JP2009030078A - High workability ferritic stainless steel sheet excellent in ridging resistance, and producing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high workability ferritic stainless steel sheet excellent in a ridging resistance and a producing method therefor, with which a texture of the product sheet and a working texture before the last annealing, are regulated to control this regulation in a cold process or a warm process after hot-rolling. <P>SOLUTION: To the ferritic stainless steel composed of by mass% of ≤0.03% C, 10-25% Cr, ≤0.030% N, ≤0.35% Ti, ≤0.1% Al, before cold-rolling, plastic working for passing through a course having the angle to the moving direction of the steel sheet is applied. Thus, in the case of setting an X-ray random strength ratio of ä001}<110> plane and ä111}<110> plane in the sheet plane at the center of the sheet thickness of the working texture structure for applying the last annealing to respectively Ia and Ib, these are regulated to be Ia≥5 and Ia/Ib>1 and the texture structure of the product sheet is made to be <0.1 mm the maximum length in ä001} and ä112} plane directional ranges and the existence ratio thereof is made to be 10-50 area%. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a highly workable ferritic stainless steel sheet having excellent ridging resistance and a method for producing the same.

  Ferritic stainless steel sheets are used in a wide range of fields such as kitchen equipment, home appliances, and electronic equipment. However, since the processability is inferior to that of an austenitic stainless steel sheet, the application may be limited.

  In recent years, ferritic stainless steel sheets with improved workability and corrosion resistance have been applied to a wide range of processing applications through the addition of stabilizing elements such as Ti and Nb. is there. This is because ferritic stainless steel has good corrosion resistance in an indoor environment and is more economical than austenitic stainless steel to which a large amount of Ni is added.

  Conventionally, the surface quality after processing of a ferritic stainless steel sheet is significantly deteriorated by a phenomenon called so-called ridging, that is, fine irregularities generated along the rolling direction when the steel sheet is press-formed. Although the origin of ridging is not necessarily clear, it is understood that colonies having similar crystal orientations arranged along the rolling direction exist and are generated based on the difference in plastic deformation behavior between the colonies. Here, it is considered that colonies are largely formed from coarse particles of solidified tissue.

  Ridging may be easily manifested by the extremely low carbon / nitrogenation of the ferritic stainless steel as described above. That is, coarse grains are easily formed in the solidified structure, and colonies having a {001} plane orientation that is a cause of ridging are easily generated.

Up to now, the improvement of ridging resistance of ferritic stainless steel with reduced carbon and nitrogen has been considered to be an effective means with the following measures as the main aim of refining coarse grains in a solidified structure and random orientation. .
(1) Refinement and random orientation in the solidification stage (2) Refinement and random orientation in the hot rolling process

  (1) is based on the idea of keeping coarse particles that cause ridging fine from the beginning. For a long time, as disclosed in Patent Document 1 and the like, it has been disclosed that electromagnetic stirrer, inoculation of solidification nuclei, and casting temperature for the purpose of equiaxial refinement and random orientation of coarse columnar crystals have been disclosed. In recent years, for example, as disclosed in Patent Document 2, Patent Document 3, and Patent Document 4, a technique for refining a solidified structure by defining inclusions by a method of inoculating components and solidified nuclei has been disclosed.

  (2) is based on the idea of breaking coarse grains that are the cause of ridging by recrystallization in hot rolling and processing strain. For example, Patent Document 5, Patent Document 6, and Patent Document 7 disclose manufacturing techniques that define in detail the relationship between rolling temperature, strain rate, rolling reduction, friction coefficient, and the like.

  On the other hand, improvement of workability of ferritic stainless steel sheet is based on the idea of improving deep drawability, that is, r value. For example, Patent Document 8 and Patent Document 9 disclose manufacturing techniques for improving the r value by defining hot rolling conditions.

  Further, the r value and the texture of the ferritic stainless steel sheet are closely related, and Patent Literature 10, Patent Document 11, and Patent Literature 12 disclose techniques for improving the r value by defining the texture. . Patent Document 10 and Patent Document 11 are based on the idea of generating a large number of {111} plane orientations effective for improving the r value and reducing the {001} plane orientation that can be a cause of a decrease in the r value. Specifically, the X-ray integral intensity ratio {111} / {001} between the {111} plane and the {001} plane is defined as 5 or more in Patent Document 10 and 15 or more in Patent Document 11. On the other hand, Patent Document 12 specifies the intensity ratio of the {111} <112> plane and the {111} <011> plane in order to reduce the in-plane anisotropy of the r value in addition to increasing the above-described intensity ratio. is doing.

