Stainless steel sheet and stainless steel foil

Abstract

A stainless steel foil having a chemical composition comprising, by mass %, C: 0.015% or less, Si: 0.50% or less, Mn: 0.50% or less, P: 0.040% or less, S: 0.010% or less, Cr: 10.0% or more and less than 16.0%, Al: 2.5 to 4.5%, N: 0.015% or less, Ni: 0.05 to 0.50%, Cu: 0.01 to 0.10%, Mo: 0.01 to 0.15%, at least one selected from the group consisting of Ti: 0.01 to 0.30%, Zr: 0.01 to 0.20%, Hf: 0.01 to 0.20%, and REM: 0.01 to 0.20%, where Ti+Zr+Hf+2REM≥0.06 and 0.30≥Ti+Zr+Hf are satisfied.

Claims

1. A stainless steel sheet having a chemical composition comprising, by mass %: C: 0.015% or less; Si: 0.50% or less; Mn: 0.50% or less; P: 0.040% or less; S: 0.010% or less; Cr: 10.0% to 14.0%; Al: 2.5 to 4.5%; N: 0.015% or less; Ni: 0.05 to 0.50%; Cu: 0.01 to 0.10%; Mo: 0.01 to 0.15%; at least one selected from the group consisting of Ti: 0.01 to 0.30%, Zr: 0.01 to 0.20%, Hf: 0.01 to 0.20%, and REM: 0.01 to 0.20%; and the balance being iron and incidental impurities, wherein the following Expression (1) and Expression (2) are satisfied:
Ti+Zr+Hf+2REM≥0.06  (1)
0.30≥Ti+Zr+Hf  (2) where Ti, Zr, Hf, and REM each represent the content, by mass %, of each respective element and are zero if not contained.

2. The stainless steel sheet according to claim 1, wherein the chemical composition further comprises, by mass %, at least one selected from the group consisting of Nb: 0.01 to 0.10%, V: 0.01 to 0.50%, B: 0.0003 to 0.0100%, Ca: 0.0002 to 0.0100%, and Mg: 0.0002 to 0.0100%.

3. A stainless steel foil comprising the steel sheet according to claim 1, wherein the stainless steel foil has a thickness of 200 μm or less.

4. The stainless steel foil according to claim 3, wherein the stainless steel foil is configured to be a catalyst carrier of an exhaust emission control device.

5. A stainless steel foil having comprising the steel sheet according to claim 2, wherein the stainless steel foil has a thickness of 200 μm or less.

6. The stainless steel foil according to claim 5, wherein the stainless steel foil is configured to be a catalyst carrier of an exhaust emission control device.

Description

DETAILED DESCRIPTION

(1) Hereinafter, the disclosed embodiments will be described. The disclosure, however, is not intended to be limited to the following specific embodiments.

(2) First, the component composition of a stainless steel sheet of the disclosed embodiments will be described in detail. The stainless steel sheet of the disclosed embodiments is a hot-rolled sheet (hot-rolled steel sheet) and/or a cold-rolled sheet (cold-rolled steel sheet) and has excellent toughness. Moreover, a stainless steel foil manufactured by using a stainless steel sheet of the disclosed embodiments exhibits satisfactory oxidation resistance and is difficult to deform even in use at a high temperature. The reasons for limiting the component composition of a stainless steel sheet are as follows.

(3) The unit “%” denoting the respective content of each of the component elements below means mass %.

(4) C: 0.015% or less

(5) When C content exceeds 0.015%, the manufacture of stainless steel sheets becomes difficult due to deterioration in toughness of hot-rolled steel sheets and/or cold-rolled steel sheets. Accordingly, C content is set to 0.015% or less, preferably 0.010% or less, and more preferably 0.008% or less. C content may be 0%, but an extremely low C content requires prolonged time for refinement, thereby making the manufacture difficult. Accordingly, C content is set to preferably 0.002% or more, more preferably 0.004% or more, and further preferably 0.005% or more.

