Ferritic stainless steel and methods for manufacturing it.

Abstract

A ferritic stainless steel sheet according to one embodiment of the present invention can be a ferritic stainless steel sheet with excellent workability, comprising, by wt%, 0.0005-0.02% of C, 0.005-0.02% of N, 0.01-1.0% of Si, 0.01-1.0% of Mn, 0.001-0.05% of P, 13.0-20.0% of Cr, 0.05-0.5% of Ti, and the balance of Fe and other inevitable impurities, and having a fraction of {111} texture in an area from a surface layer up to 1 / 4 thickness of 50% or more.

Description

Ferritic stainless steel and its manufacturing method

[0001] The present invention relates to ferritic stainless steel, and more specifically, to ferritic stainless steel having excellent processability by controlling the grain structure and a manufacturing method thereof.

[0002] Ferritic stainless steels are used in a variety of industrial fields, including home appliances, kitchenware, and automotive parts, and require high machinability to support a variety of processing methods. However, because ferritic stainless steels have a BCC crystal structure, they do not have the TRIP characteristic of austenitic stainless steels, resulting in relatively low elongation. On the other hand, ferritic stainless steels have the characteristic of forming a high {111} texture under appropriate manufacturing conditions, which can be utilized to obtain a high R value, making them advantageous for deep drawing. Therefore, ferritic stainless steels have a lower elongation than austenitic stainless steels, and technology is needed to ensure that ferritic stainless steels can support a variety of processing methods in the various fields in which they are applied.

[0003] The purpose of the present invention to solve the above-described problem is to provide a ferritic stainless steel and a method for manufacturing the same, which have improved workability by controlling the grain structure by optimizing the steel composition and manufacturing process.

[0004] The problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

[0005] As a means for achieving the above-described purpose, a ferritic stainless steel sheet according to an example of the present invention may be a ferritic stainless steel sheet having excellent workability, which includes, in wt%, C: 0.0005 to 0.02%, N: 0.005 to 0.02%, Si: 0.01 to 1.0%, Mn: 0.01 to 1.0%, P: 0.001 to 0.05%, Cr: 13.0 to 20.0%, Ti: 0.05 to 0.5%, the remainder Fe and unavoidable impurities, and has a {111} texture fraction of 50% or more in a region from the surface layer to 1 / 4 thickness.

[0006] A ferritic stainless steel sheet according to an example of the present invention may be a ferritic stainless steel sheet having excellent processability and an R-bar value of 1.7 or more.

[0007] A method for manufacturing a ferritic stainless steel sheet according to an example of the present invention comprises the steps of: manufacturing a slab including, in wt%, C: 0.0005 to 0.02%, N: 0.005 to 0.02%, Si: 0.01 to 1.0%, Mn: 0.001 to 0.05%, P: 13.0 to 20.0%, Ti: 0.05 to 0.5%, the remainder Fe and unavoidable impurities; hot rolling the manufactured slab in a heating furnace at 1100 to 1300°C; first rolling at a reduction ratio of 25 to 65% after the hot rolling; hot rolling annealing at 900 to 1100°C after the first rolling; second rolling; It may be a method for manufacturing a ferritic stainless steel sheet having excellent processability, including a step of cold rolling and annealing.

[0008] A method for manufacturing a ferritic stainless steel sheet according to an example of the present invention may be a method for manufacturing a ferritic stainless steel sheet with excellent processability, in which the reduction ratio in the secondary rolling step is 40% or more.

[0009] A method for manufacturing a ferritic stainless steel sheet according to an example of the present invention may be a method for manufacturing a ferritic stainless steel sheet with excellent processability, in which the cold rolling annealing step is performed at 850 to 1050°C.

[0010] A method for manufacturing a ferritic stainless steel sheet according to an example of the present invention may be a method for manufacturing a ferritic stainless steel sheet having excellent processability, in which a hot-rolled material subjected to hot rolling and annealing has a {111} texture fraction of 10% or more in a region from the surface layer to 1 / 4 thickness.

