JP4083669B2 - Ferritic stainless steel sheet excellent in deep drawability and method for producing the same - Google Patents

Description

  The present invention relates to a ferritic stainless steel sheet excellent in deep drawability and a method for producing the same.

  Ferritic stainless steel sheets have improved formability due to recent advances in manufacturing technology, and are used for molding materials such as kitchens and automobile exhaust system parts. Recently, ferritic stainless steel sheets have been used for interior parts such as refrigerators, rice cookers, and other home appliances and doorknobs.

  When forming a ferritic stainless steel sheet, particularly deep drawing typified by a cylindrical shape, as shown in FIG. 1, irregularities due to in-plane anisotropy called ears may occur after forming. . As shown in FIG. 1, when an ear is generated after deep drawing, the convex portion is cut at a place where the ear height is the lowest to produce a product, so that the yield decreases.

  As a method of improving the in-plane anisotropy of a stainless steel sheet, a method of controlling the cold rolling reduction distribution between the primary cold rolling and the final cold rolling during primary cold rolling, intermediate annealing, and final cold rolling. (For example, Patent Document 1), methods for controlling hot rolling conditions (for example, Patent Documents 2 and 3), and methods for controlling precipitates and textures in an integrated manufacturing process (for example, Patent Document 4) are known. . In these methods, as described in JIS Z 2254, r values (ranks) in three directions, ie, the rolling direction (L direction), the direction 45 ° from the rolling direction (D direction), and the direction 90 ° from the rolling direction (C direction). Ford value, plastic strain ratio), Δr = (rL + rC−2 × rD) / 2 calculated from rL, rC, and rD, respectively, is improved.

  Also, a method of controlling the annealing and cold rolling methods to reduce the difference between the maximum r value and the minimum r value of rL, rC, and rD as in-plane anisotropy (for example, Patent Document 5). Is known.

Japanese Patent Laid-Open No. 52-039595 JP 07-268461 A Japanese Patent Laid-Open No. 08-311542 JP 2002-194507 A Japanese Patent Laid-Open No. 2003-160846

  However, even in the inventions described in the above-mentioned patent documents, a large amount of ears may occur when the cylindrical deep drawing is actually performed. Even when Δr, which is an index of in-plane anisotropy, is small, the cause of the increase in the ear height when performing cylindrical deep drawing is considered as follows. First, as shown in FIG. 2A, when rD is the lowest, Δr and ear height show a good correlation, and the ear comes out in four D directions. However, as shown in FIG. 2B, for example, when rL is minimum and rC is maximum, Δr is small, but the ear comes out in two L directions. Further, as shown in FIG. 2C, even when rL, rD, and rC are substantially equal, the r value in the direction 60 ° from the rolling direction (referred to as the 60 ° direction) is the maximum value and the minimum value. In some cases, six 60 ° directions (including two L directions) are heard.

  That is, the actual ear height is considered to be determined by the difference in material inflow during molding between the direction with the highest r value and the direction with the lowest r value. There have been no studies on improvement methods. In order to improve the in-plane anisotropy of the r value, it is effective to set the texture to a random orientation. However, when the texture is random orientation, the in-plane anisotropy of the r value is improved, but the average r value in the L direction, D direction, and C direction is about 1.0, and the deep drawability is insufficient. It becomes.

  In view of the above-mentioned present situation, the present invention secures excellent deep drawability by setting the simple average value of r values measured every 10 ° from the L direction to the C direction to 2.0 or more, and the ear height at the time of deep drawing. A ferritic stainless steel sheet excellent in deep drawability with reduced in-plane anisotropy correlated with the above and a method for producing the same.

  The inventors of the present invention diligently studied a stainless steel plate having an optimum texture for securing excellent deep drawability and ear rate and a manufacturing method thereof, and {111} <112> plane perpendicular to the plate surface. , {100} <011> plane and {111} <011> plane have been found to be effective to optimize the X-ray random intensity. The present invention has been made based on the above findings, and the gist thereof is as follows.

