Ferritic stainless steel and manufacturing method thereof

Abstract

A ferritic stainless steel according to an embodiment of the present invention may contain, in wt%, 11.00-25.00% of Cr, 0.01-1.00% of Mn, 0.01-1.00% of Si, 0.001-0.100% of C, 0.001-0.100% of N, 0.001-0.200% of Al, and 0.001-0.300% of Ti, with the remainder comprising Fe and inevitable impurities, satisfy expression (1): 3[Si]+[Cr]-11 > 1, and have improved bendability, wherein the proportion of shear plane after shearing is 45% or less.

Description

Ferritic stainless steel and method of manufacturing the same

[0001] The present invention relates to a ferritic stainless steel with excellent bendability and a method for manufacturing the same.

[0002] Ferritic stainless steel is cheaper than austenitic stainless steel and offers good surface gloss, drawability, and oxidation resistance. Therefore, it is used to fix, store, support, and transport parts or products, such as components supporting architectural exterior materials and structural materials used for storing monitors during transport.

[0003] When ferritic stainless steel is used for supporting purposes, it may be bent into an L-shape or a U-shape to ensure sufficient support. Bending is a process in which force is applied using a press or impact is applied to bend the material. During this bending process, bursting, cracking, or fissures often occur at the bent section.

[0004] Conventionally, slowing down the processing speed was utilized to prevent bursting, cracking, and splitting in the bending section. However, this leads to a decrease in productivity. Another method involves increasing the radius of curvature during bending. In this case, however, there is a design constraint that the radius of curvature of the bending section must inevitably be large. Therefore, there is a need for a method that can improve the bendability of the material itself, without the need for such external control methods.

[0005] The present invention aims to provide a ferritic stainless steel with improved bendability by controlling the alloy composition and the ratio of the shear plane, and a method for manufacturing the same.

[0006] However, the problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below.

[0007] As a means to achieve the above-mentioned purpose, a ferritic stainless steel with improved bendability according to one embodiment of the present invention comprises, in weight %, Cr: 11.00% to 25.00%, Mn: 0.01% to 1.00%, Si: 0.01% to 1.00%, C: 0.001% to 0.100%, N: 0.001% to 0.100%, Al: 0.001% to 0.200%, Ti: 0.001% to 0.300%, and the remainder being Fe and impurities, and satisfies the following formula (1), and the ratio of the shear surface after shear processing can satisfy a range of 45% or less.

[0008] Equation (1): 3[Si]+[Cr]-11 > 1

[0009] In the above equation (1), [Si] and [Cr] represent the content (weight%) of each element.

[0010] A ferritic stainless steel with improved bendability according to one embodiment of the present invention may have an average grain diameter of 100 μm or less.

[0011] A ferritic stainless steel with improved bendability according to one embodiment of the present invention may have a tensile strength of 400 MPa or more.

[0012] A ferritic stainless steel with improved bendability according to one embodiment of the present invention may have an elongation of 20% to 30%.

[0013] A method for manufacturing a ferritic stainless steel with improved bendability according to one embodiment of the present invention may include the steps of: manufacturing a steel material satisfying the following formula (1), comprising, in weight %, Cr: 11.00% to 25.00%, Mn: 0.01% to 1.00%, Si: 0.01% to 1.00%, C: 0.001% to 0.100%, N: 0.001% to 0.100%, Al: 0.001% to 0.200%, Ti: 0.001% to 0.300%, and the remainder being Fe and impurities; reheating the steel material and hot rolling it to manufacture a hot-rolled material; and coiling the hot-rolled material at 500℃ to 850℃.

[0014] Equation (1): 3[Si]+[Cr]-11 > 1

[0015] In the above equation (1), [Si] and [Cr] represent the content (weight%) of each element.

[0016] In a method for manufacturing ferritic stainless steel with improved bendability according to one embodiment of the present invention, the reheating step may be performed at a temperature of 1150°C to 1250°C for 1 hour to 3 hours.

[0017] In a method for manufacturing ferritic stainless steel with improved bendability according to one embodiment of the present invention, the hot-rolled material may have a thickness of 5.0 mm to 7.0 mm.

[0018] In a method for manufacturing ferritic stainless steel with improved bendability according to one embodiment of the present invention, the step of annealing at 700 to 850°C for 3 to 20 hours after the coiling step may be further included.

[0019] In a method for manufacturing ferritic stainless steel with improved bendability according to one embodiment of the present invention, the ratio of the shear surface after shear processing may be 45% or less.

