JP2002275595A - Ferritic stainless steel sheet having excellent ridging resistance and deep drawability and method of manufacturing for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ferritic stainless steel sheet having excellent ridging resistance and deep drawability without entailing an increase of a steel making cost and degradation in the productivity of a hot rolled steel strip and a method of manufacturing for the same. SOLUTION: This stainless steel contains, by mass %, <=0.10 C, 10.0 to 20.0% Cr and further a prescribed amount of Si, Mn, In, Ti, etc., and consists of the balance substantially Fe. In addition, the γmax defined by equation (1) is >=20 to <80 and the ratio of the large angular grain boundaries at which the deviation in the bearings of the adjacent crystal grains among the grain boundaries of the rolled surface at a depth half the depth of the sheet-metal gage is >=90%. The steel has formula (2). Formula (1): γmax=420-11.5Si+7Mn+23Ni-11.5Cr-12Mo+9Cu-49Ti-50Nb-52Al+470N+189. Formula (2): X/Y>=5, where X is the area of the crystal grains within 5 deg. of the deviation from the 111} face of the rolled surface at the depth half the depth of the sheet-metal gage and Y is the area of the crystal grains within 5 deg. of the deviation from the 100} face of the rolled surface at the depth half the depth of the sheet-metal gage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to parts of household equipment such as sinks, various appliances and stove burners, and parts of industrial equipment such as fuel tanks, oil supply pipes, motor cases, covers and flanges. The present invention relates to a ferritic stainless steel sheet excellent in ridging resistance and deep drawing workability mainly used for press working and a method for producing the steel sheet. The steel sheet in the present invention includes a steel sheet and a steel strip.

[0002]

2. Description of the Related Art A ferritic stainless steel represented by SUS430 has a good corrosion resistance and is expensive.
It is widely used, especially in durable consumer goods, because it does not contain iron and has economic advantages as compared with austenitic stainless steel. However, in recent years, in press forming of stainless steel, severer processing is often performed, and a ferritic stainless steel sheet having more excellent workability is demanded.

[0003] The workability of ferritic stainless steel sheet is as follows.
Generally, it is inferior to austenitic stainless steel, and has a unique wrinkle-like surface irregularity called ridging at the time of press forming. Therefore, if the press workability and ridging resistance of ferritic stainless steel are improved, the less expensive ferritic stainless steel that was conventionally difficult to apply to places where austenitic stainless steel was used due to severe workability. Stainless steel can be used.

It is known that the press formability of ferritic stainless steel depends on the r-value. As an index indicating the r value, r indicating an average r value is used. Many techniques for improving the r value have been tried so far. For example, Japanese Patent Application Laid-Open No. 53-48018 proposes a technique in which C and N are reduced as much as possible, and the r value is improved by adding one or both of Ti and Nb. However, this technique requires a long time for refining to reduce C and N, and expensive Ti and N
Since the raw material cost becomes high due to the addition of b, the cost of steelmaking increases.

In order to improve the ridging property, a technique using so-called delay rolling in which the material is temporarily made to stand by during rolling to increase the time between passes is proposed in, for example, Japanese Patent Application Laid-Open No. 62-197721. Have been. However, the above-mentioned technique is a method of giving a large distortion in a low temperature region, so that a biting failure or a shape failure is caused,
This causes an increase in the rolling time and a decrease in productivity. Therefore, it is hardly an economical method.

[0006]

SUMMARY OF THE INVENTION The present invention has been devised in order to solve such a problem, and can be performed by press working without increasing steelmaking cost or reducing productivity of hot-rolled steel strip. It is an object of the present invention to propose a ferritic stainless steel having a required deep drawability and a satisfactory ridging resistance, and a working heat treatment technique after hot rolling that can exhibit such properties.