(6) Si: 0.50% or less

(7) When Si content exceeds 0.50%, the manufacture of stainless steel sheets becomes difficult due to deterioration in toughness of hot-rolled steel sheets and/or cold-rolled steel sheets. Accordingly, Si content is set to 0.50% or less, preferably 0.30% or less, and more preferably 0.20% or less. However, attempting to achieve Si content of less than 0.01% makes refinement difficult. Accordingly, Si content is preferably 0.01% or more, more preferably 0.08% or more, and further preferably 0.11% or more.

(8) Mn: 0.50% or less

(9) When Mn content exceeds 0.50%, oxidation resistance of steel deteriorates. Accordingly, Mn content is set to 0.50% or less, preferably 0.30% or less, and more preferably 0.15% or less. However, attempting to achieve Mn content of less than 0.01% makes refinement difficult. Accordingly, Mn content is preferably 0.01% or more, more preferably 0.05% or more, and further preferably 0.10% or more.

(10) P: 0.040% or less

(11) When P content exceeds 0.040%, the manufacture of stainless steel sheets becomes difficult due to deterioration in toughness and impaired ductility of steel. Accordingly, P content is set to 0.040% or less and preferably 0.030% or less, and more preferably, P content is decreased as much as possible. Meanwhile, an excessive decrease in P content results in increased manufacturing costs. To suppress an increase in manufacturing costs, the lower limit of P content is preferably 0.005%.

(12) S: 0.010% or less

(13) When S content exceeds 0.010%, the manufacture of hot-rolled steel sheets becomes difficult due to deterioration in hot workability. Accordingly, S content is set to 0.010% or less, preferably 0.006% or less, and more preferably 0.004% or less. Meanwhile, an excessive decrease in S content results in increased manufacturing costs. To suppress an increase in manufacturing costs, the lower limit of S content is preferably 0.001%.

(14) Cr: 10.0% or more and less than 16.0%

(15) Cr is an essential element for ensuring high-temperature oxidation resistance. When Cr content is less than 10.0%, satisfactory oxidation resistance cannot be ensured. Meanwhile, when Cr content reaches 16.0% or more, the manufacture in a continuous tandem rolling mill becomes difficult due to deterioration in toughness of hot-rolled sheets and/or cold-rolled sheets. Accordingly, Cr content is set to 10.0% or more and less than 16.0%. The lower limit is preferably 11.0% or more and more preferably 12.0% or more. The upper limit is preferably 15.0% or less, more preferably 14.0% or less, further preferably less than 13%, and still further preferably 12.5% or less.

(16) Al: 2.5 to 4.5%

(17) Al is an element that improves oxidation resistance by forming an oxide layer containing Al.sub.2O.sub.3 as a main component during high-temperature oxidation. Such an effect is obtained when Al content is 2.5% or more. Meanwhile, when Al content exceeds 4.5%, the manufacture in a continuous tandem rolling mill becomes difficult due to deterioration in toughness of hot-rolled sheets and/or cold-rolled sheets. Accordingly, Al content is 2.5 to 4.5%. The lower limit is preferably 3.0% or more and more preferably 3.2% or more. The upper limit is preferably 4.0% or less and more preferably 3.8% or less.

(18) N: 0.015% or less

(19) When N content exceeds 0.015%, the manufacture of stainless steel becomes difficult due to deterioration in toughness of steel. Accordingly, N content is set to 0.015% or less, preferably 0.010% or less, and more preferably 0.008% or less. N content may be 0%, but an extremely low content requires prolonged time for refinement, thereby making the manufacture difficult. Accordingly, N content is set to preferably 0.002% or more and more preferably 0.005% or more.

(20) Ni: 0.05 to 0.50%

(21) Ni effectively improves brazability while forming into a catalyst carrier. Accordingly, Ni content is set to 0.05% or more. Ni is, however, an austenite-forming element. When the content exceeds 0.50%, an austenite phase is formed after Al in foil is consumed with progression of high-temperature oxidation. Such an austenite phase increases the thermal expansion coefficient of the foil and thus causes foil defects, such as constriction and fracture. Accordingly, Ni content is set to 0.05% to 0.50%. The lower limit is preferably 0.10% or more and more preferably 0.13% or more. The upper limit is preferably 0.20% or less and more preferably 0.17% or less.