[0020] In a method for manufacturing ferritic stainless steel with improved bendability according to one embodiment of the present invention, the stainless steel may have an average grain diameter of 100 μm or less.

[0021] In a method for manufacturing ferritic stainless steel with improved bendability according to one embodiment of the present invention, the stainless steel may have a tensile strength of 400 MPa or more.

[0022] In a method for manufacturing ferritic stainless steel with improved bendability according to one embodiment of the present invention, the stainless steel may have an elongation of 20% to 30%.

[0023] According to an embodiment of the present invention, a ferritic stainless steel with improved bendability and a method for manufacturing the same can be provided by controlling the alloy composition and the ratio of the shear plane.

[0024] The effects obtainable from this invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art to which this invention pertains from the description below.

[0025] Figure 1 is a photograph of the cross-section bent after shear processing of Example 1.

[0026] Figure 2 is a photograph of the cross-section of the bending process after shearing process of Comparative Example 1.

[0027] Figure 3 is a photograph of the microstructure of Example 1 after etching taken with an optical microscope.

[0028] Figure 4 is a photograph of the microstructure of Comparative Example 1 after etching taken with an optical microscope.

[0029] Preferred embodiments of the present invention are described below. However, embodiments of the present invention may be modified in various other forms, 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 completely explain the present invention to those with average knowledge in the relevant technical field.

[0030] The terms used in this application are used merely to describe specific examples. For this reason, singular expressions include plural expressions unless the context clearly requires them to be singular. Additionally, it should be noted that terms such as “comprising” or “comprising” 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 existence of other features, steps, functions, components, or combinations thereof.

[0031] Meanwhile, unless otherwise defined, all terms used in this specification shall be understood to have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Accordingly, unless explicitly defined in this specification, specific terms should not be interpreted in an overly ideal or formal sense.

[0032] Additionally, terms such as "about," "substantially," etc., in this specification are used to mean at or near the stated value when inherent manufacturing and material tolerances are presented in the said sense, and are used to prevent unscrupulous infringers from unfairly exploiting the disclosed content in which precise or absolute values ​​are mentioned to aid in understanding the invention.

[0033] Unless otherwise specifically stated in this specification, the % indicating the content of each element is based on weight.

[0034] A ferritic stainless steel with improved bendability according to one embodiment of the present invention may comprise, in weight %, Cr: 11.00% to 25.00%, Mn: 0.01% to 1.00%, Si: 0.01% to 1.00%, C: 0.001% to 0.100%, N: 0.001% to 0.100%, Al: 0.001% to 0.200%, Ti: 0.001% to 0.300%, and the remainder being Fe and impurities.

[0035] The reason for limiting the composition range of each alloying element is explained below.

[0036] The content of Cr (chromium) can be 11.00% to 25.00%.

[0037] Cr is an effective element for ensuring the corrosion resistance of steel. Considering this, Cr can be added in an amount of 11.00% or more. However, if the Cr content is excessive, a large amount of delta ferrite may be formed within the material, which can reduce hot workability and formability. Taking this into account, the upper limit of the Cr content may be restricted to 25.00%. Although a higher Cr content facilitates securing tensile strength, it is costly, so an appropriate combination with Si, as described later, is required.

[0038] The content of Mn (manganese) may be 0.01% to 1.00%.

[0039] If the Mn content is less than 0.01%, it is disadvantageous to secure tensile strength. Considering this, Mn may be added at a rate of 0.01% or more. If the Mn content exceeds 1.00%, the elongation may be less than 20%. Therefore, the upper limit of the Mn content may be limited to 1.00%.

[0040] The content of Si (silicon) may be 0.01% to 1.00%.

[0041] If the Si content is less than 0.01%, it is disadvantageous to secure tensile strength. On the other hand, if the Si content exceeds 1.00%, the elongation may be less than 20%. Considering this, the Si content may be limited to 0.01% to 1.00%.

[0042] The content of C (carbon) can be 0.001% to 0.100%.

[0043] Carbon, an interstitial element, is necessary for securing tensile strength. Therefore, it can be added in an amount of 0.001% or more. However, if the carbon content is less than 0.001%, it becomes excessively soft, which is disadvantageous for securing tensile strength, and the elongation may exceed 30%. If the carbon content exceeds 0.100%, corrosion resistance and formability may be reduced.

[0044] The content of N (nitrogen) can be 0.001% to 0.100%.

