HOT ROLLED STEEL SHEET AND PRODUCTION METHOD THEREOF

Abstract

A hot-rolled steel sheet has a predetermined chemical composition in which a microstructure includes 99% or more of martensite by volume fraction and a remainder in microstructure including residual austenite and ferrite, in a cross section parallel to a rolling direction, an average aspect ratio of prior austenite grains is less than 3.0, a proportion of sulfides having an aspect ratio of more than 3.0 among sulfides having an area of 1.0 μm.sup.2 or more is 1.0% or, less, in a thickness middle portion, and a pole density of {211} <011> orientation is 3.0 or less, and a tensile strength TS is 980 MPa or higher.

Claims

1. A hot-rolled steel sheet comprising, as a chemical composition, by mass %: C: 0.08% to 0.25%; Si: 0.01% to 1.00%; Mn: 0.8% to 2.0%; P: 0.020% or less; S: 0.001% to 0.010%; Al: 0.005% to 1.000%; N: 0.0010% to 0.0100%; Ti: 0.005% to 0.30%; Ca: 0.0005% to 0.0100%; Nb: 0% to 0.30%; V: 0% to 0.50%; Cr: 0% to 3.0%; Mo: 0% to 3.0%; Ni: 0% to 5.0%; Cu: 0% to 3.0%; B: 0% to 0.0100%; Mg: 0% to 0.0100%; Zr: 0% to 0.0500%; REM: 0% to 0.050%; and a remainder including Fe and impurities, wherein a microstructure includes 99% or more of martensite by volume fraction and a remainder in microstructure including residual austenite and ferrite, in a cross section parallel to a rolling direction, an average aspect ratio of prior austenite grains is less than 3.0, a proportion of sulfides having an aspect ratio of more than 3.0 among sulfides having an area of 1.0 μm.sup.2 or more is 1.0% or less, and in a thickness middle portion, a pole density of {211}<011> orientation is 3.0 or less, and a tensile strength TS is 980 MPa or higher.

2. The hot-rolled steel sheet according to claim 1, wherein the tensile strength TS is 1180 MPa or higher.

3. The hot-rolled steel sheet according to claim 2, wherein a volume fraction of tempered martensite is less than 5%.

4. The hot-rolled steel sheet according to claim 1, wherein, in a cross section perpendicular to the rolling direction, a difference ΔHv between a maximum value and a minimum value of Vickers hardness is 50 or less.

5. The hot-rolled steel sheet according to claim 4, wherein a volume fraction of fresh martensite is less than 3%.

6. The hot-rolled steel sheet according to claim 1, further comprising a galvanized layer on a surface.

7. The hot-rolled steel sheet according to claim 6, wherein the galvanized layer is a galvannealed layer.

8. The hot-rolled steel sheet according to claim 1, wherein the chemical composition includes, by mass %, one kind or two or more kinds selected from the group of: Nb: 0.005% to 0.30%; V: 0.01% to 0.50%; Cr: 0.05% to 3.0%; Mo: 0.05% to 3.0%; Ni: 0.05% to 5.0%; Cu: 0.10% to 3.0%; B: 0.0003% to 0.0100%; Mg: 0.0005% to 0.0100%; Zr: 0.0010% to 0.0500%; and REM: 0.0010% to 0.050%.

