KR101301440B1 - method of manufacturing ferritic stainless steel with improved formability and ridging property - Google Patents

Abstract

The present invention is in weight percent, C: greater than 0, 0.10% or less, Si: greater than 0, 1.0% or less, Mn: greater than 0, 1.0% or less, P: greater than 0, 0.050% or less, S: greater than 0, 0.020%, less than Ni: 0 More than 2.0% or less, Cr: 8.0 to 30%, Cu: greater than 0% or less 1.0%, Ti: 0.01 to 0.50%, Nb: 0.01 to 0.50%, Al greater than 0% 0.10%, N: greater than 0% and 0.05% or less And optionally one or more of Mo: more than 0% and less than 1.0%, V: 0.01% to 0.30%, Zr: 0.01% to 0.30%, and B: 0.0010% to 0.0100%, and the rest are made of Fe and other unavoidable impurities. In the conventional method, the hot rolled hot rolled sheet is annealed at a temperature of 900 to 1100 ° C. or the hot rolled sheet is annealed, and then cold rolling and subsequent annealing are performed twice, respectively. It is cold rolled with the above and final cold rolling reduction ratio of 76% or more to provide a ferritic stainless steel having excellent ridging property and formability, and a manufacturing method thereof.

Ferrite, Stainless Steel, Leasing, Formability, EBSD, Crystal Orientation Area Ratio

Description

{Method of manufacturing ferritic stainless steel with improved formability and ridging property}

The present invention relates to a ferritic stainless steel and a method of manufacturing the same, and in particular to a ferritic stainless steel and its manufacturing method for improving the formability and leasing properties by controlling the texture by using a reduction ratio in the production of cold-rolled stainless steel sheet will be.

In general, ferritic stainless steel is mainly used in automobile exhaust system parts, building materials, kitchen containers, home appliances, etc., and is manufactured by forming a part by deep drawing, which is one of the important quality characteristics. It is also important to reduce the occurrence of ridging defects formed on the surface after molding.

The r value, which is an index indicating the formability of the ferritic stainless steel, has a close correlation with the formation of the texture. As the {111} orientation develops well, the r value is large and the formability is improved. On the other hand, when {001} is formed, the r value is lowered, resulting in poor moldability.

On the other hand, ferritic stainless steel has wrinkled surface defects parallel to the rolling direction during molding, which is called ridging. The cause of leasing is mainly caused by the coarse casting structure, i.e., when the casting structure remains in the coarse band structure without being destroyed in the rolling or annealing process, the width and thickness direction deformation are different from the recrystallization structure around the tensile process. It is expressed by the dissolution of behavior.

Such ridging defects not only degrade the appearance of the product, but also cause necking during molding, thereby degrading the formability. In addition, if ridging is severe, an additional polishing step is required after molding, which may cause an increase in manufacturing cost of the final product.

Many researchers have proposed various manufacturing methods for improving the formability and ridging properties of ferritic stainless steel.

Basically, as disclosed in Sawatani's research report (Nippon Steel Tech. Rep. 21 (1983), p.275), there is a method to improve the ridging property by reducing the fraction of columnar tablets by improving the equiaxed crystal ratio. . This isotropic rate control is a method of solving the root cause causing the leasing, the lower limit of the equiaxed rate should be 60% level in order to obtain a steel sheet excellent in ridging resistance by ordinary rolling.

In addition, as a representative example of improving moldability and suppressing leasing by controlling process variables in the manufacturing process, hot rolling temperature is controlled to promote recrystallization (Japanese Patent Laid-Open Publication No. 2000-256748), or hot rolling rough rolling rate is controlled (Japan JP2000-256749) or controlling the hot rolling reduction rate (Japanese Laid-Open Patent No. 1994-271944) and the like are known. In addition, various methods have been known, such as the optimization of annealing temperature or the like (Japanese Patent Laid-Open No. 1983-199822) or the addition of an intermediate annealing process during cold rolling to increase the number of re-crystallization recrystallization (Japanese Patent Laid-Open No. 1989-118341).

Recently, Japanese Patent Application Laid-Open No. 2005-256124 and the like have been known as a parameter patent on the correlation between the strength of crystal orientation components and manufacturing process factors in relation to control of texture.

