U.S. patent application number 14/719760 was filed with the patent office on 2015-09-10 for steel shell for a suction roll and a method of producing a steel product.
This patent application is currently assigned to OUTOKUMPU OYJ. The applicant listed for this patent is OUTOKUMPU OYJ. Invention is credited to Conny BERGKVIST, Pelle JOHANSSON, Mats LILJAS.
Application Number | 20150252529 14/719760 |
Document ID | / |
Family ID | 33308722 |
Filed Date | 2015-09-10 |
United States Patent
Application |
20150252529 |
Kind Code |
A1 |
LILJAS; Mats ; et
al. |
September 10, 2015 |
STEEL SHELL FOR A SUCTION ROLL AND A METHOD OF PRODUCING A STEEL
PRODUCT
Abstract
A suction roll shell having a plurality of through holes is made
of a stainless ferrite-austenite steel having a micro-structure
essentially consisting of 35-65% by volume of ferrite and 35-65% by
volume of austenite. The steel has a composition containing, among
other things, 0.005-0.07 C and 0.15-0.30 N, in % by weight.
Inventors: |
LILJAS; Mats; (AVESTA,
SE) ; JOHANSSON; Pelle; (AVESTA, SE) ;
BERGKVIST; Conny; (FURUSUND, SE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
OUTOKUMPU OYJ |
Espoo |
|
FI |
|
|
Assignee: |
OUTOKUMPU OYJ
Espoo
FI
|
Family ID: |
33308722 |
Appl. No.: |
14/719760 |
Filed: |
May 22, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11574266 |
Feb 26, 2007 |
|
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PCT/SE2005/001220 |
Aug 19, 2005 |
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14719760 |
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Current U.S.
Class: |
162/372 |
Current CPC
Class: |
C22C 38/42 20130101;
C22C 38/40 20130101; C22C 38/50 20130101; D21F 1/50 20130101; C22C
38/58 20130101; C22C 38/34 20130101; C22C 38/44 20130101; C22C
38/48 20130101; C22C 38/001 20130101; C22C 38/004 20130101; C22C
38/52 20130101; D21F 3/105 20130101; C22C 38/02 20130101 |
International
Class: |
D21F 1/50 20060101
D21F001/50; C22C 38/34 20060101 C22C038/34; C22C 38/02 20060101
C22C038/02; C22C 38/52 20060101 C22C038/52; C22C 38/42 20060101
C22C038/42; C22C 38/44 20060101 C22C038/44; C22C 38/50 20060101
C22C038/50; C22C 38/48 20060101 C22C038/48; C22C 38/58 20060101
C22C038/58; C22C 38/00 20060101 C22C038/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 7, 2004 |
SE |
0402141-6 |
Claims
1-19. (canceled)
20. A suction roll shell with a plurality of drilled through holes,
wherein the shell is formed of a plurality of segments united by
circular joints and subjected to a working by turning and cutting
in order to have through holes in the shell, and the shell is made
of a stainless ferrite-austenite steel having a microstructure
essentially consisting of 35-65% by volume of ferrite and 35-65% by
volume of austenite, and having a chemical composition containing
0.005-0.07 C, 0.1-2.0 Si, 3-8 Mn, 19-23 Cr, 0.5-1.7 Ni, 0.15-0.30
N, in % by weight, and wherein the steel does not contain additives
for improving cuttability.
21. A suction roll shell according to claim 20, wherein the steel
contains up to 1.0 (Mo+W/2) and up to 1.0 Cu, balance being iron
and impurities, and for the chromium and nickel equivalents
20<Creq<24.5, 10<Nieq, where Creq=Cr+1.5 Si+Mo+2 Ti+0.5
Nb, and Nieq=Ni+0.5 Mn+30(C+N)+0.5 (Cu+Co) and wherein the steel
contain no sulphur as an additive for improving cuttability.
22. A suction roll shell according to claim 20, wherein the steel
contains 0.02-0.05 C.
23. A suction roll shell according to claim 20, wherein the steel
contains 0.18-0.26 N.