(1) By mass%, C: 0.001 to 0.010%, Si: 0.01 to 1.00%, Mn: 0.01 to 1.00%, P: 0.040% or less, S: Less than 0.010%, Al: 0.005-0.100%, N: 0.001-0.015%, Cr: 10.0-20.0%, Ti: 0.05-0.40% And the balance is made of Fe and inevitable impurities, and the {111} <112> plane X-ray random intensity ratio Ia and the {111} <011> plane X-ray random intensity ratio Ib in the direction perpendicular to the plate surface are Ia ≧ 7.0, Ib ≧ 7.0, Ia / Ib: satisfying the relationship of 0.6 to 1.5, the random intensity ratio Ic of {100} <011> plane is less than 2.0, From the rolling direction of the steel sheet to the direction of 90 °, the simple average value of the r value measured every 10 ° is 2.0 or more. Wherein the difference between the values is 0.5 or less, deep drawing excellent in ferritic stainless steel.
(2) The ferritic stainless steel sheet having excellent deep drawability as described in (1) above, further containing Mg: 0.0001 to 0.0100% by mass.
(3) The ferritic stainless steel sheet having excellent deep drawability as described in (1) or (2) above, further containing, by mass%, B: 0.0005 to 0.0050%.
(4) Furthermore, it is excellent in the deep drawability as described in any one of (1) to (3) above, characterized by containing Mo: 0.10 to 2.50% by mass%. Ferritic stainless steel sheet.
(5) The ferritic stainless steel sheet excellent in deep drawability according to any one of (1) to (4) above, wherein the average crystal grain size is 30 to 60 μm.

(6) A ferritic stainless steel piece made of the component described in any one of (1) to (4) above is heated to a range of 1050 to 1250 ° C. and subjected to rough hot rolling with a total rolling reduction of 80% or more. The hot-rolled sheet is subjected to finish hot rolling at a temperature of 1050 ° C. or lower and a total rolling reduction of 80 to 95%, wound at a temperature of 700 ° C. or lower, pickled without annealing, and rolled at a rolling rate of 40% or higher. The primary cold-rolled sheet is made into a primary cold-rolled sheet, subjected to intermediate annealing at 750 to 850 ° C., and further subjected to a final cold-rolled sheet with a cold rolling rate of 60% or more to form a final cold-rolled sheet, 800 to 900 Final annealing at ℃, the thickness t1 of the slab, the thickness t2 of the rough hot-rolled sheet, the thickness t3 of the primary cold-rolled sheet, and the thickness t4 of the final cold-rolled sheet are the following formulas (1) to (3) A method for producing a ferritic stainless steel sheet excellent in deep drawability, characterized by satisfying
However,
t2 / t1 ≦ 0.2 (1)
t3 / t2 ≦ 0.15 (2)
t4 / t3 ≦ 0.35 (3)
It is.

  The present invention makes it possible to provide a ferritic stainless steel sheet with excellent deep drawability and reduced ear height and a method for producing the same, and can greatly expand the application of ferritic stainless steel, making industrial contributions extremely high. It is remarkable.

The inventors first investigated an index correlating with the ear height using 17% Cr-0.20% Ti-0.002% C-0.008% N ferritic stainless steel manufactured under various conditions. . From a 0.8 mm thick steel plate, the longitudinal direction was changed by 10 ° from the rolling direction, and JIS Z 2201 No. 13 B tensile test specimens were collected, and the r value in each direction was measured according to JIS Z 2254. did. Further, a cylindrical deep drawing test was performed, and the ear height was determined from the obtained molded product sample. The ear height is the difference between the highest and lowest portions of the irregularities generated at the end after deep drawing shown in FIG. The cylindrical deep drawing test was performed under the following conditions.
Punch: φ50mm, shoulder radius 5mm
Dice: φ52mm, shoulder radius 5mm
Lubricating oil: kinematic viscosity at 40 ° C. 1200 mm ² / sec
Aperture ratio: 2.20 (blank diameter: φ110mm)

The results are shown in FIGS. 4 (a) and 4 (b). FIG. 4A shows the relationship between Δr measured by the r values in the L direction, the D direction, and the C direction and the ear height, but there is no correlation between Δr and the ear height. On the other hand, the relationship between the difference r _max −r _min between the maximum value r _max and the minimum value r _min of the r value measured every 10 ° from the rolling direction and the ear height is as shown in FIG. A good correlation was observed. That is, it was found that the ear height can be reduced by establishing a method for reducing r _max −r _min .