9. A method of manufacturing the hot-rolled steel sheet according to claim 1, comprising: a heating process of heating a cast slab to 1350° C. or higher and 1400° C. or lower directly or after being temporarily cooled, the cast slab including, as a chemical composition, by mass %, C: 0.08% to 0.25%, Si: 0.01% to 1.00%, Mn: 0.8% to 2.0%, P: 0.020% or less, S: 0.001% to 0.010%, Al: 0.005% to 1.000%, N: 0.0010% to 0.0100%, Ti: 0.005% to 0.30%, Ca: 0.0005% to 0.0100%, Nb: 0% to 0.30%, V: 0% to 0.50%, Cr: 0% to 3.0%, Mo: 0% to 3.0%, Ni: 0% to 5.0%, Cu: 0% to 3.0%, B: 0% to 0.0100%, Mg: 0% to 0.0100%, Zr: 0% to 0.0500%, REM: 0% to 0.050%, and a remainder including Fe and impurities; a hot rolling process of hot-rolling the cast slab after the heating process to obtain a hot-rolled steel sheet; and a coiling process of coiling the hot-rolled steel sheet after the hot rolling process in a temperature range of 100° C. or lower, wherein, in the hot rolling process, the cast slab is rolled such that a finish rolling temperature is 1000° C. or higher, first cooling is performed such that cooling starts within 0.10 seconds after completion of the rolling and a temperature decrease at an average cooling rate of 100° C./sec or faster is 50° C. or higher, light reduction rolling where a rolling reduction is 5% or more and 20% or less is performed at a temperature of an Ar3 transformation point or higher after the first cooling, and second cooling is performed such that an average cooling rate from completion of the light reduction rolling to 200° C. or lower is 50° C./sec or faster.

10. A method of manufacturing the hot-rolled steel sheet according to claim 4, comprising: a heating process of heating a cast slab to 1350° C. or higher and 1400° C. or lower directly or after being temporarily cooled, the cast slab including, as a chemical composition, by mass %, C: 0.08% to 0.25%, Si: 0.01% to 1.00%, Mn: 0.8% to 2.0%, P: 0.020% or less, S: 0.001% to 0.010%, Al: 0.005% to 1.000%, N: 0.0010% to 0.0100%, Ti: 0.005% to 0.30%, Ca: 0.0005% to 0.0100%, Nb: 0% to 0.30%, V: 0% to 0.50%, Cr: 0% to 3.0%, Mo: 0% to 3.0%, Ni: 0% to 5.0%, Cu: 0% to 3.0%, B: 0% to 0.0100%, Mg: 0% to 0.0100%, Zr: 0% to 0.0500%, REM: 0% to 0.050%, and a remainder including Fe and impurities; a hot rolling process of hot-rolling the cast slab after the heating process to obtain a hot-rolled steel sheet; a coiling process of coiling the hot-rolled steel sheet after the hot rolling process in a temperature range of 100° C. or lower; a temper rolling process of performing temper rolling at an elongation ratio of 0.7% or more on the hot-rolled steel sheet after the coiling process; and a tempering process of performing tempering where the hot-rolled steel sheet is heated up to 430° C. to 560° C. after the temper rolling, wherein, in the hot rolling process, the cast slab is rolled such that a finish rolling temperature is 1000° C. or higher, first cooling is performed such that cooling starts within 0.10 seconds after completion of the rolling and a temperature decrease at an average cooling rate of 100° C./sec or faster is 50° C. or higher, light reduction rolling where a rolling reduction is 5% or more and 20% or less is performed at a temperature of an Ar3 transformation point or higher after the first cooling, and second cooling is performed such that an average cooling rate from completion of the light reduction rolling to 200° C. or lower is 50° C./sec or faster.

11. A method of manufacturing the hot-rolled steel sheet according to claim 6, comprising: a heating process of heating a cast slab to 1350° C. or higher and 1400° C. or lower directly or after being temporarily cooled, the cast slab including, as a chemical composition, by mass %, C: 0.08% to 0.25%, Si: 0.01% to 1.00%, Mn: 0.8% to 2.0%, P: 0.020% or less, S: 0.001% to 0.010%, Al: 0.005% to 1.000%, N: 0.0010% to 0.0100%, Ti: 0.005% to 0.30%, Ca: 0.0005% to 0.0100%, Nb: 0% to 0.30%, V: 0% to 0.50%, Cr: 0% to 3.0%, Mo: 0% to 3.0%, Ni: 0% to 5.0%, Cu: 0% to 3.0%, B: 0% to 0.0100%, Mg: 0% to 0.0100%, Zr: 0% to 0.0500%, REM: 0% to 0.050%, and a remainder including Fe and impurities; a hot rolling process of hot-rolling the cast slab after the heating process to obtain a hot-rolled steel sheet; a coiling process of coiling the hot-rolled steel sheet after the hot rolling process in a temperature range of 100° C. or lower; a temper rolling process of performing temper rolling at an elongation ratio of 0.7% or more on the hot-rolled steel sheet after the coiling process; and a galvanizing process of performing Ni pre-plating on the hot-rolled steel sheet, heating the hot-rolled steel sheet up to 430° C. to 480° C. at a temperature rising rate of 20° C./sec or faster, and galvanizing the hot-rolled steel sheet, wherein, in the hot rolling process, the cast slab is rolled such that a finish rolling temperature is 1000° C. or higher, first cooling is performed such that cooling starts within 0.10 seconds after completion of the rolling and a temperature decrease at an average cooling rate of 100° C./sec or faster is 50° C. or higher, light reduction rolling where a rolling reduction is 5% or more and 20% or less is performed at a temperature of an Ar3 transformation point or higher after the first cooling, and second cooling is performed such that an average cooling rate from completion of the light reduction rolling to 200° C. or lower is 50° C./sec or faster.