  As described above, to improve the ridging resistance, it is effective to make the colonies formed from the solidified structure finer and randomly oriented at the stage of solidification or hot rolling. On the other hand, for improving the r value, it is effective to control the texture to increase the abundance of the {111} plane orientation and reduce the abundance of the {001} plane orientation. That is, the prior art achieves improvement in ridging resistance and r value by thoroughly reducing the {001} plane orientation that can be a factor of colonies derived from the solidified tissue.

JP 50-123294 A Japanese Patent Laid-Open No. 10-324956 JP 2000-192199 A JP 2001-294991 A Japanese Examined Patent Publication No. 4-9851 JP 7-310122 A JP-A-10-280046 JP 62-77423 A JP-A-7-268485 JP-A-3-81036 JP 2002-285300 A JP 2005-163139 A

  As described above, ferritic stainless steel tends to generate colonies derived from a solidified structure due to extremely low carbon and nitrogenation. That is, a colony having a {001} plane orientation may remain even in a hot-rolled steel sheet. In other words, the measures of the prior art that impose many restrictions in the solidification or hot rolling process may not always work effectively. In such a case, in the current process after hot rolling, no effective prior art has yet emerged that reduces or renders the above-mentioned colony effects harmless.

  The purpose of the present invention is to reduce and render harmless after the hot rolling of ferritic stainless steel, in which the influence of colonies derived from the solidified structure by reducing carbon and nitrogen is likely to remain in the hot-rolled steel sheet. And

That is, the present invention solves the above-mentioned problems by defining the texture of the product plate and the processed texture before final annealing, and controlling it in the cold or warm process after hot rolling. The present invention provides a highly workable ferritic stainless steel sheet having excellent properties and a method for producing the same.
(1) In mass%, C: 0.03% or less, Si: 1% or less, Mn: 1% or less, P: 0.05% or less, S: 0.01% or less, Cr: 10-25% N: 0.030% or less, Ti: 0.35% or less, Al: 0.1% or less, the balance being Fe and unavoidable impurities, and {001} and {112} The maximum length of the plane orientation region is less than 0.1 mm and the presence thereof is 10 to 50 area%, the average r value of 0 °, 45 °, 90 ° with respect to the rolling direction is 1.6 or more, and the Δr value is A highly workable ferritic stainless steel sheet having excellent ridging resistance, characterized by being 0.5 or less.
(2) The processed texture to be subjected to the final annealing of the steel has the X-ray random intensity ratios of the {001} <110> plane and the {111} <110> plane as Ia and Ib, respectively, in the plate surface at the plate thickness center. The high workability ferritic stainless steel sheet having excellent ridging resistance according to (1), wherein the relationship of Ia ≧ 5 and Ia / Ib> 1 is satisfied.
(3) The high workability ferrite having excellent ridging resistance according to (1) or (2), wherein the ridging height after applying an elongation strain of 16% in the rolling direction is 5 μm or less Stainless steel sheet.
(4) The steel is further in mass%, Mg: 0.005% or less, Nb: 1% or less, Mo: 2% or less, Ni: 2% or less, Cu: 2% or less, B: 0.005 % High-workability ferritic stainless steel sheet having excellent ridging resistance according to any one of (1) to (3).
(5) In the method of manufacturing a steel sheet, which is hot-rolled by hot rolling the ferritic stainless steel slab having the steel component described in (1) or (4), and then repeating annealing and cold rolling, the movement of the steel sheet It is excellent in ridging resistance according to any one of (1) to (4), characterized in that it is annealed after being subjected to plastic working passing through a path that is angled with respect to the direction. A method for producing a highly workable ferritic stainless steel sheet.
(6) In the method of manufacturing a steel sheet, the ferritic stainless steel slab having the steel component described in (1) or (4) is hot-rolled to form a hot-rolled sheet, and then subjected to annealing and cold rolling. According to any one of (1) to (4), the plastic working that passes through a path that is angled with respect to the direction is performed, and then annealing is performed, followed by cold rolling and annealing. A method for producing a highly workable ferritic stainless steel sheet having excellent ridging resistance.