  Next, a method for improving the deep drawability while ensuring in-plane anisotropy was examined. In general, it is well known that the r value is improved by accumulation of {111} <112> planes. However, if the degree of integration of only the {111} <112> plane is increased, the r value in the 45 ° direction decreases and the r value in the C direction increases, so that the in-plane anisotropy increases.

  Therefore, the present inventors have rotated the {111} <112> plane by 30 ° about the plate direction to reduce the in-plane anisotropy without reducing the average r value. The method of increasing the degree of integration of the 011> plane to the same degree as the degree of integration of the {111} <112> plane was directed. This is because the {111} <112> plane and the {111} <011> plane have in-plane anisotropies in opposite directions. That is, it is considered that when the degree of integration of both the {111} <112> plane and the {111} <011> plane is increased, the effect of canceling out the in-plane anisotropy appears.

  Furthermore, in order to increase the r value, the {100} <011> orientation that reduces the r value is not preferable, and it is considered effective to reduce the degree of integration of the {100} <011> orientation.

  The above image will be schematically described. First, the representation of crystal orientation is shown in FIG. Ferritic stainless steel has a body-centered cubic structure, and the {111} plane and {100} plane are hatched planes in FIGS. 5 (a) and 5 (b), respectively. The {100} <011> orientation indicates that the above-mentioned {100} plane is directed in the plate surface direction, and the <011> direction in the plate surface is directed in the rolling direction (FIG. 5C). . The {111} <112> and {111} <011> orientations mean that the {111} plane faces the plate surface direction, and the <112> direction (FIG. 5 (d)) and <011> direction (FIG. 5) in the rolling direction, respectively. (E)) indicates that it is suitable. Conventionally, in order to improve the r value, the existence probability of a crystal grain having a {111} <112> orientation with a high r value has been increased, that is, the existence state of the crystal grain as shown in FIG. However, in such a crystal grain orientation distribution, the r value is high, but the in-plane anisotropy is large, and the ear height when deep drawing is large. In the present invention, similarly to the {111} <112> orientation, the r value is high, and the presence probability of {111} <011> orientation grains having in-plane anisotropy in the direction opposite to the orientation is set to {111} <112> orientation. It succeeded in raising to the same extent as a grain, and has reached the present invention. FIG. 6 (b) conceptually shows the existence state of crystal grains in the present invention.

Based on the above examination, the present inventors examined an optimum texture for reducing the average r value to 2.0 or more and reducing r _max −r _min , and a manufacturing method for obtaining it. The following findings were obtained.

First, to improve the average r value,
(1) It is necessary to increase the X-ray random intensity ratio of the {111} <112> plane perpendicular to the plate surface and reduce the X-ray random intensity ratio of the {100} <011> plane. It is effective to develop a rolling texture in which {111} <112> planes perpendicular to the plate surface are accumulated after primary cold rolling. In order to obtain such a texture,
(A) increasing the rolling ratio of hot rolling rough rolling,
(B) lowering the finish rolling temperature and coiling temperature of hot rolling to suppress recrystallization, omitting hot-rolled sheet annealing, and performing primary cold rolling,
(C) It is effective to increase the cold rolling rate of the final cold rolling.

Next, to reduce r _max −r _min ,
(2) It is necessary to make the X-ray random intensity of the {111} <011> plane substantially equal to the X-ray random intensity ratio of the {111} <112> plane.
(D) A two-time cold rolling method comprising primary cold rolling, intermediate annealing, final cold rolling, and final annealing is effective.

  The present invention is described in detail below.

  First, the reasons for limiting the steel components will be described. In the following description,% indicates mass%.