12. A method of manufacturing the hot-rolled steel sheet according to claim 7, comprising: a heating process of heating a cast slab to 1350° C. or higher and 1400° C. or lower directly or after being temporarily cooled, the cast slab including, as a chemical composition, by mass %, C: 0.08% to 0.25%, Si: 0.01% to 1.00%, Mn: 0.8% to 2.0%, P: 0.020% or less, S: 0.001% to 0.010%, Al: 0.005% to 1.000%, N: 0.0010% to 0.0100%, Ti: 0.005% to 0.30%, Ca: 0.0005% to 0.0100%, Nb: 0% to 0.30%, V: 0% to 0.50%, Cr: 0% to 3.0%, Mo: 0% to 3.0%, Ni: 0% to 5.0%, Cu: 0% to 3.0%, B: 0% to 0.0100%, Mg: 0% to 0.0100%, Zr: 0% to 0.0500%, REM: 0% to 0.050%, and a remainder including Fe and impurities; a hot rolling process of hot-rolling the cast slab after the heating process to obtain a hot-rolled steel sheet; a coiling process of coiling the hot-rolled steel sheet after the hot rolling process in a temperature range of 100° C. or lower; a temper rolling process of performing temper rolling at an elongation ratio of 0.7% or more on the hot-rolled steel sheet after the coiling process; a galvanizing process of performing Ni pre-plating on the hot-rolled steel sheet, heating the hot-rolled steel sheet up to 430° C. to 480° C. at a temperature rising rate of 20° C./sec or faster, and galvanizing the hot-rolled steel sheet; and an alloying process of performing alloying at 470° C. to 560° C. for 10 seconds to 40 seconds after the galvanizing process, wherein, in the hot rolling process, the cast slab is rolled such that a finish rolling temperature is 1000° C. or higher, first cooling is performed such that cooling starts within 0.10 seconds after completion of the rolling and a temperature decrease at an average cooling rate of 100° C./sec or faster is 50° C. or higher, light reduction rolling where a rolling reduction is 5% or more and 20% or less is performed at a temperature of an Ar3 transformation point or higher after the first cooling, and second cooling is performed such that an average cooling rate from completion of the light reduction rolling to 200° C. or lower is 50° C./sec or faster.

13. The hot-rolled steel sheet according to claim 2, further comprising a galvanized layer on a surface.

14. The hot-rolled steel sheet according to claim 3, further comprising a galvanized layer on a surface.

15. The hot-rolled steel sheet according to claim 4, further comprising a galvanized layer on a surface.

16. The hot-rolled steel sheet according to claim 5, further comprising a galvanized layer on a surface.

17. The hot-rolled steel sheet according to claim 2, wherein the chemical composition includes, by mass %, one kind or two or more kinds selected from the group of: Nb: 0.005% to 0.30%; V: 0.01% to 0.50%; Cr: 0.05% to 3.0%; Mo: 0.05% to 3.0%; Ni: 0.05% to 5.0%; Cu: 0.10% to 3.0%; B: 0.0003% to 0.0100%; Mg: 0.0005% to 0.0100%; Zr: 0.0010% to 0.0500%; and REM: 0.0010% to 0.050%.

