EP4610382A1

EP4610382A1 - Ferritic stainless steel and manufacturing method therefor

Info

Publication number: EP4610382A1
Application number: EP23903768.2A
Authority: EP
Inventors: Jieon PARK; Minam PARK
Original assignee: Posco Co Ltd
Current assignee: Posco Holdings Inc
Priority date: 2022-12-16
Filing date: 2023-11-09
Publication date: 2025-09-03
Also published as: WO2024128565A1; CN120344696A; JP2025542027A; KR20240094683A

Abstract

A ferritic stainless steel plate according to an embodiment of the present invention may be a ferritic stainless steel plate 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 one-quarter of the thickness of 50% or more.

Description

[Technical Field]

The present invention relates to a ferritic stainless steel, and more specifically, to a ferritic stainless steel having excellent workability achieved by controlling a texture and a method for manufacturing the same.

[Background Art]

Ferritic stainless steels are products used in various industrial fields, including home appliances, kitchenware, and automobile parts, and therefore require high workability that may accommodate various processing methods. However, ferritic stainless steels have a body-centered cubic (BCC) crystal structure, and lack transformation-induced plasticity (TRIP) as in austenitic stainless steels, resulting in relatively low elongation. On the other hand, since ferritic stainless steels have a characteristic of forming a high {111} texture under appropriate manufacturing conditions, with which a high R value may be obtained, thereby providing a benefit in deep drawing processes. Accordingly, considering the lower elongation of ferritic stainless steels compared to austenitic stainless steels, there is a need for technologies that allows ferritic stainless steels to accommodate various processing methods across diverse fields in which ferritic stainless steels are applied.

[Disclosure]

[Technical Problem]

To resolve the above-described issues, the present invention is directed to providing a ferritic stainless steel with improved workability and a method for manufacturing the same by controlling the texture through optimization of the steel composition and manufacturing process.
The technical objectives of the present invention are not limited to the above, and other objectives that are not described above will be clearly understood by those skilled in the art from the above detailed description.

[Technical Solution]

A ferritic stainless steel plate according to an example of the present invention may be a ferritic stainless steel plate having excellent workability, including, in percent by weight (wt%), 0.0005 to 0.02% of carbon (C), 0.005 to 0.02% of nitrogen (N), 0.01 to 1.0% of silicon (Si), 0.01 to 1.0% of manganese (Mn), 0.001 to 0.05% of phosphorus (P), 13.0 to 20.0% of chromium (Cr), 0.05 to 0.5% of titanium (Ti), the remainder of Iron (Fe), and inevitable impurities, wherein a fraction of a {111} texture in a region from a surface layer to one-quarter of the thickness is 50% or more.
A ferritic stainless steel plate according to an example of the present invention may be a ferritic stainless steel plate having excellent workability, wherein an R-bar value is 1.7 or more.
A method for manufacturing a ferritic stainless steel plate according to an example of the present invention is a method for manufacturing a ferritic stainless steel plate having excellent workability, the method including: preparing a slab comprising, in percent by weight (wt%), 0.0005 to 0.02% of carbon (C), 0.005 to 0.02% of nitrogen (N), 0.01 to 1.0% of silicon (Si), 0.01 to 1.0% of manganese (Mn), 0.001 to 0.05% of phosphorus (P), 13.0 to 20.0% of chromium (Cr), 0.05 to 0.5% of titanium (Ti), the remainder of Iron (Fe), and inevitable impurities; performing hot rolling on the prepared slab in a heating furnace at 1100 to 1300°C; performing primary rolling at a reduction ratio of 25 to 65% after the hot rolling; performing hot annealing at 900 to 1100°C after the primary rolling; performing secondary rolling; and performing cold annealing.
A method for manufacturing a ferritic stainless steel plate according to an example of the present invention is a method for manufacturing a ferritic stainless steel plate having excellent workability, wherein a reduction ratio in the secondary rolling is 40% or more.
A method for manufacturing a ferritic stainless steel plate according to an example of the present invention is a method for manufacturing a ferritic stainless steel plate having excellent workability, wherein the cold annealing is performed at 850 to 1050°C.
A method for manufacturing a ferritic stainless steel plate according to an example of the present invention is a method for manufacturing a ferritic stainless steel plate having excellent workability, wherein a hot-rolled material subjected to the hot annealing has a fraction of a {111} texture of 10% or more in a region from a surface layer to one-quarter of the thickness.
A method for manufacturing a ferritic stainless steel plate according to an example of the present invention is a method for manufacturing a ferritic stainless steel plate having excellent workability, wherein a cold-rolled material subjected to the cold annealing has a fraction of a {111} texture of 50% or more in a region from a surface layer to one-quarter of the thickness.
A method for manufacturing a ferritic stainless steel plate according to an example of the present invention is a method for manufacturing a ferritic stainless steel plate having excellent workability, wherein an R-bar value is 1.7 or more.