(22) Cu: 0.01 to 0.10%

(23) Cu effectively improves high-temperature strength through precipitation in steel. Such an effect is obtained by containing Cu at 0.01% or more. Meanwhile, a content exceeding 0.10% results in deterioration in toughness of steel. Accordingly, Cu content is set to 0.01 to 0.10%. The lower limit is preferably 0.02% or more and more preferably 0.03% or more. The upper limit is preferably 0.07% or less and more preferably 0.05%.

(24) Mo: 0.01 to 0.15%

(25) Mo effectively improves shape stability during high-temperature use. Such an effect is obtained by containing Mo at 0.01% or more. Meanwhile, a content exceeding 0.15% results in deterioration in toughness, thereby making the manufacture in a continuous tandem rolling mill difficult. Accordingly, Mo content is set to 0.01 to 0.15%. The lower limit is preferably 0.02% or more and more preferably 0.04% or more. The upper limit is preferably 0.10% or less and more preferably 0.06% or less.

(26) In addition to the above-described components, a stainless steel sheet of the disclosed embodiments further contains at least one of Ti: 0.01 to 0.30%, Zr: 0.01 to 0.20%, Hf: 0.01 to 0.20%, and REM: 0.01 to 0.20%.

(27) An Al.sub.2O.sub.3 oxide layer formed on an Fe—Cr—Al-type stainless steel foil that lacks these components has poor adhesion to substrate iron. As a result, the Al.sub.2O.sub.3 oxide layer spalls off each time the temperature changes from high to low during use, and consequently, good oxidation resistance cannot be achieved. Ti, Zr, Hf, or REM effectively improves adhesion and suppresses spalling of the Al.sub.2O.sub.3 oxide layer, thereby increasing oxidation resistance.

(28) Ti: 0.01 to 0.30%

(29) Ti improves adhesion of an Al.sub.2O.sub.3 oxide layer, thereby improving oxidation resistance. In addition, Ti improves the toughness of hot-rolled sheets and/or cold-rolled sheets by stabilizing C and N. Such effects are obtained at a Ti content of 0.01% or more. Meanwhile, when Ti content exceeds 0.30%, a large amount of Ti oxide is mixed into the Al.sub.2O.sub.3 oxide layer, thereby increasing the growth rate of the oxide layer and deteriorating oxidation resistance. Accordingly, Ti content is set to 0.01 to 0.30%. The lower limit is preferably 0.10% or more and more preferably 0.12% or more. The upper limit is preferably 0.20% or less and more preferably 0.18% or less.

(30) Zr: 0.01 to 0.20%

(31) Zr improves adhesion of an Al.sub.2O.sub.3 oxide layer and decreases the growth rate thereof, thereby improving oxidation resistance. In addition, Zr improving toughness by stabilizing C and N. Such effects are obtained at a Zr content of 0.01% or more. Meanwhile, when Zr content exceeds 0.20%, a large amount of Zr oxide is mixed into the Al.sub.2O.sub.3 oxide layer, thereby increasing the growth rate of the oxide layer and deteriorating oxidation resistance. Moreover, Zr forms an intermetallic compound with Fe and the like, thereby deteriorating toughness. Accordingly, Zr content is set to 0.01 to 0.20%. The lower limit is preferably 0.02% or more, and the upper limit is preferably 0.10% or less and more preferably 0.05% or less.

(32) Hf: 0.01 to 0.20%

(33) Hf improves adhesion to steel of an Al.sub.2O.sub.3 oxide layer and decreases the growth rate thereof, thereby improving oxidation resistance. Such an effect is obtained at a Hf content of 0.01% or more. Meanwhile, when Hf content exceeds 0.20%, a large amount of Hf oxide is mixed into the Al.sub.2O.sub.3 oxide layer, thereby increasing the growth rate of the oxide layer and deteriorating oxidation resistance. Moreover, Hf forms an intermetallic compound with Fe and the like, thereby deteriorating toughness. Accordingly, Hf content is set to 0.01 to 0.20%. The lower limit is preferably 0.02% or more, and the upper limit is preferably 0.10% or less and more preferably 0.05% or less.