As described above, in order to improve the formability and the ridging property, it is important not only to improve the casting structure such as slab equiaxed rate but also to control the texture by controlling the manufacturing process variables. In particular, the polishing is performed to remove the ridging generated after the deep drawing molding, but when the ridging height is different for each direction, a problem arises in that the polishing time is lengthened to remove the severely generated ridging. Therefore, it is necessary to uniformly reduce the ridging height of each direction in order to reduce the polishing time of the molded article.

Accordingly, the present invention has been made in accordance with the above requirements, in order to improve the formability of the final cold-rolled material and to lower the ridging height for each direction, the cold rolling total rolling rate and the final cold rolling rate are adjusted in two cold rolling and annealing. The purpose of the present invention is to provide a method for producing ferritic stainless steel which improves moldability and leasing properties while improving the texture.

One aspect of the present invention for achieving the above object is performed by annealing the hot-rolled steel sheet hot-rolled ferritic stainless steel at a temperature of 900 ~ 1100 ℃ or omitting the hot-rolled sheet annealing, followed by cold rolling and subsequent annealing twice In the method of manufacturing a ferritic stainless steel, the present invention provides a method for producing ferritic stainless steel having excellent ridging property and formability which is cold rolled at a cold rolling total reduction rate of 89% or more and a final cold rolling reduction rate of 76% or more. .

Further, in the present invention, the ferritic stainless steel has an r value of 1.7 or more and less than 3.0 for each tissue direction, and a r-bar value of 1.9 or more and less than 3.0 for each tissue direction.

In addition, the leaching height of the ferritic stainless steel in the present invention is 10㎛ or less.

In the present invention, the ridging height is a ridging height measured by a tensile test in a direction of 0 degrees and 45 degrees with respect to the rolling direction.

Further, in the present invention, the ferritic stainless steel has an area ratio of {111} <uvw> / {001} <110> and {111} <uvw> / {001} <100> measured by EBSD attached to a scanning electron microscope. Provided is a method for producing ferritic stainless steel having excellent ridging property and formability of 30 or more.

Another aspect of the invention is to provide a ferritic stainless steel produced by any one of the above methods. The present invention is in weight percent, C: greater than 0, 0.10% or less, Si: greater than 0, 1.0% or less, Mn: greater than 0, 1.0% or less, P: greater than 0, 0.050% or less, S: greater than 0, 0.020%, less than Ni: 0 More than 2.0% or less, Cr: 8.0 to 30%, Cu: greater than 0% or less 1.0%, Ti: 0.01 to 0.50%, Nb: 0.01 to 0.50%, Al greater than 0% 0.10%, N: greater than 0% and 0.05% or less And optionally one or more of Mo: more than 0% and less than 1.0%, V: 0.01% to 0.30%, Zr: 0.01% to 0.30%, and B: 0.0010% to 0.0100%, and the rest are made of Fe and other unavoidable impurities. A ferritic stainless steel having excellent ridging property and moldability can be obtained.

Further, in the present invention, the ferritic stainless steel has an r value of 1.7 or more and less than 3.0 for each tissue direction, and a r-bar value of 1.9 or more and less than 3.0 for each tissue direction.

In addition, the leaching height of the ferritic stainless steel in the present invention is 10㎛ or less, which is the ridging height measured by the tensile test in the direction of 0 degrees and 45 degrees with respect to the rolling direction.

In addition, the ferritic stainless steel of the present invention has an area ratio of {111} <uvw> / {001} <110> and {111} <uvw> / {001} <100> measured by EBSD attached to a scanning electron microscope. That's all.

As described above, the ferritic stainless steel production method provided by the present invention optimally controls the cold rolling total pressure reduction rate, that is, performing cold rolling and subsequent annealing twice, that is, the cold rolling total pressure reduction rate is 89% or more. However, if the final cold rolling reduction rate is carried out at 76% or more to control the texture of the structure, the r value of each direction can be improved and at the same time, the effect of significantly lowering the ridging height of the surface stripe shape generated during the molding of the product can be expected. This leasing improvement can reduce the manufacturing cost by reducing the polishing process time of the final product.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

In the present invention, by weight% C: greater than 0, 0.10% or less, Si: greater than 0, 1.0% or less, Mn: greater than 0, 1.0% or less, P: greater than 0, 0.050% or less, S: greater than 0, 0.020%, less than Ni: greater than 0 2.0% or less, Cr: 8.0 to 30%, Cu: greater than 0% or less, Ti: 0.01 to 0.50%, Nb: 0.01 to 0.50%, Al greater than 0.10%, N: greater than 0% and 0.05% or less Optionally, a ferritic stainless steel further containing one or two or more of Mo: more than 1.0%, V: 0.01 to 0.30%, Zr: 0.01 to 0.30%, and B: 0.0010 to 0.0100% can be obtained. The reason for the limited composition range for the ferritic stainless steel of the present invention is as follows.