[0045] N, an interstitial element, is an element necessary for securing tensile strength, just like C. Therefore, it can be added in an amount of 0.001% or more. However, if the N content is less than 0.001%, it becomes excessively soft, which is disadvantageous for securing tensile strength, and the elongation may exceed 30%. If the N content exceeds 0.100%, it may lead to a decrease in impact toughness and formability.

[0046] The content of Al (aluminum) may be 0.001% to 0.200%.

[0047] If the Al content is less than 0.001%, the refining cost for producing high-purity products may increase. Al is an element that can preferentially combine with interstitial elements such as C and N to form precipitates. If the Al content exceeds 0.200%, it may combine with C or N, thereby reducing the contribution of C or N to tensile strength. Taking this into consideration, the Al content may be between 0.001% and 0.200%.

[0048] The content of Ti (titanium) may be 0.001% to 0.300%.

[0049] If the Ti content is less than 0.001%, the refining cost for producing high-purity products may increase. Ti is an element that can preferentially combine with interstitial elements such as C and N to form precipitates. If the Ti content exceeds 0.300%, it may combine with C or N to reduce the contribution of C or N to tensile strength. Taking this into consideration, the Ti content may be between 0.001% and 0.300%.

[0050] The remaining component of the present invention is iron (Fe). However, since unintended impurities from raw materials or the surrounding environment may inevitably be incorporated during the ordinary manufacturing process, they cannot be excluded. As these impurities are known to any person skilled in the ordinary manufacturing process, all details thereof are not specifically mentioned in this specification.

[0051] In addition, the ferritic stainless steel with improved bending workability according to one embodiment can satisfy the following formula (1).

[0052] Equation (1): 3[Si]+[Cr]-11 > 1

[0053] In the above equation (1), [Si] and [Cr] represent the content (weight%) of each element.

[0054] In the present invention, a compositional relationship formula was derived to control the content of Si and Cr in order to secure the tensile strength of stainless steel. Si and Cr are elements that have a significant effect in contributing to securing tensile strength. Therefore, the tensile strength targeted in the present invention can be secured by appropriately combining the Si and Cr content so that the value of Equation (1), calculated by the alloy composition, exceeds 1. If the value of Equation (1) is 1 or less, the targeted tensile strength cannot be secured.

[0055] According to one embodiment, the ferritic stainless steel with improved bendability may have a shear surface ratio of 45% or less after shear processing.

[0056] When ferritic stainless steel is press-processed for use as a support, a shear section is formed. This shear section consists of a shear surface and a fracture surface. The above terms may be replaced with other terms used in industry or academia. The shear surface is the surface formed at the contact point during the initial stage of shearing when the shear blade penetrates the material. The fracture surface is the surface formed on the material as it subsequently fractures and separates.

[0057] In a stainless steel according to one embodiment of the present invention, the ratio of the shear surface to the total area of ​​the shear surface and the fracture surface during press processing may be 45% or less. In this case, the shear droop at the very beginning of the shearing process or the area of ​​the burr at the very end is ignored. If the ratio of the shear surface exceeds 45%, it is susceptible to cracking, and if subsequent bending processing is performed, crack propagation is facilitated, increasing the likelihood of fracture.

[0058] A ferritic stainless steel with improved bendability according to one embodiment may have an average grain diameter of 100 μm or less. If the average grain diameter exceeds 100 μm, crack propagation is facilitated during bending, making it susceptible to cracking.

[0059] According to one embodiment, the tensile strength of a ferritic stainless steel with improved bendability during uniaxial tension may be 400 MPa or higher. If the tensile strength is lower than 400 MPa, it becomes excessively soft, and cracks propagate easily. If the tensile strength is 400 MPa or higher, crack propagation can be prevented during bending, thereby improving bendability.

[0060] According to one embodiment, the elongation during uniaxial tensile of a ferritic stainless steel with improved bendability may be 20% to 30%. If the elongation exceeds 30%, it becomes excessively soft, and cracks propagate easily. If the elongation is less than 20%, cracks themselves occur frequently, which may lower the workability. By satisfying the range of elongation to 20% to 30%, crack propagation during bending can be prevented, thereby improving bendability.