24. A suction roll shell according to claim 20, wherein the steel
contains 20-23 Cr.
25. A suction roll shell according to claim 20, wherein the steel
contains 0.8-1.70 Ni.
26. A suction roll shell according to claim 25, wherein the steel
contains 1.35-1.7 Ni.
27. A suction roll shell according to claim 20, wherein the steel
contains 0.22 N, 21.5 Cr, 1.5 Ni, 0.3 Mo, 5 Mn, no more than 0.04
C.
28. A suction roll, comprising a suction roll shell according to
claim 20.
29. A suction roll shell according to claim 20, wherein the steel
contains 0.3 Cu and 0.7 Si.
30. A suction roll shell according to claim 20, wherein the drilled
through holes can be drilled with an uncoated high-speed twist
drill for a drilled length of 1000 m at a cutting speed of 36 m/min
with tool failure.
Description
TECHNICAL FIELD
[0001] The invention relates to a steel shell for a suction roll
and a method of producing a steel product, in which method a piece
of steel material is worked by a cutting operation such as milling,
turning and/or drilling.
BACKGROUND OF THE INVENTION
[0002] Stainless steel is used in fields in which a high corrosion
resistance is necessary. A high corrosion resistance may be
required in environments within off-shore, paper and pulp industry
and chemical industry. One example is suction roll shells for paper
machines, that are manufactured from stainless steel. One type of
stainless steel is the so called duplex steels that contain ferrite
and austenite. Duplex steels are known to combine a high mechanical
strength and toughness with a good corrosion resistance, in
particular in terms of stress corrosion and corrosion fatigue. For
corrosion resistance as well as mechanical properties such as
weldability, it is important that the steel is well balanced in
terms of the essential components austenite and ferrite. In modem
development of duplex steels, it is desired to have a
micro-structure containing 35-65% ferrite, the remainder being
austenite. In fields requiring high strength and good corrosion
resistance, duplex steels are increasingly competing with
traditional austenite stainless steels. Such a steel material is
described in published US Patent Application No. 2003/0172999. The
steel material described in this publication is a ferrite-austenite
stainless steel having a micro-structure essentially consisting of
35-65% by volume ferrite and 35-65% by volume austenite. The steel
in question has a chemical composition containing 0.005-0.07 C,
0.1-2.0 Si, 3-8 Mn, 19-23 Cr, 0.15-0.30 N och 0.5-1.7 Ni, in % by
weight. Some other components may also be included.
[0003] Nitrogen is of considerable importance to the steel
described in US 2003/0172999, since nitrogen is dominant as
austenite former and contributes to the strength of the steel as
well as to its corrosion resistance. For this reason, it was
estimated that the nitrogen content of the steel should be in the
range of 0.15-0.30%, and preferably in the range of 0.20-0.24%.
However, it has been previously shown that steel types of such a
high nitrogen content are poor in cuttability.
[0004] Most often, a stainless steel intended to be used for a
particular product must be subjected to some type of cutting
operation, such as milling, turning or drilling. In their selves,
austenite and duplex stainless steels are poor in cuttability and
hence various measures are undertaken in order to increase
cuttability of the stainless steel. It is previously known that the
presence of nitrogen in stainless steel decreases cuttability. In
for example U.S. Pat. No. 4,769,213, a method is suggested for
increasing cuttability of a martensite stainless steel by reducing
carbon and nitrogen contents such that the total content of carbon
and nitrogen together is not more than 0.05% by weight. However,
compared with duplex steels, martensite steels have a poorer
corrosion resistance. For austenite stainless steels, it is
suggested in U.S. Pat. No. 5,482,674 that the content of carbon and
nitrogen should be reduced such that neither the content of carbon
nor the content of nitrogen is more than about 0.035% by weight. It
is also known that the addition of sulphur may increase
cuttability. Accordingly, U.S. Pat. No. 4,784,828 suggests that
sulphur should be added to an austenite stainless steel in order to
increase cuttability. It is also stated that the contents of carbon
and nitrogen should be very low, in total up to 0.065% by weight.
However, compared with duplex steels, austenite steels have a lower
strength.