[0011] A method for manufacturing ferritic stainless steel according to an example of the present invention may be a method for manufacturing a ferritic stainless steel sheet having excellent processability, in which a cold-rolled annealed cold-rolled material has a {111} texture fraction of 50% or more in a region from the surface layer to 1 / 4 thickness.

[0012] A method for manufacturing a ferritic stainless steel according to an example of the present invention may be a method for manufacturing a ferritic stainless steel sheet having excellent processability and an R-bar value of 1.7 or more.

[0013] According to one embodiment of the present invention, a ferritic stainless steel having excellent workability and a method for manufacturing the same can be provided by forming a {111} texture including a step of primary rolling and hot rolling annealing.

[0014] Figure 1 is a drawing showing the {111} texture of the hot-rolled material of Invention Example 5 measured by EBSD.

[0015] Figure 2 is a drawing showing the {111} texture of the hot-rolled material of Comparative Example 2 measured by EBSD.

[0016] Figure 3 is a diagram showing the {111} texture fraction of hot-rolled and cold-rolled materials.

[0017] Figure 4 is a diagram showing the relationship between the reduction ratio of the first rolling and the {111} texture fraction in the area from the surface layer to 1 / 4 thickness of the cold-rolled material.

[0018] Figure 5 is a diagram showing the relationship between the {111} aggregate texture fraction and the R-bar in the area from the surface to 1 / 4 thickness.

[0019] Preferred embodiments of the present invention are described below. However, the embodiments of the present invention may be modified in various ways, and the technical concept of the present invention is not limited to the embodiments described below. Furthermore, the embodiments of the present invention are provided to more fully explain the present invention to those of ordinary skill in the art.

[0020] The terminology used in this application is solely for the purpose of describing specific examples. Therefore, for example, singular expressions include plural expressions unless the context clearly dictates otherwise. Additionally, it should be noted that terms such as "comprise" or "have" used in this application are used to clearly indicate the presence of features, steps, functions, components, or combinations thereof described in the specification, and are not used to preliminarily exclude the presence of other features, steps, functions, components, or combinations thereof.

[0021] Meanwhile, unless otherwise defined, all terms used herein should be considered to have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Therefore, unless explicitly defined herein, specific terms should not be interpreted in an overly idealistic or formal sense.

[0022] In addition, the terms "about", "substantially", etc. in this specification are used in the sense of or close to the numerical value when manufacturing and material tolerances inherent to the meanings mentioned are presented, and are used to prevent unscrupulous infringers from unfairly using the disclosure contents in which exact or absolute numerical values ​​are mentioned to aid in the understanding of the present invention.

[0023] A ferritic stainless steel according to an example of the present invention may be a ferritic stainless steel that includes, in wt%, C: 0.0005 to 0.02%, N: 0.005 to 0.02%, Si: 0.01 to 1.0%, Mn: 0.01 to 1.0%, P: 0.001 to 0.05%, Cr: 13.0 to 20.0%, Ti: 0.05 to 0.5%, the remainder Fe and unavoidable impurities, and has a {111} texture fraction of 50% or more in a region from the surface layer to 1 / 4 thickness.

[0024] A ferritic stainless steel according to an example of the present invention may be a ferritic stainless steel having an R-bar value of 1.7 or more.

[0025] The reasons for limiting the composition range of each alloy element are described below.

[0026] The content of C may be 0.0005 to 0.02 wt%.

[0027] If C is less than 0.0005%, the refining cost for producing a high-purity product increases, and if C exceeds 0.02%, corrosion resistance and formability may be poor. Taking this into account, the C content may be 0.0005 to 0.02 wt%.

[0028] The content of N may be 0.005 to 0.02 wt%.

[0029] If N is less than 0.005%, TiN crystallization is low, which reduces the equiaxed crystallinity of the slab. If N exceeds 0.02%, corrosion resistance and formability may be poor. Considering this, the N content may be 0.005 to 0.02%.

[0030] The content of Si can be 0.01 to 1.0 wt%.