Since C is an element that forms carbide and is present in an invasive form, excessively high content causes an increase in strength but deterioration of impact toughness, corrosion resistance and formability. Therefore, the content is preferably 0.1% by weight or less.

Si is an effective element for improving the oxidation resistance and corrosion resistance, and when the dilution increases, the oxidation resistance is improved, but the elongation is lowered, resulting in the deterioration of moldability. Therefore, the content is preferably 1.0% by weight or less.

If the content of Mn is high, MnS elutes and lowers the corrosion resistance.

P and S decrease the pitting resistance and hot workability as their content increases, so P is preferably 0.050% by weight or less and S is 0.020% by weight or less.

Ni is an element that improves the corrosion resistance, and if it is added in a large amount, it is preferable not only to harden but also to cause stress corrosion cracking.

If the content of Cr is small, the corrosion resistance is lowered. If the content is large, the corrosion resistance is improved, but the elongation is lowered and the moldability is worsened. Therefore, the content is preferably 8.0% by weight to 30.0% by weight.

Cu may contain more than 0% and less than 1.0% to improve corrosion resistance. However, if it exceeds 1%, there is a problem that workability is lowered.

Ti and Nb are elements that are effective in improving corrosion resistance and formability by depositing solid solution C and N as carbonitrides. However, when a large amount is added, appearance defects and toughness due to inclusions are reduced. Therefore, it is preferable to add 0.01-0.50%.

Al is an element added as a deoxidizer, and when it is added in a large amount, it is preferable to limit it to 0.10% by weight or less.

Since N is an element that forms nitride and is present in an invasive form, excessively contained N increases strength, but causes impact toughness, corrosion resistance and moldability deterioration. Therefore, the content is preferably 0.05% by weight or less.

Mo is an element added in order to improve corrosion resistance, especially corrosion resistance. However, when a large amount is added, it is preferable to add 1.0% or less since workability is lowered.

V and Zr are elements added to fix C and N. It is an element added especially when the precipitation of Cr carbonitride in a weld part is suppressed and corrosion resistance is improved and high temperature strength is needed. Since it is expensive, it is preferable to add 0.01-0.30%.

B segregates at the grain boundaries and enhances the grain strength, thereby improving secondary processing brittleness. However, if a large amount is added, the hot workability is lowered, so it is preferable to add 0.0010 to 0.01%.

In the present invention, after hot-rolled hot rolled stainless steel sheet having the composition described above in a conventional manner at 900 to 1100 ° C. or omitting the hot-rolled sheet annealing, and then performing cold rolling and subsequent annealing twice, respectively. For ferritic stainless steels produced by cold rolling with a total rolling reduction rate of 89% or more and a final cold rolling rate of 76% or more, the r value in each direction is 1.7 or more, the r-bar value is 1.9 or more, and 0 degrees in the rolling direction. Rising grade after tensile test in 45 ° direction is Grade 1 and measured by EBSD attached to scanning electron microscope {111} <uvw> / {001} <110> and {111} <uvw> / {001} <100 It is a manufacturing method of the ferritic stainless steel characterized by the above-mentioned.

1 is a graph showing the result of calculating the r value for each direction of a specific crystal orientation.

Usually, the mechanism of leasing is reported to be due to the difference in plastic anisotropy between grain group or band structure with low r value {001} crystal orientation and matrix with high r value {111} <uvw> crystal orientation. . As shown in FIG. 1, the r values of the {001} <110> and {001} <100> crystal directions vary depending on the direction. {001} <110> has the lowest r value in the 0 degree direction with respect to the rolling direction, and {001} <100> has the lowest r value in the 45 degree direction. Therefore, when grain group or band structure having {001} <110> crystal orientation exists, the difference in r value between {001} <110> and {111} <uvw> becomes large when it is deformed in the 0 degree direction. Becomes the highest. On the other hand, in the presence of grain groups or band tissues having a {001} <100> crystal orientation, the difference between r values between {001} <100> and {111} <uvw> when deforming in the 45 degree direction is increased. The height is the highest.