  C, N: If a large amount of C, N is added, the moldability is lowered, the amount of Ti required for fixing them is increased, and the production cost is increased. Therefore, the upper limits of the amount of C and N added are C: 0.010% or less and N: 0.015% or less, respectively. Moreover, although the lower limit of the addition amount of C and N is preferable, in consideration of the refining cost, both C and N are set to 0.001% or more.

  Si: Si is an element used as a deoxidizing element. When the amount of Si exceeds 1.0%, the moldability is remarkably lowered, so the upper limit of the amount of Si is set to 1.00% or less. Considering the cost in the refining process, since the Si amount of 0.01% or more is inevitably mixed, the lower limit of the Si addition amount is set to 0.01% or more.

  Mn: When a large amount of Mn is added, the moldability deteriorates, so 1.00% or less was made the upper limit of the Mn addition amount. The lower limit of the Mn addition amount is set to 0.01% in consideration of the refining process cost.

  P: When P is added in a large amount, the deep drawability deteriorates, so 0.040% or less is made the upper limit of the P amount. In addition, since the texture which is advantageous for deep drawability is formed as the P content is lower, the P content is preferably 0.020% or less.

  S: When S is added in a large amount, the corrosion resistance deteriorates, so less than 0.010% was made the upper limit of the S amount. Since the lower limit of the amount of S is preferably as low as possible, it is not particularly specified. However, if the amount of S is less than 0.0001%, the cost of the refining process increases, so the lower limit of the amount of S may be made 0.0001% or more. preferable.

  Al: Al is an element used for deoxidation, and the lower limit of the amount of Al is set to 0.005% or more as a deoxidizable level. On the other hand, when a large amount of Al is added, the formability deteriorates, so the upper limit of the Al amount is set to 0.100% or less.

  Cr: Cr is an element necessary for ensuring corrosion resistance, which is a basic characteristic of stainless steel. Since addition of 10.0% or more significantly improves corrosion resistance, the lower limit of Cr addition is 10.0% or more. It was. On the other hand, if adding more than 20.0% of Cr, the formability deteriorates, so 20.0% or less was made the upper limit of the Cr addition amount.

  Ti: Ti is an element that combines with C, N, etc. to produce precipitates, thereby purifying the steel substrate (matrix) and improving formability. The level of the Ti addition amount necessary for improving the moldability is 0.05% or more, and this is set as the lower limit of the Ti addition amount. On the other hand, when Ti is added in excess of 0.40%, the formability may be adversely deteriorated. Therefore, the upper limit of Ti content is set to 0.40% or less.

  Hereinafter, the elements that can be selectively added, Mg, B, and Mo will be described.

  Mg: Mg is an element that refines the structure of the welded portion to improve the formability of the welded portion and suppresses the generation of ridging during forming. Since the effect of improving the formability of the welded portion due to the addition of Mg is exhibited at 0.0001% or more, the lower limit of the Mg addition amount is preferably set to 0.0001% or more. On the other hand, if Mg is added in excess of 0.0100%, the raw material cost increases, so the upper limit of the amount of Mg added is preferably 0.0100% or less.

  B: B is an element that improves the secondary workability, and it is effective to add it when molding is performed in a plurality of steps. In order to obtain the effect of improving the secondary workability by adding B, the lower limit is preferably made 0.0005% or more. On the other hand, when B is added in excess of 0.0050%, the toughness may deteriorate, so 0.0050% is preferable as the upper limit.

  Mo: Mo is an element that improves corrosion resistance. In order to exhibit the effect of improving the corrosion resistance due to the addition of Mo, addition of 0.10% or more of Mo is preferable. Further, if Mo is added in excess of 2.50%, deep drawability may be lowered, so the upper limit is preferably made 2.50% or less.

  Next, the texture of the ferritic stainless steel sheet of the present invention will be described.