[0031] If Si is less than 0.01%, refining costs increase, and if Si exceeds 1.0%, impurities increase, which may result in poor formability. Considering this, the Si content may be 0.01 to 1.0%.

[0032] The content of Mn may be 0.01 to 1.0 wt%.

[0033] If the manganese content is less than 0.01%, the refining cost increases, and if the manganese content exceeds 1.0%, impurities increase, which may result in poor formability. Taking this into account, the manganese content may be 0.01 to 1.0%.

[0034] The content of P may be 0.001 to 0.05 wt%.

[0035] If P is less than 0.001%, the refining cost increases, and if P exceeds 0.05%, impurities increase, which may result in poor formability. Taking this into account, the P content may be 0.001 to 0.05%.

[0036] The Cr content may be 13.0 to 20.0 wt%.

[0037] If Cr is less than 13.0%, corrosion resistance may be poor, and if Cr exceeds 20.0%, formability may be poor. Taking this into account, the Cr content may be 13.0 to 20.0%.

[0038] The content of Ti may be 0.05 to 0.5 wt%.

[0039] If Ti is less than 0.05%, recrystallization is insufficient during hot rolling, and if Ti exceeds 0.5%, a large amount of steelmaking inclusions may be generated. Considering this, the Ti content may be 0.05 to 0.5%.

[0040] The content of Ti / (C+N) can be 1.25% or more.

[0041] If the Ti / (C+N) content is less than 1.25%, recrystallization during hot rolling is insufficient, and corrosion resistance and formability may be inferior. If the Ti / (C+N) content is 1.25% or more, pre-rolling milling, that is, pre-rolling reduction, can be applied before hot rolling annealing to accumulate the deformation energy of the hot rolled material, thereby inducing recrystallization and securing elongation and drawability in the final product.

[0042] The remaining component is iron (Fe). However, since unintended impurities from raw materials or the surrounding environment can inevitably be mixed in during the normal manufacturing process, this cannot be ruled out. Since these impurities are readily apparent to anyone skilled in the normal manufacturing process, their full details are not specifically mentioned in this specification.

[0043] The method for manufacturing ferritic stainless steel of the present invention can perform hot rolling - primary rolling - hot rolling annealing on the manufactured slab, and can further perform secondary rolling - cold rolling annealing.

[0044] A method for manufacturing a ferritic stainless steel according to an example of the present invention comprises the steps of: manufacturing a slab including, in wt%, C: 0.0005 to 0.02%, N: 0.005 to 0.02%, Si: 0.01 to 1.0%, Mn: 0.001 to 0.05%, P: 13.0 to 20.0%, Ti: 0.05 to 0.5%, the remainder Fe and unavoidable impurities; hot rolling the manufactured slab in a heating furnace at 1100 to 1300°C; first rolling at a reduction ratio of 25 to 65% after the hot rolling; hot rolling annealing at 900 to 1100°C after the first rolling; second rolling; It may be a method for manufacturing ferritic stainless steel, including a step of cold rolling and annealing.

[0045] The alloy composition of the method for manufacturing ferritic stainless steel according to an example of the present invention may be the same as the ferritic stainless steel according to an example of the present invention described above.

[0046] The hot rolling step of the ferritic stainless steel manufacturing method of the present invention may be a step of hot rolling the slab in a heating furnace at 1100 to 1300°C.

[0047] If the temperature of the hot rolling stage is below 1100℃, bundles and sheeting may be difficult due to hot rolling defects. If the temperature exceeds 1300℃, bending and sheeting of the slab may be difficult. Considering this, the hot rolling stage may be performed at a temperature of 1100 to 1300℃.

[0048] The first rolling step of the method for manufacturing ferritic stainless steel of the present invention may be a step of reducing at a reduction ratio of 25 to 65%.