18. The hot-rolled steel sheet according to claim 3, wherein the chemical composition includes, by mass %, one kind or two or more kinds selected from the group of: Nb: 0.005% to 0.30%; V: 0.01% to 0.50%; Cr: 0.05% to 3.0%; Mo: 0.05% to 3.0%; Ni: 0.05% to 5.0%; Cu: 0.10% to 3.0%; B: 0.0003% to 0.0100%; Mg: 0.0005% to 0.0100%; Zr: 0.0010% to 0.0500%; and REM: 0.0010% to 0.050%.

19. The hot-rolled steel sheet according to claim 4, wherein the chemical composition includes, by mass %, one kind or two or more kinds selected from the group of: Nb: 0.005% to 0.30%; V: 0.01% to 0.50%; Cr: 0.05% to 3.0%; Mo: 0.05% to 3.0%; Ni: 0.05% to 5.0%; Cu: 0.10% to 3.0%; B: 0.0003% to 0.0100%; Mg: 0.0005% to 0.0100%; Zr: 0.0010% to 0.0500%; and REM: 0.0010% to 0.050%.

20. The hot-rolled steel sheet according to claim 5, wherein the chemical composition includes, by mass %, one kind or two or more kinds selected from the group of: Nb: 0.005% to 0.30%; V: 0.01% to 0.50%; Cr: 0.05% to 3.0%; Mo: 0.05% to 3.0%; Ni: 0.05% to 5.0%; Cu: 0.10% to 3.0%; B: 0.0003% to 0.0100%; Mg: 0.0005% to 0.0100%; Zr: 0.0010% to 0.0500%; and REM: 0.0010% to 0.050%.

Description

EXAMPLES

[0183] Hereinafter, the effects of the present invention will be described in more detail using examples. These examples are merely exemplary in order to verify the effects of the present invention and do not limit the present invention.

[0184] Steels having chemical compositions shown in Tables 1-1 and 1-2 were cast, and heating, rolling, first cooling, light reduction rolling, second cooling, and coiling were performed under conditions shown in Tables 2-1, 2-2, 4-1, 4-2, 6-1 to 6-4. In Tables 6-1 to 6-4, the heating temperatures are the heating temperatures of the cast pieces, and the rolling completion temperatures are the finish temperatures of hot rolling before the first cooling.

[0185] Next, regarding Nos. 1 to 24 in Tables 2-1 and 2-2, temper rolling, Ni pre-plating, hot-dip galvanizing, and alloying were performed under conditions shown in Table 2-2. As a result, galvanized hot-rolled steel sheets (hot-dip galvannealed hot-rolled steel sheets) shown in Tables 3-1 and 3-2 were obtained.

[0186] In addition, regarding Nos. 25 to 46 in Tables 4-1 and 4-2, temper rolling, Ni pre-plating, and hot-dip galvanizing (on both surfaces; 45 g/m.sup.2 per single surface) were performed under conditions shown in Tables 4-1 and 4-2. As a result, galvanized hot-rolled steel sheets (hot-dip galvanized hot-rolled steel sheets) shown in Tables 5-1 and 5-2 were obtained.

[0187] In addition, regarding Nos. 47 to 88 in Tables 6-1 and 6-4, temper rolling and tempering were performed on some steel sheets under conditions shown in Tables 6-1 to 6-4. As a result, hot-rolled steel sheets (non-galvanized hot-rolled steel sheets) shown in Tables 7-1 to 7-4 were obtained.

[0188] In both the galvanized hot-rolled steel sheets and the hot-rolled steel sheets that were finally obtained, the sheet thickness values were 5.0 mm. In both the galvanized hot-rolled steel sheets and the hot-rolled steel sheets that were finally obtained, the prior austenite grain sizes were in a range of 12 μm or more and 100 μm or less except for No. 13, No. 37, No. 59, and No. 81. In No. 13, No. 37, No. 59, and No. 81, the prior austenite grain sizes were more than 100 μm.

