U.S. patent application number 16/087486 was filed with the patent office on 2019-04-11 for ferritic stainless steel sheet.
This patent application is currently assigned to JFE Steel Corporation. The applicant listed for this patent is JFE Steel Corporation. Invention is credited to Mitsuyuki Fujisawa, Tomohiro Ishii, Chikara Kami, Shuji Nishida.
Application Number | 20190106775 16/087486 |
Document ID | / |
Family ID | 59963174 |
Filed Date | 2019-04-11 |
United States Patent
Application |
20190106775 |
Kind Code |
A1 |
Nishida; Shuji ; et
al. |
April 11, 2019 |
FERRITIC STAINLESS STEEL SHEET
Abstract
A ferritic stainless steel sheet is provided. The ferritic
stainless steel includes, in mass %, C: 0.020% or less, Si: 0.05 to
0.50%, Mn: 0.05 to 0.50%, P: 0.040% or less, S: 0.030% or less, Al:
0.001 to 0.150%, Cr: 18.0 to 25.0%, Ti: 0.01 to 0.50%, Ca: 0.0001
to 0.0015%, O (oxygen): 0.0015 to 0.0040%, and N: 0.025% or less,
with the balance being Fe and incidental impurities. The ferritic
stainless steel sheet further satisfies formula (1), below:
0.5.ltoreq.PBI.ltoreq.20.0 . . . (1) (where
PBI=(7Al+2Ti+Si+10Zr+130Ca).times.O (oxygen).times.1000, and Al,
Ti, Si, Zr, Ca, and O (oxygen) in the formula each represent a
content [mass %] of a corresponding element in the ferritic
stainless steel sheet, and the content of an element not included
in the ferritic stainless steel sheet is 0).
Inventors: |
Nishida; Shuji; (Chiyoda-ku,
Tokyo, JP) ; Ishii; Tomohiro; (Chiyoda-ku, Tokyo,
JP) ; Fujisawa; Mitsuyuki; (Chiyoda-ku, Tokyo,
JP) ; Kami; Chikara; (Chiyoda-ku, Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
JFE Steel Corporation |
Tokyo |
|
JP |
|
|
Assignee: |
JFE Steel Corporation
Tokyo
JP
|
Family ID: |
59963174 |
Appl. No.: |
16/087486 |
Filed: |
February 24, 2017 |
PCT Filed: |
February 24, 2017 |
PCT NO: |
PCT/JP2017/006973 |
371 Date: |
September 21, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C22C 38/26 20130101;
C22C 38/44 20130101; C22C 38/48 20130101; C22C 38/02 20130101; C21D
8/0236 20130101; C22C 38/30 20130101; C22C 38/50 20130101; C22C
38/28 20130101; C21D 8/0226 20130101; C21D 2211/005 20130101; C22C
38/001 20130101; C22C 38/60 20130101; C22C 38/06 20130101; C22C
38/005 20130101; C22C 38/32 20130101; C22C 38/42 20130101; C22C
38/54 20130101; C21D 9/46 20130101; C22C 38/22 20130101; C21D
8/0263 20130101; C21D 6/004 20130101; C21D 6/005 20130101; C22C
38/04 20130101; C22C 38/24 20130101; C22C 38/20 20130101; C22C
38/52 20130101; C21D 6/008 20130101; C21D 8/0205 20130101; C22C
38/002 20130101; C22C 38/008 20130101; C21D 6/007 20130101; C22C
38/46 20130101 |
International
Class: |
C22C 38/54 20060101
C22C038/54; C22C 38/52 20060101 C22C038/52; C22C 38/50 20060101
C22C038/50; C22C 38/48 20060101 C22C038/48; C22C 38/46 20060101
C22C038/46; C22C 38/44 20060101 C22C038/44; C22C 38/42 20060101
C22C038/42; C22C 38/06 20060101 C22C038/06; C22C 38/04 20060101
C22C038/04; C22C 38/02 20060101 C22C038/02; C22C 38/00 20060101
C22C038/00; C21D 9/46 20060101 C21D009/46; C21D 8/02 20060101
C21D008/02; C21D 6/00 20060101 C21D006/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 29, 2016 |
JP |
2016-065695 |
Claims
1. A ferritic stainless steel sheet comprising, in mass %, C:
0.020% or less, Si: 0.05 to 0.50%, Mn: 0.05 to 0.50%, P: 0.040% or
less, S: 0.030% or less, Al: 0.001 to 0.150%, Cr: 18.0 to 25.0%,
Ti: 0.01 to 0.50%, Ca: 0.0001 to 0.0015%, O (oxygen): 0.0015 to
0.0040%, and N: 0.025% or less, with the balance being Fe and
incidental impurities, the ferritic stainless steel sheet further
satisfying formula (1), below: 0.5.ltoreq.PBI.ltoreq.20.0 (1)
(where PBI=(7Al+2Ti+Si+10Zr+130Ca).times.O (oxygen).times.1000, and
Al, Ti, Si, Zr, Ca, and O (oxygen) in the formula each represent a
content [mass %] of a corresponding element in the ferritic
stainless steel sheet, and a content of an element not contained in
the ferritic stainless steel sheet is 0).
2. The ferritic stainless steel sheet according to claim 1, further
comprising, in mass %, at least one selected from Zr: 0.01 to
0.80%, Nb: 0.01% or greater and less than 0.40%, and V: 0.01 to
0.50%.
3. The ferritic stainless steel sheet according to claim 1 or 2,
further comprising, in mass %, at least one selected from Cu: 0.30
to 0.80%, Ni: 0.01 to 2.50%, Co: 0.01 to 0.50%, Mo: 0.01 to 2.00%,
and W: 0.01 to 0.50%.
4. The ferritic stainless steel sheet according to claim 2, further
comprising, in mass %, at least one selected from Cu: 0.30 to
0.80%, Ni: 0.01 to 2.50%, Co: 0.01 to 0.50%, Mo: 0.01 to 2.00%, and
W: 0.01 to 0.50%.
5. The ferritic stainless steel sheet according to claim 1, further
comprising, in mass %, at least one selected from B: 0.0003 to
0.0030%, Mg: 0.0005 to 0.0100%, Y: 0.001 to 0.20%, REM (rare earth
metal): 0.001 to 0.10%, Sn: 0.01 to 0.50%, and Sb: 0.01 to
0.50%.
6. The ferritic stainless steel sheet according to claim 2, further
comprising, in mass %, at least one selected from B: 0.0003 to
0.0030%, Mg: 0.0005 to 0.0100%, Y: 0.001 to 0.20%, REM (rare earth
metal): 0.001 to 0.10%, Sn: 0.01 to 0.50%, and Sb: 0.01 to
0.50%.
7. The ferritic stainless steel sheet according to claim 3, further
comprising, in mass %, at least one selected from B: 0.0003 to
0.0030%, Mg: 0.0005 to 0.0100%, Y: 0.001 to 0.20%, REM (rare earth
metal): 0.001 to 0.10%, Sn: 0.01 to 0.50%, and Sb: 0.01 to
0.50%.
8. The ferritic stainless steel sheet according to claim 4, further
comprising, in mass %, at least one selected from B: 0.0003 to
0.0030%, Mg: 0.0005 to 0.0100%, Y: 0.001 to 0.20%, REM (rare earth
metal): 0.001 to 0.10%, Sn: 0.01 to 0.50%, and Sb: 0.01 to
0.50%.
9. The ferritic stainless steel sheet according to claim 1, wherein
the ferritic stainless steel sheet has low susceptibility to
exfoliation of black spots in a weld zone during bending.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This is the U.S. National Phase application of
PCT/JP2017/006973, filed Feb. 24, 2017, which claims priority to
Japanese Patent Application No. 2016-065695, filed Mar. 29, 2016,
the disclosures of these applications being incorporated herein by
reference in their entireties for all purposes.
TECHNICAL FIELD OF THE INVENTION
[0002] The present invention relates to a ferritic stainless steel
sheet. In particular, the present invention relates to a ferritic
stainless steel sheet that has excellent weld penetration
characteristics and which has low susceptibility to exfoliation of
black spots on the weld bead during bending.
BACKGROUND OF THE INVENTION
[0003] Ferritic stainless steel sheets are less costly and have
better price stability than austenitic stainless steel sheets,
which contain a high amount of Ni. Furthermore, ferritic stainless
steel sheets have excellent corrosion resistance and are thus used
in a variety of applications, such as building materials, transport
equipment, home appliances, and kitchen equipment.
[0004] Among ferritic stainless steel sheets there is a
Ti-stabilized ferritic stainless steel sheet, which includes Ti, a
stabilizing element. Containing Ti results in formation of Ti
carbonitride in the steel, which reduces dissolved C and dissolved
N, and also promotes development of a {111} recrystallization
texture. As a result, the steel sheet has excellent workability.
When a Ti-stabilized ferritic stainless steel sheet is subjected to
TIG welding (Tungsten Inert Gas welding), however, oxides called
black spots tend to form on the weld bead even when sufficient gas
shielding is provided.
[0005] Techniques for reducing the formation of black spots on the
weld bead are disclosed in Patent Literature 1 and 2.
[0006] Patent Literature 1 discloses a ferritic stainless steel
that achieves a reduced formation of black spots. The ferritic
stainless steel satisfies a BI value (3Al+Ti+0.5Si+200Ca) expressed
by the steel composition being 0.8 or less.