[0007]

The ferritic stainless steel having excellent ridging resistance and deep drawability according to the present invention has a C content of 0.1% by mass in order to achieve the object.
0% or less, Si: 1.5% or less, Mn: 1.0% or less,
P: 0.050% or less, S: 0.015% or less, Ni:
2.0% or less, Cr: 10.0 to 20.0%, Al:
0.10% or less, N: 0.05% or less, and if necessary, Ti: 0.05% or less, Nb: 0.05%
Hereinafter, Mo: 1.0% or less, Cu: 1.0% or less, B:
0.0010 to 0.0100% of one or more kinds, the balance being Fe and unavoidable impurities, and γmax defined by the formula (5) is 20 or more and less than 80. The ratio of the large-angle grain boundaries in which the misorientation of adjacent crystal grains is 15 ° or more in the grain boundaries of the rolled surface at a depth of １ ／ of the thickness is 90% or more.
It is characterized by having equation (6).

Formula (5) γmax = 420C-11.5Si + 7Mn + 23Ni-11.5Cr-12Mo + 9Cu-49Ti-5
0Nb-52Al + 470N + 189 Equation (6) X / Y ≧ 5, where X is {11} of the rolled surface at a half depth of the plate thickness.
Y is the area of the crystal grains whose deviation from the 1｝ plane is within 5 °, and Y is the area of the crystal grains whose deviation from the {100} plane of the rolling plane at a half depth of the plate thickness is within 5 °.

In order to achieve the object, the production method of the present invention is characterized in that, when producing the above ferritic stainless steel, a steel slab composed of the components described in each section is subjected to hot rolling through hot rolling. When producing a cold-rolled steel sheet or a steel strip by combining cold rolling and annealing with a hot-rolled steel strip, a hot-rolled steel strip is heated to a two-phase region of ferrite and austenite at a temperature of _{1 to} 1100 ° C. After performing phase annealing in a continuous annealing furnace, further perform intermediate cold rolling at a rolling reduction of 10% or more and 50% or less, and then perform annealing in a box furnace, and perform finish cold rolling and recrystallization annealing. It is characterized by the following.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS To solve the above-mentioned problems, the present inventors have developed a deep drawing and ridging resistance of a ferritic stainless steel sheet without increasing steelmaking cost and productivity of a hot-rolled steel strip. The alloy composition, the metal structure, and the thermomechanical treatment after hot rolling have been studied in detail. In addition, the selected materials were subjected to press working, and the characteristics required for press working were investigated. as a result,
The hot-rolled sheet is annealed with two or more phases of Ac at _one point or more, and the obtained (ferrite + martensite) two-phase structure is processed by cold rolling, followed by annealing in a box furnace.
It has been found that the ferritic stainless steel sheet subjected to finish cold rolling and recrystallization annealing has remarkably improved ridging resistance and deep drawability. In addition, characteristics required for press working were clarified. The present invention has been completed based on this finding. Hereinafter, embodiments of the invention will be described based on experimental results.

Using a hot-rolled sheet having a chemical composition shown in steel type A in Table 1 and having a thickness of 4 mm and having a thickness of 4 mm, a hot-rolled sheet → double-phase annealing (1050 ° C. × soaking at 0 sec) → intermediately Cold rolling → intermediate annealing (830 ° C. × soaking 9 hours) → finish cold rolling → finish annealing was performed to obtain an annealed sheet having a thickness of 0.8 mm. Here, the cold rolling reduction distribution of the intermediate rolling and the finish rolling was changed. Further, the above-described hot rolled sheet is produced by a conventional production method, that is,
Hot rolled sheet → Hot rolled sheet annealing (830 ° C x 9hr) → Finish cold rolling → Finish annealing (one time cold rolling annealing) and hot rolled sheet → Hot rolled sheet annealing (830 ° C x 9hr) → Intermediate cold rolling → Intermediate annealing → Finish cold rolling → Finish annealing (twice cold rolling annealing).