[0189] In the obtained hot-dip galvanized hot-rolled steel sheet or the obtained hot-rolled steel sheet, the microstructural fractions of martensite (including fresh martensite and tempered martensite), residual austenite, ferrite, and other structures, the average aspect ratio of prior austenite grain, the prior austenite grain size, the proportion of sulfides having an aspect ratio of more than 3.0 among sulfides having an area of 1.0 μm.sup.2 or more, the pole density of {211} <011> orientation, the difference ΔHv between a maximum value and a minimum value of Vickers hardness, the Fe content, the Ni content, and the Al content in the galvanized layer were evaluated using the above-described method.

[0190] In addition, regarding mechanical properties, JIS No. 5 tensile test pieces were collected from an L direction (rolling direction) and a C direction (direction perpendicular to the rolling direction) to perform a tensile test according to JIS Z 2241:2011. Using a stress-strain curve of the tensile test, a tensile strength (TS) and total elongation (EL) were obtained.

[0191] Toughness was evaluated by collecting V-notch Charpy test pieces having a subsize of 5 mm width (×10 mm×55 mm length) from the L direction and the C direction and performing a Charpy test according to JIS Z 2242:2018.

[0192] When the tensile strength (the L direction and the C direction) was 980 MPa or higher, the total elongation was 10.0% or more, and the Charpy absorbed energy (vE-40° C.) at −40° C. (the L direction and the C direction) were 50 J/cm.sup.2 or more, it was determined that the steel sheet had high strength, excellent ductility, and excellent toughness.

[0193] In addition, when the product of the tensile strength (TS) in the C direction and the hole expansion ratio (λ) satisfied TS (MPa)×λ(%)≥38000 MP.Math.%, it was determined that the steel sheet had excellent hole expansibility. When TS (MPa)×λ(%)≥40000 MP.Math.%, it was determined that the steel sheet had excellent hole expansibility.

[0194] In addition, when a ratio (the value in the L direction/the value in the C direction) of the characteristic value in the L direction to the characteristic value in the C direction was 0.90 or more and 1.10 or less, it was determined that anisotropy was low.

[0195] Regarding the external appearance of the plating, whether or not bare spots occurred was determined by visual inspection. When bare spots were not observed by visual inspection, the plated steel sheet was determined to have excellent plating external appearance and was evaluated as “Pass”. When bare spots were observed, the plated steel sheet was determined to have poor practicability and was evaluated as “Fail”.

[0196] Regarding the adhesion of the galvanized layer, a sample on which a cupping test (punch diameter: 40 mm, blank holder force (BHF): 1 ton, drawing ratio: 2.0) was performed was degreased with a solvent, a tape was peeled off from the side surface, and the degree of blackening of the tape was measured. The degree of blackening was obtained by measuring the luminosity (L value) and obtaining a difference from the L value of a blank tape. A case where the degree of blackening was less than 30% was determined as “Pass” and is shown as “OK” in the field of adhesion in the table. A case where the degree of blackening was 30% or more was determined as “Fail” and is shown as “NG” in the field of adhesion in the table.

[0197] The results are shown in Tables 3-1, 3-2, 5-1, 5-2, and 7-1 to 7-4.

[0198] The Fe content shown in Tables 3-2 and 5-2 represents the Fe content in the galvanized layer. In the hot-dip galvannealed steel sheets (Examples) in Tables 3-1 and 3-2 that were alloyed, the Fe contents were 7.0 mass % to 15.0 mass %, which shows that alloying progressed sufficiently. In the hot-dip galvanized steel sheets (Examples) in Tables 5-1 and 5-2 that were not alloyed, the Fe contents were less than 7.0 mass %.