[0007] Patent Literature 2 discloses a ferritic stainless steel
that achieves a reduced formation of black spots. The ferritic
stainless steel satisfies the above described BI value by the steel
composition being 0.8 or less.
CITATION LIST
Patent Literature
[0008] PTL 1: Japanese Unexamined Patent Application Publication
No. 2010-202973
[0009] PTL 2: Japanese Unexamined Patent Application Publication
No. 2012-36444
SUMMARY OF THE INVENTION
[0010] When large and thick black spots form, one problem is as
follows. In the case that the steel sheet including the weld bead
is subjected to bending, black spots may exfoliate and the sites
after such black spots have exfoliated may act as initiation sites
for crevice corrosion, which may result in deterioration of
corrosion resistance. Neither of the technologies disclosed in
Patent Literature 1 and 2 sufficiently inhibits exfoliation, during
bending, of black spots of Ti-stabilized ferritic stainless steel
sheets. Furthermore, since the upper limits of the contents of Si,
Al, Ti, and Ca, which have a deoxidizing effect, are strictly
limited, the oxygen concentration in the ferritic stainless steel
tends to increase. Thus, oxides tend to form in the steel and, in
the process of steel sheet production, scabs and surface defects
tend to form. The technologies disclosed in Patent Literature 1 and
2 pose such problems.
[0011] Currently, Ti-stabilized ferritic stainless steel sheets,
described above, are widely used in household appliances in order
to reduce product costs. On the other hand, structures of such home
appliances are increasingly complex, and accordingly, there are
cases in which a Ti-stabilized ferritic stainless steel sheet is
applied to a portion that is to be exposed to a severe corrosive
environment after its weld zone is processed by bending. Thus,
there is a need for a Ti-stabilized stainless steel sheet that has
low susceptibility to crevice corrosion attack which is caused by
exfoliation of black spots even in the case that the weld bead is
processed by bending.
[0012] Aspects of the present invention are directed toward
providing a ferritic stainless steel sheet that has low
susceptibility to exfoliation of black spots in a TIG weld zone
during bending.
[0013] To address the problems described above, the present
inventors conducted extensive research to inhibit exfoliation of
black spots during bending. As a result, the following was found.
The steel composition may be defined to have an O (oxygen) content
of not greater than a specific value and have a PBI value,
expressed by "(7Al+2Ti+Si+10Zr+130Ca).times.O (oxygen).times.1000",
of not greater than a specific value. This composition reduces the
occurrence of exfoliation of black spots during bending regardless
of the ratio of the total lengths of black spots in the bead
direction to the full length of the weld bead (black spot formation
length ratio).
[0014] Also, it was found that, in the case that the O (oxygen)
content or the PSI value is extremely small, the weld bead has less
tendency to penetrate in the sheet thickness direction and thus the
weld penetration characteristics are degraded. Accordingly, the
present inventors discovered that, by formulating defining the
steel composition to have an O (oxygen) content within a specific
range and have a PBI value within a specific range, good weld
penetration characteristics and good inhibition of black spot
exfoliation can both be achieved. The mechanism is believed to be
as follows.
[0015] During TIG welding, the black spot moves on the weld bead as
if the black spot were dragged by the electrode with increasing in
size, and after being increased to a certain size or larger, the
black spot is fixed to the edge of the weld bead. In a ferritic
stainless steel sheet, when the content of an element having a high
affinity for oxygen or the content of oxygen is low, the surface
tension of the molten pool that forms during TIG welding decreases
as the temperature increases. As a result, a strong flow forms on
the surface of the molten pool, in a direction from the center of
the weld bead, where the temperature is high, to the edge of the
weld bead, where the temperature is low. With this strong flow,
outward Marangoni convection becomes active. As a result, the black
spot, in a state of being relatively small, is fixed to the bead
edge. Thus, the individual black spots are thin and small, which
results in a reduced occurrence of exfoliation during bending.
[0016] If the content of an element having a high affinity for
oxygen or the content of oxygen is excessively low in a ferritic
stainless steel sheet, outward Marangoni convection becomes
extremely active and thus the "depth to width" ratio of the molten
pool becomes extremely small. Consequently, characteristics of weld
bead penetration in the sheet thickness direction are degraded.
[0017] Further studies were conducted based on the above findings,
and aspects of the present invention were made. The object
according to aspects of the invention is as follows.
[1] A ferritic stainless steel sheet including, in mass %, C:
0.020% or less, Si: 0.05 to 0.50%, Mn: 0.05 to 0.50%, P: 0.040% or
less, S: 0.030% or less, Al: 0.001 to 0.150%, Cr: 18.0 to 25.0%,
Ti: 0.01 to 0.50%, Ca: 0.0001 to 0.0015%, O (oxygen): 0.0.0015 to
0.0040%, and N: 0.025% or less, with the balance being Fe and
incidental impurities, the ferritic stainless steel sheet further
satisfying formula (1), below.
0.5.ltoreq.PBI.ltoreq.20.0 (1)
(Here, PBI=(7Al+2Ti+Si+10Zr+130Ca).times.O (oxygen).times.1000, and
Al, Ti, Si, Zr, Ca, and O (oxygen) in the formula each represent a
content [mass %] of a corresponding element in the ferritic
stainless steel sheet, and the content of an element not contained
in the ferritic stainless steel sheet is 0). [2] The ferritic
stainless steel sheet according to [1], further including, in mass
%, at least one selected from Zr: 0.01 to 0.80%, Nb: 0.01% or
greater and less than 0.40%, and V: 0.01 to 0.50%. [3] The ferritic
stainless steel sheet according to [1] or [2], further including,
in mass %, at least one selected from Cu: 0.30 to 0.80%, Ni: 0.01
to 2.50%, Co: 0.01 to 0.50%, Mo: 0.01 to 2.00%, and W: 0.01 to
0.50%. [4] The ferritic stainless steel sheet according to any one
of [1] to [1], further including, in mass %, at least one selected
from B: 0.0003 to 0.0030%, Mg: 0.0005 to 0.0100%, Y: 0.001 to
0.20%, REM (rare earth metal): 0.001 to 0.10%, Sn: 0.01 to 0.50%,
and Sb: 0.01 to 0.50%. [5] The ferritic stainless steel sheet
according to any one of [1] to [4], wherein the ferritic stainless
steel sheet has low susceptibility to exfoliation of black spots in
a weld zone during bending.
[0018] Aspects of the present invention provide a ferritic
stainless steel sheet that has low susceptibility to exfoliation of
black spots in a TIG weld zone during bending. Furthermore, the
ferritic stainless steel sheet according to aspects of the present
invention has excellent characteristics of weld bead penetration
and also exhibits excellent corrosion resistance even at its bent
portion.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a diagram illustrating the appearance of black
spots that formed in Example No. 3, of Table 1, which will be
described later.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0020] Embodiments of the present invention, including the best
mode, will be described below.
[0021] The ferritic stainless steel sheet according to aspects of
the present invention satisfies the following formula (1).
0.5.ltoreq.PBI.ltoreq.20.0 (1)
Here, PBI=(7Al+2Ti+Si+10Zr+130Ca).times.O (oxygen).times.1000 (In
formula (1), Al, Ti, Si, Zr, Ca, and O (oxygen) each represent the
content [mass %] of the corresponding element in the ferritic
stainless steel sheet, and the content of an element not contained
in the ferritic stainless steel sheet is 0).
[0022] Al, Ti, Si, Zr, and Ca are elements having a particularly
high affinity for oxygen and tend to form oxides. When the product
of the value of the contents of these elements and the value of the
oxygen content is large, black spots tend to exfoliate during
bending. In equation (1), the coefficients of Al, Ti, Si, Zr, and
Ca are determined based on the magnitude of the influence on the
characteristics of weld bead penetration and on the magnitude of
the influence that causes exfoliation of black spots during
bending.
[0023] In the case that the PBI value is greater than 20.0, black
spots exfoliate during bending. To inhibit such exfoliation, the
PBI value is not greater than 20.0. In the case that the PBI value
is not greater than 5.0, the exfoliation of black spots during
bending can be further inhibited effectively.
[0024] In the case that the PBI value is less than 0.5, the
characteristics of weld bead penetration in the sheet thickness
direction is deteriorated. Accordingly, the PBI value is not less
than 0.5 in accordance with aspects of the present invention. In
the case that the PBI value is 1.5 or greater, the characteristics
of weld bead penetration are excellent.
[0025] Furthermore, in the case that the PBI value is 1.5 or
greater, good inhibition of exfoliation of black spots during
bending is achieved compared with the case in which the PBI value
is less than 1.5. This is believed to be due to the fact that, as
described above, the weld penetration characteristics are better in
the case that the PBI value is 1.5 or greater than in the case that
the PBI value is less than 1.5. Thus, in accordance with aspects of
the present invention, it is further preferable that the PBI value
be 1.5 or greater and 5.0 or less.
[0026] Next, reasons for limiting the chemical composition to the
aforementioned ranges in accordance with aspects of the present
invention will be described. The percentages indicating the
chemical composition of the steel are mass percentages unless
otherwise specified.