  Hereinafter, the inventions related to the steel sheets (1) to (4) and the inventions related to the manufacturing methods (5) and (6) are referred to as the present invention. The inventions (1) to (6) may be collectively referred to as the present invention.

  As described above, the ferritic stainless steel sheet of the present invention can improve both ridging resistance and r value by defining the texture of the product sheet and the processed texture before the final annealing. This ferritic stainless steel sheet can be controlled to the target texture in the manufacturing process after hot rolling by the manufacturing method of the present invention.

  In order to solve the above-mentioned problems, the present inventors have intensively studied the influence of the texture of the product plate and the processed texture before the final annealing on the ridging and r value of the ferritic stainless steel sheet with reduced carbon and nitrogen. To complete the present invention. The typical experimental results will be described below.

  Using hot rolled sheets of 4 mm thick actual ferritic stainless steel having the components shown in Table 1, hot rolled sheet annealing was performed and pickling was performed. Next, the hot-rolled annealed plate was subjected to plastic working by passing through a die having a path with an angle of 120 ° as shown in FIG. The extrusion direction was the rolling direction. Thereafter, a cold rolled sheet having a thickness of 0.6 mm was formed by cold rolling once and twice without annealing or annealing. In the case of cold rolling twice, the intermediate material was 2 mm thick. The cold-rolled sheet was subjected to final annealing and pickling, and was subjected to ridging height and r-value evaluation and texture investigation / analysis. The annealing temperature was all performed at 920 ° C.

  As a comparative material, a 0.6 mm thick cold-rolled annealed sheet was manufactured from a 4 mm-thick hot-rolled sheet by two cold rollings including one time and intermediate annealing without applying the plastic working shown in FIG. In the cold rolling twice, the intermediate material was 2 mm thick.

For the ridging height, a JIS No. 5 test piece was sampled, an elongation strain of 16% was applied in the rolling direction, the surface profile was measured with a two-dimensional roughness measuring instrument, and the maximum unevenness height was obtained. For the r value, JIS13B tensile test pieces were sampled in the 0 °, 45 °, and 90 ° directions with respect to the rolling direction, and the values at 16% elongation strain were obtained. The average r value and Δr value were calculated by the following formula.
Average r = (r _{0 °} + 2r _{45 °} + r _{90 °} ) / 4
Δr = (r _{0 °} -2r _{45 °} + r _{90 °} ) / 2

  For the final annealed material, the crystal orientation map is measured at a magnification of 100 on the plate surface at the center of the plate thickness by the EBSP method, the orientation for each crystal grain is confirmed, and the region composed of {001} and {112} plane orientations is the same. Can be displayed in color. Hereinafter, a region composed of {001} and {112} plane orientations displayed in the same color will be referred to as a {001} plane orientation region. Measurement by such an EBSP method was performed to determine the maximum length and area ratio of the {001} and {112} plane orientation regions. The 0.6 mm thick cold-rolled material was measured for the grain orientation distribution function (ODF) by X-ray diffraction on the plate surface at the center of the plate thickness, and X on the {001} <110> plane and the {111} <110> plane. The line random intensity ratio was determined.

  Table 2 shows the experimental results described above. As is clear from Table 2, the reference numerals 1 to 4 are obtained by performing plastic working through which a die as shown in FIG. 1 is passed, and the average r value is higher than the reference numerals 5 and 6 of the comparative material. The Δr value is low and the ridging height is small.

  In the textures of reference numerals 1 to 4, the maximum length of the {001} and {112} plane orientation regions is small and the area ratio is large on the plate surface at the center of the thickness of the cold-rolled annealed plate. Furthermore, the working texture of the cold-rolled material subjected to final annealing has a feature that the X-ray random intensity ratio of the {001} <110> plane is also large.

  On the other hand, the reference numerals 5 and 6 indicate that the maximum length of the {001} and {112} plane orientation regions exceeds 0.1 mm even though the area ratio of the {001} and {112} plane orientation regions is small. It is observed as a colony in which a plurality of crystal grains are connected in the direction. The maximum length of the {001} and {112} plane orientation regions of reference numerals 1 to 4 is less than 0.1 mm. In reference numerals 3 and 4, the {001} and {112} plane orientation regions are close to the crystal grain size. It has the feature of being distributed in size.