[0049] If the reduction ratio of the first rolling is less than 25%, the strain energy is low, resulting in insufficient recrystallization, which may make it difficult to secure a {111} texture fraction of 10% or more in the area from the surface to 1 / 4 thickness. If the reduction ratio of the first rolling exceeds 65%, the second reduction ratio is insufficient, which may make it difficult to secure a {111} texture fraction of 50% or more in the area from the surface to 1 / 4 thickness in the final cold-rolled material. If the {111} texture fraction in the area from the surface to 1 / 4 thickness is not secured, the R-bar value may not be secured. Considering this, the reduction ratio of the first rolling can be set to 25 to 65%.

[0050] The hot rolling annealing step of the ferritic stainless steel manufacturing method of the present invention may be a step of hot rolling annealing at 900 to 1100°C.

[0051] If the temperature during the hot-rolling annealing step is below 900°C, recrystallization may not occur, preventing the formation of a grain structure. If the temperature exceeds 1100°C, grains may coarsen and sheet fracture may occur. Considering this, the hot-rolling annealing step may be performed at a temperature between 900 and 1100°C.

[0052] By including a primary rolling step before hot rolling annealing, the deformation energy of the hot rolled material can be accumulated and recrystallized through hot rolling annealing.

[0053] After the hot rolling step, the first rolling step, and the hot annealing step of the method for manufacturing ferritic stainless steel of the present invention, the hot-rolled annealed hot-rolled material may have a {111} texture fraction of 10% or more in the region from the surface layer to 1 / 4 thickness.

[0054] The second rolling step of the ferritic stainless steel manufacturing method of the present invention may be a step of reducing at a reduction ratio of 40% or more.

[0055] When the reduction ratio of the secondary rolling is 40% or more, recrystallization occurs, and the {111} texture fraction in the area from the surface layer to 1 / 4 thickness of the final cold-rolled material can be secured at 50% or more. When the {111} texture fraction in the area from the surface layer to 1 / 4 thickness is secured, the R-bar value can be secured. Taking this into account, the reduction ratio of the secondary rolling can be set to 40% or more.

[0056] The cold rolling annealing step of the ferritic stainless steel manufacturing method of the present invention may be a cold rolling annealing step at 850 to 1050°C.

[0057] When the temperature of the cold rolling annealing step is 850°C or higher, recrystallization can occur, forming a grain structure. When the temperature of the cold rolling annealing step is 1050°C or lower, grain coarsening and sheet fracture can be prevented. Considering this, the cold rolling annealing step can be performed at a temperature of 850 to 1050°C.

[0058] After the secondary rolling step and the cold rolling annealing step of the method for manufacturing ferritic stainless steel of the present invention, the cold rolled annealed cold rolled material may have a {111} texture fraction of 50% or more in the region from the surface layer to 1 / 4 thickness.

[0059] In the method for manufacturing ferritic stainless steel of the present invention, the ferritic stainless steel subjected to cold rolling and annealing after secondary rolling, including primary rolling, can secure an R-bar value of 1.7 or higher by securing a {111} texture fraction of 50% or higher in the region from the surface layer to 1 / 4 thickness.

[0060] Here R-bar is (R0+ R 90 + 2*R 45 ) / 4, which can be greater than 1.7. For the rolling direction of the specimen, R0 is the R value in the 0° direction, R 45 is the R value in the 45° direction, R 90 is the R value in the 90° direction. The R value is the width strain / thickness strain. A higher R-bar value means that it is advantageous for elongation and deep drawing processing.

[0061] Hereinafter, the present invention will be described in more detail through examples and drawings. However, these descriptions are merely illustrative of the implementation of the present invention and are not intended to limit the scope of the present invention. This is because the scope of the present invention is determined by the matters set forth in the claims and matters reasonably inferred therefrom.

[0062] {Example}

[0063] An alloy composition was prepared according to Table 1 below.