[0027] C: 0.020% or less
[0028] C is an effective element for increasing the strength of
steel. Thus, it is preferable that the C content not be less than
0.001%. On the other hand, if the C content is greater than 0.020%,
corrosion resistance and workability deteriorate significantly.
Thus, the C content is not greater than 0.020%. The C content is
preferably not greater than 0.015% and more preferably not greater
than 0.010%.
[0029] Si: 0.05 to 0.50%
[0030] Si is an element which is useful as a deoxidizer. This
effect is obtained when the Si content is 0.05% or greater. It is
preferable that the Si content not be less than 0.08%. If the Si
content is greater than 0.50%, the steel hardens and workability is
deteriorated. In addition, even when the composition satisfies
formula (1), black spots formed in TIG welding of a ferritic
stainless steel sheet tend to exfoliate during bending, and the
sites after such exfoliation may act as initiation sites for
crevice corrosion. Thus, the Si content is not greater than 0.50%.
The Si content is preferably not greater than 0.30% and more
preferably not greater than 0.15%.
[0031] Mn: 0.05 to 0.50%
[0032] Mn acts as a deoxidizes. This effect is obtained when the Mn
content is 0.05% or greater. The Mn content is preferably not less
than 0.10%, more preferably not less than 0.15%, and even more
preferably not less than 0.17%. If the Mn content is greater than
0.50%, precipitation and coarsening of MnS is promoted, which
causes deterioration of corrosion resistance. Thus, the Mn content
is not greater than 0.50%. The Mn content is preferably less than
0.30% and more preferably not greater than 0.20%.
[0033] P: 0.040% or less
[0034] P is an element that deteriorates corrosion resistance. In
addition, P deteriorates hot workability due to segregation at
grain boundaries. For this reason, the P content is desirably as
low as possible and is thus not greater than 0.040%. It is
preferable that the P content not be greater than 0.030%. The lower
limit of the P content is not particularly specified.
[0035] S: 0.030% or less
[0036] S, together with Mn, forms precipitated MnS. Such MnS
deteriorates corrosion resistance due to acting as corrosion
initiation sites. Thus, the S content is desirably low and is thus
not greater than 0.030%. It is preferable that the S content not be
greater than 0.020%. The S content is more preferably not greater
than 0.010% and even more preferably not greater than 0.005%. The
lower limit of the S content is not particularly specified.
[0037] Al: 0.001 to 0.150%
[0038] Al is an effective element for deoxidation. This effect is
obtained when the Al content is 0.001% or greater. The Al content
is preferably not less than 0.005% and more preferably not less
than 0.01.0%. If the Al content is greater than 0.150%, formation
of scales on the slab upper surface, which produce a lubricating
effect in hot rolling, is reduced and thus surface defects tend to
form, which deteriorates productivity. In addition, if the Al
content is greater than 0.150%, black spots formed in TIG welding
of steel sheets tend to exfoliate during bending even when the
composition satisfies formula (1), and the sites after such
exfoliation may act as initiation sites for crevice corrosion.
Thus, the Al content is not greater than 0.150%. The Al content is
preferably not greater than 0.100% and more preferably not greater
than 0.050%.
[0039] Cr: 18.0 to 25.0%
[0040] Cr is an element that enhances corrosion resistance by
forming a passivation film on the surface. If the Cr content is
less than 18.0%, sufficient corrosion resistance is not achieved.
Thus, the Cr content is not less than 18.0, preferably not less
than 20.0%, and more preferably not less than 20.5%. If the Cr
content is greater than 25.0%, toughness tends to be deteriorated
because of the influence of the .sigma. phase or 475.degree. C.
embrittlement. Thus, the Cr content is not greater than 25.0%. The
Cr content is preferably not greater than 23.0% and more preferably
not greater than 21.5%.
[0041] Ti: 0.01 to 0.50%
[0042] Ti is an effective element for deoxidation. Also, Ti is an
effective element to improve corrosion resistance, because it
suppresses formation of Cr carbonitrides and Cr-depleted zones by
stabilizing C and N. Furthermore, Ti improves workability by
promoting development of a {111} recrystallization texture. These
effects are obtained when the Ti content is 0.01% or greater. The
Ti content is preferably not less than 0.05% and more preferably
not less than 0.20%. If the Ti content is greater than 0.50%, the
ferritic stainless steel sheet hardens and thus bendability is
deteriorated. Further, TiN acts as corrosion initiation sites,
which deteriorates corrosion. In addition, if the Ti content is
greater than 0.50%, black spots formed in TIG welding of a steel
sheet tend to exfoliate during bending even when the composition
satisfies formula (1), and the sites after such exfoliation may act
as initiation sites for crevice corrosion. For the above reasons,
the Ti content is not greater than 0.50%. The Ti content is
preferably not greater than 0.40% and more preferably not greater
than 0.30%.
[0043] Ca: 0.0001 to 0.0015%
[0044] Ca is an effective element for deoxidation. This effect is
obtained when the Ca content is 0.0001% or greater. The Ca content
is preferably not less than 0.0002% and more preferably not less
than 0.0003%. If Ca is contained in an amount of greater than
0.0015%, black spots formed in TIG welding of a steel sheet tend to
exfoliate during bending even when the composition satisfies
formula (1), and the sites after such exfoliation may act as
initiation sites for crevice corrosion. Thus, the Ca content is not
greater than 0.0015%. The Ca content is preferably not greater than
0.0010% and more preferably not greater than 0.0005%.
[0045] O (oxygen): 0.0015 to 0.0040%
[0046] O (oxygen) is an element that improves characteristics of
weld bead penetration in the sheet thickness direction in TIG
welding. This effect is obtained when the O (oxygen) content is
0.0015% or greater. The O (oxygen) content is preferably not less
than 0.0020% and more preferably not less than 0.0025%. If O
(oxygen) is contained in an amount of greater than 0.0040%, black
spots formed in TIG welding of a steel sheet tend to exfoliate
during bending even when the composition satisfies formula (1), and
the sites after such exfoliation may act as initiation sites for
crevice corrosion. Thus, the O (oxygen) content is not greater than
0.0040%. The O (oxygen) is preferably not greater than 0.0035% and
more preferably not greater than 0.0030%.
[0047] N: 0.025% or less
[0048] If N is contained in an amount of greater than 0.025%,
corrosion resistance and workability significantly is deteriorated.
Thus, the N content is not greater than 0.025%. It is desirable
that N be reduced as much as possible. The N content is preferably
not greater than 0.020% and more preferably not greater than
0.015%. The lower limit of the N content is not particularly
specified.
[0049] While basic components have been described above, other
elements, described below, can be contained in accordance with
aspects of the present invention.
[0050] Zr: 0.01 to 0.80%
[0051] Similarly to Ti, Zr is an effective element for deoxidation.
In addition, Zr is an element that improves corrosion resistance,
since it suppresses formation of Cr carbonitrides and Cr-depleted
zones and prevent sensitization by stabilizing C and N. In order to
obtain these effects, it is preferable that the Zr content not be
less than 0.01%. The Zr content is more preferably not less than
0.02% and even more preferably not less than 0.03%. On the other
hand, if the Zr content is greater than 0.80%, the ferritic
stainless steel sheet hardens and thus bendability may be
deteriorated. In addition, if the Zr content is greater than 0.80%,
black spots formed in TIG welding of a steel sheet tend to
exfoliate during bending even when the composition satisfies
formula (1), and this may result in initiation sites for crevice
corrosion. Thus, the Zr content is not greater than 0.80%. The Zr
content is more preferably not greater than 0.30% and even more
preferably not greater than 0.10%.
[0052] Nb: 0.01% or greater and less than 0.40%
[0053] Similarly to Ti, Nb is an element that improves corrosion
resistance, since it suppresses formation of Cr carbonitrides and
Cr-depleted zones and prevent sensitization by stabilizing. C and
N. In order to obtain this effect, it is preferable that the Nb
content not be less than 0.01%. The Nb content is more preferably
not less than 0.03% and even more preferably not less than 0.05%.
If the Nb content is 0.40% or greater, the ferritic stainless steel
sheet hardens and may thus have deteriorated bendability, and in
addition, the recrystallization temperature increases, which
deteriorates productivity. Thus, it is preferable that the Nb
content be less than 0.40%. The Nb content is more preferably not
greater than 0.30% and even more preferably not greater than
0.15%.
[0054] V: 0.01 to 0.50%
[0055] V is an element that improves the crevice corrosion
resistance of the ferritic stainless steel sheet. In order to
obtain this effect, it is preferable that the V content not be less
than 0.01%. The V content is more preferably not less than 0.03%
and even more preferably not less than 0.05%. If the V content is
greater than 0.50%, workability may be deterioarated. Thus, it is
preferable that the V content not be greater than 0.50%. The V
content is more preferably not greater than 0.30% and even more
preferably not greater than 0.10%.
[0056] Cu: 0.30 to 0.80%
[0057] Cu is an element that improves corrosion resistance by
strengthening the passivation film. If Cu is contained in excessive
amounts, .epsilon.-Cu tends to precipitate, which may deteriorate
corrosion resistance. Thus, it is preferable that the Cu content be
from 0.30 to 0.80%. The lower limit of the Cu content is more
preferably not less than 0.35% and even more preferably not less
than 0.40%. The upper limit of the Cu content is more preferably
not greater than 0.50% and even more preferably not greater than
0.45%.