[Advantageous Effects]

According to an embodiment of the present invention, a ferritic stainless steel having excellent workability and a method for manufacturing the same can be provided by performing primary rolling and hot annealing to form a {111} texture.

[Description of Drawings]

FIG. 1 is a view showing the {111} texture of the hot-rolled material of Inventive Example 5, measured by electron backscatter diffraction (EBSD).
FIG. 2 is a view showing the {111} texture of the hot-rolled material of Comparative Example 2, measured by EBSD.
FIG. 3 is a graph showing the fraction of the {111} texture in the hot-rolled material and the cold-rolled material.
FIG. 4 is a graph showing the relationship between the reduction ratio in the primary rolling and the fraction of the {111} texture in the region from the surface layer to one-quarter of the thickness of the cold-rolled material.
FIG. 5 is a graph showing the relationship between the fraction of the {111} texture in the region from the surface layer to one-quarter of the thickness and the R-bar.

[Modes of the Invention]

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The embodiments of the present disclosure may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art.
Also, the terms used herein are merely used to describe particular embodiments. An expression used in the singular encompasses the expression of the plural, unless otherwise indicated. Throughout the specification, the terms such as "including" or "having" are intended to indicate the existence of features, operations, functions, components, or combinations thereof disclosed in the specification, and are not intended to preclude the possibility that one or more other features, operations, functions, components, or combinations thereof may exist or may be added.
Meanwhile, unless otherwise defined, all terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Thus, these terms should not be interpreted in an idealized or overly formal sense unless expressly so defined herein. As used herein, the singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise.
The terms "about", "substantially", etc. used throughout the specification means that when a natural manufacturing and a substance allowable error are suggested, such an allowable error corresponds the value or is similar to the value, and such values are intended for the sake of clear understanding of the present invention or to prevent an unconscious infringer from illegally using the disclosure of the present invention.
A ferritic stainless steel plate according to an example of the present invention may be a ferritic stainless steel plate including, in percent by weight (wt%), 0.0005 to 0.02% of carbon (C), 0.005 to 0.02% of nitrogen (N), 0.01 to 1.0% of silicon (Si), 0.01 to 1.0% of manganese (Mn), 0.001 to 0.05% of phosphorus (P), 13.0 to 20.0% of chromium (Cr), 0.05 to 0.5% of titanium (Ti), the remainder of Iron (Fe), and inevitable impurities, and having a fraction of a {111} texture of 50% or more in a region from a surface layer to one-quarter of the thickness.
A ferritic stainless steel plate according to an example of the present invention may be a ferritic stainless steel plate having an R-bar value of 1.7 or more.
The reasons for limiting the compositional range of each alloying element are described below.
The content of carbon(C) may be 0.0005 to 0.02 wt%.
When the content of C is less than 0.0005%, the refining cost for producing a high-purity product may increase, and when the content of C exceeds 0.02%, corrosion resistance and formability may be degraded. Considering this, the content of C may be 0.0005 to 0.02 wt%.
The content of nitrogen (N) may be 0.005 to 0.02 wt%.
When the content of N is less than 0.005%, TiN crystallization may decrease, which reduces the equiaxed crystallinity of the slab, and when the content of N exceeds 0.02%, corrosion resistance and formability may be degraded. Considering this, the content of N may be 0.005 to 0.02%.
The content of silicon (Si) may be 0.01 to 1.0 wt%.
When the content of Si is less than 0.01%, the refining price may increase, and when the content of Si exceeds 1.0%, the amount of impurities increase and formability may be degraded. Considering this, the content of Si may be 0.01 to 1.0%.
The content of manganese (Mn) may be 0.01 to 1.0 wt%.
When the content of Mn is less than 0.01%, the refining price may increase, and when the content of Mn exceeds 1.0%, the amount of impurities increase and formability may be degraded. Considering this, the content of Mn may be 0.01 to 1.0%.
The content of phosphorus (P) may be 0.001 to 0.05 wt%.
When the content of P is less than 0.001%, the refining price may increase, and when the content of P exceeds 0.05%, the amount of impurities increase and formability may be degraded. Considering this, the content of P may be 0.001 to 0.05%.
The content of chromium (Cr) may be 13.0 to 20.0 wt%.
When the content of Cr is less than 13.0%, corrosion resistance may be degraded, and when the content of Cr exceeds 20.0%, formability may be degraded. Considering this, the content of Cr may be 13.0 to 20.0%.
The content of titanium (Ti) may be 0.05 to 0.5 wt%.
When the content of Ti is less than 0.05%, recrystallization may be insufficient during hot rolling, and when the content of Ti exceeds 0.5%, a large amount of steelmaking inclusions may be generated. Considering this, the content of Ti may be 0.05 to 0.5%.
A content of Ti/(C+N) may be 1.25% or more.
When the content of Ti/(C+N) is less than 1.25%, recrystallization may be insufficient during hot rolling, and corrosion resistance and formability may be degraded. When the content of Ti/(C+N) is 1.25% or more, applying a pre-rolling milling before hot annealing, that is, a thickness reduction before hot annealing may allow deformation energy of the hot-rolled material to accumulate, which enables recrystallization and ensures elongation and drawability in the final product.
The remainder is iron (Fe). However, unintended impurities from raw materials or the surrounding environment may inevitably be introduced during typical manufacturing process, and thus cannot be excluded. Since such impurities may be well known to those skilled in the typical manufacturing process, details thereof are not specifically described in this specification.
A method for manufacturing a ferritic stainless steel according to the present invention may include performing hot rolling, primary rolling, and hot annealing on the prepared slab, and may further include performing secondary rolling and cold annealing.
