 22 55 15
200.degree. C. 0.66 30 min 3-15 Ti--0.8Cu--1Al Al--15Si 45 37 80
200.degree. C. 1.26 30 min 3-16 Ti--1Cu Al--5Si 21 7 15 200.degree.
C. 0.41 30 min 3-17 Ti--1Cu Al--4Si 15 26 19 250.degree. C. 0.45 20
min Rate of reduction Rate of reduction of Typical surface of
thickness thickness after 700.degree. products Remaining no. Dupont
after 700.degree. C. C. high temperature after 700.degree. C. of
squares in type Sample high temperature salt damage retest high
temperature cross-cut tape impact no. salt damage test (%) after
flaw (%) salt damage test peeling test/100 test Remarks 3-1 1.5 1.8
Ti.sub.3Al, Al.sub.2O.sub.3, 100/100 No cracks Inv. ex.
Ti.sub.5Si.sub.3, SiO.sub.2 3-2 1.3 1.7 Ti.sub.3Al,
Al.sub.2O.sub.3, 100/100 No cracks Inv. ex. Ti.sub.5Si.sub.3,
SiO.sub.2 3-3 1.1 1.3 Ti.sub.3Al, Al.sub.2O.sub.3, 100/100 No
cracks Inv. ex. Ti.sub.5Si.sub.3, SiO.sub.2 3-4 1.6 1.9 Ti.sub.3Al,
Al.sub.2O.sub.3, 100/100 No cracks Inv. ex. Ti.sub.5Si.sub.3,
SiO.sub.2 3-5 1.0 1.3 Ti.sub.3Al, Al.sub.2O.sub.3, 100/100 No
cracks Inv. ex. Ti.sub.5Si.sub.3, SiO.sub.2 3-6 1.1 1.3 Ti.sub.3Al,
Al.sub.2O.sub.3, 100/100 No cracks Inv. ex. Ti.sub.5Si.sub.3,
SiO.sub.2 3-7 1.8 2.0 Ti.sub.3Al, Al.sub.2O.sub.3, 100/100 No
cracks Inv. ex. Ti.sub.5Si.sub.3, SiO.sub.2 3-8 0.9 1.1 Ti.sub.3Al,
Al.sub.2O.sub.3, 100/100 No cracks Inv. ex. Ti.sub.5Si.sub.3,
SiO.sub.2 3-9 1.3 1.6 Ti.sub.3Al, Al.sub.2O.sub.3, 100/100 No
cracks Inv. ex. Ti.sub.5Si.sub.3, SiO.sub.2 3-10 1.0 1.2
Ti.sub.3Al, Al.sub.2O.sub.3, 100/100 No cracks Inv. ex.
Ti.sub.5Si.sub.3, SiO.sub.2 3-11 28.2 -- TiO.sub.2 -- -- Comp. ex.
3-12 15.1 -- TiO.sub.2 -- -- Comp. ex. 3-13 14.9 -- TiO.sub.2 -- --
Comp. ex. 3-14 3.1 -- Ti.sub.3Al, Al.sub.2O.sub.3 38/100 Peeling
Comp. ex. 3-15 12.3 -- Ti.sub.3Al, Ti.sub.5Si.sub.3 44/100 Peeling
Comp. ex. 3-16 2.1 10.8 Ti.sub.3Al, Al.sub.2O.sub.3 82/100 Peeling
Comp. ex. 3-17 2.5 11.3 Ti.sub.3Al, Al.sub.2O.sub.3 74/100 Peeling
Comp. ex.