[0058] Ni: 0.01 to 2.50%
[0059] Ni is an element that suppresses acid-induced anode reaction
and thus makes it possible to maintain a passive state even at a
lower pH. That is, Ni is highly effective in improving crevice
corrosion resistance and noticeably suppresses the progress of
corrosion in a state of active dissolution, and thus improves
corrosion resistance. In order to obtain this effect, it is
preferable that the Ni content not be less than 0.01%. The Ni
content is more preferably not less than 0.05% and even more
preferably not less than 0.10%. If the Ni content is greater than
2.50%, hydrogen embrittlement cracking tends to occur at worked
portions. Thus, it is preferable that the Ni content not be greater
than 2.50%. The Ni content is more preferably not greater than
0.80% and even more preferably not greater than 0.25%.
[0060] Co: 0.01 to 0.50%
[0061] Co is an element that improves the crevice corrosion
resistance of the ferritic stainless steel. In order to obtain this
effect, it is preferable that the Co content not be less than
0.01%. It is more preferable that the Co content not be less than
0.10%. If the Co content is greater than 0.50%, workability may be
deterioarated. Thus, it is preferable that the Co content not be
greater than 0.50%. The Co content is more preferably not greater
than 0.30% and even more preferably not greater than 0.15%.
[0062] Mo: 0.01 to 2.00%
[0063] Mo has the effect of improving the crevice corrosion
resistance of the ferritic stainless steel sheet. In order to
obtain this effect, it is preferable that the Mo content not be
less than 0.01%. The Mo content is more preferably not less than
0.10 and even more preferably not less than 0.30%. If the Mo
content is greater than 2.00%, coarse intermetallic compounds may
form, which may deterioarate toughness. Thus, it is preferable that
the Mo content not be greater than 2.00%. The Mo content is more
preferably not greater than 1.00% and even more preferably not
greater than 0.60%.
[0064] W: 0.01 to 0.50%
[0065] W is an element that improves the crevice corrosion
resistance of the ferritic stainless steel sheet. In order to
obtain this effect, it is preferable that the W content not be less
than 0.01%. It is more preferable that the W content not be less
than 0.10%. If the W content is greater than 0.50%, workability may
be deteriorated. Thus, it is preferable that the W content not be
greater than 0.50%. It is more preferable that the W content not be
greater than 0.30%.
[0066] B: 0.0003 to 0.0030%
[0067] B is an element that improves hot workability and secondary
workability. It is known that addition of B to a Ti-containing
steel is effective. In order to obtain this effect, it is
preferable that the B content not be less than 0.0003%. It is more
preferable that the B content not be less than 0.0010%. If the B
content is greater than 0.0030%, toughness may be deteriorated.
Thus, it is preferable that the B content not be greater than
0.0030%. It is more preferable that the B content not be greater
than 0.0025%.
[0068] Mg: 0.0005 to 0.0100%
[0069] Mg acts as deoxidizer by forming a Mg oxide together with Al
in molten steel. In order to obtain this effect, it is preferable
that the Mg content not be less than 0.0005%. It is more preferable
that the Mg content not be less than 0.0010%. If the Mg content is
greater than 0.0100%, the toughness of the steel is deteriorated,
which may reduce productivity. Thus, it is preferable that the Mg
content not be greater than 0.0100%. The Mg content is more
preferably not greater than 0.0050% and even more preferably not
greater than 0.0030%.
[0070] Y: 0.001 to 0.20%
[0071] Y is an element that prevents a decrease in viscosity of
molten steel and improves the cleanliness of the molten steel. In
order to obtain this effect, it is preferable that the Y content
not be less than 0.001%. If the Y content is greater than 0.20%,
workability may be deteriorated. Thus, it is preferable that the Y
content not be greater than 0.20%. It is more preferable that the Y
content not be greater than 0.10%.
[0072] REM (rare earth metal): 0.001 to 0.10%
[0073] REMs (rare earth metals: elements having atomic numbers from
57 to 71, e.g., La, Ce, and Nd) are elements that improve
high-temperature oxidation resistance. In order to obtain this
effect, it is preferable that the REM content not be less than
0.001%. It is more preferable that the REM content not be less than
0.005%. If the REM content is greater than 0.10%, surface defects
may form during hot rolling. Thus, it is preferable that the REM
content not be greater than 0.10%. It is more preferable that the
REM content not be greater than 0.05%.
[0074] Sn: 0.01 to 0.50%
[0075] Sn is effective in reducing the formation of work-induced
surface roughness composed of a deformation zone which is
inevitably induced during rolling.
[0076] In order to obtain this effect, it is preferable that the Sn
Content not be less than 0.01%. It is more preferable that the Sn
content not be less than 0.03%. If the Sn content is greater than
0.50%, workability may be deteriorated. Thus, it is preferable that
the Sn content not be greater than 0.50%. It is more preferable
that the Sn content not be greater than 0.20%.
[0077] Sb: 0.01 to 0.50%
[0078] Similarly to Sn, Sb is effective in reducing the formation
of work-induced surface roughness composed of a deformation zone
which is inevitably induced during rolling.
[0079] In order to obtain this effect, it is preferable that the Sb
content not be less than 0.01%. It is more preferable that the Sb
content not be less than 0.03%. If the Sb content is greater than
0.50%, workability may be deteriorated. Thus, it is preferable that
the Sb content not be greater than 0.50%. It is more preferable
that the Sb content not be greater than 0.20%
[0080] The balance, other than the elements described above, is Fe
and incidental impurities.
[0081] Next, a suitable method for producing the ferritic stainless
steel sheet according to aspects of the present invention will be
described. Steelmaking is performed by a known method using, for
example, a converter, an electric furnace, or a vacuum melting
furnace to obtain a steel having the chemical composition described
above. Next, secondary refining is performed by, for example, VOD
(vacuum oxygen decarburization) to control the oxygen
concentration. Thereafter, a continuous casting process or an ingot
casting-slabbing process is performed to produce a steel material
(slab). The steel material is heated to a temperature of
1000.degree. C. to 1200.degree. C. and is thereafter hot-rolled to
a sheet thickness of 2.0 mm to 5.0 mm under conditions including a
finishing temperature of 700.degree. C. to 1000.degree. C. The
hot-rolled sheet, produced in this manner, is annealed at a
temperature of 850.degree. C. to 1100.degree. C. and pickled and is
next cold-rolled and then subjected to cold-rolled-sheet annealing
at a temperature of 800.degree. C. to 1000.degree. C. After
cold-rolled-sheet annealing, pickling is performed for descaling.
The descaled cold-rolled sheet may be subjected to skin pass
rolling.
[0082] The ferritic stainless steel sheet according to aspects of
the present invention is effectively used not only as a cold-rolled
sheet product as described above, but also as a hot-rolled sheet
product. In addition, the ferritic stainless steel sheet according
to aspects of the present invention is suitable for bending.
Furthermore, the ferritic stainless steel sheet according to
aspects of the present invention is suitable for applications in
which the weld zone is processed by bending. Such a weld zone may
be formed by any welding method. Preferably, such a weld zone is
formed by TIG welding.
EXAMPLE
[0083] Examples of the present invention will be described below.
The scope of the present invention is not limited to the examples
described below.
[0084] Steelmaking was performed to produce 100-kg ingots of
ferritic stainless steels having chemical compositions shown in
Tables 1 to 5 (the balance being Fe and incidental impurities).
Thereafter, heating to a temperature of 1200.degree. C. was
performed and hot rolling was performed to obtain a hot-rolled
sheet of 3.0 mm sheet thickness. Subsequently, annealing was
performed at 1050.degree. C. and pickling was performed by a common
method. Thereafter, cold rolling was performed to a sheet thickness
of 1.0 mm, and further, annealing was performed at 900.degree. C.
and pickling was performed by a common method.
[0085] Pieces of 35 mm.times.200 mm were cut from the obtained
cold-rolled and annealed sheet, and both sides of flat surface were
dry-polished with #600 emery paper. Thereafter, the edge surface
was scraped to obtain test pieces. I-shaped groove TIG welding was
performed on the obtained test pieces to prepare welded members.
The TIG welding conditions included a welding current of 70 A, a
welding voltage of 11 V, and a welding speed of 40 cm/min. The
shielding gas used was argon, with a flow rate of 15 L/min for the
torch side and 10 L/min for the back side.
[0086] <Black Spot Exfoliation During Bending>
[0087] To evaluate black spot exfoliation during bending, bending
test pieces of 30 mm.times.200 mm, including the weld bead, were
cut from the obtained welded members. The test pieces were
subjected to 180.degree. tight bending such that the black spot
formation area was the center of bending. Only a region including
the front edge, in the bend, was cut and the front edge of the bend
was observed with an optical microscope and a scanning electron
microscope at a magnification of 120.times. and 3000.times.,
respectively. Test pieces that had no exfoliation observed through
either of the optical microscopes or the scanning electron
microscope were given a rating of ".largecircle." (pass:
excellent), test pieces that had no exfoliation observed through
the optical microscope but had exfoliation observed through the
scanning electron microscope were given a rating of ".quadrature."