On the other hand, depending on the total rolling rate during cold rolling, the final cold rolling rate, and the number of rolling, the texture is changed. That is, the fractions of {001} <110>, {001} <100>, and {111} <uvw> crystal directions are changed. Lowering the fraction of the {001} <110> and {001} <100> crystal orientations and increasing the fraction of the {111} <uvw> crystal orientations may not only improve the ridging but also improve the formability.

The present invention is a result of examining the correlation between the total rolling reduction rate, the final cold rolling reduction rate and the number of rolls and the formation of the texture structure during cold rolling, by uniformly adjusting the cold rolling process parameters to improve the texture structure uniformly to the ridging height for each direction In addition to reducing, the r value of each direction is increased to improve moldability.

In the present invention, a method for measuring the area ratio of {001} <110>, {001} <100>, and {111} <uvw> crystal orientations will be described. The crystal orientation analysis program by EBSD (Electron Back Scatter Diffraction) measured using an Orientation Image Microscopy (OIM) apparatus attached to a scanning electron microscope (SEM) was used. FIG. 2 shows the area ratio of crystal grains having {001} <110>, {001} <100>, and {111} <uvw> crystal orientations measured by EBSD. Here, the area ratio of each crystal orientation means the area ratio of gray grains. As can be seen in FIG. 2, the area ratio of the crystal grains having the {001} <110> crystal orientation is about 2.9. This is the value obtained under repressurization, and in the case of {001} <100>, it is shown as 3.8 when the forging is performed. On the other hand, it can be seen that the area ratio of the crystal grains having the {111} <uvw> crystal orientation is 47.9. In this case, lowering the fraction of {001} <110> and {001} <100> crystal orientations and increasing the fraction of {111} <uvw> crystal orientations may not only improve leasing but also formability.

(Example)

The present invention will be described using the following examples.

Several commercially produced ferritic stainless steels were used in the experiment. Cold rolling and annealing were performed from a 4-5 mm thick hot rolled sheet hot rolled from a continuously cast slab. From the results of microstructure and texture analysis using EBSD attached to the SEM, the area ratio of grains having a specific crystal orientation was measured.

To measure the r value, the plastic anisotropy index, cut the specimen in 0, 45, and 90 degrees with respect to the rolling direction, process the tensile specimen, measure 15% of tensile strain, and measure the width change before and after the tensile test. Calculated using.

r = ε _w / ε _t = -ln (W _f / W _o ) / (ln ((W _f / W _o ) + ln (1.15))

(ε _w : strain in width direction, ε _t : strain in thickness direction, W _f : width after tensile test W _o : width before tensile test)

In order to evaluate the leasing, the specimens were cut in the directions of 0 and 45 degrees with respect to the rolling direction, the tensile specimens were processed, and 15% tensile deformation was used to measure the ridging height by measuring the roughness with a surface roughness. The measured ridding height is 6 grades (1 grade: 10 μm or less, 2 grades: 10 μm or more and 14 μm or less, 3 grades: 14 μm or more and 18 μm or less, 4 grades: 18 μm or more and 22 μm or less, 5 grade: 22 μm) Greater than 26 μm or less, and grade 6: greater than 26 μm).

Table 1 shows the thickness and rolling rate of the cold rolled annealing plate according to the cold rolling conditions of the ferritic stainless steel used in this example.

division number Thickness (mm) Cold rolling rate (%) Remarks Hot rolled Primary cold rolled steel Secondary cold rolled steel Primary Secondary gun Hot rolled
Annealing Recompression A 5.0 2.3 0.5 54.0 78.3 90.0 Honor B 5.0 2.3 0.5 54.0 78.3 90.0 Honor C 5.0 2.3 0.5 54.0 78.3 90.0 Honor D 5.0 2.3 0.5 54.0 78.3 90.0 Honor E 4.5 2.0 0.5 55.6 75.0 88.9 Comparative Example F 4.5 1.9 0.5 58.7 73.1 88.9 Comparative Example G 4.5 1.5 0.5 66.7 66.7 88.9 Comparative Example H 4.0 1.5 0.5 62.5 66.7 87.5 Comparative Example I 4.0 1.5 0.5 62.5 66.7 87.5 Comparative Example Pressure J 5.0 0.5 90.0 Comparative Example K 4.5 0.5 88.9 Comparative Example L 4.3 0.5 88.4 Comparative Example Hot rolled
Annealing Recompression M 5.0 2.3 0.5 54.0 78.3 90.0 Honor N 5.0 2.3 0.5 54.0 78.3 90.0 Honor Pressure O 5.0 0.5 90.0 Comparative Example

