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(11) | EP 4 800 144 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
| published in accordance with Art. 153(4) EPC |
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| (54) | FERRITIC STAINLESS STEEL AND MANUFACTURING METHOD THEREOF |
| (57) The present disclosure relates to a ferritic stainless steel and a method for manufacturing
the same, and more specifically, to a ferritic stainless steel comprising, based on
a total weight of the ferritic stainless steel: C: 0.0030 to 0.0200 %, N: 0.0030 to
0.0200 %, Si: 0.05 to 0.50 %, Mn: 0.10 to 1.50 %, Cr: 19.0 to 25.0 %, Mo: 0.01 to
2.00 %, Nb: 0.05 to 1.00 %, Ti: 0.010 to 0.200 %, the balance being Fe and inevitable
impurities, and satisfying the following Formula (1). (wherein Cr, Mn, Nb, and Mo represent the content (wt%) of each element) |
[Technical Field]
[0001] The present disclosure relates to a ferritic stainless steel and a method for manufacturing the same.
[Background Art]
[0002] The excellent corrosion resistance and oxidation resistance of stainless steel facilitate its application in various fields from room temperature to high temperatures. Among these applications, extensive research is underway for manufacturing components, such as fuel cell separator plates, from stainless steel for operation in high-temperature environments.
[0003] Application of stainless steel to high-temperature fuel cells necessitates preventing the scale thickness formed on the stainless steel surface in a high-temperature oxidizing environment from becoming excessively thick and preventing an increase in interfacial contact resistance (ICR).
[0004] Upon oxidation of stainless steel, chromium oxide (Cr2O3) forms on the surface. Corrosion resistance results from an oxide scale composed of the chromium oxide. However, the scale formed at this time exhibits excellent corrosion resistance while possessing low interfacial conductivity properties.
[0005] Additionally, the characteristic of a bipolar plate operated in a high-temperature environment, wherein insufficient excellent strength at high temperatures degrades fuel cell durability, necessitates sufficient strength in a high-temperature operating environment.
[0006] Therefore, the application of stainless steel as fuel cell components requires excellent strength and conductive properties at high temperatures.
[Disclosure]
[Technical Problem]
[0007] An objective of the present disclosure is to provide a ferritic stainless steel maintaining low interfacial contact resistance (ICR) even in a high-temperature oxidation environment while simultaneously having excellent high-temperature strength properties.
[0008] The technical problems to be solved in the present disclosure are not limited to the technical problems mentioned above, and other technical problems not explicitly mentioned will be clearly understood by one of ordinary skill in the art to which the present disclosure pertains from the following description.
[Technical Solution]
[0009] A ferritic stainless steel according to an example of the present disclosure comprises, in percent by weight: C: 0.0030 to 0.0200 %, N: 0.0030 to 0.0200 %, Si: 0.05 to 0.50 %, Mn: 0.10 to 1.50 %, Cr: 19.0 to 25.0 %, Mo: 0.01 to 2.00 %, Nb: 0.05 to 1.00 %, Ti: 0.010 to 0.200 %, the balance being Fe and inevitable impurities, wherein the ferritic stainless steel satisfies the following Formula (1).
(wherein Cr, Mn, Nb, and Mo represent the content (wt%) of each element)
wherein the stainless steel satisfies the following Formula (2)
(wherein Cr and Mn represent the content (wt%) of each element)
[0010] The stainless steel has a yield strength (YS) of 30 MPa or more at 800°C.
wherein the stainless steel has a creep rupture time of 100 hrs or more under a stress condition of 30 MPa at 700°C.
[0011] The stainless steel has a high-temperature interfacial contact resistance (ICR) of 40 mΩ·cm2 or less at 800°C.
[0012] Also, a method for manufacturing a ferritic stainless steel according to an example of the present disclosure may comprise: reheating a slab at 1050 to 1280°C, wherein the slabcomprising, in percent by weight: C: 0.0030 to 0.0200%, N: 0.0030 to 0.0200 %, Si: 0.05 to 0.50%, Mn: 0.10 to 1.50%, Cr: 19.0 to 25.0%, Mo: 0.01 to 2.00%, Nb: 0.05 to 1.00%, Ti: 0.010 to 0.200%, the balance being Fe and inevitable impurities, and satisfying the following Formula (1); producing a hot-rolled material by hot rolling the slab after the reheating, and then performing hot-rolled annealing at 900 to 1150°C; and performing cold rolling and cold-rolled annealing at 900 to 1150°C on the hot-rolled material.