(34) REM (rare earth metals): 0.01 to 0.20%

(35) REM refers to Sc, Y, and lanthanides (elements of atomic number 57 to 71, such as La, Ce, Pr, Nd, and Sm). REM improves adhesion of an Al.sub.2O.sub.3 oxide layer and exerts an extremely remarkable effect of improving spalling resistance of the Al.sub.2O.sub.3 oxide layer in an environment that is subjected to cyclic oxidation. Accordingly, REM is particularly preferably contained when excellent oxidation resistance is required. Such an effect is obtained by containing REM at 0.01% in total. Meanwhile, when REM content exceeds 0.20%, the manufacture of hot-rolled steel sheets becomes difficult due to the deterioration of hot workability. Accordingly, REM content is set to 0.01 to 0.20%. The lower limit is preferably 0.03% or more and more preferably 0.05% or more. The upper limit is preferably 0.15% or less, more preferably 0.10% or less, and further preferably 0.08% or less. Here, REM may be added as an unseparated, unpurified metal (misch metal, for example) thereof to decrease costs.
Ti+Zr+Hf+2REM≥0.06  (1)

(36) As in the foregoing, in the disclosed embodiments, at least one of Ti, Zr, Hf, and REM is contained in a predetermined content range to improve oxidation resistance. The present inventors further found, as a result of intensive research, that oxidation resistance deteriorates and that desired shape stability during high-temperature use cannot be obtained when Ti+Zr+Hf+2REM (sum of Ti, Zr, and Hf contents and two-fold REM content) is less than 0.06%. Accordingly, in the disclosed embodiments, Ti+Zr+Hf+2REM is set to 0.06% or more and more preferably 0.10% or more, in addition to setting Ti content, Zr content, Hf content, and REM content to the above-described respective ranges. The upper limit is not particularly limited, but is preferably 0.60% or less and more preferably 0.35% or less. In Expression (1), Ti, Zr, Hf, and REM represent the content (mass %) of each respective element.
0.30≥Ti+Zr+Hf  (2)

(37) Excessive Ti, Zr, and Hf contents result in an increased oxidation rate and deterioration in shape stability during high-temperature use. Accordingly, Ti+Zr+Hf (sum of Ti content, Zr content, and Hf content) is set to 0.30% or less, preferably 0.25% or less, and more preferably 0.20% or less, in addition to setting Ti content, Zr content, and Hf content to the above-described respective ranges. In Expression (2), Ti, Zr, and Hf represent the content (mass %) of each respective element.

(38) A stainless steel sheet of the disclosed embodiments preferably further contains at least one selected from Nb, V, B, Ca, and Mg in a predetermined amount, in addition to the above-described components.

(39) Nb: 0.01 to 0.10%

(40) Nb stabilizes C and N, thereby improves toughness. Such an effect is obtained at a Nb content of 0.01% or more. Meanwhile, when Nb content exceeds 0.10%, a large amount of Nb oxide is incorporated into an Al.sub.2O.sub.3 oxide layer, thereby increasing the growth rate of the oxide film and deteriorating oxidation resistance. Accordingly, Nb content is set to 0.01 to 0.10%. The lower limit is preferably 0.02% or more and more preferably 0.04% or more. The upper limit is preferably 0.07% or less and more preferably 0.05% or less.

(41) V: 0.01 to 0.50%

(42) V is combined with C and N contained in steel, thereby improving toughness. Such an effect is obtained at a V content of 0.01% or more. Meanwhile, when V content exceeds 0.50%, oxidation resistance deteriorates in some cases. Accordingly, when V is contained, V content is set to the range of 0.01 to 0.50%. The lower limit is preferably 0.03% or more and more preferably 0.05% or more. The upper limit is preferably 0.40% or less and more preferably 0.10% or less.

(43) B: 0.0003 to 0.0100%

(44) B in an appropriate amount is an element that effectively improves oxidation resistance. Such an effect is obtained at a B content of 0.0003% or more. Meanwhile, when B content exceeds 0.0100%, toughness deteriorates. Accordingly, B content is set to the range of 0.0003 to 0.0100%. The lower limit is preferably 0.0005% or more and more preferably 0.0008% or more. The upper limit is preferably 0.0030% or less and more preferably 0.0015% or less.