TABLE-US-00006 TABLE 6 Content of Oxidation Al alloy Al alloy in
weight gain average protective after heating particle film as a
Coating at 700.degree. C., 200 h Sample Al alloy size whole
thickness Heating in atmosphere no. Substrate (numbers: mass %)
(.mu.m) (mass %) (.mu.m) temp./time (mg/cm.sup.2) 3-18 Ti--1Cu
Al--10Si--1Mg 15 32 15 180.degree. C. 0.35 40 min 3-19 Ti--1Cu
Al--12Si 11 25 15 180.degree. C. 0.26
Mg.sub.3SiO.sub.4O.sub.10(OH).sub.2 10 5 40 min 3-20 Ti--1Cu
Al--12Si 11 25 15 180.degree. C. 0.31 Al--10Mg 10 5 40 min 3-21
Ti--1Cu Al--12Si 11 25 15 180.degree. C. 0.34 Al--7Si--0.4Mg 10 5
40 min 3-22 Ti--1Cu Al--12Si 11 25 15 180.degree. C. 0.41
Al--8Si--0.5Mg 10 5 40 min 3-23 Ti--1Cu Al--12Si 11 25 15
180.degree. C. 0.29 Mg.sub.3SiO.sub.4O.sub.10(OH).sub.2 10 5 40 min
Rate of reduction Rate of reduction of Typical surface of thickness
thickness after 700.degree. products Remaining no. Dupont after
700.degree. C. C. high temperature after 700.degree. C. of squares
in type Sample high temperature salt damage retest high temperature
cross-cut tape impact no. salt damage test (%) after flaw (%) salt
damage test peeling test/100 test Remarks 3-18 1.3 1.5 Ti.sub.3Al,
Al.sub.2O.sub.3, 100/100 No cracks Inv. ex. Ti.sub.5Si.sub.3,
SiO.sub.2, MgO 3-19 0.9 1.2 Ti.sub.3Al, Al.sub.2O.sub.3, 100/100 No
cracks Inv. ex. Ti.sub.5Si.sub.3, SiO.sub.2, MgO 3-20 0.8 1.1
Ti.sub.3Al, Al.sub.2O.sub.3, 100/100 No cracks Inv. ex.
Ti.sub.5Si.sub.3, SiO.sub.2, MgO 3-21 1.2 1.4 Ti.sub.3Al,
Al.sub.2O.sub.3, 100/100 No cracks Inv. ex. Ti.sub.5Si.sub.3,
SiO.sub.2, MgO 3-22 1.1 1.3 Ti.sub.3Al, Al.sub.2O.sub.3, 100/100 No
cracks Inv. ex. Ti.sub.5Si.sub.3, SiO.sub.2, MgO 3-23 0.8 1.0
Ti.sub.3Al, Al.sub.2O.sub.3, 100/100 No cracks Inv. ex.
Ti.sub.5Si.sub.3, SiO.sub.2, MgO
[0115] Nos. 3-1 to 3-10 of Table 5 are titanium sheets covered with
protective films of the present invention. These titanium sheets
had a maximum rate of reduction of thickness after the high
temperature salt damage test of a small 1.5% or less in each case
or a sufficient high temperature salt damage resistance, while the
titanium sheets of Nos. 3-11 to 3-13 not covered with a protective
film had a large reduction of thickness after the high temperature
salt damage test. Further, in the titanium sheets covered with
protective films of the present invention, the maximum rate of
reduction of thickness was a small 2.5% in each case or a
sufficient high temperature salt damage resistance and durability
even when making a flaw and performing the high temperature salt
damage test again after the high temperature salt damage test.
[0116] On the other hand, in No. 3-14 with a content of Al alloy
with respect to the protective film as a whole over the range of
the present invention and as a result with a small silicone
content, the adhesion of the protective film was poor, over half of
the 1 mm squares were peeled off in the cross cut tape peeling
test, and peeling occurred in the Dupont type impact test as well.
Further, in No. 3-15 with an average particle size of the Al alloy,
a content with respect to the protective film, and a coating
thickness over the upper limits of the present invention, the
maximum rate of reduction after the high temperature salt damage
test was one order of magnitude greater than the present invention,
that is, the high temperature salt damage resistance was
insufficient. In No. 3-16 with an amount of Al alloy in the
protective film below the lower limit of the present invention and
in No. 3-17 with a content of Si in the Al alloy below the lower
limit of the present invention, the maximum rate of reduction of
thickness at the time of introduction of a flaw and performing the
high temperature salt damage test again was large and the flaw
resistance was inferior to the titanium sheet covered with a
protective film of the present invention.