[0012]

A test piece was sampled from the annealed plate manufactured in the above process, and the r value was measured, ridging was judged, and the EBSP method (El
ectron Backscattering Pattern) and press working test. Note that r and Δr are r = (r _L + 2r _D + r _T ) / 4 and Δr =
(R _L -2r _D + r _T ) / 2. However, r _L , r _D and r _T are respectively 45 degrees with respect to the rolling direction and the rolling direction.
The r value in the 90 ° direction with respect to the ° direction and the rolling direction is shown. In addition, the determination of ridging resistance was made such that A had the best ridging resistance and D had the lowest ridging resistance.
A, B, C, and D were evaluated in four steps. Table 2 shows criteria for ridging resistance.

[0014]

In the crystal orientation distribution measurement by the EBSP method, the crystal orientation distribution in the range of 500 μm in the rolling direction and 800 μm in the width direction is measured for each steel sheet with respect to a rolled sheet at a half depth of the sheet thickness. Based on the obtained data, the ratio of the large-angle grain boundaries in which the deviation of the orientation of adjacent crystal grains is 15 ° or more and (the area of the crystal grains whose deviation from the {111} plane is within 5 °) / (｛100 (｝) The area of the crystal grains whose deviation from the plane is within 5 °) was analyzed.

In the pressing test, a square cylinder having a punch size of 200 mm × 270 mm, a drawing depth of 100 mm, and a die shoulder radius of 10 mm was drawn. It was determined. Table 3 shows r and Δ
The influence of the cold rolling reduction of intermediate rolling and finish rolling on the results of r, ridging judgment, crystal distribution analysis by the EBSP method, and the press working test is shown.

[0017]

As shown in Table 3, there is a good correspondence that the ridging resistance is improved when the ratio of the large-angle grain boundaries is large. Generally, the occurrence of ridging is caused by a group (colonies) of crystal grains having a close crystal orientation existing in the cold-rolled annealed sheet. The origin of the colony is that coarse unrecrystallized ferrite grains extending in the rolling direction, formed by solidification columnar crystals remaining after hot rolling annealing, disperse the crystal orientation due to recrystallization even during annealing after cold rolling. Due to their small size, colonies are formed. The colony has an apparently fine crystal structure inside, but when subjected to plastic deformation such as press molding due to the small dispersion of the crystal orientation, the colony deforms like a large single crystal, and the plastic deformation of each colony changes. Ridging occurs due to the difference in anisotropy.

Here, the crystal grain boundaries inside the colony have small deviations in the orientation of adjacent crystals, and very few large angle boundaries with deviations of 15 ° or more. In other words, a steel sheet having a small proportion of large-angle grain boundaries has a large colony formation and ridging, whereas a large proportion of large-angle grain boundaries has a small formation of colonies that cause ridging of the steel sheet and has a small ridging resistance. In particular, when the ratio of large-angle grain boundaries is 90% or more, ridging is reduced, and sufficient ridging resistance of ridging judgment B or more is obtained.

Also, {111} is a good surface for deep drawing.
There is a {100} plane as a plane that has an adverse effect on the r value, and the order of the good surface and the area that adversely affects the thickness center makes it possible to clearly determine the superiority of the r value. That is,
(Area of crystal grain whose deviation from the {111} plane of the rolled surface at a half depth of the plate thickness is within 5 °) / (from the {100} plane of the rolled surface at a half depth of the plate thickness) The area of the crystal grains having a deviation of 5 ° or less) corresponds well to r. In particular, the tendency becomes remarkable when the area of {111} plane / area of {100} plane is 5 or more, and r is 1.4 or more. Become. In Table 3,
In the press molding test, the area of {111} plane / area of {100} plane is 5 or more, while the area of {111} plane / area of {100} plane is smaller than 5. The sample had insufficient deep drawability and severe cracking occurred during pressing.

However, in the case of the twice cold-rolled annealed material of the conventional method, the area of {111} plane / area of {100} plane is 5.
5 and r is sufficiently high at 1.40, but cracks occur in the press working test. In this steel sheet, the ratio of the large-angle grain boundaries in which the misorientation of the adjacent crystal grains in the crystal grain boundaries is 15 ° or more is relatively low at 81%, and the ridging resistance is low.
Since Δr indicating the value anisotropy was large, cracks occurred at the corners. In other words, even if the {111} texture has developed, large-angle grain boundaries have few colonies,
Satisfactory press formability was not obtained, and it became clear that the area of {111} face / area of {100} face was 5 or more, and the ratio of large-angle grain boundaries was 90% or more.