(pass), and test pieces that had exfoliation observed through both
microscopes were given a rating of ".tangle-solidup." (fail). The
evaluation results are shown in the column "Exfoliation during
bending" in Tables 1 to 5.
[0088] <Corrosion Resistance of Bent Portion with Black
Spots>
[0089] To evaluate the corrosion resistance of the bent portion
with black spots, a compound cycle corrosion test was conducted on
the aforementioned bending test pieces processed by bending. The
end portions of the test piece were covered by vinyl tape, and
thereafter the test piece was placed in a testing apparatus, with
the front edge of the bent portion oriented upward in the vertical
direction. The test environment was in accordance with JASO
M609-91. One cycle was as follows: salt spray (5% NaCl), 2
h.fwdarw.drying (60.degree. C.), 4 h.fwdarw.exposure to humidity
(50.degree. C.), 2 h. Test pieces that had no outflow rust observed
after 10 cycles of the test were given a rating of ".largecircle."
(pass: excellent), test pieces that had no outflow rust observed at
the time when 5 cycles of the test were completed but had outflow
rust observed after 10 cycles of the test were given a rating of
".quadrature." (pass), and test pieces that had outflow rust
observed at the time when 5 cycles of the test were completed were
given a rating of ".tangle-solidup." (fail). The evaluation results
are shown in the column "Corrosion resistance" in Tables 1 to
5.
[0090] <Weld Penetration Characteristics>
[0091] To evaluate the characteristics of weld bead penetration in
the sheet thickness direction, the bead widths of the front bead
and the back bead of the aforementioned welded member were
measured. Then, the bead width of the front bead was divided by the
bead width of the back bead to obtain a value (bead width of front
bead/bead width of back bead value) for evaluation. Test pieces
having a value of 2 or less were given a rating of ".largecircle."
(pass: excellent), test pieces having a value of greater than 2 and
not greater than 3 were given a rating of ".quadrature." (pass),
and test pieces having a value of greater than 3 were given a
rating of ".tangle-solidup." (fail). The evaluation results are
shown in the column "Weldability" in Tables 1 to 5.
TABLE-US-00001 TABLE 1 Test Chemical composition (mass %) No. C Si
Mn P S Al Cr Ti Ca O 1 0.008 0.14 0.15 0.022 0.003 0.046 18.1 0.28
0.0004 0.0026 2 0.010 0.11 0.21 0.022 0.003 0.039 19.5 0.29 0.0005
0.0027 3 0.013 0.09 0.19 0.024 0.002 0.027 21.1 0.22 0.0003 0.0028
4 0.007 0.09 0.17 0.023 0.003 0.028 22.8 0.25 0.0004 0.0028 5 0.009
0.12 0.22 0.020 0.002 0.032 24.7 0.26 0.0004 0.0030 6 0.010 0.15
0.15 0.029 0.003 0.001 21.0 0.25 0.0003 0.0027 7 0.011 0.10 0.23
0.024 0.001 0.012 21.2 0.29 0.0004 0.0029 8 0.007 0.12 0.25 0.022
0.003 0.094 20.7 0.26 0.0005 0.0028 9 0.009 0.13 0.21 0.027 0.001
0.147 21.3 0.30 0.0004 0.0027 10 0.013 0.14 0.19 0.028 0.001 0.042
21.8 0.02 0.0004 0.0028 11 0.009 0.12 0.16 0.027 0.003 0.024 21.1
0.08 0.0004 0.0029 12 0.012 0.11 0.31 0.025 0.001 0.022 21.3 0.27
0.0005 0.0027 13 0.008 0.09 0.17 0.024 0.003 0.035 21.1 0.49 0.0005
0.0027 14 0.008 0.06 0.19 0.028 0.002 0.022 20.7 0.21 0.0004 0.0026
15 0.010 0.08 0.16 0.027 0.002 0.030 20.5 0.24 0.0001 0.0028 16
0.012 0.14 0.19 0.028 0.003 0.021 21.2 0.28 0.0005 0.0028 17 0.013
0.45 0.24 0.022 0.001 0.030 21.3 0.26 0.0003 0.0029 18 0.008 0.11
0.16 0.020 0.001 0.028 20.9 0.24 0.0001 0.0027 19 0.013 0.09 0.21
0.022 0.003 0.027 21.2 0.25 0.0002 0.0026 20 0.007 0.11 0.17 0.024
0.001 0.026 21.3 0.27 0.0009 0.0026 21 0.008 0.09 0.18 0.029 0.003
0.022 21.2 0.23 0.0015 0.0026 22 0.008 0.11 0.21 0.023 0.003 0.038
21.5 0.27 0.0003 0.0016 23 0.009 0.12 0.24 0.022 0.002 0.030 20.5
0.29 0.0003 0.0022 24 0.008 0.08 0.21 0.021 0.002 0.033 21.3 0.21
0.0001 0.0034 25 0.011 0.09 0.15 0.028 0.001 0.023 21.5 0.30 0.0002
0.0038 26 0.008 0.33 0.16 0.022 0.002 0.044 20.7 0.38 0.0008 0.0035
27 0.011 0.45 0.22 0.027 0.001 0.098 21.3 0.25 0.0013 0.0038 28
0.010 0.43 0.20 0.027 0.001 0.136 20.9 0.46 0.0014 0.0034 29 0.011
0.47 0.20 0.029 0.001 0.147 21.1 0.48 0.0013 0.0039 30 0.012 0.08
0.17 0.026 0.002 0.030 21.2 0.12 0.0002 0.0026 31 0.008 0.09 0.18
0.030 0.002 0.026 21.5 0.11 0.0005 0.0022 32 0.007 0.10 0.16 0.023
0.001 0.024 20.7 0.12 0.0002 0.0018 33 0.012 0.09 0.15 0.027 0.002
0.022 21.4 0.16 0.0002 0.0015 34 0.008 0.08 0.17 0.027 0.002 0.021
20.7 0.03 0.0003 0.0026 35 0.008 0.06 0.25 0.022 0.002 0.002 21.0
0.11 0.0001 0.0018 Chemical composition (mass %) Exfoliation Test
Other Other Other during Corrosion No. N elements (1) elements (2)
elements (3) PBI bending resistance Weldability Remarks 1 0.011 2.8
.largecircle. .largecircle. .largecircle. Invention Example 2 0.007
2.8 .largecircle. .largecircle. .largecircle. Invention Example 3
0.012 2.1 .largecircle. .largecircle. .largecircle. Invention
Example 4 0.011 2.3 .largecircle. .largecircle. .largecircle.
Invention Example 5 0.011 2.7 .largecircle. .largecircle.
.largecircle. Invention Example 6 0.008 1.9 .largecircle.
.largecircle. .largecircle. Invention Example 7 0.009 2.4
.largecircle. .largecircle. .largecircle. Invention Example 8 0.008
3.8 .largecircle. .largecircle. .largecircle. Invention Example 9
0.009 4.9 .largecircle. .largecircle. .largecircle. Invention
Example 10 0.012 1.5 .largecircle. .largecircle. .largecircle.
Invention Example 11 0.011 1.5 .largecircle. .largecircle.
.largecircle. Invention Example 12 0.011 2.3 .largecircle.
.largecircle. .largecircle. Invention Example 13 0.011 3.7
.largecircle. .largecircle. .largecircle. Invention Example 14
0.008 1.8 .largecircle. .largecircle. .largecircle. Invention
Example 15 0.009 2.2 .largecircle. .largecircle. .largecircle.
Invention Example 16 0.008 2.6 .largecircle. .largecircle.
.largecircle. Invention Example 17 0.010 3.5 .largecircle.
.largecircle. .largecircle. Invention Example 18 0.008 2.2
.largecircle. .largecircle. .largecircle. Invention Example 19
0.011 2.1 .largecircle. .largecircle. .largecircle. Invention
Example 20 0.008 2.5 .largecircle. .largecircle. .largecircle.
Invention Example 21 0.012 2.3 .largecircle. .largecircle.
.largecircle. Invention Example 22 0.011 1.5 .largecircle.
.largecircle. .largecircle. Invention Example 23 0.010 2.1
.largecircle. .largecircle. .largecircle. Invention Example 24
0.009 2.5 .largecircle. .largecircle. .largecircle. Invention
Example 25 0.012 3.3 .largecircle. .largecircle. .largecircle.
Invention Example 26 0.013 5.3 .quadrature. .largecircle.
.largecircle. Invention Example 27 0.012 6.9 .quadrature.
.largecircle. .largecircle. Invention Example 28 0.012 8.4
.largecircle. .quadrature. .largecircle. Invention Example 29 0.010
10.2 .quadrature. .quadrature. .largecircle. Invention Example 30
0.009 1.4 .largecircle. .largecircle. .quadrature. Invention
Example 31 0.008 1.2 .quadrature. .largecircle. .quadrature.
Invention Example 32 0.008 1.0 .largecircle. .quadrature.
.quadrature. Invention Example 33 0.013 0.9 .quadrature.