[0117] Nos. 3-19 to 3-23 of Table 6 are examples of the case
containing, in addition to an Al--Si alloy, one or more of MgO,
SiO.sub.2, an Al--Mg alloy, an Al--Mg--Si alloy, and other
dispersed substances. No. 3-18 is an example of the case of
containing only an Al--Mg--Si alloy as a dispersed substance. No.
3-19 and No. 3-23 are cases containing an Al-12 mass % Si alloy and
hydrous magnesium silicate in contents with respect to the
protective film as a whole of 25 mass % and 5 mass %. An extremely
superior high temperature salt damage resistance in both the
maximum rate of reduction of thickness after the initial high
temperature salt damage test and the maximum rate of reduction of
thickness after the retesting after introduction of a flaw and
durability were exhibited.
[0118] No. 3-20 is the case containing an Al-12 mass % Si and an
Al-10 mass % Mg alloy in contents with respect to the protective
film as a whole of 25 mass % and 5 mass %, while Nos. 3-21 and 3-22
are cases containing an Al-12 mass % Si alloy and an Al--Mg--Si
alloy in contents with respect to the protective film as a whole of
25 mass % and 5 mass %. In each case, both the maximum rate of
reduction of thickness after the initial high temperature salt
damage test and the maximum rate of reduction of thickness after
the retesting after the introduction of a flaw were smaller than
the cases of the present invention of Example No. 3-1 to No. 3-10,
and extremely superior high temperature salt damage resistance and
durability were exhibited.
[0119] After the high temperature salt damage test, the substances
formed on the surface were identified by X-ray diffraction. The
main produced substances found as a result are shown in Table 5 and
Table 6. In Nos. 3-1 to 3-10, Al.sub.2O.sub.3, SiO.sub.2, Ti--Al
intermetallic compounds, and Ti--Si intermetallic compounds were
formed. On the other hand, in Nos. 3-11 to 3-13 not formed with the
protective film, the surface products were almost all TiO.sub.2 and
oxidation progressed. Further, in No. 3-14, Al.sub.2O.sub.3 and
Ti--Al intermetallic compounds were formed, but the content of the
Al alloy with respect to the protective film as a whole was over
the range of the present invention and as a result the silicone was
small, so the adhesion of the film was poor and peeling occurred in
the cross cut tape peeling test and Dupont type impact test. In No.
3-15, Ti--Al intermetallic compounds and Ti--Si intermetallic
compounds were formed, but the average particle size of the
dispersed substances, the content with respect to the protective
film as a whole, and the coating thickness were over the upper
limits of the present invention, so peeling of the protective film
occurred in the cross cut tape peeling test and the impact
test.
[0120] In Nos. 3-16 and 3-17, Ti--Al intermetallic compounds and
Al.sub.2O.sub.3 were formed, but the maximum rate of reduction of
thickness at the time of making flaws and performing the high
temperature salt damage test again was large and the flaw
resistance of the protective film was inferior to the Invention
Nos. 3-1 to 3-10.
[0121] In Nos. 3-19 to 3-23 containing, in addition to the Al--Si
alloy, one or more of MgO, SiO.sub.2, Al--Mg alloy, Al--Mg--Si
alloy, etc., one or more of Al.sub.2O.sub.3, SiO.sub.2, Ti--Al
intermetallic compounds, and Ti--Si intermetallic compounds were
formed, MgO was formed or present, the maximum rates of reduction
of thickness after the high temperature salt damage test and after
the retesting after introduction of a flaw were small, and
protective films extremely superior in high temperature salt damage
resistance and flaw resistance were obtained.
* * * * *