The 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, including: preparing a slab comprising, in percent by weight (wt%), 0.0005 to 0.02% of carbon (C), 0.005 to 0.02% of nitrogen (N), 0.01 to 1.0% of silicon (Si), 0.01 to 1.0% of manganese (Mn), 0.001 to 0.05% of phosphorus (P), 13.0 to 20.0% of chromium (Cr), 0.05 to 0.5% of titanium (Ti), the remainder of Iron (Fe), and inevitable impurities; performing hot rolling on the prepared slab in a heating furnace at 1100 to 1300°C; performing primary rolling at a reduction ratio of 25 to 65% after the hot rolling; performing hot annealing at 900 to 1100°C after the primary rolling; performing secondary rolling; and performing cold annealing.
The alloy composition in the method for manufacturing the ferritic stainless steel according to the example of the present invention may be the same as that of the ferritic stainless steel according to the example of the present invention described above.
The performing of the hot rolling in the method for manufacturing a ferritic stainless steel according to the present invention may be an operation of performing hot rolling on the slab in a heating furnace at 1100 to 1300°C.
When the temperature of the hot rolling is below 1100°C, coiling and sheet forming may be difficult due to hot rolling defects. When the temperature of the hot rolling exceeds 1300°C, bending of the slab and sheet forming may be difficult. Considering this, the hot rolling may be performed at a temperature of 1100 to 1300°C.
The performing of the primary rolling in the method for manufacturing a ferritic stainless steel according to the present invention may be an operation of performing thickness reduction at a reduction ratio of 25 to 65%.
When the reduction ratio of the primary rolling is less than 25%, the deformation energy is low, resulting in insufficient recrystallization, which makes it difficult to ensure a {111} texture fraction of 10% or more in a region from the surface layer to one-quarter of the thickness. When the reduction ratio of the primary rolling exceeds 65%, the reduction ratio in the secondary rolling may become insufficient, making it difficult to ensure a {111} texture fraction of 50% or more in the region from the surface layer to one-quarter of the thickness in the final cold-rolled material. When the fraction of the {111} texture in the region from the surface layer to one-quarter of the thickness is not ensured, the R-bar value may not be ensured. Considering this, the reduction ratio of the primary rolling may be set to 25 to 65%.
The performing of the hot annealing in the method for manufacturing a ferritic stainless steel according to the present invention may be an operation of performing hot annealing at 900 to 1100°C.
When the temperature of the hot annealing is below 900°C, recrystallization may not occur and thus the texture may not be formed. When the temperature of the hot annealing exceeds 1100°C, the grains may become coarser and plate fracture may occur. Considering this, the hot annealing may be performed at a temperature of 900 to 1100°C.
By including the primary rolling before the hot annealing, the deformation energy of the hot-rolled material may be accumulated, and recrystallization may be achieved through the hot annealing.
After the hot rolling, the primary rolling, and the hot annealing in the method for manufacturing a ferritic stainless steel according to the present invention, the hot-rolled material subjected to the hot annealing may have a fraction of a {111} texture of 10% or more in the region from the surface layer to the one-quarter of the thickness.
The performing of the secondary rolling in the method for manufacturing a ferritic stainless steel according to the present invention may be an operation of performing thickness reduction at a reduction ratio of 40% or more.
When the reduction ratio of the secondary rolling is 40% or more, recrystallization occurs, and thus the fraction of the {111} texture of the final cold-rolled material may be ensured at 50% or more in the region from the surface layer to one-quarter of the thickness. When the fraction of the {111} texture in the region from the surface layer to the one-quarter of the thickness is ensured, the R-bar value may be ensured. Considering this, the reduction ratio of the secondary rolling may be set to 40% or more.
The performing of the cold annealing in the method for manufacturing a ferritic stainless steel according to the present invention may be an operation of performing a cold annealing at 850 to 1050°C.
When the temperature of the cold annealing is 850°C or higher, recrystallization may occur to form a texture. When the temperature of the cold annealing is 1050°C or lower, grain coarsening and plate fracture may be prevented. Considering this, the cold annealing may be performed at a temperature of 850 to 1050°C.
After the secondary rolling and the cold annealing in the method for manufacturing a ferritic stainless steel according to the present invention, the cold-rolled material subjected to the cold annealing may have a fraction of a {111} texture of 50% or more in the region from the surface layer to the one-quarter of the thickness.
The ferritic stainless steel subjected to the secondary rolling and then the cold annealing after the primary rolling in the method for manufacturing a ferritic stainless steel according to the present invention may ensure a fraction of a {111} texture of 50% or more in the region from the surface layer to the one-quarter of the thickness and therefore ensure an R-bar value of 1.7 or higher.
Here, the R-bar is a value calculated as (R₀ + R₉₀ + 2*R₄₅ ) / 4, and may be a value of 1.7 or higher. With respect to the rolling direction of the specimen, R0 is a R value in the 0-dgree direction, R45 is a R value in the 45-degree direction, and R90 is a R value in the 90-degree direction. The R value is the width strain / thickness strain. A higher R-bar value indicates improved elongation and suitability for deep drawing processing.
Hereinafter, the present invention will be described in more detail through embodiments. However, the descriptions of the embodiments are only for illustrating the implementation of the present invention, and the present invention is not limited by the descriptions of the embodiments. This is because the scope of the rights of the present invention is determined by matters described in the scope of claims and matters reasonably inferred therefrom.