(wherein Cr, Mn, Nb, and Mo represent the content (wt%) of each element)
[0013] According to an example of the present disclosure, the stainless steel can satisfy the following Formula (2).
(wherein Cr and Mn represent the content (wt%) of each element)
[0014] According to an example of the present disclosure, the finish rolling temperature during the hot rolling is 700 to 950°C.
[Advantageous Effects]
[0015] According to an example of the present disclosure, a ferritic stainless steel is provided, maintaining low interfacial contact resistance (ICR) even in a high-temperature oxidizing environment, and having excellent high-temperature strength characteristics.
[0016] Advantageous effects obtainable from the present disclosure are not limited to the aforementioned advantageous effects, and other unmentioned advantageous effects will be clearly understood by a person of ordinary skill in the art to which the present disclosure pertains from the following description.
[Modes of the Invention]
[0017] The examples of the present disclosure are described in detail with reference to the accompanying drawings. The following examples are provided to sufficiently convey the spirit of the present disclosure to a person of ordinary skill in the art to which the present disclosure pertains. The present disclosure is not limited to the examples presented herein and can be embodied in other forms. The drawings, for clarity of the present disclosure, omit illustration of portions not relevant to the description, and for ease of understanding, may somewhat exaggerate the size of components.
[0018] Furthermore, a description of any part 'comprising' any component signifies that, absent specific contrary disclosure, it does not exclude other components but may further include other components.
[0019] Singular expressions include plural expressions unless the context clearly dictates otherwise.
[0020] The present disclosure aims to manufacture a ferritic stainless steel exhibiting excellent interfacial conductivity characteristics, characterized by low interfacial contact resistance (ICR), at high temperatures and simultaneously exhibiting excellent strength characteristics at high temperatures.
[0021] An example ferritic stainless steel of the present disclosure comprises, in percent by weight: C: 0.0030 to 0.0200%, N: 0.0030 to 0.0200%, Si: 0.05 to 0.50%, Mn: 0.10 to 1.50%, Cr: 19.0 to 25.0%, Mo: 0.01 to 2.00%, Nb: 0.05 to 1.00%, Ti: 0.010 to 0.200%, the balance being Fe and inevitable impurities.
[0022] A specific description of the reasons for limiting the composition of the steel is provided below. The following compositional ranges represent % unless otherwise specified.
[0024] C is an essential element for the stainless steel manufacturing process. An excessive increase in the C content forms precipitates such as chromium carbides, adversely affecting the composition and oxidation properties of the base material. Considering this, the upper limit of C is preferably limited to 0.0200%. However, control of the C content to an extremely low level causes an excessive cost increase. Considering this, the lower limit of C is preferably limited to 0.0030%.
[0026] An excessive increase in the N content may cause various nitrides to precipitate or pores to generate, adversely affecting quality. Considering this, the upper limit of N is desirably limited to 0.0200%. However, an extremely low control of the N content causes an excessive cost increase. Considering this, the lower limit of N is desirably limited to 0.0030%.
[0028] Si is a component requiring strict limitation due to its formation of film-shaped precipitates at the interface between the scale and the base material upon the material's exposure to high temperatures, thereby forming an insulating film. Considering this, the upper limit of Si is desirably limited to 0.50%. However, for the purpose of reducing the Si content to 0.05% or less, high-cost processes, such as vacuum melting, are required, and in consideration thereof, the lower limit of Si is desirably limited to 0.05%.
[0030] Mn rapidly diffuses to form dense manganese/chromium oxides in the outer layer of the scale when the stainless steel oxidizes at high temperatures. In consideration of this, the lower limit of Mn is preferably limited to 0.10%. However, excessive addition of Mn excessively promotes the growth of the scale, which may cause peeling of the scale. In consideration of this, the upper limit of Mn is preferably limited to 1.50%.
[0032] Cr is an essential element for securing the corrosion resistance of stainless steel. Prevention of Cr depletion due to long-term oxidation in a high-temperature oxidizing environment is required. For this reason, the lower limit of Cr is preferably limited to 19.0%. However, for the prevention of increased manufacturing costs and the precipitation of chromium carbides and intermetallic compounds, the upper limit of Cr is preferably limited to 25.0%.
[0034] Mo is an element capable of increasing the strength of the material in a high-temperature environment. Therefore, a limitation of the lower limit of Mo to 0.01% is preferable. However, Mo being an expensive element necessitates the suppression of an increase in manufacturing cost. In consideration thereof, a limitation of the upper limit of Mo to 2.00% is preferable.