  As the texture of the steel sheet of the present invention, the X-ray random intensity ratio Ia of the {111} <112> plane perpendicular to the plate surface and the X-ray random intensity ratio Ib of the {111} <011> plane are Ia ≧ 7. 0, Ib ≧ 7.0 must be satisfied. Moreover, it is necessary to satisfy the relationship of Ia / Ib: 0.6-1.5. This increases the X-ray random intensity ratio Ia of the {111} <112> plane having different in-plane anisotropies and the X-ray random intensity ratio of the {111} <011> plane to 7.0 or more, and This is because the average r value can be increased to 2.0 or more by setting Ia / Ib to 0.6 to 1.5. On the other hand, since the r value increases as Ia and Ib increase, the upper limit is not particularly specified. However, in consideration of the existing equipment capacity, 22.0 is preferable as the upper limit.

  The X-ray random intensity ratio Ia of the {111} <112> plane is {111} <112> based on the X-ray intensity ratio of the {111} <112> plane of a standard sample having a random crystal orientation. It is the ratio of the X-ray intensity of the surface. Similarly, the X-ray random intensity ratio Ib of the {111} <011> plane is {111} <011 based on the X-ray intensity ratio of the {111} <011> plane of a standard sample having a random crystal orientation. > The ratio of the X-ray intensity of the surface.

  Further, since the {100} <011> plane is an orientation that reduces the r value, the integration degree of the {100} <011> plane needs to be less than 2.0. Note that the X-ray random intensity ratio of the {100} <011> plane is the X of the {100} <011> plane based on the X-ray intensity of the {100} <011> plane of a standard sample having a random crystal orientation. Since this is the ratio of the line intensities, the lower limit of the X-ray random intensity ratio of the {100} <011> plane is zero.

  The method for measuring the X-ray random strength ratio of the ferritic stainless steel sheet according to the present invention is such that the surface (ND surface) parallel to the plate surface at the center of the thickness of the product plate obtained is X-rayed by the transmission method or the reflection method. Using a crystal orientation analyzer such as a diffraction method or EBSP, a crystal grain orientation distribution function (also called ODF) is displayed. This function is published in January 20, 1984 from Maruzen Co., Ltd., written by Junichi Nagashima, as described in P29-39. This function uniquely specifies the crystal grain orientation with respect to the material coordinate axis system. It is a function of variables (φ, φ1, φ2). φ, φ1, and φ2 are Euler angles defined by the Bunge method. On the φ2 = 45 ° cross section shown in FIG. 7, the intensity of the {111} <011> plane is φ = 54.7 °, and the {111} <1-10> plane at φ1 = 0 ° and φ = 54. The average value of the X-ray random intensity ratio of the {111} <0-11> plane at 7 ° and φ1 = 60 ° is used. The intensity of the {111} <112> plane is {111} <1-21 plane when φ = 54.7 ° and φ1 = 30 °, and {111} <− when φ = 54.7 ° and φ1 = 90 °. The average value of the X-ray random intensity ratio of the 1-12> plane is used. The intensity of the {100} <011> plane is {100} <1-10> plane at φ = 0 ° and φ1 = 0 ° and {100} <− 1-10> at φ = 0 ° and φ1 = 90 °. The average value of the X-ray random intensity ratio of the surface is used.

  Moreover, it is preferable that the average grain size of a steel plate is 30-60 micrometers. If the average crystal grain size is less than 30 μm, it is difficult not only to satisfy the aforementioned Ia ≧ 7.0, Ib ≧ 7.0, Ia / Ib: 0.6 to 1.5, but also the material strength is Since it may increase and the deep drawability may be reduced, the lower limit of the average grain size is preferably 30 μm or more. Further, if the average crystal grain size is more than 60 μm, surface irregularities called “skin roughness” may occur during deep drawing, so the upper limit of the average crystal grain size is preferably 60 μm or less. The average crystal grain size is calculated based on JIS G 0552.