[0061] A method for manufacturing a ferritic stainless steel with improved bendability according to one embodiment of the present invention may include the steps of: manufacturing a steel material satisfying the following formula (1), comprising, in weight %, Cr: 11.00% to 25.00%, Mn: 0.01% to 1.00%, Si: 0.01% to 1.00%, C: 0.001% to 0.100%, N: 0.001% to 0.100%, Al: 0.001% to 0.200%, Ti: 0.001% to 0.300%, and the remainder being Fe and impurities; reheating the steel material and hot rolling it to manufacture a hot-rolled material; and coiling the hot-rolled material at 500℃ to 850℃.

[0062] Equation (1): 3[Si]+[Cr]-11 > 1

[0063] In the above equation (1), [Si] and [Cr] represent the content (weight%) of each element.

[0064] The reason for limiting the alloy composition value of the steel is the same as the reason for limiting the alloy composition value of the steel above. The form of the steel may be any form, including slabs, billets, blooms, ingots, etc. Preferably, the form of the steel may be a slab of 140 mm to 250 mm. If the thickness of the slab is excessively thin, less than 140 mm, productivity decreases. On the other hand, if the thickness of the slab is thicker than 250 mm, the total reduction ratio to the final product thickness increases, and the elongation may drop to less than 20%.

[0065] In a method for manufacturing ferritic stainless steel with improved bendability according to one embodiment, the reheating step may be performed at a temperature of 1150°C to 1250°C for 1 hour to 3 hours.

[0066] If the reheating temperature is lower than 1150℃ or the reheating time is shorter than 1 hour, the temperature of the steel is lowered during hot rolling, causing a large load of deformation energy, and the elongation may be less than 20%. On the other hand, if the reheating temperature exceeds 1250℃ or the reheating time exceeds 3 hours, it becomes excessively soft, and the tensile strength may be less than 400 MPa. More preferably, reheating can be performed at 1200℃ to 1240℃ for 1.5 to 2.5 hours.

[0067] In a method for manufacturing ferritic stainless steel with improved bendability according to one embodiment, the hot-rolled material may have a thickness of 5.0 mm to 7.0 mm. More preferably, it may be hot-rolled to 6 mm.

[0068] In a method for manufacturing ferritic stainless steel with improved bendability according to one embodiment, the method may include the step of coiling the hot-rolled material at 500°C to 850°C. More preferably, it may be coiled at 750°C to 850°C.

[0069] If the coiling temperature is less than 500℃, the recovery of deformation energy received during the hot rolling stage is insufficient, so the elongation may decrease to less than 20%. If the coiling temperature exceeds 850℃, the elongation may exceed 30%. By satisfying a coiling temperature range of 500℃ to 850℃, the coil can recover the deformation energy received during the hot rolling stage as it cools slowly in the air, thereby achieving the elongation and tensile strength intended by the present invention. More preferably, the internal coil temperature of the coil after coiling can be maintained at 600℃ to 750℃ for at least 30 minutes.

[0070] In a method for manufacturing ferritic stainless steel with improved bendability according to one embodiment, the method may further include a step of annealing at 700°C to 850°C for 3 to 20 hours after the coiling step. Since this is based on reaching the atmosphere temperature, it may take as little as 3 hours or as long as 45 hours depending on the condition of the annealing furnace to place the coil into the annealing furnace and de-furnish it.

[0071] If the sum of the C and N content in the coil components after the winding step exceeds 0.03%, the above-mentioned annealing step may be further included. If the sum of C and N exceeds 0.03%, a martensite phase is formed in the material and the elongation becomes less than 20%, so the martensite phase can be removed through annealing.

[0072] In a method for manufacturing ferritic stainless steel with improved bendability according to one embodiment of the present invention, the ratio of the shear surface after shear processing may be 45% or less.

[0073] In a method for manufacturing ferritic stainless steel with improved bendability according to one embodiment of the present invention, the stainless steel may have an average grain diameter of 100 μm or less.

[0074] In a method for manufacturing ferritic stainless steel with improved bendability according to one embodiment of the present invention, the stainless steel may have a tensile strength of 400 MPa or more.

[0075] In a method for manufacturing ferritic stainless steel with improved bendability according to one embodiment of the present invention, the stainless steel may have an elongation of 20% to 30%.

[0076] As described above, the tensile strength and elongation of ferritic stainless steel can be secured by optimizing not only the alloy composition and compositional relationship but also the reheating, hot rolling, and annealing processes.

[0077] Hereinafter, the structure and operation of the present invention will be explained in more detail through preferred embodiments of the present invention. However, these are presented as preferred examples of the present invention and should not be interpreted in any way as limiting the present invention.