[0005] U.S. Pat. No. 4,964,924 suggests use of a martensite
stainless steel in a suction roll. In that publication, it is
stated that since they are difficult to drill, stainless
ferrite-austenite duplex steels are unsuitable as materials for
suction rolls. Instead, it is suggested that a stainless steel
suitable for a suction roll shell should be of martensite type,
among other things containing carbon at a % by weight of more than
0 but not more than 0.06, silicon at a % by weight above 0 but not
more than 2, manganese at a % by weight above 0 but not more than
2, nickel at 3-6% by weight, chromium at 14-17% by weight,
molybdenum at 1-3% by weight and copper at a % by weight of from
0.5 to 1.5.
[0006] The present invention aims at providing a solution to the
problem of finding a steel material that exhibits a high strength
as well as a good corrosion resistance, and that moreover is
suitable for cutting operations without having to be subjected to
sulphur addition treatment. It is also an object of the invention
to provide a suction roll shell with good corrosion resistance,
which is easy to manufacture by cutting operations.
ACCOUNT OF THE INVENTION
[0007] Surprisingly, the present inventors have found that a steel
material of the type described in above mentioned US 2003/0172999,
not only has a high strength and a good corrosion resistance, but
that the material in question also is suitable for cutting
operations such as turning, milling and drilling, without the
material in question having been treated by addition of sulphur.
The inventors have also found that the material in question is
particularly suitable as a material for paper machine suction
rolls, and that it is advantageous to manufacture a suction roll
shell of such a material. Accordingly, the invention relates to a
suction roll shell of this material. The invention can also be
understood as a method for cutting operations, in particular when
manufacturing suction roll shells, but also in manufacturing of
other products, e.g. rotating machine parts, such as shafts. The
invention can also be defined in terms of a use of said steel as a
workpiece in cutting operation of steel.
[0008] Hence, the invention relates to a suction roll shell having
a plurality of through holes. The suction roll shell according to
the invention is made of a stainless ferrite-austenite steel having
a micro-structure essentially consisting of 35-65% by volume of
ferrite and 35-65% by volume of austenite. The steel composition
will be described in greater detail in the detailed
description.
[0009] The invention also relates to a suction roll comprising the
inventive suction roll shell.
[0010] In a preferred embodiment, the cutting operation comprises
drilling of at least one through hole, and preferably drilling of a
plurality of holes. In a particularly advantageous embodiment, the
method comprises drilling of hundreds of thousands of holes. A
corresponding drilled length is several kilometres. The cutting
operation may also comprise turning of outside and inside faces of
the shell.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 shows the bending of a blank for a suction roll
shell.
[0012] FIG. 2 shows a blank having been bent and welded together to
form a shell.
[0013] FIG. 3 shows schematically a first step of working the shell
shown in FIG. 2.
[0014] FIG. 4 shows a second step of working the shell.
[0015] FIG. 5 shows a completed suction roll shell.
[0016] FIGS. 6-9 show the result of comparative tests in which the
steel used according to the invention is compared with other steels
in terms of cuttability.
DETAILED DESCRIPTION OF THE INVENTION
[0017] In the following, the manufacturing of suction roll shells
is schematically described. With reference to FIG. 1, a first step
in the manufacturing of a suction roll shell is shown. As is shown
in FIG. 1, an essentially planar blank 1 is roller bent between two
rollers 2, 3, as is known as such and need not be described in
greater detail herein. After bending to an essentially circular
shape, the ends of the blank 1 are welded together such that a weld
joint unites the blank 1 to form a segment 9. A plurality of
segments are then united by circular joints to form a shell that is
heat treated after the welding. FIG. 3 shows how the thus achieved
shell 9 can be subjected to a working operation, such as turning.
FIG. 3 shows a turning tool 5 acting on the face of the shell 9.