The reason why the deep drawing property and the ridging resistance are improved in the production method in which the dual phase annealing is performed is considered as follows. First, when a hot-rolled sheet of ferritic stainless steel is subjected to dual-phase annealing at _one or more Ac points, a (ferrite + martensite) two-phase structure is obtained. Since the ferrite phase is much softer than the martensite phase, strain is accumulated in the ferrite phase when processed by intermediate rolling. By subjecting this to long-term annealing in a box furnace, the martensite phase sufficiently precipitates carbides and recrystallizes into a ferrite phase, and at the same time promotes recrystallization of a ferrite phase in which very strain is accumulated. . At this time, recrystallization of coarse ferrite grains derived from solidified columnar crystals that cause ridging is also promoted, the crystal orientation of the recrystallized grains is greatly dispersed, colony formation is inhibited, and the ratio of large angle grain boundaries Increase.

In Table 3, as the intermediate rolling reduction after the dual-phase annealing in the production method of the present invention increases, the ratio of the large-angle grain boundaries in which the misorientation of adjacent crystal grains is 15 ° or more in the crystal grain boundaries increases. Increased results and improved ridging resistance also support this. In addition, since the formation of colonies is inhibited after box-shaped annealing, the formation of colonies of {100}, which lowers the r value that is likely to remain in the normal process, is small, and the subsequent finish rolling and finish annealing are effective for r values. {111}
The texture develops, the {111} plane area / {100} plane area is 5 or more, and the ratio of large-angle grain boundaries is 90%.
The above steel sheet could be manufactured.

Next, the reasons for limiting the components, characteristics, and manufacturing conditions of the ferritic stainless steel of the present invention will be described.
In the following description, all percentages indicate mass%. C: 0.10% or less C is an alloying element exhibiting an effect of increasing γmax. In the two-phase structure (ferrite + martensite) obtained after the dual-phase annealing, a sufficient amount of martensite and its hardness Works effectively to get However, since it is a component that increases the strength after cold rolling annealing, and if it is contained excessively, it reduces the ductility, so the upper limit of the C content is 0.10.
%.

Si: 1.5% or less Si is an alloy component added as a deoxidizing agent during steel making, but has a high solid solution strengthening ability, and if contained excessively, hardens the material and lowers ductility. The upper limit of the content is 1.
It was set to 5%. Mn: 1.0% or less Mn is an austenite-forming element and can be used for controlling γmax. Further, since the solid solution strengthening ability is small, the effect of hardening the material is small. However, if contained excessively, it has an adverse effect such as formation of Mn-based fume during welding, so the upper limit of the content was set to 1.0%.

P: 0.005% or less P lowers hot workability in accordance with its content, so the upper limit of the content was made 0.005%. S: 0.015% or less S, if its content increases, segregates at the crystal grain boundaries and embrittles the crystal grain boundaries, so the upper limit of the content is 0.015%.
Set to. Ni: 2.0% or less Ni is an austenite forming element like Mn, and γ
It can be used for max control. However, an excessive content of Ni also leads to an increase in cost. Therefore, the upper limit of the content is set to 2.0%.

Cr: 10.0 to 20.0% In order to obtain corrosion resistance as stainless steel, Cr is added to 10.10% .
It is necessary to contain 0% or more. However, when the Cr content is increased, the toughness and workability are reduced, so the content is set to 20.0% or less. Al: 0.10% or less Al is an alloy component added as a deoxidizing agent during steelmaking, but excessive addition increases nonmetallic inclusions and causes toughness reduction and surface defects. The upper limit of the amount is 0.
10%.