[0078] Examples

[0079] A slab having the alloy composition shown in Table 1 below was manufactured, heated at 1200 to 1240°C for 1.5 to 2.5 hours, and hot-rolled to a thickness of 6 mm. The hot-rolled coil was wound at 750 to 850°C, cooled in air, and pickled. It was sheared using a shearing machine and bent to a radius of curvature of 6 mm.

[0080] Classification CrMnSiCNAlTi Example 1 12.10.20.40.05 0.020.005 0.002 Example 2 11.10.10.40.020.0220.010.003 Example 3 17.60.80.20.08 0.04 0.18 0.002 Example 4 12.50.20.80.020.08 0.0020.002 Example 5 11.30.30.5 0.006 0.009 0.010.2 Example 6 11.90.20.80.010.020.10.28 Comparative Example 1 11.30.20.20.010.010.005 0.002 Comparative Example 211.50.20.50.0080.0060.0020.21Comparative Example 318.21.11.10.110.080.0020.21Comparative Example 418.20.80.50.030.110.0020.21

[0081] Table 2 below shows the values ​​of Equation (1), defined as 3[Si]+[Cr]-11, for steels having the alloy composition of Table 1. In addition, the average grain diameter, the ratio of the shear plane after shear processing, bending characteristics, tensile strength, and elongation were measured and are shown in Table 2 below.

[0082] The average grain diameter refers to the average grain diameter obtained by measuring backscattered electron diffraction attached to a scanning electron microscope (SEM).

[0083] The shear plane ratio after shearing refers to the ratio of the shear plane to the combined area of ​​the shear plane and the fracture plane. In this case, the shear droop at the very beginning of the shearing process or the area of ​​the burr at the very end is ignored.

[0084] The bending characteristics were indicated as poor if fracture occurred when bent with a radius of curvature of 6 mm, and good if fracture did not occur.

[0085] Tensile strength refers to the tensile strength obtained after performing a tensile test on a JIS13B tensile test specimen at room temperature in the crosshead range of 10 mm / min to 20 mm / min using a tensile testing machine from Zwick Roell.

[0086] The elongation was calculated from the value obtained by dividing the amount of elongation until the moment of fracture when stainless steel is subjected to uniaxial tension by the initial length.

[0087] Classification Formula (1) Value (Weight%) Average Grain Diameter (μm) Ratio of Shear Surface After Shearing (%) Bending Characteristics Tensile Strength (MPa) Elongation (%) Example 1 2.3 15 15 Good 5 24 25 Example 2 1.3 24 1 Good 4 20 29 Example 3 7.2 30 22 Good 4 80 28 Example 4 3.9 25 28 Good 5 10 26 Example 5 1.8 88 42 Good 4 11 29 Example 6 3.3 76 41 Good 4 30 28 Comparative Example 1 0.9 10 25 0 Cracked 3 95 31 Comparative Example 2 21 50 60 Cracked 3 30 33 Comparative Example 3 10.5 30 5 Cracked 7 20 15 Comparative Example 4 8.7 30 5 Cracked 6 10 16

[0088] Examples 1 to 6 can secure a tensile strength of 400 MPa or more as the alloy composition range of the present invention and the value of Equation (1) is greater than 1. Comparative Example 1 can be seen to have a tensile strength of less than 400 MPa because the value of Equation (1) is 1 or less.

[0089] Examples 1 to 6 satisfy the alloy composition range and manufacturing method of the present invention, thereby securing an elongation range of 20% to 30%. Comparative Examples 3 and 4 do not satisfy the alloy composition range or manufacturing method of the present invention, so the elongation was less than 20%. Consequently, fracture occurred as a result of bending processing. On the other hand, Comparative Examples 1 and 2 do not satisfy the alloy composition range or manufacturing method of the present invention, so the elongation exceeds 30%, making them excessively soft and allowing cracks to propagate easily.

[0090] Figure 1 is a photograph of a cross-section of a bending process after shearing in Example 1 of the present invention. The ratio of the shear surface to the combined area of ​​the shear surface and the fracture surface is approximately 15%, satisfying the condition of 45% or less. Therefore, it can be confirmed that no fracture occurred as a result of bending with a radius of curvature of 6 mm. Similarly, referring to Table 2 above, in the cases of Examples 2 to 6, where the ratio of the shear surface to the combined area of ​​the shear surface and the fracture surface is 45% or less, no fracture occurred during bending.