[0036] Nb is an element which oxidizes at the scale/base metal interface due to its excellent oxidation properties, forming oxides, thereby suppressing the formation of insulating silicon oxides and contributing to an improvement in the material's strength. Thus, the lower bound of Nb is preferably limited to 0.05%. Conversely, excessive addition of Nb hinders hot formability and increases manufacturing costs. Therefore, the upper bound of Nb is preferably limited to 1.00%.
[0038] Ti is an element that increases the strength of the material by forming internal oxides at high temperatures immediately below the interface between the base material and the scale, that is, near the surface of the base material. Considering this, a lower limit of the Ti content is preferably restricted to 0.010%. However, excessive addition of Ti causes an increase in manufacturing costs and forms titanium oxides outside the scale; considering this, an upper limit of the Ti content is preferably restricted to 0.200 %,
[0039] The balance being Fe and inevitable impurities. The remaining component is Fe. However, in a typical manufacturing process, unintended impurities may inevitably be incorporated from raw materials or the surrounding environment, and such impurities cannot be completely excluded. Since such impurities are generally known to those skilled in the art, they are not specifically described herein.
[0040] Among the alloy components of the present disclosure, Nb and Mo improve the strength of the material at high temperatures. Accordingly, the present disclosure, through consideration of the correlation between the ratio of Nb and Mo and high-temperature strength, and by derivation of the following relational expression, enables the manufacturing of a stainless steel having excellent strength characteristics at high temperatures and simultaneously excellent electrical conductivity characteristics.
[0041] The ferritic stainless steel of an example of the present disclosure satisfies the following Formula (1).
(wherein Cr, Mn, Nb, and Mo represent the content (wt%) of each element).
[0042] A value of (Cr/Mn) × 10 × (Nb+Mo) in Formula (1) being excessively low or excessively high can lead to a degradation of strength at high temperature and high-temperature creep strength, or a deteriotationof high-temperature interfacial contact resistance (ICR), and a degradation of manufacturability due to a decrease in hot formability. Therefore, satisfying a range of 240.00 or more and 520.00 or less for the value of (Cr/Mn) × 10 × (Nb+Mo) is desirable for obtaining a material with excellent high-temperature strength; more desirably, satisfying a range of 240.00 or more and 500.00 or less; and most desirably, satisfying a range of 250.00 or more and 480.00 or less.
[0043] The ferritic stainless steel of an example of the present disclosure has a yield strength (YS) of 30 MPa or more at 800°C and has a creep rupture time of 100 hrs or more under a stress condition of 30 MPa at 700°C.
[0044] A yield strength of less than 30 MPa at 800°C or a creep rupture time of less than 100 hrs under a stress condition of 30 MPa at 700°C may render impossible the manufacture of a material with excellent strength in a high-temperature oxidizing environment.
[0045] Specifically, the present disclosure enables the manufacture of a ferritic stainless steel having improved high-temperature strength characteristics, with a yield strength (YS) of 30 MPa or more at 800°C and a creep rupture time of 100 hrs or more under a stress condition of 30 MPa at 700°C, by controlling the ratio of Nb and Mo, alloying elements related to the high-temperature strength of the material, and by controlling the value of Formula (1) to be 240.00 or more and 520.00 or less.
[0046] Additionally, the ferritic stainless steel according to an example of the present disclosure satisfies the following Formula (2).
(wherein Cr and Mn represent the content (wt%) of each element)
[0047] Satisfaction of the value of (Cr/Mn) × 10 × (Nb+Mo) in Formula (1) in a range of 240.00 or more to 520.00 or less, without satisfaction of the Cr/Mn value of Formula (2), may result in difficulty securing the high-temperature interfacial contact resistance (ICR) intended by the present disclosure. That is, the ferritic stainless steel of the present disclosure achieves excellent interfacial conductivity characteristics at high temperatures, with a high-temperature interfacial contact resistance (ICR) of 40 mΩ·cm2 or less at 800°C, through the simultaneous satisfaction of the value of Formula (1) and satisfaction of the value of Formula (2) in a range of 35.00 or more to 60.00 or less. Therefore, the Cr/Mn value of Formula (2) is preferably satisfied within a range of 35.00 or more to 60.00 or less, more preferably 35.00 or more to 55.00 or less, and most preferably 37.00 or more to 54.00 or less.
[0048] Thus, the present disclosure, through control of the ratio of Nb and Mo, satisfies excellent strength characteristics in a high-temperature oxidation environment and, simultaneously, through control of the ratio of Cr and Mn, can also secure excellent electrical conductivity at high temperatures.