As the invention example and the comparative example are contrasted in the above Table 1, in the present invention, either hot-rolled annealing or hot-rolled annealing is possible, but cold rolling is preferably a repressurization condition which is performed twice each. In the case of repressurizing the steel sheet subjected to hot-rolling annealing, the cold rolling reduction rate will be described. As for the value shown to the said invention examples A-D, the rolling reduction in a primary is 54% and 55% or less. Or in the invention example, the secondary, ie final reduction, is 78.3%. In comparison with the comparison, it is preferable to be 76% or more. Moreover, although the cold rolling total pressure reduction rate is 90%, compared with a comparative example, it is preferable to set it as 89% or more. Therefore, the preferred reduction ratio for controlling the texture in the present invention is the initial pressure reduction rate of 89% or more, the final cold rolling rate is 76% or more. Meanwhile, in the present invention, even in the case of hot-annealed annealing steel, the same value as in the case of hot-annealed annealing steel can be obtained. (Invention Examples M, N) In the case of conventional re-pressurization, the final cold rolling rate is less than 75%.

Next, Table 2 shows the r value, the ridging height, and the ridging grade of the cold rolled annealing plate according to the cold rolling conditions.

number r value Leasing Height (Rt, ㎛) Leasing Class Remarks 0 45 90 r-bar dr 0 45 0 45 A 2.42 1.70 2.47 2.07 0.75 7.3 9.5 One One Honor B 2.14 1.82 2.55 2.08 0.53 8.9 9.1 One One Honor C 2.21 2.03 2.67 2.23 0.41 9.4 9.7 One One Honor D 2.16 1.87 2.54 2.11 0.48 7.9 9.3 One One Honor E 2.26 1.44 2.36 1.88 0.87 8.4 10.5 One 2 Comparative Example F 2.26 1.44 2.40 1.89 0.89 8.5 11.3 One 2 Comparative Example G 2.24 1.29 2.47 1.82 1.06 8.3 12.0 One 2 Comparative Example H 1.89 1.33 2.43 1.74 0.83 9.7 12.1 One 2 Comparative Example I 2.11 1.45 2.54 1.89 0.88 9.6 11.6 One 2 Comparative Example J 1.60 1.93 1.97 1.86 -0.15 10.1 8.9 2 One Comparative Example K 1.60 1.61 1.76 1.64 0.07 12.5 8.7 2 One Comparative Example L 1.53 1.70 1.79 1.68 -0.05 13.9 10.5 2 2 Comparative Example M 2.06 1.96 2.51 2.12 0.32 9.9 7.1 One One Honor N 2.29 1.83 2.42 2.09 0.53 7.9 8.7 One One Honor O 1.08 2.06 1.66 1.71 -0.69 21.0 8.8 4 One Comparative Example

As can be seen from the table, in the case of A, B, C, D and M, N of the present invention, it can be seen that the minimum value of the r value for each direction is 1.7. In addition, for the r-bar value, the minimum value is 2.07. However, in comparison with other comparative examples, it can be seen that the r-bar value is preferably 1.9 or more. It turns out that it comes out as above. Further, in the present invention, the leasing height was obtained as the first grade, up to 9.9.

Table 3 shows the results of measuring the area ratio of the crystal grains having a specific orientation.

number Crystal orientation area ratio (%) Remarks {111} <uvw> / {001} <100> {111} <uvw> / {001} <110> A 35.4 51.1 Honor B 70.3 30.1 Honor C 95.8 43.5 Honor D 83.2 32.0 Honor E 22.8 82.0 Comparative Example F 24.1 51.1 Comparative Example G 12.1 50.3 Comparative Example H 26.3 43.8 Comparative Example I 28.8 31.0 Comparative Example J 154.3 27.2 Comparative Example K 79.4 22.1 Comparative Example L 137.3 24.2 Comparative Example M 63.0 38.8 Honor N 55.9 44.7 Honor O 164.5 8.7 Comparative Example

In the case of A, B, C, and D, which are the invention examples of Table 3, the ratio of the area ratio of {111} <uvw> / {001} <100> appears to be at least 35.4 to at most 154.3. In addition, in the case of the invention examples M and N, the area ratio ratio of {111} <uvw> / {001} <110> is shown as minimum 30.1 to maximum 82.0.