(45) Ca: 0.0002 to 0.0100%, Mg: 0.0002 to 0.0100%

(46) An appropriate amount of Ca or Mg improves adhesion of an Al.sub.2O.sub.3 oxide layer to steel and decreases the growth rate thereof, thereby improving oxidation resistance. Such an effect is obtained at a Ca content of 0.0002% or more and at a Mg content of 0.0002% or more. More preferably, Ca content is 0.0010% or more and Mg content is 0.0015% or more. Meanwhile, excessive addition of these elements deteriorates toughness and/or oxidation resistance. Accordingly, Ca and Mg are each contained at preferably 0.0100% or less and more preferably 0.0050% or less.

(47) The balance other than the above-described components is Fe and incidental impurities. Examples of incidental impurities include Co, Zn, and Sn, and the content of each of these elements is preferably 0.3% or less. When an optional component with the lower limit described above, among the above-described components, is contained at less than the lower limit, such an optional component is deemed to be contained as an incidental impurity.

(48) Next, a preferable manufacturing method will be described. Such a manufacturing method is not particularly limited, and an exemplary method includes: refining steel having the above-described component composition in a converter and/or an electric furnace; further refining through VOD (vacuum oxygen decarburization), AOD (argon oxygen decarburization), or the like, followed by slabbing and rolling or continuous casting into a slab; heating the slab to 1,050° C. to 1,250° C.; and hot rolling. Subsequently, a hot-rolled sheet obtained by this method is preferably subjected to continuous annealing at a temperature of 850° C. to 1,050° C. as necessary, followed by descaling through pickling, polishing, or the like. In pickling, sulfuric acid or a mixed solution of nitric acid and hydrofluoric acid, for example, may be used. As necessary, scale may be removed by shot blasting before pickling.

(49) A cold-rolled steel sheet is manufactured by repeating annealing and cold rolling of such a hot-rolled steel sheet as necessary. Cold rolling in this case may be performed once or two or more times via intermediate annealing in view of productivity and/or surface quality. Such cold rolling can be performed in a continuous tandem rolling mill to increase productivity. Intermediate annealing is performed at a temperature of preferably 850° C. to 1,000° C. and more preferably 900° C. to 950° C. The resulting cold-rolled sheet may be subjected to: as necessary, continuous annealing at a temperature of 850° C. to 1,050° C., followed by descaling through pickling, polishing, or the like; or bright annealing at a temperature of 850° C. to 1,050° C.

(50) Now, stainless steel foil will be described. A stainless steel foil of the disclosed embodiments is manufactured to a desired thickness by further cold rolling of the above-described stainless steel cold-rolled sheet (as cold-rolled material, cold-rolled annealed material, cold-rolled annealed and descaled material). Cold rolling in this case may be performed once or two or more times via intermediate annealing in view of productivity and/or surface quality. Intermediate annealing is performed at a temperature of preferably 800° C. to 1,000° C. and more preferably 850° C. to 950° C. The resulting stainless steel foil may be subsequently subjected to bright annealing at a temperature of 800° C. to 1,050° C. as necessary.

(51) The thickness of a stainless steel foil is not particularly limited, but when a stainless steel foil of the disclosed embodiments is applied to a catalyst carrier of an exhaust emission control device, a smaller thickness is more advantageous due to decreased exhaust back pressure. Stainless steel foil is easily deformed as the thickness decreases, and problems, such as breaking or folding of the stainless steel foil, result in some cases. Accordingly, the thickness of a stainless steel foil is preferably 200 μm or less and more preferably 20 to 200 m. Meanwhile, a catalyst carrier of an exhaust emission control device is required to have excellent vibration resistance and/or durability in some cases. In such cases, the thickness of a stainless steel foil is preferably set to about 100 to 200 μm. Further, a catalyst carrier of an exhaust emission control device is required to have a high cell density and/or a low back pressure in some cases. In such cases, the thickness of a stainless steel foil is more preferably set to about 20 to 100 μm.

EXAMPLES

(52) Hereinafter, the disclosed embodiments will be described specifically in accordance with the Examples. The disclosure, however, is not intended to be limited to the following Examples.