.largecircle. .quadrature. Invention Example 34 0.012 0.8
.largecircle. .quadrature. .quadrature. Invention Example 35 0.010
0.6 .quadrature. .quadrature. .quadrature. Invention Example
TABLE-US-00002 TABLE 2 Test Chemical composition (mass %) No. C Si
Mn P S Al Cr Ti Ca O 36 0.009 0.11 0.16 0.023 0.001 0.021 20.9 0.30
0.0004 0.0029 37 0.011 0.11 0.16 0.022 0.002 0.033 21.0 0.28 0.0002
0.0026 38 0.009 0.10 0.23 0.022 0.003 0.025 21.3 0.28 0.0003 0.0027
39 0.008 0.09 0.45 0.029 0.002 0.031 21.3 0.24 0.0004 0.0025 40
0.011 0.11 0.16 0.028 0.003 0.029 21.0 0.28 0.0003 0.0027 41 0.010
0.10 0.23 0.020 0.003 0.023 20.8 0.27 0.0002 0.0026 42 0.008 0.11
0.24 0.023 0.003 0.037 20.7 0.20 0.0001 0.0027 43 0.008 0.11 0.18
0.029 0.001 0.032 20.7 0.27 0.0003 0.0028 44 0.008 0.05 0.25 0.024
0.003 0.001 20.9 0.20 0.0001 0.0025 45 0.011 0.15 0.24 0.026 0.002
0.098 20.7 0.38 0.0014 0.0028 46 0.012 0.38 0.19 0.022 0.003 0.073
21.4 0.22 0.0012 0.0035 47 0.008 0.36 0.21 0.030 0.002 0.135 21.5
0.48 0.0005 0.0036 48 0.012 0.29 0.19 0.028 0.001 0.042 20.6 0.38
0.0003 0.0038 49 0.011 0.05 0.22 0.028 0.002 0.011 20.6 0.11 0.0002
0.0028 50 0.003 0.06 0.25 0.022 0.001 0.014 21.0 0.02 0.0003 0.0016
51 0.010 0.08 0.18 0.023 0.002 0.031 21.1 0.30 0.0001 0.0027 52
0.008 0.11 0.19 0.028 0.002 0.039 20.8 0.23 0.0005 0.0029 53 0.010
0.09 0.19 0.026 0.002 0.022 20.6 0.24 0.0003 0.0030 54 0.010 0.10
0.24 0.028 0.001 0.035 20.7 0.21 0.0005 0.0028 55 0.013 0.09 0.22
0.026 0.003 0.021 21.1 0.21 0.0004 0.0030 56 0.010 0.09 0.17 0.027
0.002 0.021 20.7 0.28 0.0002 0.0025 57 0.007 0.12 0.23 0.020 0.002
0.032 21.4 0.26 0.0004 0.0028 58 0.012 0.11 0.16 0.029 0.002 0.036
20.6 0.27 0.0005 0.0027 59 0.013 0.11 0.17 0.027 0.001 0.020 20.5
0.21 0.0003 0.0028 60 0.012 0.11 0.23 0.029 0.001 0.037 21.3 0.30
0.0002 0.0028 61 0.012 0.09 0.23 0.023 0.001 0.021 21.4 0.22 0.0004
0.0028 62 0.011 0.12 0.24 0.021 0.002 0.025 21.1 0.27 0.0002 0.0027
63 0.008 0.10 0.19 0.020 0.002 0.039 21.1 0.26 0.0002 0.0028 64
0.009 0.08 0.20 0.028 0.001 0.027 21.4 0.23 0.0003 0.0030 65 0.010
0.09 0.20 0.023 0.003 0.033 20.7 0.20 0.0004 0.0026 66 0.007 0.11
0.16 0.025 0.001 0.030 20.6 0.20 0.0001 0.0026 67 0.011 0.11 0.24
0.023 0.003 0.026 20.7 0.25 0.0004 0.0029 Chemical composition
(mass %) Exfoliation Test Other Other Other during Corrosion No. N
elements (1) elements (2) elements (3) PBI bending resistance
Weldability Remarks 36 0.009 Zr: 0.01 2.9 .largecircle.
.largecircle. .largecircle. Invention Example 37 0.012 Zr: 0.02 2.9
.largecircle. .largecircle. .largecircle. Invention Example 38
0.008 Zr: 0.03 3.2 .largecircle. .largecircle. .largecircle.
Invention Example 39 0.013 Zr: 0.05 3.3 .largecircle. .largecircle.
.largecircle. Invention Example 40 0.007 Zr: 0.09 4.9 .largecircle.
.largecircle. .largecircle. Invention Example 41 0.010 Zr: 0.15 6.1
.quadrature. .largecircle. .largecircle. Invention Example 42 0.011
Zr: 0.28 9.7 .largecircle. .quadrature. .largecircle. Invention
Example 43 0.012 Zr: 0.49 16.3 .quadrature. .quadrature.
.largecircle. Invention Example 44 0.010 Zr: 0.75 19.9 .quadrature.
.quadrature. .largecircle. Invention Example 45 0.009 Zr: 0.16 9.5
.quadrature. .largecircle. .largecircle. Invention Example 46 0.007
Zr: 0.22 12.9 .quadrature. .quadrature. .largecircle. Invention
Example 47 0.011 Zr: 0.25 17.4 .quadrature. .quadrature.
.largecircle. Invention Example 48 0.013 Zr: 0.38 19.7 .quadrature.
.quadrature. .largecircle. Invention Example 49 0.012 Zr: 0.01 1.3
.quadrature. .largecircle. .quadrature. Invention Example 50 0.002
Zr: 0.02 0.7 .quadrature. .largecircle. .quadrature. Invention
Example 51 0.012 Nb: 0.12 2.5 .largecircle. .largecircle.
.largecircle. Invention Example 52 0.008 Nb: 0.05 2.6 .largecircle.
.largecircle. .largecircle. Invention Example 53 0.012 V: 0.08 2.3
.largecircle. .largecircle. .largecircle. Invention Example 54
0.012 V: 0.03 2.3 .largecircle. .largecircle. .largecircle.
Invention Example 55 0.009 Zr: 0.06, Nb: 0.08 3.9 .largecircle.
.largecircle. .largecircle. Invention Example 56 0.009 Zr: 0.09,
Nb: 0.03 4.3 .largecircle. .largecircle. .largecircle. Invention
Example 57 0.012 Zr: 0.04, V: 0.09 3.7 .largecircle. .largecircle.
.largecircle. Invention Example 58 0.010 Zr: 0.07, V: 0.14 4.5
.largecircle. .largecircle. .largecircle. Invention Example 59
0.008 Zr: 0.03, Nb: 0.06, 2.8 .largecircle. .largecircle.
.largecircle. Invention Example V: 0.05 60 0.010 Zr: 0.06, Nb:
0.13, 4.5 .largecircle. .largecircle. .largecircle. Invention
Example V: 0.03 61 0.012 Cu: 0.40 2.0 .largecircle. .largecircle.
.largecircle. Invention Example 62 0.010 Ni: 0.25 2.3 .largecircle.
.largecircle. .largecircle. Invention Example 63 0.012 Co: 0.14,
Mo: 2.6 .largecircle. .largecircle. .largecircle. Invention Example
0.31, W: 0.18 64 0.007 B: 0.0013 2.3 .largecircle. .largecircle.
.largecircle. Invention Example 65 0.012 Mg: 0.0022 2.0
.largecircle. .largecircle. .largecircle. Invention Example 66
0.012 Sn: 0.01 1.9 .largecircle. .largecircle. .largecircle.
Invention Example 67 0.012 Y: 0.02, La: 2.4 .largecircle.