Next, in this invention, r value of a ferritic stainless steel plate is limited as follows. The measurement method of the r value is obtained by changing the longitudinal direction of the JIS No. 13 B tensile specimen from the rolling direction (L direction) every 10 ° to a direction perpendicular to the rolling direction (C direction) in a total of 10 directions. Each is measured based on JIS Z 2254, and a simple average value is defined as an average r value. In addition, the in-plane anisotropy index is represented by the difference r _max −r _min between the maximum r value r _max and the minimum r value r _min among the r values in 10 directions. In addition, in order to obtain | require r value by a test, a lot of test pieces and time are required. Therefore, recently, a program that can calculate the r value from the texture, for example, Hiroshi Inoue, Naoji Inaba, “Evaluation of the r value of the aluminum alloy sheet by quantitative analysis of the texture”, Light Metal, Vol. 44, No. 2, The Japan Institute of Light Metals, February 28, 1994, p. 97 to 103 have been developed. If such a method is used, the r value can be calculated without actually measuring the r value. However, when this program is used, it is necessary to actually measure the r values in the L direction, the D direction, and the C direction and confirm that the difference from the r value obtained by the calculation is within ± 5%.

  If the average r value is less than 2.0, it may be insufficient for deep drawing applications. The upper limit of the average r value is not particularly specified, but the upper limit is preferably set to 3.0 or less in consideration of the current facilities and productivity.

If r _max −r _min is 0.50 or more, the ear height at the time of deep drawing is high and the yield is greatly reduced. Since this reference is determined by the r value every 10 °, a better correlation with the ear height is seen than Δr calculated from the L direction, the D direction, and the C direction.

  The manufacturing method of the ferritic stainless steel sheet of this invention is demonstrated below.

  Hot rolling heating temperature: Ferritic stainless steel pieces are heated to a range of 1050 to 1250 ° C. The lower limit of the heating temperature for hot rolling is set to 1050 ° C. or more because when the heating temperature is lower than 1050 ° C., deformation resistance is high, and thus seizure flaws may occur during hot rolling. is there. Moreover, the reason why the upper limit of the heating temperature for hot rolling is 1250 ° C. or less is that when the heating temperature is higher than 1250 ° C., the crystal grains become coarse and the texture necessary for the product plate cannot be obtained.

  Total rolling reduction of rough hot rolling: In the hot rolling step, first, rough hot rolling requiring a plurality of passes is performed. If the total rolling reduction ratio of the rough hot rolling, that is, the ratio t2 / t1 of the thickness t1 of the slab and the thickness t2 of the rough hot rolled sheet is more than 0.2, the crystal grains after the completion of the rough hot rolling become large and deep drawability It is not possible to obtain a texture that is advantageous to the above. The lower limit of t2 / t1 is not particularly specified, but it is preferably set to 0.07 or more in consideration of productivity because finish hot rolling is performed after rough hot rolling.

  Finishing hot rolling temperature: After rough hot rolling, finishing hot rolling of a plurality of passes is performed at a temperature of 1050 ° C. or lower. This is because the finish hot rolling is performed without recrystallization, and when the finish hot rolling is performed at a temperature higher than 1050 ° C., recrystallization occurs between passes to inhibit the development of the rolling texture.

  Winding temperature of hot rolling: After finishing hot rolling, winding is performed at a temperature of 700 ° C. or lower in order to suppress recrystallization. This is because recrystallization proceeds during winding when the winding temperature exceeds 700 ° C.

  Hot-rolled sheet annealing: Hot-rolled sheet annealing is not performed. This is because if the recrystallized structure is obtained by hot-rolled sheet annealing, the target texture of the product sheet cannot be obtained.

  The pickling after hot rolling may be performed with a normal liquid such as sulfuric acid or nitric hydrofluoric acid. Pickling and sandblasting before pickling improves pickling performance.

  Cold rolling consists of primary cold rolling and final cold rolling, and intermediate annealing is performed between the primary cold rolling and final cold rolling.

  The cold rolling mill may be a reversible 20-stage Sendzimir mill, 6-stage or 12-stage mill, or a tandem mill that continuously rolls a plurality of passes. However, the larger the work roll diameter, the less the introduction of shear strain during rolling and the easier development of the rolling texture. Therefore, it is preferable to use a rolling mill having a work roll diameter of 200 mm or more.