  As is apparent from FIGS. 2 and 3, the above-described symbols 1 to 4 are called α-fiber {001}, which is understood as a factor of decrease in r value and ridging resistance in the concept of the prior art. In addition, although the abundance of the {112} plane orientation region is large, it has a high r value, a small plastic anisotropy (Δr), and good ridging resistance. In order to consider the reason, in addition to the EBSP method and the X-ray diffraction method, detailed structural analysis using a TEM (transmission electron microscope) was performed, and the following new findings were obtained.

(A) When plastic working that passes through an angled path with respect to the moving direction of the steel sheet is performed, a deformation band having a high dislocation density is introduced into the cold-rolled material, and the texture changes.
(B) The deformation zone is also introduced into a colony having a {001} plane orientation. Here, the colony refers to a colony whose maximum length of the {001} plane orientation region exceeds 0.1 mm when the EBSP orientation map is measured from the plate surface. The colony shape also means that it exceeds 0.1 mm.
(C) The texture is changed such that {110} <001> and {112} <111> appear newly.
(D) Next, when cold-rolling, the colony consisting of the {001} plane and {112} plane orientation region is divided by the deformation band.
(E) The processed texture after cold rolling is characterized in that {111} <112> and {001} <110> develop.
(F) It is considered that the factor that {001} <110> develops after cold rolling is a cold-rolled texture derived from the {112} <111> orientation that appears in the cold-rolled material.
(G) Subsequently, when the final annealing is performed, the deformation band acts as a nucleation site for recrystallization, and the colonies derived from the {001} plane orientation region are divided and pulverized. That is, the {001} plane orientation region derived from the solidified structure is dispersed in a size close to a crystal grain unit without being continuous in a colony shape.
(H) Based on the cold-rolled texture, {111} <112> to {554} <225> develop as main orientations in the recrystallized texture after the final annealing, and {001} to {112} <110 There are relatively many azimuths as sub-azimuths.
(I) It is inferred that the ridging resistance was improved by dispersing the {001} to {112} <110> plane orientation regions in a size close to a crystal grain unit without being continuous in a colony shape. Moreover, in order to make the influence of a colony harmless and to improve ridging resistance, it is also effective to perform intermediate annealing before cold rolling.
(J) It is presumed that the r value is improved by the development of the {111} <112> to {554} <225> orientation as the texture of the matrix. Furthermore, the presence of a relatively large amount of {112} orientation contributes to the improvement of the r value in the 45 ° orientation, and is effective in reducing the in-plane anisotropy Δr value.

  The present inventions (1) to (6) have been completed based on the findings (a) to (j).

  Hereinafter, each requirement of the present invention will be described in detail. In addition, "%" display of the content of each element means "mass%".

  (A) The reason for limitation of a component is demonstrated below.

  Since C deteriorates moldability and corrosion resistance, the lower the content, the better. Therefore, the upper limit is made 0.03%. However, excessive reduction leads to an increase in refining costs, so the lower limit is preferably 0.001%. More preferably, it is 0.002 to 0.005% in consideration of corrosion resistance and manufacturing cost.

  Si may be added as a deoxidizing element. However, since it is a solid solution strengthening element and its content is preferably as small as possible from the suppression of the decrease in elongation, the upper limit is made 1%. However, excessive reduction leads to an increase in refining costs, so the lower limit is preferably 0.01%. More preferably, it is 0.03 to 0.30% in consideration of workability and manufacturing cost.

  Since Mn is a solid solution strengthening element like Si, the smaller the content, the better. The upper limit is made 1% in order to suppress the decrease in elongation. However, excessive reduction leads to an increase in refining costs, so the lower limit is preferably 0.01%. More preferably, it is 0.03 to 0.30% in consideration of workability and manufacturing cost.

  Since P is a solid solution strengthening element like Si and Mn, the smaller the content, the better. The upper limit is made 0.05% in order to suppress the decrease in elongation. However, excessive reduction leads to an increase in refining costs, so the lower limit is preferably 0.005%. More preferably, considering the manufacturing cost and workability, the content is made 0.010 to 0.030%.