Examples

(53) Steels that were melted in a 50 kg small vacuum melting furnace and each had the chemical composition shown in Table 1 were heated to 1,200° C. and then hot-rolled in a temperature range of 900° C. to 1,200° C. to yield 3 mm-thick hot-rolled steel sheets. Subsequently, each hot-rolled steel sheet was subjected to: annealing under conditions in air at 900° C. for one minute; removal of surface scale through pickling with sulfuric acid, followed by pickling with a mixed solution of nitric acid and hydrofluoric acid; and subsequently, cold rolling to a thickness of 1.0 mm to yield a cold-rolled steel sheet. Then, the cold-rolled steel sheet was subjected to repeated cold rolling in a cluster mill and intermediate annealing a plurality of times to yield a stainless steel foil with a width of 100 mm and a thickness of 50 μm. Intermediate annealing was performed under conditions at 900° C. for one minute, and the surface after intermediate annealing was polished with No. 600 emery paper to remove a surface oxide layer.

(54) The thus-obtained hot-rolled steel sheets and stainless steel foils were each evaluated for the toughness of the hot-rolled steel sheet, as well as high-temperature oxidation resistance and shape stability of the stainless steel foil.

(55) (1) Toughness of Hot-Rolled Steel Sheet

(56) The toughness of the hot-rolled steel sheets was evaluated by a Charpy impact test. Specimens were prepared according to the V-notch specimen of JIS standards (JIS Z 2202 (1998)). Only the thickness (width in JIS standards) was set to 3 mm without processing of the original materials. Specimens were taken such that the longitudinal direction became parallel to the rolling direction and the specimens were notched perpendicularly to the rolling direction. The tests were performed according to JIS standards (JIS Z 2242 (1998)) for three specimens at each temperature, and the absorbed energy and percent brittle fracture were measured to obtain a transition curve. A ductile-brittle transition temperature (DBTT) was set as a temperature at which a percent brittle fracture reaches 50%. The transition temperature of 75° C. or lower and that of higher than 75° C. were respectively evaluated as ◯ (satisfactory) and x (unsatisfactory). It was confirmed in advance that stable cold rolling in a continuous tandem rolling mill is possible at a normal temperature when a DBTT obtained by the Charpy impact test is 75° C. or lower.

(57) (2) High-Temperature Oxidation Resistance of Stainless Steel Foil

(58) Each 50 μm-thick stainless steel foil was heat-treated by holding at 1,200° C. for 30 minutes (treatment corresponding to heat treatment during diffusion bonding or joining through brazing) in a vacuum of 5.3×10.sup.−3 Pa or lower. Three specimens (20 mm width×30 mm length) were taken from the stainless steel foil after heat treatment. These specimens were oxidized through heat treatment by holding in air atmosphere at 900° C. for 400 hours, and the mass gain due to oxidation (value of a change in mass from before heating to after heating divided by an initial surface area) was measured as an average of the three specimens. In this step, no spalling of an oxide layer was observed in each specimen. The measured result of the average mass gain by oxidation was evaluated as ◯ (satisfactory) for 10 g/m.sup.2 or less and x (unsatisfactory) for more than 10 g/m.sup.2, and ◯ satisfies the object of the disclosed embodiments.

(59) (3) High-Temperature Shape Stability of Stainless Steel Foil

(60) Each 50 μm-thick stainless steel foil was heat-treated by holding at 1,200° C. for 30 minutes (treatment corresponding to heat treatment during diffusion bonding or joining through brazing) in a vacuum of 5.3×10.sup.3 Pa or lower. Three specimens were each prepared by rolling up a foil (100 mm width×50 mm length) taken from the foil after heat treatment into a 5 mm-diameter cylinder in the longitudinal direction and by fixing the ends through spot welding. These specimens were oxidized through heat treatment by holding in air atmosphere at 900° C. for 400 hours, and a change in length (ratio of an increase in cylinder length after heating to a cylinder length before heating) of three specimens was measured and averaged. The measured result of the average change in length was evaluated as ◯ (satisfactory) for 5% or less and x (unsatisfactory) for more than 5%, and ◯ satisfies the object of the disclosed embodiments.