N: 0.05% or less N is an element exhibiting an effect of increasing γmax similarly to C, increases austenite generated at the time of dual phase annealing, works effectively for microstructure formation, and has ridging resistance. Improve. However, since it is a component that increases the strength after cold rolling annealing, and if contained excessively, it reduces the ductility, the upper limit of the content is set to 0.05%. Ti: 0.05% or less Ti is an element that fixes C and N and improves workability. However, addition of Ti causes an increase in steel material cost. Therefore, the upper limit of the content is 0.05%. And

Nb: 0.05% or less Nb is an element that fixes C and N and improves workability. However, the addition of Nb causes an increase in steel material cost. Therefore, the upper limit of the content is 0%. 0.05%. Mo: 1.0% or less Mo is an element added as necessary and contributes to improvement of corrosion resistance. However, when Mo is added in excess,
Since the hot workability decreases, the upper limit of the content is 1.0.
%.

Cu: 1.0% or less Cu is a component mixed from scrap or the like at the time of smelting, and if its content increases, it adversely affects hot workability and corrosion resistance, so the upper limit is 1.0%. I do. B: 0.0010 to 0.0100% B is an element added as necessary, and has an effect of uniformly dispersing the transformed phase of the hot-rolled sheet and improving ridging resistance. The effect of adding B becomes remarkable at a content of 0.0010% or more, but an excessive addition exceeding 0.0100% causes a reduction in hot workability and weldability.

Γmax: 20 or more and less than 80 In the present invention, annealing is performed by heating the hot-rolled sheet to a two-phase region of ferrite + austenite having _one or more Ac points by a continuous annealing furnace to obtain a two-phase structure of ferrite + martensite. It is characterized by the effective use of dual-phase annealing. Therefore, in the present invention, the definition of γmax is an important matter. That is, if γmax is less than 20, the amount of martensite obtained in the dual-phase annealing is small, sufficient strain is not accumulated in the ferrite phase in the intermediate rolling step, and recrystallization of the ferrite band is not promoted. No improvement in r value and ridging resistance can be obtained. On the other hand, in order to increase γmax, it is necessary to increase the content of austenite-forming elements such as C, N, Mn, and Ni. However, since these increase the hardness of steel and increase the cost, γmax is increased.
Must be less than 80.

Double-phase annealing temperature: Ac ₁ point to 1100 ° C. At a high temperature, a two-phase structure of ferrite + austenite is obtained.
In order to obtain a two-phase structure of ferrite + martensite after the annealing for multiple phases, it is essential to perform annealing at a temperature of at least _one point of Ac. However, when annealing is performed at a temperature exceeding 1100 ° C., the crystal grain size becomes coarse, and furthermore,
The risk of cutting the steel sheet due to the decrease in high-temperature strength increases. Therefore, the temperature of the dual-phase annealing is ₁ point or more of Ac 1100
It should be in the range of ℃ or less.

Intermediate cold rolling reduction : 10 to 50% In intermediate rolling after dual-phase annealing, strain is accumulated in the ferrite phase, but at a rolling reduction of less than 10%, the effect cannot be obtained. If intermediate rolling exceeding 50% is performed, the rolling reduction in finish rolling is reduced, and the development of an effective texture for the r value cannot be obtained. Therefore, the rolling reduction in intermediate rolling is set to 10% or more and 50% or less. . In addition, intermediate annealing requires long-time annealing to recrystallize martensite into carbide and ferrite, and if it is to be manufactured in a continuous annealing furnace, it is very inefficient and not economical.
Long-time annealing using a box-type annealing furnace.

Ratio of large-angle grain boundaries: 90% or more, from the rolled surface
In the pressing of ferritic stainless steel sheets, r indicating an average r value has been used as a factor indicating the workability of the ferrite stainless steel sheet. However, in actual press working,
Even if the r value is high, a material having a large Δr and a large anisotropy or a material in which ridging is remarkably generated often cannot be processed. A preferable material in actual press working is a material having small anisotropy and having both deep drawability and ridging resistance. From the results of the preliminary evaluation shown in FIG. 1, in order to satisfy these characteristics, the proportion of the large-angle grain boundaries in which the misorientation of adjacent crystal grains is 15 ° or more in the crystal grain boundaries is 90% or more. (The area of the crystal grains whose deviation from the {111} plane of the rolled surface at a half depth of the plate thickness is within 5 °) / ({100} of the rolled surface at a half depth of the plate thickness)
(Area of crystal grains whose deviation from the plane is within 5 °) is defined as 5 or more.