  S is an impurity element and inhibits hot workability and corrosion resistance, so the smaller the content, the better. Therefore, the upper limit is made 0.01%. However, excessive reduction leads to an increase in refining costs, so the lower limit is preferably 0.0001. More preferably, it is 0.0010 to 0.0050% in consideration of corrosion resistance and manufacturing cost.

  Cr is an essential element for ensuring corrosion resistance, and its lower limit is 10%. However, addition over 25% impairs manufacturability due to a decrease in toughness and degrades elongation. Preferably, considering the corrosion resistance and manufacturability and workability, the content is made 16 to 19%.

  N, like C, deteriorates moldability and corrosion resistance, so the lower the content, the better. Therefore, the upper limit is made 0.030%. However, excessive reduction may cause TiN which becomes the nucleus of ferrite grain formation at the time of solidification, the solidified structure becomes columnar crystals, and the ridging resistance at the time of product plate forming may be deteriorated. Therefore, the lower limit is preferably 0.001%. More preferably, considering the manufacturing cost and the corrosion resistance, the content is made 0.005 to 0.015%.

  Ti combines with C, N, S, and P to improve corrosion resistance, intergranular corrosion resistance, and formability, and contributes to refinement of a solidified structure. Therefore, the lower limit is preferably 0.05%. On the other hand, Ti is also a solid solution strengthening element, and excessive addition leads to a decrease in elongation, so the upper limit is made 0.35%. More preferably, it is 0.10 to 0.20% in consideration of the intergranular corrosion property and formability of the welded portion.

  Al is an effective element as a deoxidizing element. However, excessive addition causes deterioration of formability, weldability and surface quality, so the upper limit is made 0.1%. Preferably, considering the refining cost, 0.01 to 0.05%.

  Mg forms Mg oxide with Al in molten steel and acts as a deoxidizer, and also acts as a crystallization nucleus of TiN. TiN becomes a solidification nucleus of the ferrite phase in the solidification process, and by facilitating crystallization of TiN, the ferrite phase can be finely formed during solidification. By refining the solidified structure, orientation grains derived from a coarse solidified structure such as ridging of the product can be reduced, and the moldability is improved. Therefore, when adding, it is 0.005% or less. If it exceeds 0.0050%, the weldability deteriorates. Aggressive formation in the molten steel of Mg oxide, which becomes a crystallization nucleus of TiN, appears stably from 0.0001%. More preferably, considering the refining cost, the content is made 0.0002 to 0.0020%.

  Nb is an element that improves moldability and corrosion resistance. When Nb is added, the Nb content is 1% or less. If it exceeds 1%, the material strength is increased and ductility is reduced. The effect appears stably from 0.01%. More preferably, it is made 0.05 to 0.6% in consideration of manufacturability, moldability and corrosion resistance.

  Mo, Ni, and Cu are elements that improve the corrosion resistance, and when added, the content is made 2.0% or less. If it exceeds 2.0%, the moldability, particularly the ductility, is lowered. The effect appears stably from 0.1%. More preferably, it is 0.3 to 1.5% in consideration of manufacturability and ductility.

  B is an element that improves secondary workability, and addition to Ti-added steel is effective. When added, the content is 0.005% or less. If it exceeds 0.005%, the ductility is lowered. The effect appears stably from 0.0001%. More preferably, considering the refining cost and ductility, the content is made 0.0003 to 0.0030%.

  (B) The reason for limitation regarding the texture will be described below.

  The ferritic stainless steel sheet of the present invention has the components described in the item (A) and defines a texture in order to improve ridging resistance and workability. That is, [1] From the viewpoint of improving ridging resistance, the {001} and {112} plane orientation regions are dispersed in a size close to the crystal unit without being connected in a colony form. [2] From the viewpoint of improving the r value The {111} <112> to {554} <225> orientation of the ground is developed.

  As described above, the final annealed plate measures the crystal orientation map by the EBSP method and grasps the orientation and dispersion state of each crystal grain. From the orientation map obtained here, the maximum length and area ratio of each orientation region can be obtained.

  The EBSP method is described in, for example, a microscope; Seiichi Suzuki, Vol. 39, no. 2, 121-124, a crystal orientation map is displayed, and the area% of {001}, {112} plane orientation can be obtained. The sample used for measurement is a plane parallel to the plate surface at the center of the plate thickness. The measurement magnification is preferably x100 to 500, and the step interval is preferably 10 μm for the annealed material and 0.2 μm for the processed material.