The object of the turning operation is to ensure that the face of
the shell 9 is smooth and regular. FIG. 4 shows schematically a
subsequent step in the manufacturing process, in which the shell 9
is drilled by a drill 6, whereby the shell is provided with a
number of through holes 7. FIG. 5 shows the completed suction roll
shell 8 with its circular cylindrical shell 9 and the through holes
7 thereof. FIG. 5 also shows schematically that the ends of the
suction roll shell 8 can be closed by side covers 10. When the
suction roll shell 8 is used, its interior will be connected to a
vacuum source (not shown), which results in air being drawn from
the outside and in via the through holes 7. Only a few holes are
shown in the drawings. It should be realised however that in real
applications the number of holes can be very large, such as 100,000
holes or more. Suction roll shells have previously been
manufactured from a material sold under the name 3RE60 Avesta SRG.
This steel is a stainless ferrite-austenite steel that has been
improved in respect of cuttability by sulphur treatment and that
has the following typical composition in % by weight.
TABLE-US-00001 C 0.02 Si 1.50 Cr 18.5 Ni 4.90 Mo 2.80 N 0.08. S
0.02
[0018] With good results, steel 3RE60 has been used for about 30
years for the manufacturing of suction roll shells, and about 10
years ago it was provided with an additive for improved cuttability
and its name was changed to 3RE60 SRG. Nowadays, the steel is
called 3RE60 Avesta SRG.
[0019] It has now been surprisingly shown that another
ferrite-austenite steel exists that has in addition a high nitrogen
content, and that has equally good or in some respects even better
cuttability than the cuttability-improved 3RE60 Avesta SRG. This
steel has a microstructure essentially consisting of 35-65% by
volume of ferrite and 35-65% by volume of austenite, and its
chemical composition contains in % by weight:
TABLE-US-00002 C 0.005 Si 0.1-2.0 Mn 3-8 Cr 19-23 Ni 0.5-1.7 N
0.15-0.3
[0020] A steel that is particularly suitable for this application
suitably contains: optionally Mo and/or W at a total content of no
more than 1.0 (Mo+W/2), optionally Cu up to a maximum of 1.0 Cu,
balance being iron and impurities. For the ferrite and austenite
formers in the alloy, i.e. chromium and nickel equivalents, the
following conditions should preferably be true:
20<Cr.sub.eeq.ltoreq.24.5
10<Ni.sub.eq, where
Cr.sub.eq=Cr+1.5 Si+Mo+2 Ti+0.5 Nb
Ni.sub.eq=Ni+0.5 Mn+30(C+N)+0.5(Cu+Co).
[0021] In an advantageous embodiment, the steel contains 0.02-0.05
C. Suitably, the steel contains 0.18-0.26 N and advantageously
20-23 Cr. In a preferred embodiment, the steel contains 0.8-1.70
Ni, and even more preferred 1.35-1.7 Ni.
[0022] A steel of this composition is described in published US
Patent Application No. 2003/0172999.
[0023] In a particularly advantageous embodiment of the invention,
the steel contains 0.22 N, 21.5 Cr, 1.5 Ni, 0.3 Mo, 5 Mn and not
more than 0.04 C. Such a steel is sold by Outokumpu Stainless AB,
Box 74, SE-774 22, AVESTA. This steel is sold by Outokumpu under
the name LDX 2101.RTM.. The name is a trademark registered in the
European Union. Accordingly, the LDX 2101.RTM. steel is
particularly suitable to be used in a suction roll shell.
Particularly suitable contents of copper and silicon are 0.3 Cu and
0.7 Si, respectively. The guideline values 0.3 Cu and 0.7 Si (in %
by weight) are used for LDX 2101.RTM..
[0024] Compared with e.g. steel 3RE60 Avesta SRG, the steel of the
type mentioned above has a relatively high nitrogen content. As it
is known that nitrogen tends to impair cuttability, it would be
expected that cuttability is poorer. However, it has been
surprisingly shown that the cuttability of the steel used according
to the present invention is considerably higher than expected.