[0091] Figure 2 is a photograph of the cross-section of Comparative Example 1 after bending following shearing. The ratio of the shear plane to the combined area of ​​the shear plane and the fracture plane is approximately 50%, which falls outside the scope of the present invention. Therefore, it can be confirmed that fracture occurred as a result of bending with a radius of curvature of 6 mm. Referring to Table 2 above, Comparative Examples 1 and 2, in which the ratio of the shear plane to the combined area of ​​the shear plane and the fracture plane exceeds 45% and the average grain diameter exceeds 100 μm, are susceptible to cracking. Therefore, it can be confirmed that cracks occur during bending. Furthermore, the elongation exceeds 30%, making the material excessively soft, which allows cracks to propagate easily.

[0092] The average grain diameter can be measured using ASTM E112 and converted to the average diameter, or measured using an Electron Back Scatter Diffraction (EBSD) analyzer attached to a Scanning Electron Microscope (SEM). Figure 3 is an optical microscope image of the microstructure of Example 1 after etching. It can be confirmed that the average grain diameter of Example 1 is 100 μm or less.

[0093] Figure 4 is an optical microscope image of the microstructure of Comparative Example 1 after etching. It can be confirmed that the average grain diameter of Comparative Example 1 is coarse, exceeding 100 μm. Referring to Table 2 above, Comparative Examples 1 and 2 show crack brittleness, with the ratio of the shear plane after shear processing exceeding 45%, which is excessively large. In addition, it can be confirmed that cracks occurred during bending processing because the average grain diameter exceeded 100 μm, and crack propagation occurred easily.

[0094] Although exemplary embodiments of the present invention have been described above, the present invention is not limited thereto, and those skilled in the art will understand that various changes and modifications are possible within the scope and concept of the claims set forth below.

Claims

1. In weight %, comprising Cr: 11.00% to 25.00%, Mn: 0.01% to 1.00%, Si: 0.01% to 1.00%, C: 0.001% to 0.100%, N: 0.001% to 0.100%, Al: 0.001% to 0.200%, Ti: 0.001% to 0.300%, and the remainder being Fe and impurities, Satisfying the following equation (1), Ferritic stainless steel with improved bendability having a shear plane ratio of 45% or less after shearing: Equation (1): 3[Si]+[Cr]-11 > 1 (In the above formula (1), [Si] and [Cr] represent the content (weight%) of each element.) 2. In Claim 1, Ferritic stainless steel with improved bendability having an average grain diameter of 100 μm or less.

3. In Claim 1, Ferritic stainless steel with improved bendability and a tensile strength of 400 MPa or more.

4. In Claim 1, Ferritic stainless steel with improved bendability having an elongation of 20% to 30%.

5. A step of manufacturing a steel material satisfying the following formula (1), comprising, in weight %, Cr: 11.00% to 25.00%, Mn: 0.01% to 1.00%, Si: 0.01% to 1.00%, C: 0.001% to 0.100%, N: 0.001% to 0.100%, Al: 0.001% to 0.200%, Ti: 0.001% to 0.300%, and the remainder being Fe and impurities; A step of manufacturing a hot-rolled material by reheating and hot-rolling the above steel material; A method for manufacturing ferritic stainless steel with improved bendability, comprising the step of coiling the above hot-rolled material at 500℃ to 850℃: Equation (1): 3[Si]+[Cr]-11 > 1 (In Equation (1), [Si] and [Cr] represent the content (weight%) of each element.) 6. In Claim 5, A method for manufacturing ferritic stainless steel with improved bendability, wherein the above reheating step is performed at a temperature of 1150℃ to 1250℃ for 1 hour to 3 hours.

7. In Claim 5, The above hot-rolled material is a method for manufacturing ferritic stainless steel with improved bendability having a thickness of 5.0 mm to 7.0 mm.

8. In Claim 5, A method for manufacturing ferritic stainless steel with improved bendability, further comprising a step of annealing at 700°C to 850°C for 3 to 20 hours after the above coiling step.

9. In Claim 5, The above stainless steel is a method for manufacturing a ferritic stainless steel with improved bendability, wherein the ratio of the shear plane after shear processing is 45% or less.

10. In Claim 5, The above stainless steel is a method for manufacturing a ferritic stainless steel with improved bendability having an average grain diameter of 100 μm or less.

11. In Claim 5, The above stainless steel is a method for manufacturing ferritic stainless steel with improved bendability having a tensile strength of 400 MPa or more.

12. In Claim 5, The above stainless steel is a method for manufacturing a ferritic stainless steel with improved bendability having an elongation of 20% to 30%.

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