  The texture of the final annealed plate is dispersed in a size close to a crystal grain unit in order to sever and break colonies in the {001} and {112} plane orientation regions. Therefore, the maximum length of the {001} and {112} plane orientation regions is less than 0.1 mm. Preferably it is 0.05 mm or less, More preferably, it is 0.03 mm or less. The orientation region described above often has a form in which a plurality of crystal grains are continuous in the rolling direction in an orientation map obtained by the EBSP method. Therefore, the maximum length of the {001} and {112} plane orientation regions is defined as the length of the long side extended in the rolling direction. As defined in (b) above, in the EBSP orientation map, the crystal grains in the {001} and {112} plane orientation regions that are continuous in the rolling direction and exceed 0.1 mm are referred to as colonies or colonies. . Further, when azimuth analysis is performed from the plate surface by EBSP, the {001} and {112} plane orientation regions often face <110> in the rolling direction. The {001} and {112} plane orientation regions include those that face the range of <100> to <110> in the rolling direction.

  The area ratio of the {001} and {112} plane orientation regions controlled to the maximum length as described above is set to 50 area% or less from the viewpoint of [1] ridging resistance improvement. Preferably it is 40 area% or less. Further, since the texture is controlled by plastic working after hot rolling, the lower limit of the area ratio is set to 10%. The range of 15 to 40% is preferable for the purpose of introducing plastic working effective for improving ridging resistance.

  In order to obtain the texture defined as described above, the processed texture subjected to the final annealing is the case where the X-ray random intensity ratio of the {001} <110> plane and the {111} <110> plane is Ia and Ib , Ia ≧ 5 and Ia / Ib> 1. In the case of Ia <5, Ia / Ib <1, colony division / destruction in the {001} and {112} plane orientation regions by the method described in the above (a) to (j) is insufficient.

  The X-ray random intensity ratio described above can be obtained from a crystal grain orientation distribution function (referred to as ODF) by an X-ray diffraction method. This function is described in, for example, light metals; Hiroshi Inoue, Vol. 42, no. 6, 358 to 367, there are three variables (ψ1, φ, ψ2) that uniquely specify the crystal grain orientation with respect to the material coordinate system. By obtaining this function, the abundance of crystal grains having Euler angles (ψ1, φ, ψ2) can be known. Here, the above-mentioned ODF was determined from pole figures of {200} plane, {110} plane, and {211} plane measured from X-ray diffraction.

  Specifically, on the cross section ψ2 = 45 °, {001} <110> is (0 °, 0 °) and (90 °, 0 °), and {111} <110> is (0 °, 54.7). The abundance can be known from the intensity of (°) and (60 °, 54.7 °). In the same analysis, {111} <112> is related as (30 °, 54.7 °) and (90 °, 54.7 °), and {112} <110> is related as (0 °, 34.7 °). You can also know the abundance of the azimuth.

  The texture of the final annealed plate is {111} <112>-{554} <225 of the matrix from the viewpoint of improving the [2] r value in addition to colony division / destruction in the {001}-{112} plane orientation region > Direction needs to be developed. When the X-ray random intensity ratio of {111} <112> in the final annealed plate is Ic, in the above analysis, preferably Ic> 5, more preferably Ic> 10.

  In the case of the texture defined in the present invention, when the ridging height, the average r value and the Δr value are measured by the method described above, the ridging height is 5 μm or less, the average r value is 1.6 or more, and the Δr value is 0.5. The following can be done. More preferably, the ridging height is 3 μm or less, the average r value is 2.0 or more, and the Δr value is 0.3 or less. These characteristics are not easy to achieve even in a manufacturing method in which cold rolling and annealing for developing the {111} orientation are repeated.

  (C) Manufacturing method

  In the ferritic stainless steel having the component described in the item (A), the following manufacturing conditions are preferable in order to obtain the texture described in the item (B) after the final annealing plate and processing.

  As long as the hot-rolled sheet used for the production has the component (A), the structure is not particularly limited. In order to form the texture of the present invention, before cold rolling using a hot-rolled sheet or a hot-rolled annealed sheet, plasticity that passes through a path that is angled with respect to the moving direction of the steel sheet in a cold or warm manner. It is preferable to apply processing.