3a and b show the r value and the ridging height for each direction of the ferritic stainless steel used in this embodiment. 3 shows an inverse correlation between the r value for each direction and the ridging height. In other words, when the r value in the 0 degree direction is low, the ridging height in the 0 degree direction is high, and when the r value in the 45 degree direction is low, the ridging height in the 45 degree direction is high. Therefore, 1.7 or more in which the difference of r value in 0 degree and 45 degree direction is small is a range of this invention. This corresponds to the value of the invention example shown in Table 2 above. 3B shows the ridging height for each direction. In the present invention, the difference between the ridging heights in the 0 and 45 degree directions is set to 10 or less.

On the other hand, Figure 4 a, b is the r value for each direction according to the ratio of the area ratio of each crystal orientation, Figure 4a is a value when 0 degrees, 4b is 45 degrees, Figure 4c is a ratio of the area ratio of each crystal orientation at 0 degrees Figure 4d shows the ridging height according to the ratio of the area ratio of each crystal orientation at 45 o'clock. In the present invention, in order to satisfy good moldability and ridging characteristics, an r value of 1.7 or more and a ridging height of 10 µm or less are required. In order to satisfy the above conditions, the area ratio ratio of {111} <uvw> / {001} <110> and {111} <uvw> / {001} <100> should be 30 or more. In the present invention, the above conditions must be satisfied in both the 0 degree and 45 degree directions, but the scope of the present invention in FIG. 4 indicates a range in which both conditions are satisfied.

As a result, in the present invention, when cold rolling and subsequent annealing are performed twice, it is understood that the present invention can obtain the desired effect only by cold rolling so that the total cold rolling reduction rate is at least 89% and the final cold rolling reduction ratio is at least 76%. Can be.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a graph showing a result of calculating r value for each direction of a specific crystal orientation.

2 is a graph showing the area ratio of crystal grains having {001} <110>, {001} <100>, and {111} <uvw> crystal orientations measured by EBSD.

Figure 3a is a graph showing the r value for each direction of the ferritic stainless steel used in the present invention.

Figure 3b is a graph showing the ridging height of the ferritic stainless steel used in the present invention.

4a to d are graphs showing the r value and the ridging height of each direction according to the area ratio ratio of each crystal orientation of the ferritic stainless steel used in the present embodiment.

Claims (8)

As a method for producing a ferritic stainless steel, annealing the hot-rolled steel sheet hot-rolled ferritic stainless steel to a temperature of 900 ~ 1100 ℃ or omitting the hot-rolled steel sheet, followed by cold rolling and subsequent annealing, respectively, In the cold rolling process, cold rolling is performed at 90% or more of the total cold rolling reduction rate and 76% or more of the final cold rolling reduction ratio, and the leasing height of the ferritic stainless steel after final cold rolling and annealing is 10 μm or less, and the r value of each tissue direction is 1.7 or more. And the r-bar value is 1.9 or more, and the ratio of {111} <uvw> / {001} <110> and {111} <uvw> / {001} <100> measured by EBSD attached to the scanning electron microscope A method for producing ferritic stainless steel having excellent ridging property and formability, characterized in that it is 30 or more. delete delete delete Ferritic stainless steel produced by the manufacturing method of claim 1 in weight%, C: greater than 0 0.10%, Si: greater than 0% 1.0% or less, Mn: greater than 0% 1.0% or less, P: greater than 0% 0.050%, S: greater than 0 and less than 0.020%, Ni: greater than 0 and less than 2.0%, Cr: greater than 8.0 and 30%, Cu: greater than 0 and less than 1.0%, Ti: 0.01 to 0.50%, Nb: 0.01 to 0.50%, Al greater than 0.10% Or less than 0% and 0.05% or less, optionally Mo: more than 0% and 1.0% or less, V: 0.01 to 0.30%, Zr: 0.01 to 0.30%, and B: 0.0010 to 0.0100%. Ferritic stainless steel with more ridging and formability, which contains more and the rest is composed of Fe and other unavoidable impurities. delete delete delete

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