{Embodiment}

Alloy compositions were prepared as shown in Table 1. [Table 1]

Steel Grade C N Si Mn P Cr Ti

A 0.0124 0.0157 0.24 0.21 0.02 13.8 0.25

B 0.0074 0.0153 0.86 0.34 0.03 16.2 0.23

C 0.0066 0.011 0.42 0.25 0.03 18.1 0.19
Table 2 below shows the fraction of the {111} texture in the region from the surface layer to one-quarter of the thickness of the hot-rolled material and the cold-rolled material, as well as the R-bar value, based on whether primary rolling was performed and the reduction ratio, using the slabs having the alloy composition shown in Table 1. The implementation of primary rolling and the control of the reduction ratio were varied as shown in Table 1 below. The reheating temperature of the hot-rolled slab was 1200°C, and the reduction ratio of the primary rolling was varied as shown in Table 1 below. The hot annealing temperature was 1000°C, the secondary rolling was performed with a reduction ratio of 40%, and the cold annealing temperature was 950°C.
The fraction (%) of the {111} texture in the region from the surface layer to one-quarter of the thickness of the hot-rolled material refers to a measured value of the fraction of the {111} texture from the surface layer to one-quarter of the depth of the hot-rolled material subjected to the hot annealing, obtained by an EBSD system attached to a scanning electron microscope.

The fraction (%) of the {111} texture in the region from the surface layer to one-quarter of the thickness of the cold-rolled material refers to a measured value of the fraction of the {111} texture from the surface layer to one-quarter of the depth of the cold-rolled material subjected to the cold annealing, obtained by an EBSD system attached to a scanning electron microscope.

[Table 2]

Embodiments	Steel grade	Reduction ratio in primary rolling(%)	Fraction of {111} texture in region from surface layer to 1/4 of thickness of hot-rolled material(%)	Fraction of {111} texture in region from surface layer to 1/4 of thickness of cold-rolled material(%)	R-bar
Inventive Example 1	A	30	16.2	55.2	1.76
Inventive Example 2	B	30	15.4	54.7	1.81
Inventive Example 3	C	30	14.9	53.7	1.72
Inventive Example 4	A	40	28.3	66.1	2.02
Inventive Example 5	B	40	25.7	62.5	2.07
Inventive Example 6	C	40	26.4	63.1	1.89
Inventive Example 7	A	60	32.1	61.5	1.96
Inventive Example 8	B	60	33.4	58.3	1.82
Inventive Example 9	C	60	31	55.7	1.78
Comparative Example 1	A	0	3.2	38.1	1.52
Comparative Example 2	B	0	2.7	40.2	1.51
Comparative Example 3	C	0	1.4	37.6	1.48
Comparative Example 4	A	20	6.7	42.2	1.55
Comparative Example 5	B	20	5.8	43.1	1.57
Comparative Example 6	C	20	5.6	41.3	1.42
Comparative Example 7	A	70	38.7	47.2	1.62
Comparative Example 8	B	70	39.2	46.2	1.52
Comparative Example 9	C	70	38.8	45.9	1.59