[0035]

EXAMPLE Steels having the chemical compositions shown in Table 1, B, C, D, and E were smelted to form slabs, and a sheet thickness of 4.0 was obtained by a hot rolling mill.
mm hot rolled sheet. As a production method of subjecting this hot-rolled sheet to dual-phase annealing, a dual-phase annealing temperature and an intermediate rolling rate shown in Table 4 are applied, and the hot-rolled sheet → double-phase annealing → intermediate rolling → intermediate annealing → finish Rolling → finish annealing was performed to obtain an annealed plate having a thickness of 0.8 mm. In addition, the above-described hot rolled sheet is manufactured by a conventional method,
That is, hot-rolled sheet → hot-rolled sheet annealing (830 ° C. × soaking for 9 hours)
r) Finish cold rolling → Finish annealing (manufacturing method of one time cold rolling annealing) and hot rolled sheet → Hot rolled sheet annealing (830 ° C x 9 hours soaking)
r) → intermediate cold rolling → intermediate annealing → finish cold rolling → finish annealing (manufacturing method of twice cold rolling annealing).

Using the steel sheet obtained by the above method as a test material, r, Δr and ridging resistance were measured by the following methods. r value : After applying a 15% tensile strain using a JIS No. 13B test piece, r _L , r _D and r _T were determined. r _L , r _D and r _T are 45 ° with respect to the rolling direction and the rolling direction, respectively.
The r value in the direction at 90 ° to the direction and the rolling direction is shown.
From the r value obtained by the above method, r and Δr are r = (r
_{L + 2r D + r T)} / 4, Δr = (r L -2r D + r T) / 2
Determined by

Ridging resistance : JI sampled from the rolling direction
After giving 20% tensile strain to the S5 test piece, ridging resistance was determined. The determination of ridging resistance was made on the basis of A, B, C, and D, with A having the best ridging resistance and D having the worst ridging resistance.

Press working test : punch size is 200
A rectangular tube having a size of 270 mm x 270 mm, a drawing depth of 100 mm, and a die shoulder radius of 10 mm was drawn. Measurement of crystal orientation distribution : The EBSP method was used to measure the rolled surface at a plate thickness of 深 depth over a range of 500 μm in the rolling direction and 800 μm in the width direction.

Table 4 also shows the characteristic values obtained under each of the above-described methods for producing steel having each chemical composition and each of the production conditions.
Further, among the grain boundaries of each steel sheet, the ratio of large-angle grain boundaries in which the direction shift of adjacent crystal grains is 15 ° or more and (お よ び 1
(Area of crystal grains whose deviation from 11 ° plane is within 5 °) /
(Area of crystal grains within 5 ° deviation from {100} plane)
FIG. 1 shows the relationship between the value of and the result of the press working test. All of those satisfying the requirements described in the claims of the present invention were satisfactory without any problems such as cracks even in the press working test. However, when the dual-phase annealing temperature was lower than the Ac ₁ point temperature and the intermediate rolling reduction was less than 10%, cracks occurred during press working.

[0040]

[0041]

As described above, according to the present invention, it is possible to increase the cost of steelmaking and reduce the productivity of hot-rolled steel strips without causing the loss of household appliances such as sinks, various appliances and burners for stoves. For parts of industrial equipment such as parts, fuel tanks, oil supply pipes, motor cases, covers, and flanges, it is possible to produce ferritic stainless steel sheets excellent in deep drawability and ridging resistance that are mainly used for press working.