  As the plastic working, there is a method of passing through a die having an angled path as shown in FIG. This method is also called an ECAP (Equal-channel angular pressing) method. As shown in FIG. 1, a material 4 is placed in a die 1 having two channels 2 having an equal cross section intersecting at an angle of φ = 90 to 170 °. It is extruded through the plunger 3 to give a simple shear deformation. The extrusion direction is not particularly specified, but it is preferable to match the rolling direction. The extrusion angle is in the range of φ = 90 to 170 ° in the schematic diagram shown in FIG. In order to obtain the texture defined in the present invention, a range of φ = 90 to 150 ° is preferable. More preferably, φ = 90 to 120 °.

  The plastic working described in the previous section is performed once or more, and may be performed a plurality of times in order to obtain the effect of improving ridging resistance. Annealing after plastic working may be performed. The processing temperature may be normal temperature, but may be performed at a temperature from normal temperature to 400 ° C.

  After introducing a deformation zone having a high dislocation density into the cold-rolled material by the above method, cold rolling is performed without annealing or annealing. The cold rolling reduction is not particularly specified, but is preferably 50% or more in order to regulate the size of the cold-rolled annealed plate.

  The annealing performed before and after the cold rolling is aimed at recrystallization for the purpose of dividing and destroying the colonies, and is preferably 750 ° C. or higher and lower than 1000 ° C. If it is less than 750 degreeC, it is difficult to make use of the introduced deformation zone as a nucleation site. The annealing temperature is more preferably 800 ° C. or higher, and further preferably 850 ° C. or higher. On the other hand, when the annealing temperature exceeds 1000 ° C., the crystal grains become coarse, which may adversely affect the surface properties of the product plate. Therefore, the annealing temperature is more preferably less than 1000 ° C. and 950 ° C. or less.

  An example of a ferritic stainless steel sheet having the texture of the present invention by carrying out the manufacturing method of the present invention will be described below.

  250 mm thick ferritic stainless steel slabs having the components shown in Table 3 were melted and hot-rolled to obtain hot-rolled steel sheets having a thickness of 3.8 mm. Using these hot-rolled steel sheets, plastic working as shown in FIG. 1 was performed prior to cold rolling to produce cold-rolled annealed sheets of 0.5 to 2.0 mm. The plastic working was performed by changing the angle φ of the die shown in FIG. 1, the number of times the die passes (number of passes), and the annealing conditions after the pass.

  For comparison, a cold-rolled annealed plate was manufactured by performing the above-described plastic working using a hot-rolled steel plate having a component that does not fall within the scope of the present invention. Furthermore, a cold-rolled annealed sheet having a thickness of 0.5 to 1.0 mm is manufactured by a manufacturing method in which annealing and cold rolling are repeated without performing the above-described plastic working using the hot-rolled steel sheet having the components specified in the present invention. did.

Various test pieces were collected from the obtained cold-rolled annealed plate, and the ridging height, average r value, Δr value and texture were evaluated. The ridging height was the maximum unevenness obtained by taking a JIS No. 5 tensile test piece, giving an elongation strain of 16% in the rolling direction, and evaluating it with a two-dimensional surface roughness measuring instrument. The average r value and Δr value were obtained by taking JIS13B tensile specimens in the 0 °, 45 °, and 90 ° directions with respect to the rolling direction, obtaining the r value in each direction at 16% elongation strain, and calculating by the following formula. .
Average r = (r _{0 °} + 2r _{45 °} + r _{90 °} ) / 4
Δr = (r _{0 °} -2r _{45 °} + r _{90 °} ) / 2

  The texture was evaluated by the EBSP method and the X-ray diffraction method on the plate surface at the center of the thickness of the cold-rolled plate and the cold-rolled annealed plate. In the EBSP method, a crystal orientation map was measured with a x100 field of view, and the orientation for each crystal grain was confirmed to determine the maximum length and area ratio of {001} and {112} plane orientation regions. The size of the azimuth area was the length of the long side in the observed visual field. The cold-rolled sheet was measured for the crystal grain orientation distribution function (ODF) by X-ray diffraction, and the X-ray random intensity ratio of the {001} <110> plane and the {111} <110> plane was determined.