[0064] Steel CNSiMnPCrTiA0.01240.01570.240.210.0213.80.25B0.00740.01530.860.340.0316.20.23C0.00660.0110.420.250.0318.10.19

[0065] Table 2 below shows the {111} texture fraction and R-bar value in the area from the surface layer to 1 / 4 thickness of hot-rolled and cold-rolled materials, which were produced according to the first rolling progress and reduction ratio of slabs having the alloy composition of Table 1. The first rolling progress and reduction ratio were controlled by changing them as shown in Table 1 below. The reheating temperature of the hot-rolled slab was 1200℃, and the reduction ratio of the first rolling was changed as shown in Table 1 below. The hot-rolling annealing temperature was 1000℃, the second rolling was performed with a reduction ratio of 40%, and the cold-rolling annealing temperature was 950℃.

[0066] The {111} texture fraction (%) in the area from the surface layer to 1 / 4 thickness of the hot-rolled material means the value of the {111} texture fraction in the area from the surface layer to 1 / 4 thickness measured by EBSD attached to a scanning electron microscope of the hot-rolled material after hot-rolling annealing.

[0067] The {111} texture fraction (%) in the area from the surface layer to 1 / 4 thickness of the cold-rolled material means the value of the {111} texture fraction in the area from the surface layer to 1 / 4 thickness measured by EBSD attached to a scanning electron microscope after cold-rolled annealing.

[0068] Example Steel grade 1st rolling reduction ratio (%) Fraction of {111} texture in the area from the surface layer of hot rolled material to 1 / 4 thickness (%) Fraction of {111} texture in the area from the surface layer of cold rolled material to 1 / 4 thickness (%) R-bar Invention example 1A3016.255.21.76 Invention example 2B3015.454.71.81 Invention example 3C3014.953.71.72 Invention example 4A4028.366.12.02 Invention example 5B4025.762.52.07 Invention example 6C4026.463.11.89 Invention example 7A6032.161.51.96 Invention example 8B6033.458.31.82 Invention example 9C603155.71.78Comparative Example 1A03.238.11.52Comparative Example 2B02.740.21.51Comparative Example 3C01.437.61.48Comparative Example 4A206.742.21.55Comparative Example 5B205.843.11.57Comparative Example 6C205.641.31.42Comparative Example 7A7038.747.21.62Comparative Example 8B7039.246.21.52Comparative Example 9C7038.845.91.59

[0069] Referring to Tables 1 and 2, Invention Examples 1 to 3, which were first rolled at a reduction ratio of 30% for steel grade A having an alloy composition satisfying the scope of the present invention, Invention Examples 4 to 6, which were first rolled at a reduction ratio of 40% for steel grade B, and Invention Examples 7 to 9, which were first rolled at a reduction ratio of 60% for steel grade C, have a {111} texture fraction of 10% or more in the region from the surface layer to 1 / 4 thickness of the hot-rolled material and a {111} texture fraction of 50% or more in the region from the surface layer to 1 / 4 thickness of the cold-rolled material, thereby satisfying the scope of the present invention. Accordingly, the R-bar value is 1.7 or more, thereby satisfying the scope of the present invention. Through this, it can be confirmed that when the first rolling is performed at a reduction ratio of 25 to 65% for a slab satisfying the alloy composition of the present invention, the {111} texture fraction in the area from the surface layer to 1 / 4 thickness of the hot-rolled material is 10% or more, and the {111} texture fraction in the area from the surface layer to 1 / 4 thickness of the cold-rolled material is 50% or more, satisfying the control range of the present invention, and as a result, the R-bar value can be secured as 1.7 or more. Comparative Examples 1 to 3 correspond to cases where the first rolling is not performed at all for steel grades A, B, and C satisfying the range of the present invention. Comparative Examples 1 to 3 do not satisfy the scope of the present invention because the {111} texture fraction in the region from the surface layer to 1 / 4 thickness of the hot-rolled material is less than 10%, and the {111} texture fraction in the region from the surface layer to 1 / 4 thickness of the cold-rolled material is less than 50%. Accordingly, the R-bar value is less than 1.7, and thus does not satisfy the scope of the present invention.