[Brief description of the drawings]

FIG. 1 shows the ratio of large-angle grain boundaries in which the direction of adjacent crystal grains in a grain boundary of each steel sheet has a deviation of 15 ° or more and the area of crystal grains in which the deviation from the {111} plane is within 5 °. )
FIG. 6 is a diagram showing the relationship between the value of / (area of crystal grains whose deviation from {100} plane is within 5 °) and press workability (including examples, comparative examples, and conventional examples).

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yasutoshi Kunitake 4976 Nomura Minamicho, Shinnanyo-shi, Yamaguchi Prefecture F-term (reference) 4N037 EA01 EA02 EA04 EA05 EA12 EA13 EA15 EA17 EA18 EA19 EA20 EA23 EA25 EA27 EA28 EA31 EB06 EB07 EB08 EB09 FF03 FG03 FH03 FM01 FM04

Claims (3)

[Claims] C. 0.10% or less by mass%, Si:
1.5% or less, Mn: 1.0% or less, P: 0.050%
Hereinafter, S: 0.015% or less, Ni: 2.0% or less, C
r: 10.0 to 20.0%, Al: 0.10% or less,
N: 0.05% or less, the balance being Fe and unavoidable impurities, and γma defined by the formula (1).
x is 20 or more and less than 80, and the ratio of the large-angle grain boundaries in which the deviation of the orientation of adjacent crystal grains is 15 ° or more among the grain boundaries on the rolled surface at a half depth of the sheet thickness is 90%. A ferritic stainless steel sheet excellent in ridging resistance and deep drawability, characterized by satisfying the expression (2). Equation (1) γmax = 420C-11.5Si + 7Mn + 23Ni-11.5Cr-52Al + 470N + 189 Equation (2) X / Y ≧ 5, where X is {11 of the rolled surface at half the plate thickness.
Y is the area of the crystal grains whose deviation from the {1} plane is within 5 °, and Y is the area of the crystal grains whose deviation from the {100} plane of the rolling plane at a half depth of the plate thickness is within 5 °. 2. In mass%, C: 0.10% or less, Si:
1.5% or less, Mn: 1.0% or less, P: 0.050%
Hereinafter, S: 0.015% or less, Ni: 2.0% or less, C
r: 10.0 to 20.0%, Al: 0.10% or less,
N: 0.05% or less, and further, Ti: 0.05%
%, Nb: 0.05% or less, Mo: 1.0% or less,
Cu: 1.0% or less, B: 0.0010 to 0.0100
% Or more, and the balance consists of Fe and unavoidable impurities, and γm defined by the formula (3).
ax is not less than 20 and less than 80, and is １ ／ of the plate thickness.
90% of the large-angle grain boundaries in which the misorientation of adjacent crystal grains is 15 ° or more in the grain boundaries on the rolled surface having a depth of 90%
A ferritic stainless steel sheet excellent in ridging resistance and deep drawability, characterized by satisfying the formula (4). Formula (3) γmax = 420C-11.5Si + 7Mn + 23Ni-11.5Cr-12Mo + 9Cu-49Ti-5
0Nb-52Al + 470N + 189 Formula (4) X / Y ≧ 5 where X is {11 of the rolled surface at half the plate thickness.
Y is the area of the crystal grains whose deviation from the 1｝ plane is within 5 °, and Y is the area of the crystal grains whose deviation from the {100} plane of the rolling plane at a half depth of the plate thickness is within 5 °. 3. In producing the ferritic stainless steel according to claim 1 or 2, a steel slab composed of the components described in each item is formed into a hot-rolled steel strip through hot rolling. When a cold-rolled steel sheet or steel strip is manufactured by combining rolling and annealing, the hot-rolled steel strip is made of _one or more points of Ac.
After performing the dual-phase annealing of heating to the two-phase region of ferrite + austenite of 0 ° C or less by a continuous annealing furnace, further performing intermediate cold rolling at a rolling reduction of 10% or more and 50% or less,
Thereafter, a method of producing a ferritic stainless steel sheet having excellent ridging resistance and deep drawability, wherein annealing is performed in a box furnace, and finish cold rolling and recrystallization annealing are performed.