[0025] FIG. 6 shows the results of a comparative test in which an
LDX 2101.RTM. steel were compared with two other,
cuttability-improved, austenite steels called 304L PRODEC.RTM. and
316L PRODEC.RTM., respectively. The steel 304L PRODEC.RTM. has the
following composition in % by weight:
TABLE-US-00003 C 0.02 Si 0.5 Mn 1.5 Cr 18.2 Ni 8.4 Mo essentially
none N 0.07 S 0.02
[0026] The steel 316L PRODEC.RTM. has the following
composition:
TABLE-US-00004 C 0.02 Si 0.5 Mn 1.5 Cr 17.2 Ni 11.2 Mo 2.3 N 0.05 S
0.02
[0027] As the nitrogen content of both cuttability-improved
austenite steels 304L PRODEC.RTM. an 316L PRODEC.RTM. is
considerably lower than in an LDX 2101.RTM. steel, it would
normally be expected for these steels to be better in cuttability
than an LDX 2101.RTM. steel. In turning tests it was however shown
that for an LDX 2101.RTM. steel, working time 30 minutes,
high-speed steel tools being used, a considerably higher cutting
speed was possible as compared with the other two steels, which is
shown in FIG. 6.
[0028] FIG. 7 shows the results of an additional comparative test
between an LDX 2101.RTM. steel and steels 304L PRODEC.RTM. and 316L
PRODEC.RTM.. FIG. 7 shows a test with a working time of 15 minutes,
in which turning was made by a cutting edge of hard metal. Under
these circumstances, a cutting speed was achieved for an LDX
2102.RTM. steel that was somewhat lower in comparison with the
other two steels. The difference is however marginal.
[0029] FIG. 8 shows another test in which the steel LDX 2101.RTM.
is compared with a conventional duplex steel sold under the name
2205. This steel, which is more highly alloyed than LDX 2101.RTM.,
is standardized (EN 1.4462) and is used in a great number of
applications. It has no cuttability-improving additives and is not
used for this type of suction roll shells. 2205 has the following
composition:
TABLE-US-00005 C 0.02 Si 0.4 Mn 1.5 Cr 22.2 Ni 5.7 Mo 3.1 N 0.17 S
0.001
[0030] In the test, a comparison was made in terms of the useful
life of the tool when milling with a cutting edge of hard metal. As
is evident from FIG. 8, the useful life of the tool was
considerably longer when working an LDX 2101.RTM. steel as compared
with working of the steel 2005.
[0031] Finally, yet another test is shown in FIG. 9. In the test
shown in FIG. 9, an LDX 2101.RTM. steel was compared with three
other steel types used for suction roll shells, i.e. 2304 Avesta
SRG, 3RE60 Avesta SRG and 2205 Avesta SRG. All steels designated
SRG (Suction Roll Grade) are cuttability-improved by sulphur
addition. The steel 2304 Avesta SRG has the following typical
composition:
TABLE-US-00006 C 0.02 Si 0.8 Mn 1.5 Cr 22.7 Ni 4.7 Mo 0.3 N 0.09 S
0.02
[0032] The steel 2205 Avesta SRG has the following typical
composition:
TABLE-US-00007 C 0.017 Si 0.6 Mn 1.35 Cr 22.0 Ni 5.7 Mo 2.9 N 0.13
S 0.02
[0033] In the test shown in FIG. 9, a comparison was made in
respect of the cutting speed that can be achieved for a drilled
length of 1000 mm without tool failure, in different materials. As
is evident from FIG. 9, LDX 2101.RTM. is considerably better than
the cuttability-improved steels 2205 Avesta SRG and 2304 Avesta
SRG, and in this respect it is equally good as the
cuttability-improved steel 3RE60 Avesta SRG, despite the fact that
LDX 2101.RTM. contains considerably more nitrogen than the steel
3RE60 Avesta SRG. It is a clear technical advantage if cuttability
of the material can be achieved without so called
cuttability-improving additives such as sulphur, as these lead to a
number of drawbacks such as impaired rollability and impaired
corrosion resistance.
[0034] It is to be understood that although the invention has been
described in terms of a suction roll shell and a method, those are
just different aspects of one and the same invention, as the method
according to the invention is suited to be used for manufacturing
of the suction roll shell according to the invention.
[0035] By the invention, the advantage is obtained, among other
things, that the completed roll shell achieves a very good
corrosion resistance.
* * * * *