  Primary cold rolling: The thickness t1 / t2 of the thickness after primary cold rolling, that is, the thickness t3 of the primary cold rolled plate and the thickness t2 after rough rolling before finish hot rolling is the finish hot rolling. And the total rolling reduction of the first cold rolling. t3 / t2 is an important factor in the present invention, and since it is not recrystallized from the start to the end of finish hot rolling, it can be handled as the total reduction ratio of the non-recrystallized zone rolling before intermediate annealing. When t3 / t2 is more than 0.15, the structure in the intermediate annealing is coarsened, the r value is lowered, and the deep drawability in the product plate is deteriorated. The lower the t3 / t2, the better the deep drawability, and it is desirable to set it to 0.11 or less. The lower limit is not particularly specified, but it is preferably 0.05 in consideration of productivity and final cold rolling reduction.

  Final cold rolling: The ratio t4 / t3 between the thickness t3 of the primary cold rolled sheet and the thickness after the final cold rolling, that is, the thickness t4 of the final cold rolled sheet is set to 0.35 or less. t4 / t3 is the rolling reduction in the final cold rolling, and if it exceeds 0.35, the deep drawability of the product plate deteriorates. The lower t4 / t3 is preferable, and 0.30 or less is desirable. The lower limit is determined by the product plate thickness, but 0.15 is preferable in the case of a normal thickness of 0.2 to 1.2 mm.

  Intermediate annealing: When the intermediate annealing temperature is less than 750 ° C., unrecrystallized remains, and not only the deep drawability of the product plate is lowered, but also ridging occurs during molding. Further, if the intermediate annealing temperature is 850 ° C. or higher, the recrystallized grains are coarsened and the deep drawability in the product plate is deteriorated. Therefore, the intermediate annealing is performed at 750 to 850 ° C.

  Final annealing: Final annealing after the final cold rolling is performed at 800 to 900 ° C. When the final annealing temperature is less than 800 ° C., the average crystal grain size becomes fine and the deep drawability deteriorates. When it exceeds 900 ° C., the crystal grain size of the product plate becomes coarser than 60 μm, This is because rough skin occurs.

  The surface finish of the steel sheet obtained by the present invention is 2D, 2B, BA, No. JIS G 4305. Any finish such as 4 can be applied. Even if temper rolling is performed at an elongation rate of 3% or less like 2B or BA, the texture is hardly changed and the same effect can be expected.

  The steel sheet obtained by the present invention is a steel sheet having excellent deep drawability and in-plane anisotropy, but a lubricating film is applied to the surface layer in order to further improve the deep drawability or to change the color tone or the like. You may apply.

  Ferritic stainless steel shown in Table 1 was melted, and a steel plate having a thickness of 0.3 to 1.1 mm was produced by hot rolling, pickling, cold rolling, intermediate annealing, cold rolling, and final annealing. The manufacturing conditions and the plate thickness during the manufacturing are shown in Table 2.

  From the obtained steel sheet, the crystal grain size of the cross-sectional structure was measured according to JIS G 0552, and the texture at the center of the plate thickness was measured by the X-ray diffraction method. Moreover, r value for every 10 degrees was calculated | required from the L direction to the C direction from the obtained texture. Further, r values in the L direction, the C direction, and the D direction were measured in accordance with JIS Z 2254 by introducing 15% tensile strain, and the r value obtained by calculation was compared with the actually measured value. For steel A, the test piece was sampled by changing the longitudinal direction in a total of 10 directions every 10 ° from the L direction to the C direction, and the r value after 15% tension was obtained based on JIS Z 2254, respectively.

The comparison results are shown in FIG. The calculated r value and the actually measured r value show good agreement in any direction. The in-plane anisotropy index was expressed as a difference r _max −r _min between the maximum r value: r _max and the minimum r value: r _min among the r values in 10 directions. The average r value and r _max −r _min are shown together in Table 2. Moreover, the cylindrical deep drawing test was performed on the obtained steel plate under the following conditions, and the ear height of the formed sample was investigated.
Punch: φ50mm, shoulder radius 5mm
Dice: φ52mm, shoulder radius 5mm
Lubricating oil: Kinematic viscosity at 40 ° C. 1200 mm ² / sec
Aperture ratio: 2.20 (blank diameter: φ110mm)

The obtained results are shown in Table 3. The steel of the present invention has an average r value of 2.0 or more, excellent deep drawability, r _max -r _min is less than 0.5, and anisotropy is extremely small.