  Table 4 shows the relationship between the manufacturing conditions, the properties of the cold-rolled annealed sheet, and the texture.

  Production No. 1-7 have the component of this invention, and satisfy | fill the texture prescribed | regulated by this invention. The texture of the present invention is controlled by performing the plastic working described in the production method of the present invention prior to cold rolling. These examples of the present invention satisfy a ridging height of 5 μm or less, an average r value of 1.6 or more, and a Δr value of 0.5 or less.

  The above-mentioned example of the present invention is manufactured by No. Compared with the steel plate obtained by the manufacturing method which repeats cold rolling and annealing shown in 9 to 13, the ridging height is greatly reduced. Further, production Nos. 1, 3 and 4 satisfy a ridging height of 3 μm or less, an average r value of 2.0 or more, and an Δr value of 0.3 or less, and develop a {111} orientation by repeating cold rolling and annealing. It can be seen that this is not easy to achieve in the manufacturing method.

  Production No. 8 is a component deviating from the definition of the present invention, and although it has good ridging resistance, a high r value specified by the present invention cannot be obtained.

  According to the present invention, the ferritic stainless steel in which the influence of colonies derived from the solidified structure by reducing carbon and nitrogen is likely to remain in the hot-rolled steel sheet also controls the texture in the process after hot rolling, A highly workable ferritic stainless steel sheet having excellent ridging resistance can be produced.

It is a schematic diagram of the plastic working implemented prior to cold rolling, (a) is a perspective view, (b) is a perspective sectional view. Relationship between area ratio of {001}, {112} plane orientation region and r value Relationship between area ratio of {001}, {112} plane orientation region and ridging height

Explanation of symbols

1 Die 2 Channel 3 Plunger 4 Material

Claims (6)

  In mass%, C: 0.03% or less, Si: 1% or less, Mn: 1% or less, P: 0.05% or less, S: 0.01% or less, Cr: 10 to 25%, N: 0.030% or less, Ti: 0.35% or less, Al: 0.1% or less, the balance is made of Fe and inevitable impurities, and the {001} and {112} plane orientation regions in the plate surface at the plate thickness center The maximum length is less than 0.1 mm and the presence thereof is 10 to 50 area%, the average r value of 0 °, 45 °, and 90 ° with respect to the rolling direction is 1.6 or more and the Δr value is 0.5. A highly workable ferritic stainless steel sheet with excellent ridging resistance, characterized by the following:   When the texture of the steel subjected to the final annealing of the steel is Ia and Ib when the X-ray random intensity ratios of the {001} <110> plane and the {111} <110> plane are Ia and Ib, respectively, in the plate thickness center plate The high workability ferritic stainless steel sheet having excellent ridging resistance according to claim 1, wherein the relationship of ≧ 5 and Ia / Ib> 1 is satisfied.   The high workability ferritic stainless steel sheet having excellent ridging resistance according to claim 1 or 2, wherein the ridging height after applying an elongation strain of 16% in the rolling direction is 5 µm or less.   The steel is further in mass%, Mg: 0.005% or less, Nb: 1% or less, Mo: 2% or less, Ni: 2% or less, Cu: 2% or less, B: 0.005% or less. The high workability ferritic stainless steel sheet excellent in ridging resistance according to any one of claims 1 to 3, which is contained in one kind or two or more kinds.   5. A method of manufacturing a steel sheet in which a ferritic stainless steel slab having the steel component according to claim 1 or 4 is hot-rolled to form a hot-rolled sheet, and then repeatedly annealed and cold-rolled, and the angle with respect to the moving direction of the steel sheet. 5. A highly workable ferritic stainless steel with excellent ridging resistance according to claim 1, wherein the steel is cold-rolled and annealed after being subjected to plastic working passing through a path with a mark. A method of manufacturing a steel sheet.   5. A method of manufacturing a steel sheet in which a ferritic stainless steel slab having the steel component according to claim 1 or 4 is hot-rolled to form a hot-rolled sheet, and then repeatedly annealed and cold-rolled, and the angle with respect to the moving direction of the steel sheet. 5. An excellent ridging resistance according to claim 1, wherein annealing is performed after plastic processing passing through a path with a mark, followed by cold rolling and annealing. Manufacturing method of workable ferritic stainless steel sheet.

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