.largecircle. .largecircle. Invention Example 0.03, Sb: 0.01
TABLE-US-00003 TABLE 3 Test Chemical composition (mass %) No. C Si
Mn P S Al Cr Ti Ca O 68 0.013 0.12 0.23 0.021 0.002 0.040 21.2 0.28
0.0003 0.0029 69 0.011 0.11 0.24 0.022 0.002 0.035 20.6 0.20 0.0003
0.0026 70 0.008 0.09 0.16 0.030 0.002 0.033 21.0 0.24 0.0004 0.0026
71 0.011 0.10 0.23 0.025 0.003 0.027 21.5 0.23 0.0003 0.0025 72
0.010 0.08 0.21 0.026 0.001 0.023 20.8 0.22 0.0002 0.0028 73 0.012
0.11 0.25 0.021 0.002 0.039 21.3 0.27 0.0003 0.0027 74 0.011 0.11
0.20 0.021 0.002 0.028 20.8 0.29 0.0005 0.0025 75 0.012 0.10 0.19
0.021 0.001 0.039 20.9 0.21 0.0004 0.0029 76 0.012 0.09 0.23 0.027
0.002 0.033 20.8 0.24 0.0002 0.0026 77 0.010 0.08 0.16 0.028 0.003
0.027 21.4 0.25 0.0002 0.0027 78 0.011 0.09 0.24 0.026 0.002 0.020
20.9 0.27 0.0004 0.0025 79 0.011 0.08 0.17 0.024 0.003 0.024 20.9
0.29 0.0002 0.0027 80 0.008 0.12 0.16 0.025 0.001 0.036 20.7 0.21
0.0004 0.0027 81 0.013 0.08 0.17 0.026 0.002 0.033 21.3 0.21 0.0001
0.0030 82 0.010 0.09 0.24 0.024 0.002 0.020 21.2 0.20 0.0003 0.0030
83 0.009 0.10 0.19 0.029 0.003 0.032 20.9 0.24 0.0002 0.0030 84
0.011 0.08 0.20 0.027 0.002 0.030 20.8 0.27 0.0002 0.0025 85 0.012
0.12 0.24 0.029 0.002 0.032 21.3 0.22 0.0003 0.0030 86 0.008 0.11
0.24 0.020 0.002 0.021 20.7 0.21 0.0002 0.0027 87 0.012 0.12 0.23
0.020 0.003 0.034 20.5 0.26 0.0001 0.0027 88 0.010 0.10 0.22 0.025
0.001 0.024 21.0 0.27 0.0003 0.0027 89 0.013 0.10 0.25 0.020 0.003
0.028 21.3 0.23 0.0002 0.0029 90 0.009 0.11 0.22 0.030 0.001 0.027
21.0 0.20 0.0002 0.0028 91 0.011 0.12 0.19 0.021 0.002 0.034 20.5
0.22 0.0003 0.0028 92 0.011 0.09 0.23 0.024 0.001 0.029 21.4 0.28
0.0002 0.0025 93 0.010 0.08 0.16 0.024 0.003 0.025 21.1 0.26 0.0002
0.0026 94 0.008 0.10 0.23 0.021 0.003 0.027 21.1 0.24 0.0004 0.0027
95 0.008 0.10 0.16 0.021 0.003 0.022 21.1 0.30 0.0004 0.0028 96
0.010 0.09 0.21 0.022 0.002 0.020 20.5 0.30 0.0001 0.0028 Chemical
composition (mass %) Exfoliation Test Other Other Other during
Corrosion No. N elements (1) elements (2) elements (3) PBI bending
resistance Weldability Remarks 68 0.009 Zr: 0.05 Co: 0.10 4.3
.largecircle. .largecircle. .largecircle. Invention Example 69
0.008 Zr: 0.10 Cu: 0.43 4.7 .largecircle. .largecircle.
.largecircle. Invention Example 70 0.012 Zr: 0.09 Cu: 0.31, Mo:
0.52 4.6 .largecircle. .largecircle. .largecircle. Invention
Example 71 0.011 Nb: 0.14 W: 0.19 2.0 .largecircle. .largecircle.
.largecircle. Invention Example 72 0.007 Nb: 0.10 Cu: 0.45 2.0
.largecircle. .largecircle. .largecircle. Invention Example 73
0.011 Nb: 0.33 Ni: 0.12, Co: 0.45 2.6 .largecircle. .largecircle.
.largecircle. Invention Example 74 0.011 V: 0.08 Ni: 0.22 2.4
.largecircle. .largecircle. .largecircle. Invention Example 75
0.008 V: 0.09 Cu: 0.80 2.5 .largecircle. .largecircle.
.largecircle. Invention Example 76 0.012 V: 0.25 Cu: 0.44, Ni:
0.15, 2.2 .largecircle. .largecircle. .largecircle. Invention
Example W: 0.28 77 0.009 Zr: 0.04, Nb: 0.14 Mo: 0.52 3.2
.largecircle. .largecircle. .largecircle. Invention Example 78
0.009 Zr: 0.06, Nb: 0.11 Cu: 0.40 3.6 .largecircle. .largecircle.
.largecircle. Invention Example 79 0.013 Zr: 0.07, Nb: 0.11 Co:
0.14, Mo: 0.48 4.2 .largecircle. .largecircle. .largecircle.
Invention Example 80 0.007 Zr: 0.03 Cu: 0.42 3.1 .largecircle.
.largecircle. .largecircle. Invention Example 81 0.008 Zr: 0.05 Cu:
0.40, W: 0.11 3.7 .largecircle. .largecircle. .largecircle.
Invention Example 82 0.011 Zr: 0.09, Nb: 0.07, Ni: 0.23 4.7
.largecircle. .largecircle. .largecircle. Invention Example V: 0.07
83 0.008 Zr: 0.03, Nb: 0.13, Cu: 0.71 3.4 .largecircle.
.largecircle. .largecircle. Invention Example V: 0.06 84 0.012 Zr:
0.07, Nb: 0.08, Cu: 0.45, 3.9 .largecircle. .largecircle.
.largecircle. Invention Example V: 0.09 Ni: 0.12 85 0.012 Zr: 0.04
B: 0.0017 3.7 .largecircle. .largecircle. .largecircle. Invention
Example 86 0.009 Zr: 0.09 Y: 0.046, 4.3 .largecircle. .largecircle.
.largecircle. Invention Example La: 0.020 87 0.008 Nb: 0.12 Mg:
0.0016 2.4 .largecircle. .largecircle. .largecircle. Invention
Example 88 0.010 Nb: 0.13 Sn: 0.19, 2.3 .largecircle. .largecircle.
.largecircle. Invention Example Sb: 0.12 89 0.007 V: 0.07 Y: 0.028
2.3 .largecircle. .largecircle. .largecircle. Invention Example 90
0.013 V: 0.08 Mg: 0.0015, 2.0 .largecircle. .largecircle.
.largecircle. Invention Example La: 0.035 91 0.009 Zr: 0.06, Nb:
0.08 Ce: 0.027 4.0 .largecircle. .largecircle. .largecircle.
Invention Example 92 0.010 Zr: 0.10, Nb: 0.11 B: 0.0010, 4.7
.largecircle. .largecircle. .largecircle. Invention Example Y:
0.048 93 0.009 Zr: 0.08, V: 0.05 Sn: 0.19 4.2 .largecircle.
.largecircle. .largecircle. Invention Example 94 0.009 Zr: 0.10, V:
0.06 B: 0.0023 4.9 .largecircle. .largecircle. .largecircle.
Invention Example Mg: 0.0012 95 0.011 Zr: 0.08, Nb: 0.11, Sb: 0.04
4.8 .largecircle. .largecircle. .largecircle. Invention Example V:
0.07 96 0.010 Zr: 0.07, Nb: 0.13, Mg: 0.0030, 4.3 .largecircle.
.largecircle. .largecircle. Invention Example V: 0.05 Sn: 0.09
TABLE-US-00004 TABLE 4 Test Chemical composition (mass %) No. C Si
Mn P S Al Cr Ti Ca O 97 0.009 0.12 0.21 0.021 0.003 0.029 21.4 0.27
0.0002 0.0029 98 0.012 0.08 0.22 0.024 0.003 0.027 20.6 0.28 0.0001
0.0028 99 0.009 0.08 0.21 0.026 0.001 0.039 20.7 0.23 0.0005 0.0027
100 0.009 0.09 0.16 0.022 0.001 0.021 20.5 0.20 0.0004 0.0026 101
0.007 0.08 0.20 0.021 0.003 0.034 21.5 0.27 0.0005 0.0026 102 0.012
0.10 0.16 0.022 0.001 0.024 21.0 0.20 0.0004 0.0025 103 0.007 0.10
0.19 0.027 0.003 0.039 21.2 0.20 0.0001 0.0027 104 0.012 0.11 0.18
0.020 0.002 0.038 20.8 0.29 0.0003 0.0030 105 0.012 0.12 0.16 0.026
0.002 0.030 20.9 0.29 0.0002 0.0025 106 0.008 0.10 0.24 0.028 0.001
0.029 21.5 0.28 0.0003 0.0027 107 0.008 0.08 0.15 0.021 0.002 0.022
20.8 0.23 0.0004 0.0030 108 0.009 0.12 0.21 0.029 0.001 0.026 21.3
0.22 0.0005 0.0027 109 0.009 0.11 0.22 0.029 0.003 0.025 21.1 0.29
0.0002 0.0028 110 0.008 0.10 0.18 0.030 0.001 0.033 20.5 0.26
0.0004 0.0025 111 0.012 0.12 0.18 0.028 0.001 0.028 21.5 0.20
0.0004 0.0029 112 0.012 0.09 0.23 0.028 0.002 0.024 21.1 0.30
0.0005 0.0027 113 0.009 0.09 0.25 0.022 0.002 0.034 20.6 0.26
0.0004 0.0027 114 0.009 0.10 0.18 0.027 0.001 0.030 21.2 0.22
0.0003 0.0029 115 0.010 0.09 0.17 0.025 0.002 0.028 20.7 0.21
0.0002 0.0027 Chemical composition (mass %) Exfoliation Test Other
Other Other during Corrosion No. N elements (1) elements (2)
elements (3) PBI bending resistance Weldability Remarks 97 0.011
Cu: 0.40 B: 0.0014 2.6 .largecircle. .largecircle. .largecircle.
Invention Example 98 0.009 Ni: 0.18, Mg: 0.0025, 2.4 .largecircle.
.largecircle. .largecircle. Invention Example W: 0.30 Y: 0.052 99
0.011 Zr: 0.07 Co: 0.13 Mg: 0.0021 4.3 .largecircle. .largecircle.
.largecircle. Invention Example 100 0.008 Zr: 0.10 Cu: 0.42 Sb:
0.13 4.4 .largecircle. .largecircle. .largecircle. Invention
Example 101 0.010 Zr: 0.10 Ni: 0.22, B: 0.0028, 5.0 .largecircle.
.largecircle. .largecircle. Invention Example Mo: 0.48 Ce: 0.027,
Sn: 0.14 102 0.008 Nb: 0.12 Mo: 0.34 Y: 0.062 1.8 .largecircle.