Referring to Tables 1 and 2, in Inventive Examples 1 to 3 in which steel grade A having an alloy composition satisfying the range according to the present invention was subjected to primary rolling at a reduction ratio of 30%, Inventive Examples 4 to 6 in which steel grade B was subjected to primary rolling at a reduction ratio of 40%, and Inventive Examples 7 to 9 in which steel grade C was subjected to primary rolling at a reduction ratio of 60%, the {111} texture fraction in the region from the surface layer to one-quarter of the thickness of the hot-rolled material is 10% or more, and the {111} texture fraction in the region from the surface layer to one-quarter of the thickness of the cold-rolled material is 50% or more, satisfying the range of the present invention. Accordingly, the R-bar value is 1.7 or higher, satisfying the range of the present invention. Through this, it can be seen that, when primary rolling is performed at a reduction ratio of 25 to 65% on a slab satisfying the alloy composition of the present invention, the {111} texture fraction in the region from the surface layer to one-quarter of the thickness of the hot-rolled material is 10% or more, and the {111} texture fraction in the region from the surface layer to one-quarter of the 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 may be ensured as 1.7 or higher. Comparative Examples 1 to 3 correspond to cases in which primary rolling is not performed at all on steel grades A, B, and C satisfying the range of the present invention. In Comparative Examples 1 to 3, the {111} texture fraction in the region from the surface layer to one-quarter of the thickness of the hot-rolled material is less than 10%, and the {111} texture fraction in the region from the surface layer to one-quarter of the thickness of the cold-rolled material is less than 50%, failing to satisfy the range of the present invention. Accordingly, the R-bar value is less than 1.7, which does not satisfy the range of the present invention.
As described above, it can be seen that even when the alloy composition is satisfied, when the primary rolling is not performed at all, the {111} texture fraction in the region from the surface layer to one-quarter of the thickness of the hot-rolled material is less than 10%, and the {111} texture fraction in the region from the surface layer to one-quarter of the 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 of 1.7 or higher may not be ensured.
Comparative Examples 4 to 6 correspond to cases in which the primary rolling was performed at a reduction ratio of 20% on steel grades A, B, and C satisfying the range of the present invention. In Comparative Examples 4 to 6, the {111} texture fraction in the region from the surface layer to one-quarter of the thickness of the hot-rolled material is less than 10%, and the {111} texture fraction in the region from the surface layer to one-quarter of the thickness of the cold-rolled material is less than 50%, which does not satisfy the range of the present invention. Accordingly, the R-bar value is less than 1.7, which does not satisfy the range of the present invention.
As described above, it can be seen that even when the alloy composition is satisfied, when the primary rolling is performed at a reduction ratio of less than 25%, the {111} texture fraction in the region from the surface layer to one-quarter of the thickness of the hot-rolled material is less than 10%, and the {111} texture fraction in the region from the surface layer to one-quarter of the thickness of the cold-rolled material is less than 50%, which may not satisfy the control range of the present invention, and as a result, the R-bar value of 1.7 or higher may not be ensured.
Comparative Examples 7 to 9 correspond to cases in which the primary rolling is performed at a reduction ratio of 70% on steel grades A, B, and C satisfying the range of the present invention. In Comparative Examples 7 to 9, the {111} texture fraction in the region from the surface layer to one-quarter of the thickness of the hot-rolled material is 10% or more, but the {111} texture fraction in the region from the surface layer to one-quarter of the thickness of the cold-rolled material is less than 50%, which does not satisfy the range of the present invention. Accordingly, the R-bar value is less than 1.7, which does not satisfy the range of the present invention.