[0070] Through this, it can be confirmed that even if the alloy composition is satisfied, if the first rolling is not performed at all, the {111} texture fraction in the area from the surface layer to 1 / 4 thickness of the hot-rolled material is less than 10%, and the {111} texture fraction in the area from the surface layer to 1 / 4 thickness of the cold-rolled material is less than 50%, so that the control range of the present invention cannot be satisfied, and as a result, the R-bar value cannot be secured as 1.7 or higher.

[0071] Comparative Examples 4 to 6 correspond to cases where the first rolling was performed at a reduction ratio of 20% for steel grades A, B, and C, which satisfy the scope of the present invention. Comparative Examples 4 to 6 do not satisfy the scope of the present invention because the {111} texture fraction in the region from the surface layer to 1 / 4 thickness of the hot-rolled material is less than 10%, and the {111} texture fraction in the region from the surface layer to 1 / 4 thickness of the cold-rolled material is less than 50%. Accordingly, the R-bar value is less than 1.7, and thus does not satisfy the scope of the present invention.

[0072] Through this, it can be confirmed that even if the alloy composition is satisfied, if the first rolling is performed at a reduction ratio of less than 25%, the {111} texture fraction in the area from the surface layer to 1 / 4 thickness of the hot-rolled material is less than 10%, and the {111} texture fraction in the area from the surface layer to 1 / 4 thickness of the cold-rolled material is less than 50%, which does not satisfy the control range of the present invention, and as a result, the R-bar value cannot be secured as 1.7 or higher.

[0073] Comparative Examples 7 to 9 correspond to cases where the first rolling was performed at a reduction ratio of 70% for steel grades A, B, and C, which satisfy the scope of the present invention. In Comparative Examples 7 to 9, the {111} texture fraction in the region from the surface layer to 1 / 4 thickness of the hot-rolled material corresponds to 10% or more, but the {111} texture fraction in the region from the surface layer to 1 / 4 thickness of the cold-rolled material is less than 50%, which does not satisfy the scope of the present invention. Accordingly, the R-bar value is less than 1.7, which does not satisfy the scope of the present invention.

[0074] Through this, even if the alloy composition is satisfied, when the first rolling is performed at a reduction ratio exceeding 65%, even if the {111} texture fraction in the area from the surface layer to 1 / 4 thickness of the hot-rolled material is secured to 10% or more, it can be confirmed that the {111} texture fraction in the area from the surface layer to 1 / 4 thickness of the cold-rolled material is less than 50%, which does not satisfy the control range of the present invention, and as a result, the R-bar value cannot be secured to 1.7 or more.

[0075] Through drawings, a method for manufacturing a ferritic stainless steel sheet having excellent processability according to an example of the present invention is described.

[0076] Figure 1 is a drawing showing the {111} texture fraction measured by EBSD in the area from the surface layer to 1 / 4 thickness of the hot-rolled material of Invention Example 5.

[0077] Figure 2 is a drawing showing the {111} texture fraction measured by EBSD in the area from the surface layer to 1 / 4 thickness of the hot-rolled material of Comparative Example 2.

[0078] Inventive Example 5 and Comparative Example 2 were carried out using a steel grade B slab that satisfies the alloy composition of the present invention. Inventive Example 5 is a case where the first rolling was carried out at a reduction ratio of 40%, and Comparative Example 2 is a case where the first rolling was not carried out at all.

[0079] In Figures 1 and 2, the portion with a higher fraction of {111} texture is shown in a darker color. When measured with EBSD, the higher the fraction of {111} texture, the lower the brightness, and the lower the fraction of {111} texture, the higher the brightness.

[0080] Referring to FIGS. 1 and 2, it can be confirmed that the case of invention example 5, which performed the first rolling, had a higher fraction of {111} aggregate structure than comparative example 2, resulting in lower brightness.

[0081] Here, high brightness means close to a bright color (e.g., white), and low brightness means close to a dark color (e.g., black).

[0082] This means that when primary rolling is performed, the {111} texture fraction of the hot-rolled material increases due to shear deformation in hot rolling.