.largecircle. .largecircle. Invention Example 103 0.009 Nb: 0.13
Cu: 0.65 Mg: 0.0020 2.1 .largecircle. .largecircle. .largecircle.
Invention Example 104 0.010 Nb: 0.06 Cu: 0.43, B: 0.0018, 3.0
.largecircle. .largecircle. .largecircle. Invention Example Co:
0.11, Sn: 0.14 W: 0.27 105 0.008 V: 0.06 W: 0.16 Y: 0.062 2.3
.largecircle. .largecircle. .largecircle. Invention Example 106
0.008 V: 0.10 Cu: 0.43 Mg: 0.0020 2.4 .largecircle. .largecircle.
.largecircle. Invention Example 107 0.011 V: 0.09 Ni: 0.16, B:
0.0016, 2.2 .largecircle. .largecircle. .largecircle. Invention
Example Co: 0.14, Mg: 0.00018, Mo: 0.39 Y: 0.072 108 0.010 Zr:
0.04, Nb: 0.14 Cu: 0.44 Sn: 0.16 3.3 .largecircle. .largecircle.
.largecircle. Invention Example 109 0.009 Zr: 0.08, Co: 0.11, Mg:
0.0022, 4.7 .largecircle. .largecircle. .largecircle. Invention
Example Nb: 0.07 W: 0.28 Y: 0.048, La: 0.023 110 0.009 Zr: 0.09, V:
0.07 Ni: 0.17 Sb: 0.02 4.5 .largecircle. .largecircle.
.largecircle. Invention Example 111 0.008 Zr: 0.07, V: 0.09 Cu:
0.48 B: 0.0024 4.3 .largecircle. .largecircle. .largecircle.
Invention Example 112 0.010 Zr: 0.04, V: 0.06 Cu: 0.41, Y: 0.026,
3.6 .largecircle. .largecircle. .largecircle. Invention Example Mo:
0.34 Sn: 0.13 113 0.013 Zr: 0.04, Nb: 0.10, Mo: 0.57 Mg: 0.0023 3.5
.largecircle. .largecircle. .largecircle. Invention Example V: 0.07
114 0.008 Zr: 0.04, Nb: 0.11, Cu: 0.30 B: 0.0014 3.4 .largecircle.
.largecircle. .largecircle. Invention Example V: 0.08 115 0.012 Zr:
0.06, Nb: 0.05, Cu: 0.44, Y: 0.088, 3.6 .largecircle. .largecircle.
.largecircle. Invention Example V: 0.07 Ni: 0.22, Sn: 0.15, Co:
0.15 Sb: 0.21
TABLE-US-00005 TABLE 5 Test Chemical composition (mass %) No. C Si
Mn P S Al Cr Ti Ca O 116 0.010 0.11 0.24 0.020 0.003 0.155 21.1
0.24 0.0001 0.0026 117 0.009 0.12 0.19 0.025 0.002 0.029 16.5 0.25
0.0003 0.0026 118 0.011 0.11 0.18 0.020 0.002 0.022 20.8 0.53
0.0002 0.0030 119 0.008 0.22 0.18 0.020 0.002 0.038 21.1 -- 0.0004
0.0029 120 0.013 0.54 0.22 0.030 0.002 0.033 20.5 0.13 0.0004
0.0028 121 0.012 0.11 0.18 0.028 0.002 0.035 21.1 0.29 0.0018
0.0029 122 0.011 0.14 0.18 0.020 0.001 0.098 18.8 0.20 0.0001
0.0056 123 0.008 0.14 0.20 0.021 0.003 0.026 21.1 0.11 0.0001
0.0069 124 0.009 0.06 0.18 0.029 0.002 0.011 21.4 0.16 0.0003
0.0008 125 0.013 0.11 0.18 0.024 0.002 0.040 20.8 0.26 0.0010
0.0014 126 0.010 0.15 0.21 0.024 0.002 0.047 21.5 0.17 0.0003
0.0028 127 0.009 0.08 0.15 0.023 0.001 0.031 21.1 0.10 0.0005
0.0015 128 0.013 0.15 0.22 0.025 0.001 0.036 20.8 0.22 0.0010
0.0029 129 0.008 0.49 0.17 0.023 0.003 0.134 21.5 0.48 0.0012
0.0038 130 0.002 0.08 0.23 0.029 0.001 0.002 20.5 0.03 0.0001
0.0016 131 0.012 0.06 0.25 0.026 0.001 0.005 21.4 0.08 0.0002
0.0015 132 0.008 0.05 0.16 0.020 0.003 0.004 20.6 0.05 0.0004
0.0018 Chemical composition (mass %) Other Other Other Exfoliation
Test elements elements elements during Corrosion No. N (1) (2) (3)
PBI bending resistance Weldability Remarks 116 0.011 4.4
.tangle-solidup. .tangle-solidup. .largecircle. Comparative Example
117 0.009 2.2 .largecircle. .tangle-solidup. .largecircle.
Comparative Example 118 0.010 Zr: 0.01 4.4 .tangle-solidup.
.tangle-solidup. .largecircle. Comparative Example 119 0.007 1.6
.largecircle. .tangle-solidup. .largecircle. Comparative Example
120 0.009 3.0 .tangle-solidup. .tangle-solidup. .largecircle.
Comparative Example 121 0.008 Zr: 0.01 3.7 .tangle-solidup.
.tangle-solidup. .largecircle. Comparative Example 122 0.009 6.9
.tangle-solidup. .tangle-solidup. .largecircle. Comparative Example
123 0.007 3.8 .tangle-solidup. .tangle-solidup. .largecircle.
Comparative Example 124 0.012 Zr: 0.04 0.7 .quadrature.
.largecircle. .tangle-solidup. Comparative Example 125 0.010 1.5
.largecircle. .largecircle. .tangle-solidup. Comparative Example
126 0.027 2.4 .largecircle. .tangle-solidup. .largecircle.
Comparative Example 127 0.008 Zr: 0.82 13.1 .tangle-solidup.
.tangle-solidup. .largecircle. Comparative Example 128 0.010 Zr:
0.65 21.7 .tangle-solidup. .tangle-solidup. .largecircle.
Comparative Example 129 0.011 Zr: 0.32 21.8 .tangle-solidup.
.tangle-solidup. .largecircle. Comparative Example 130 0.001 0.3
.largecircle. .largecircle. .tangle-solidup. Comparative Example
131 0.010 0.4 .quadrature. .largecircle. .tangle-solidup.
Comparative Example 132 0.008 0.4 .largecircle. .quadrature.
.tangle-solidup. Comparative Example
[0092] The results obtained are shown in Tables 1 to 5. Invention
Examples were evaluated as "pass" for all "Exfoliation during
bending", "Corrosion resistance", and "Weldability". Furthermore,
Invention Examples having a PSI value of 1.5 or greater and 5.0 or
less, of all the Invention Examples, were excellent because the
examples had a rating of ".largecircle." for all of the following:
evaluation of black spot exfoliation during bending; corrosion
resistance of the black spot formation area after bending; and
characteristics of weld bead penetration in the sheet thickness
direction. That is, it is seen that, in those examples, no black
spots exfoliated during bending of the weld bead and thus corrosion
resistance was excellent, and further the weld bead easily
penetrated.
[0093] In Comparative Examples of Test Nos. 116, 118, 120 to 123
and 127, the contents of Al, Ti, Si, Ca, O, and Zr were each above
the range in the present invention. As a result, black spots
exfoliated during bending and the regions after such exfoliation
had low corrosion resistance.
[0094] In Comparative Examples of Test Nos. 117 and 119, the
contents of Cr and Ti were each below the range in the present
invention. As a result, although no black spots exfoliated during
bending, the regions including black spots had low corrosion
resistance.
[0095] In Comparative Examples of Test Nos. 124 and 125, the
content of O (oxygen) was below the range in the present invention.
As a result, characteristics of weld bead penetration were
poor.
[0096] In Comparative Example of Test No. 126, the content of N was
above the range in the present invention. As a result, although no
black spots exfoliated during bending, the regions including black
spots had low corrosion resistance.
[0097] In Comparative Examples of Test Nos. 128 and 129, the
contents of the elements were within the ranges in the present
invention respectively, but the PBI value of each was greater than
20.0. As a result, black spots exfoliated during bending and the
regions after such exfoliation had low corrosion resistance.
[0098] In Comparative Examples of Test Nos. 130 to 132, the
contents of the elements were within the ranges in the present
invention respectively, but the PBI value of each was less than
0.5. As a result, characteristics of weld bead penetration were
poor.
INDUSTRIAL APPLICABILITY
[0099] The stainless steel sheet according to aspects of the
present invention has excellent characteristics of weld bead
penetration, has low susceptibility to exfoliation, during bending,
of black spots that form during welding, and has low susceptibility
to occurrence of crevice corrosion due to exfoliation of black
spots. Thus, the ferritic stainless steel sheet according to
aspects of the present invention is suitable for elevator inner
panels, interiors, duct hoods, muffler cutters, lockers, home
appliance parts, office equipment parts, automotive interior parts,
automotive exhaust pipes, building materials, drain covers, marine
transport containers, vessels, kitchen equipment, building interior
and exterior materials, automotive parts, escalators, railway
vehicles, and electrical device housing panels, for example.
* * * * *