As described above, it can be seen that even when the alloy composition is satisfied, when the primary rolling is performed at a reduction ratio exceeding 65%, the {111} texture fraction in the region from the surface layer to one-quarter of the thickness of the hot-rolled material is ensured to 10% or more, but the {111} texture fraction in the region from the surface layer to one-quarter of the 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 of 1.7 or higher may not be ensured.
A method for manufacturing a ferritic stainless steel plate having excellent workability according to an example of the present invention is described with reference to accompanying drawings.
FIG. 1 is a view showing the fraction of the {111} texture, measured by EBSD in the region from the surface layer to one-quarter of the thickness of the hot-rolled material according to Inventive Example 5.
FIG. 2 is a view showing the fraction of the {111} texture, measured by EBSD in the region from the surface layer to one-quarter of the thickness of the hot-rolled material according to Comparative Example 2.
Inventive Example 5 and Comparative Example 2 were provided using a slab of steel grade B satisfying the alloy composition of the present invention. Inventive Example 5 was provided by performing a primary rolling at a reduction ratio of 40%, and Comparative Example 2 was provided without performing a primary rolling at all.
In FIGS. 1 and 2, areas with a high fraction of the {111} texture are indicated by a dark color. When measured by EBSD, the higher the fraction of {111} texture, the lower the brightness, and the lower the fraction of {111} texture, the higher the brightness.
Referring to FIGS. 1 and 2, it can be seen that Inventive Example 5 subjected to the primary rolling shows a higher {111} texture fraction than Comparative Example 2, and thus has a lower brightness.
In this case, a high brightness refers to a color close to a bright color (e.g., white), and a low brightness refers to a color close to a dark color (e.g., black).
This indicates that performing the primary rolling increases the {111} texture fraction in the hot-rolled material as a result of shear deformation during the hot rolling.
FIG. 3 is a graph showing the fraction of the {111} texture in the hot-rolled material and the cold-rolled material. It can be seen that when the fraction of the {111} texture of the hot-rolled material is high, the fraction of the {111} texture of the cold-rolled material is high.
FIG. 4 is a graph showing the relationship between the reduction ratio in the primary rolling and the fraction of the {111} texture in the region from the surface layer to one-quarter of the thickness of the cold-rolled material.
Referring to FIG. 4, it can be seen that when the primary rolling is performed at a reduction ratio of 25 to 65%, the fraction of the {111} texture of the cold-rolled material is ensured to 50% or more.
Referring to FIGS. 1 to 4, it can be seen that performing the primary rolling ensures a high fraction of the {111} texture of 10% or more in the region from the surface layer to one-quarter of the thickness of the hot-rolled material, and ensures a fraction of the {111} texture of 50% or more in the region from the surface layer to one-quarter of the thickness of the cold-rolled material.
FIG. 5 is a graph showing the relationship between the fraction of the {111} texture in the region from the surface layer to one-quarter of the thickness and the R-bar.
Referring to FIG. 5, it can be seen that when the fraction of the {111} texture in the region from the surface layer to one-quarter of the thickness of the cold-rolled material is 50% or more, the R-bar value is ensured as 1.7 or higher.
Referring to FIGS. 1 to 5, it can be seen that performing the primary rolling ensures a high fraction of the {111} texture of 10% or more in the region from the surface layer to one-quarter of the thickness of the hot-rolled material, and ensures a fraction of the {111} texture of 50% or more in the region from the surface layer to one-quarter of the thickness of the cold-rolled material, thereby ensuring an R-bar value of 1.7 or higher.