It is a figure which illustrates roughly the generation | occurrence | production of the ear | edge after deep drawing by a perspective view. It is a figure explaining roughly which shows three typical examples of the in-plate anisotropy of r value. It is a figure explaining the measuring method of ear height roughly. It is a figure explaining the relationship between the conventional Δr and the ear height in (a), and comparing the relationship between r _max −r _min and the ear height used in the present invention in (b). It is a figure which illustrates notionally the existence state of the crystal grain of each crystal orientation with a perspective view. It is a figure which illustrates notionally the distribution state of the crystal grain of each crystal orientation, contrasting with a prior art (a) and this invention (b). It is a figure which shows the existence position of the crystal orientation in (phi) 2 = 45 degree cross section. It is a figure which compares and shows r value obtained by measurement and r value obtained by calculation.

Claims (6)

% By mass
C: 0.001 to 0.010%,
Si: 0.01 to 1.00%,
Mn: 0.01 to 1.00%,
P: 0.040% or less,
S: less than 0.010%,
Al: 0.005 to 0.100%,
N: 0.001 to 0.015%,
Cr: 10.0-20.0%,
Ti: 0.05 to 0.40%
The balance is composed of Fe and inevitable impurities, and the {111} <112> plane X-ray random intensity ratio Ia and the {111} <011> plane X-ray random intensity ratio Ib in the direction perpendicular to the plate surface But,
Ia ≧ 7.0,
Ib ≧ 7.0,
Ia / Ib: 0.6 to 1.5
The random strength ratio Ic of the {100} <011> plane is less than 2.0, and the simple average value of r values measured every 10 ° from the rolling direction of the steel plate to the direction of 90 ° is A ferritic stainless steel sheet excellent in deep drawability, characterized in that it is 2.0 or more and the difference between the maximum value and the minimum value of the r value is 0.5 or less. Furthermore, in mass%,
Mg: 0.0001 to 0.0100%
The ferritic stainless steel sheet excellent in deep drawability according to claim 1, characterized by comprising: Furthermore, in mass%,
B: 0.0005 to 0.0050%
The ferritic stainless steel sheet excellent in deep drawability according to claim 1 or 2, characterized by comprising: Furthermore, in mass%,
Mo: 0.10 to 2.50%
The ferritic stainless steel sheet excellent in deep drawability according to any one of claims 1 to 3, characterized in that   The ferritic stainless steel sheet excellent in deep drawability according to any one of claims 1 to 4, wherein an average crystal grain size is 30 to 60 µm. A ferritic stainless steel piece made of the component according to any one of claims 1 to 4 is heated to a range of 1050 to 1250 ° C and subjected to rough hot rolling with a total rolling reduction of 80% or more to obtain a rough hot rolled sheet. Then, finish hot rolling at a temperature of 1050 ° C. or lower and a total rolling reduction of 80 to 95%, winding at a temperature of 700 ° C. or lower, pickling without annealing, and performing primary cold rolling at a rolling rate of 40% or higher. To perform a primary cold-rolled sheet, intermediate annealing is performed at 750-850 ° C., further cold-rolled at a rate of 60% or more to obtain a final cold-rolled sheet, and finally annealed at 800-900 ° C., The thickness t1 of the slab, the thickness t2 of the rough hot-rolled sheet, the thickness t3 of the primary cold-rolled sheet, and the thickness t4 of the final cold-rolled sheet satisfy the following formulas (1) to (3). The manufacturing method of the ferritic stainless steel plate excellent in deep drawability.
However,
t2 / t1 ≦ 0.2 (1)
t3 / t2 ≦ 0.15 (2)
t4 / t3 ≦ 0.35 (3)
It is.