[0049] A ferritic stainless steel according to the present disclosure, upon exposure to an oxidizing environment of 300 to 900°C, can form manganese/chromium oxides including Cr and Mn on the surface of the ferritic stainless steel. The uniform formation of the manganese/chromium oxides can ensure excellent electrical conductivity. Satisfaction of the alloy composition of the ferritic stainless steel within the scope of the present disclosure, along with the Cr/Mn × 10 × (Nb+Mo) of Formula (1) satisfying the range of 240.00 ≤ (Cr/Mn) × 10 × (Nb+Mo) ≤ 520.00 and simultaneously the Cr/Mn of Formula (2) satisfying the range of 35.00 ≤ Cr/Mn ≤ 60.00, results in fine and uniform manganese/chromium oxides forming on the surface layer, exhibiting excellent electrical conductivity characteristics at high temperatures, and simultaneously exhibiting excellent strength characteristics at high temperatures.
[0050] Next, a method for manufacturing a ferritic stainless steel according to an example of the present disclosure is described.
[0051] A method for manufacturing a ferritic stainless steel according to an example of the present disclosure comprises: reheating a slabcomprising, in percent by weight: C: 0.0030 to 0.0200%, N: 0.0030 to 0.0200%, Si: 0.05 to 0.50%, Mn: 0.10 to 1.50%, Cr: 19.0 to 25.0%, Mo: 0.01 to 2.00%, Nb: 0.05 to 1.00%, Ti: 0.010 to 0.200%, the balance being Fe and inevitable impurities, and satisfying the following Formula (1); producing a hot-rolled material by hot rolling the slab and hot-rolled annealing after the reheating; and performing cold rolling and cold-rolled annealing on the hot-rolled material. Formula (1): 240.00 ≤ (Cr/Mn) × 10 × (Nb+Mo) ≤ 520.00 (wherein Cr, Mn, Nb, and Mo represent the content (wt%) of each element)
[0052] The rationale for limiting the content ranges of the respective alloy elements is as previously described, and hereinafter, the respective manufacturing steps are described in more detail.
[0053] After manufacturing a slab satisfying said alloy composition, a series of processes comprising reheating, hot rolling, hot-rolled annealing, cold rolling, and cold-rolled annealing can be performed.
[0054] First, reheating the slab at 1050°C to 1280°C, and producing a hot-rolled material by hot rolling the slab and hot-rolled annealing after the reheating.
[0055] The reheating temperature is 1050°C or more for the reduction of a hot rolling load, and is limited to 1280°C or less for the prevention of internal grain coarsening.
[0056] The finish rolling temperature during the hot rolling is 700 to 950°C, and the thickness of the thus hot-rolled material is 2 to 6 mm.
[0057] A finish rolling temperature less than 700°C during the hot rolling may increase the rolling load and shape defects, thereby decreasing productivity. A finish rolling temperature greater than 950°C may decrease surface quality due to an increase in oxides from excessive high-temperature operation.
[0059] A hot-rolled annealing temperature less than 900°C may lead to non-occurrence of recrystallization, thereby preventing formation of a texture; a hot-rolled annealing temperature greater than 1150°C may cause grain coarsening and weakening of the material's strength.
[0060] The hot-rolled material that has undergone hot-rolled annealing can be cold rolled and cold-rolled annealed.
[0061] The cold-rolled annealing can be performed at 900 to 1150°C, and the thickness of the final cold-rolled product can be 0.05 to 2 mm.
[0062] The cold-rolled annealing temperature being less than 900°C results in insufficient removal of stress formed during rolling, potentially leading to a decrease in formability, and the cold-rolled annealing temperature being greater than 1150°C results in grain coarsening and potential plate fracture.
[0063] The present disclosure is described in more detail through examples. However, the description of these examples is merely for illustrating the modes of the present disclosure, and the present disclosure is not limited by the description of these examples. The scope of rights of the present disclosure is determined by the matters described in the CLAIMS and matters reasonably inferred therefrom.
Examples
[0065] A manufactured ingot was reheated at a temperature of 1250°C, hot rolling was performed such that a finish rolling temperature was 900°C, and then hot-rolled annealing was performed at a temperature of 1050°C, manufacturing a hot-rolled material with a thickness of 5.0 mm. The hot-rolled material was cold rolled to a thickness of 1.0 mm, cold-rolled annealing was performed at a temperature of 1050°C, and a 15 mm × 15 mm sample was prepared to manufacture a ferritic stainless steel specimen.