(61) These results are shown in Table 2. Steel Nos. 1 to 12 and 27 to 29 of the disclosed embodiments had excellent toughness of the hot-rolled steel sheet, as well as high-temperature oxidation resistance and shape stability of the foil. Meanwhile, Steel Nos. 13 to 26 as Comparative Examples were inferior in at least one of characteristic of toughness of the hot-rolled steel sheet, high-temperature oxidation resistance, or shape stability of the foil. As the above results reveal, according to the disclosed embodiments, it becomes possible to obtain a stainless steel foil having good manufacturability, excellent oxidation resistance, and high-temperature shape stability.

(62) TABLE-US-00001 TABLE 1 Component composition (mass %) Steel No. C Si Mn P S Cr Al N Ni Cu Mo Ti, Zr, Hf, REM  1 0.008 0.13 0.11 0.022 0.001 11.1 2.8 0.005 0.15 0.01 0.06 Ti: 0.21  2 0.009 0.15 0.12 0.025 0.002 11.0 3.4 0.009 0.21 0.03 0.10 Ti: 0.26  3 0.008 0.16 0.11 0.027 0.002 14.4 2.7 0.007 0.18 0.05 0.04 Ti: 0.22, Zr: 0.03, Hf: 0.02, REM: 0.02  4 0.011 0.15 0.17 0.023 0.001 10.7 4.3 0.008 0.19 0.01 0.02 Ti: 0.15  5 0.012 0.22 0.19 0.022 0.001 11.6 3.1 0.008 0.16 0.05 0.03 Zr: 0.03, REM: 0.05  6 0.008 0.13 0.15 0.025 0.002 11.4 3.3 0.006 0.14 0.08 0.01 Zr: 0.02, REM: 0.07  7 0.009 0.15 0.16 0.026 0.003 11.2 3.2 0.007 0.17 0.03 0.05 Ti: 0.11, Hf: 0.02  8 0.010 0.10 0.18 0.032 0.001 11.1 3.1 0.005 0.15 0.01 0.09 Ti: 0.13  9 0.011 0.12 0.11 0.022 0.001 15.7 3.2 0.008 0.18 0.05 0.04 Ti: 0.03, REM: 0.04 10 0.012 0.31 0.15 0.024 0.006 14.8 3.4 0.007 0.26 0.02 0.03 Ti: 0.02, REM: 0.02 11 0.006 0.16 0.16 0.021 0.002 13.2 3.8 0.005 0.15 0.04 0.04 Ti: 0.01, Zr: 0.02, Hf: 0.01, REM: 0.01 12 0.005 0.13 0.13 0.025 0.001 14.9 3.3 0.006 0.21 0.02 0.03 Hf: 0.05, REM: 0.08 27 0.006 0.13 0.17 0.022 0.003 12.2 3.4 0.007 0.16 0.03 0.05 Ti: 0.18 28 0.005 0.11 0.15 0.024 0.001 12.4 3.4 0.008 0.13 0.05 0.06 Hf: 0.04, REM: 0.06 29 0.007 0.12 0.14 0.025 0.001 12.1 3.5 0.006 0.15 0.04 0.04 Zr: 0.03, REM: 0.07 13 0.010 0.31 0.17 0.020 0.004  9.8 3.2 0.006 0.15 0.08 0.05 Ti: 0.08 14 0.011 0.17 0.11 0.022 0.001 16.8 3.9 0.008 0.19 0.06 0.03 Ti: 0.23 15 0.008 0.13 0.15 0.024 0.003 11.0 2.1 0.005 0.15 0.04 0.02 Ti: 0.15 16 0.006 0.34 0.17 0.021 0.001 11.9 4.8 0.006 0.16 0.02 0.03 Ti: 0.11, REM: 0.03 17 0.009 0.12 0.14 0.025 0.005 11.2 3.3 0.009 0.19 0.05 — Ti: 0.18 18 0.012 0.17 0.15 0.026 0.006 11.6 3.5 0.008 0.22 0.08 0.24 Ti: 0.22, REM: 0.05 19 0.010 0.21 0.16 0.021 0.004 11.3 3.1 0.006 0.13 0.03 0.03 20 0.012 0.18 0.13 0.032 0.003 11.2 3.3 0.007 0.15 0.03 0.04 Ti: 0.03, Zr: 0.02 21 0.008 0.15 0.14 0.033 0.004 10.8 3.4 0.009 0.21 0.04 0.03 Ti: 0.02, Hf: 0.01, REM: 0.01 22 0.007 0.18 0.21 0.024 0.004 10.9 3.0 0.006 0.16 0.02 0.06 REM: 0.02 23 0.006 0.19 0.17 0.025 0.003 11.3 3.2 0.007 0.14 0.04 0.05 Ti: 0.35 24 0.009 0.14 0.20 0.027 0.002 11.2 3.1 0.006 0.17 0.03 0.03 Ti: 0.20, Zr: 0.11, Hf: 0.03, REM: 0.01 25 0.007 0.22 0.18 0.028 0.001 11.5 3.3 0.005 0.26 0.03 0.08 Zr: 0.22 26 0.006 0.25 0.20 0.025 0.002 11.1 3.2 0.007 0.19 0.03 0.04 Hf: 0.28 Component composition (mass %) Steel No. Others Ti + Zr + Hf + 2REM Ti + Zr + Hf Note  1 0.21 0.21 Example  2 0.26 0.26 Example  3 0.31 0.27 Example  4 0.15 0.15 Example  5 Nb: 0.05 0.13 0.03 Example  6 0.16 0.02 Example  7 V: 0.02 0.13 0.13 Example  8 B: 0.0009 0.13 0.13 Example  9 Mg: 0.0044 0.11 0.03 Example 10 Ca: 0.0037 0.06 0.02 Example 11 0.06 0.04 Example 12 V: 0.03, Ca: 0.0029, 0.21 0.05 Example Mg: 0.0032 27 0.18 0.18 Example 28 Nb: 0.06, B: 0.0005 0.16 0.04 Example 29 V: 0.02, Ca: 0.0017, 0.17 0.03 Example Mg: 0.0021 13 0.08 0.08 Comparative Example 14 0.23 0.23 Comparative Example 15 0.15 0.15 Comparative Example 16 0.17 0.11 Comparative Example 17 0.18 0.18 Comparative Example 18 0.32 0.22 Comparative Example 19 0.00 0.00 Comparative Example 20 0.05 0.05 Comparative Example 21 0.05 0.03 Comparative Example 22 0.04 0.00 Comparative Example 23 0.35 0.35 Comparative Example 24 0.36 0.34 Comparative Example 25 0.22 0.22 Comparative Example 26 0.28 0.28 Comparative Example Note: underlined parts represent being outside the range of the disclosed embodiments.