[0083] Figure 3 is a diagram showing the {111} texture fraction of hot-rolled and cold-rolled materials. It can be confirmed that when the {111} texture fraction of the hot-rolled material is high, the {111} texture fraction of the cold-rolled material is also high.

[0084] Figure 4 is a diagram showing the relationship between the reduction ratio of the first rolling and the {111} texture fraction in the area from the surface layer to 1 / 4 thickness of the cold-rolled material.

[0085] Referring to Fig. 4, it can be confirmed that when the first rolling is performed at a reduction ratio of 25 to 65%, the fraction of {111} texture of the cold-rolled material is secured at 50% or more.

[0086] Referring to FIGS. 1 to 4, it can be confirmed that when primary rolling is performed, the {111} texture fraction in the area from the surface layer to 1 / 4 thickness of the hot-rolled material can be secured as high as 10% or more, and the {111} texture fraction in the area from the surface layer to 1 / 4 thickness of the cold-rolled material can be secured as high as 50% or more.

[0087] Figure 5 is a diagram showing the relationship between the {111} texture fraction and R-bar in the area from the surface layer to 1 / 4 thickness of the cold-rolled material.

[0088] Referring to Figure 5, it can be confirmed that when the {111} texture fraction in the area from the surface layer to 1 / 4 thickness of the cold-rolled material is 50% or more, the R-bar value is secured as 1.7 or more.

[0089] Referring to FIGS. 1 to 5, it can be confirmed that when primary rolling is performed, the {111} texture fraction in the area from the surface layer to 1 / 4 thickness of the hot-rolled material can be secured as high as 10% or more, and the {111} texture fraction in the area from the surface layer to 1 / 4 thickness of the cold-rolled material can be secured as high as 50% or more, thereby securing an R-bar value of 1.7 or more.

Claims

DEPCT6910 / 09 / 25681. A ferritic stainless steel plate with excellent formability, composed of the following elements in percentages by weight (% by weight): Carbon (C) 0.0005 to 0.02%, Nitrogen (N) 0.005 to 0.02%, Silicon (Si) 0.01 to 1.0%, Manganese (Mn) 0.01 to 1.0%, Phosphorus (P) 0.001 to 0.05%, Chromium (Cr) 13.0 to 20.0%, Titanium (Ti) 0.05 to 0.5%, the remainder being Iron (Fe) and unavoidable impurities, where the proportion of the surface texture in the area from the surface layer to one-quarter of the thickness is 50.

1. % or more.

2. Ferritic stainless steel plates according to claim 1, where the R-bar value is 1.7 or more.

3. A method for the manufacture of ferritic stainless steel plates with excellent shapeability in which the assembly method involves the preparation of flat bars containing the following elements in percentages by weight (% by weight): Carbon (C) 0.0005 to 0.02%, Nitrogen (N) 0.005 to 0.02%, Silicon (Si) 0.01 to 1.0%, Manganese (Mn) 0.01 to 1.0%, Phosphorus (P) 0.001 to 0.05%, Chromium (Cr) 13.0 to 20.0%, Titanium (Ti) 0.05 to 0.05.5%, the remainder being iron (Fe) and unavoidable impurities; hot rolling operation on flat billets prepared in a furnace heated to 1100 to 1300 degrees Celsius; first rolling operation at a reduction rate of 25 to 65% after hot rolling; hot annealing operation at 900 to 1100 degrees Celsius after the first rolling; second rolling operation and cold annealing operation; 4. Method according to claim 3 where the reduction rate in the second rolling is 40% or more; 5. Method according to claim 3 where the annealing... Cold annealing is performed at 850 to 1050 degrees Celsius.

6. Method according to claim 3 where the hot-rolled material subjected to hot annealing has a surface texture {111} of 10% or more in the area from the surface layer to one-quarter of the thickness.

7. Method according to claim 3 where the cold-rolled material subjected to cold annealing has a surface texture {111} of 50% or more in the area from the surface layer to one-quarter of the thickness.

8. Method according to claim 3 where the R-bar value is 1.7 or more;

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