[0066] The units in Table 1 below are %.
[Table 1]
| Category | C | Si | Mn | Cr | Mo | Ti | Nb | N | (Cr/Mn) ×10× (Nb+Mo) | Cr/Mn |
| Inventive Example 1 | 0.0060 | 0.11 | 0.46 | 22.4 | 0.20 | 0.048 | 0.50 | 0.0072 | 340.87 | 48.70 |
| Inventive Example 2 | 0.0050 | 0.14 | 0.49 | 21.5 | 0.20 | 0.069 | 0.51 | 0.0060 | 311.53 | 43.88 |
| Inventive Example 3 | 0.0053 | 0.13 | 0.53 | 21.9 | 0.01 | 0.053 | 0.71 | 0.0058 | 297.51 | 41.32 |
| Comparative Example 1 | 0.0060 | 0.12 | 0.29 | 21.6 | 0.20 | 0.035 | 0.50 | 0.0049 | 521.38 | 74.48 |
| Comparative Example 2 | 0.0050 | 0.11 | 0.66 | 22.5 | 0.20 | 0.050 | 0.49 | 0.0056 | 235.23 | 34.09 |
| Comparative Example 3 | 0.0050 | 0.13 | 0.67 | 21.5 | 0.001 | 0.043 | 0.51 | 0.0060 | 163.98 | 32.09 |
| Comparative Example 4 | 0.0069 | 0.13 | 0.36 | 22.7 | 0.21 | 0.067 | 0.001 | 0.0102 | 133.05 | 63.06 |
| Comparative Example 5 | 0.0051 | 0.13 | 0.47 | 21.6 | 0.20 | 0.048 | 0.002 | 0.0057 | 92.83 | 45.96 |
[0067] Table 2 below presents the high-temperature strength, creep rupture time, and high-temperature interfacial contact resistance (ICR) of the said manufactured ferritic stainless steel. The sampling and testing for high-temperature strength were performed in accordance with the KS D 0026 standard. The fabricated samples were mounted on a tensile testing machine and tensile tested at 800°C until fracture to measure the yield strength.
[0068] Measurement of creep rupture time involved sample preparation and testing conducted in accordance with ASTM E139, wherein the time to rupture was determined by applying a stress of 30 MPa at 700°C.
[0069] High-temperature interfacial contact resistance (ICR) measurement involved applying Pt paste to both surfaces of a high-temperature oxidized specimen, followed by pre-drying at 200°C and sintering at 800°C for 3 hours. The prepared specimen, with Pt sintered on both surfaces, then underwent lamination of Pt mesh on both surfaces, subsequent application of a 15g load, drawing out of Pt wires as 4 terminals, placement in a furnace, and temperature elevation to 800°C. Measurement of resistance at 500 hours was performed by a DC 4-point probe method, thereby calculating a resistance value.
[Table 2]
| Category | Yield Strength at 800°C (MPa) | Creep Rupture Time (hrs) | Interfacial Contact Resistance at 800°C (mΩ·cm2) |
| Inventive Example 1 | 42.0 | 133.9 | 9.33 |
| Inventive Example 2 | 40.7 | 125.7 | 5.66 |
| Inventive Example 3 | 31.5 | 103.3 | 8.72 |
| Comparative Example 1 | 38.5 | 101.8 | 49.2 |
| Comparative Example 2 | 39.8 | 112.5 | 40.9 |
| Comparative Example 3 | 21.0 | 71.8 | 50.8 |
| Comparative Example 4 | 27.3 | 51.8 | 41.8 |
| Comparative Example 5 | 27.6 | 47.7 | 6.25 |
[0070] As shown in Table 2, example 1 to 3, satisfying the alloy composition and Formula (1) presented in the present disclosure, have a yield strength (YS) of 30 MPa or more at 800°C and a creep rupture time of 100 hrs or more under a stress condition of 30 MPa at 700°C, confirming superior strength characteristics at high temperatures. Further, example 1 to 3, satisfying a Cr/Mn of 35.00 or more and 60.00 or less in Formula (2), exhibit excellent electrical conductivity characteristics at high temperatures with a high-temperature interfacial contact resistance (ICR) of 40 mΩ·cm2 or less. On the other hand, comparative example 1, satisfying the alloy composition presented in the present disclosure, but with a value of Formula (1) greater than 520.00 and a value of Formula (2) greater than 60, and comparative example 2, satisfying the alloy composition presented in the present disclosure, but with a value of Formula (1) less than 240.00 and a value of Formula (2) less than 35, have high contents of Nb and Mo alloying elements, which affect high-temperature strength, with yield strengths at 800°C of 38.5 MPa and 39.8 MPa, respectively, and creep rupture times under a stress condition of 30 MPa at 700°C of 101.8 hrs and 112.5 hrs, respectively, exhibiting a trend adjacent to the values defined in the present disclosure. However, it was confirmed that the high-temperature interfacial contact resistance (ICR) was inferior due to not satisfying the value of Formula (2).