Claims

A ferritic stainless steel plate having excellent workability, comprising, in percent by weight (wt%), 0.0005 to 0.02% of carbon (C), 0.005 to 0.02% of nitrogen (N), 0.01 to 1.0% of silicon (Si), 0.01 to 1.0% of manganese (Mn), 0.001 to 0.05% of phosphorus (P), 13.0 to 20.0% of chromium (Cr), 0.05 to 0.5% of titanium (Ti), the remainder of Iron (Fe), and inevitable impurities,
wherein a fraction of a {111} texture in a region from a surface layer to one-quarter of thickness is 50% or more.
The ferritic stainless steel plate of claim 1, wherein an R-bar value is 1.7 or more.
A method for manufacturing a ferritic stainless steel plate having excellent workability, the method comprising:
preparing a slab comprising, in percent by weight (wt%), 0.0005 to 0.02% of carbon (C), 0.005 to 0.02% of nitrogen (N), 0.01 to 1.0% of silicon (Si), 0.01 to 1.0% of manganese (Mn), 0.001 to 0.05% of phosphorus (P), 13.0 to 20.0% of chromium (Cr), 0.05 to 0.5% of titanium (Ti), the remainder of Iron (Fe), and inevitable impurities;

performing hot rolling on the prepared slab in a heating furnace at 1100 to 1300°C;

performing primary rolling at a reduction ratio of 25 to 65% after the hot rolling;

performing hot annealing at 900 to 1100°C after the primary rolling;

performing secondary rolling; and

performing cold annealing.
The method of claim 3, wherein a reduction ratio in the secondary rolling is 40% or more.
The method of claim 3, wherein the cold annealing is performed at 850 to 1050°C.
The method of claim 3, wherein a hot-rolled material subjected to the hot annealing has a fraction of a {111} texture of 10% or more in a region from a surface layer to one-quarter of thickness.
The method of claim 3, wherein a cold-rolled material subjected to the cold annealing has a fraction of a {111} texture of 50% or more in a region from a surface layer to one-quarter of thickness.
The method of claim 3, wherein an R-bar value is 1.7 or more.