(63) TABLE-US-00002 TABLE 2 Toughness High-temperature of hot-rolled oxidation steel sheet resistance High-temperature (3 mm thick) Evaluation of shape stability Steel Evaluation mass gain due Evaluation of No. of DBTT to oxidation shape changes Note 1 ∘ ∘ ∘ Example 2 ∘ ∘ ∘ Example 3 ∘ ∘ ∘ Example 4 ∘ ∘ ∘ Example 5 ∘ ∘ ∘ Example 6 ∘ ∘ ∘ Example 7 ∘ ∘ ∘ Example 8 ∘ ∘ ∘ Example 9 ∘ ∘ ∘ Example 10 ∘ ∘ ∘ Example 11 ∘ ∘ ∘ Example 12 ∘ ∘ ∘ Example 27 ∘ ∘ ∘ Example 28 ∘ ∘ ∘ Example 29 ∘ ∘ ∘ Example 13 ∘ x x Comparative Example 14 x ∘ ∘ Comparative Example 15 ∘ x x Comparative Example 16 x ∘ ∘ Comparative Example 17 ∘ ∘ x Comparative Example 18 x ∘ ∘ Comparative Example 19 ∘ x x Comparative Example 20 ∘ ∘ x Comparative Example 21 ∘ ∘ x Comparative Example 22 ∘ ∘ x Comparative Example 23 ∘ ∘ x Comparative Example 24 ∘ ∘ x Comparative Example 25 ∘ x x Comparative Example 26 ∘ x x Comparative Example