[0071] Furthermore, for Comparative Examples 3 and 4, which neither satisfy the alloy composition proposed in the present disclosure nor satisfy the values of Formula (1) and Formula (2), it was confirmed that the yield strength, creep rupture time, and high-temperature interfacial contact resistance (ICR) were all inferior.
[0072] Meanwhile, in the case of Comparative Example 5 not satisfying the alloy composition presented in the present disclosure and Formula (1) but satisfying Formula (2), the yield strength and the creep rupture time were inferior, while the high-temperature interfacial contact resistance (ICR) was confirmed to be good.
[0073] From these results, it was confirmed that a ferritic stainless steel, satisfying not only excellent electrical conductivity characteristics at high temperatures but also high-temperature strength characteristics, can be manufactured by simultaneously satisfying Formula (1) and Formula (2), which control the ratio of Nb and Mo, along with the alloy composition presented in the present disclosure, and that said ferritic stainless steel can be efficiently applied to a fuel cell operating in a high-temperature environment.
[0074] Although examples of the present disclosure have been shown and described above, the present disclosure is not limited to the specific examples described above, and various modifications are possible by those skilled in the art to which the present disclosure pertains without departing from the gist of the claims.
1. A ferritic stainless steel comprising, based on a total weight of the ferritic stainless
steel: C: 0.0030 to 0.0200%, N: 0.0030 to 0.0200%, Si: 0.05 to 0.50%, Mn: 0.10 to
1.50%, Cr: 19.0 to 25.0%, Mo: 0.01 to 2.00%, Nb: 0.05 to 1.00%, Ti: 0.010 to 0.200%,
the balance being Fe and inevitable impurities,
wherein the ferritic stainless steel satisfies the following Formula (1)
(wherein Cr, Mn, Nb, and Mo represent the content (wt%) of each element).
2. The ferritic stainless steel of Claim 1, wherein the stainless steel satisfies the
following Formula (2)
(wherein Cr and Mn represent the content (wt%) of each element)
(wherein Cr and Mn represent the content (wt%) of each element)
3. The ferritic stainless steel of Claim 1,
wherein the stainless steel has a yield strength (YS) of 30 MPa or more at 800°C.
wherein the stainless steel has a yield strength (YS) of 30 MPa or more at 800°C.
4. The ferritic stainless steel of Claim 1,
wherein the stainless steel has a creep rupture time of 100 hrs or more under a stress condition of 30 MPa at 700°C.
wherein the stainless steel has a creep rupture time of 100 hrs or more under a stress condition of 30 MPa at 700°C.
5. The ferritic stainless steel of Claim 1,
wherein the stainless steel has a high-temperature interfacial contact resistance (ICR) of 40 mΩ·cm2 or less at 800°C.
wherein the stainless steel has a high-temperature interfacial contact resistance (ICR) of 40 mΩ·cm2 or less at 800°C.
6. A method for manufacturing a ferritic stainless steel, comprising: reheating a slab
at 1050 to 1280°C, wherein the slabcomprising, in percent by weight: C: 0.0030 to
0.0200 %, N: 0.0030 to 0.0200 %, Si: 0.05 to 0.50 %, Mn: 0.10 to 1.50 %, Cr: 19.0
to 25.0 %, Mo: 0.01 to 2.00 %, Nb: 0.05 to 1.00 %, Ti: 0.010 to 0.200 %, the balance
being Fe and inevitable impurities, and satisfying the following Formula (1);
producing a hot-rolled material by hot rolling the slab after the reheating, and then performing hot-rolled annealing at 900 to 1150°C;
and performing cold rolling and cold-rolled annealing at 900 to 1150°C on the hot-rolled
material;
(wherein Cr, Mn, Nb, and Mo represent the content (wt%) of each element)
7. The method of Claim 6,
wherein the stainless steel satisfies the following Formula (2)
(wherein Cr and Mn represent the content (wt%) of each element)
8. The method of Claim 6, wherein a finish rolling temperature during the hot rolling
is 700 to 950°C.