TABLE-US-00001 TABLE 1-1 Steel Chemical composition (mass %), remainder: Fe and impurities No. C Si Mn P S Al N Ti Ca A1 0.11 0.50 1.9 0.007 0.003 0.040 0.0023 0.01 0.0032 B1 0.12 0.30 1.8 0.005 0.006 0.030 0.0035 0.13 0.0025 C1 0.14 0.04 2.0 0.012 0.005 0.060 0.0028 0.16 0.0029 D1 0.16 0.40 1.3 0.006 0.004 0.210 0.0042 0.03 0.0065 E1 0.22 0.30 1.1 0.015 0.005 0.007 0.0021 0.01 0.0037 F1 0.14 0.90 1.8 0.009 0.003 0.150 0.0038 0.02 0.0018 A2 0.09 0.30 1.8 0.005 0.003 0.030 0.0030 0.01 0.0025 B2 0.10 0.20 1.7 0.008 0.005 0.040 0.0026 0.11 0.0038 C2 0.12 0.03 1.8 0.006 0.004 0.050 0.0023 0.17 0.0032 D2 0.13 0.30 1.2 0.017 0.006 0.230 0.0045 0.03 0.0062 E2 0.21 0.20 0.9 0.007 0.003 0.008 0.0031 0.02 0.0027 F2 0.12 0.80 1.6 0.012 0.005 0.140 0.0036 0.01 0.0045 G1 0.07 0.40 1.8 0.013 0.007 0.030 0.0032 0.03 0.0023 H1 0.12 1.90 1.0 0.009 0.006 0.040 0.0045 0.06 0.0015 I1 0.14 0.30 0.7 0.015 0.005 0.050 0.0036 0.01 0.0021 J1 0.12 0.20 2.7 0.007 0.008 0.030 0.0041 0.02 0.0018 K1 0.35 0.40 1.9 0.016 0.009 0.060 0.0035 0.03 0.0016 G2 0.06 0.30 1.7 0.007 0.006 0.040 0.0028 0.02 0.0013 H2 0.11 1.80 0.9 0.012 0.005 0.030 0.0035 0.05 0.0021 I2 0.12 0.20 0.6 0.008 0.006 0.050 0.0031 0.01 0.0018 J2 0.10 0.10 2.5 0.011 0.007 0.040 0.0047 0.03 0.0024 K2 0.32 0.20 1.7 0.015 0.009 0.050 0.0032 0.01 0.0012 (Note) An underline represents a condition outside of the range of the present invention.

TABLE-US-00002 TABLE 1-2 Steel Chemical composition (mass %), remainder: Fe and impurities No. Nb V Cr Mo Ni Cu B Mg REM Zr A1 B1 0.03 C1 0.05 0.0013 D1 0.5 0.0032 E1 0.3 0.026 F1 0.1 0.2 0.0034 A2 0.1 0.0012 B2 0.0015 C2 0.3 0.0025 D2 0.03 0.5 E2 0.02 0.6 0.017 F2 0.1 0.2 0.0038 G1 H1 0.3 I1 0.01 J1 0.018 K1 G2 H2 0.01 I2 0.0023 J2 0.2 K2 (Note) An underline represents a condition outside of the range of the present invention.

TABLE-US-00003 TABLE 2-1 First cooling Light reduction rolling. Heating Rolling Time from finish Temperature condition Heating Rolling finish rolling completion Average Cooling stop decrease Rolling Rolling Steel Ar3 temperature temperature temperature to start cooling rate temperature by cooling temperature reduction No. No. (° C.) (° C.) (° C.) of cooling (s) (° C./s) (° C.) (° C.) (° C.) (%) 1 A1 721 1370 1030 0.07 130 900 130 880  7 2 B1 720 1350 1010 0.05 150 940  70 920 11 3 C1 693 1380 1070 0.09 100 950 120 920  5 4 D1 726 1360 1050 0.07 160 900 150 880 18 5 E1 733 1390 1060 0.10 120 920 140 890 14 6 F1 711 1370 1020 0.08 170 910 110 880  6 21 A1 721 1370 1040 0.08 120 920 120 900  6 7 G1 741 1360 1040 0.09 110 950  90 930  6 8 H1 801 1350 1060 0.08 130 990  70 960  9 9 I1 791 1390 1050 0.10 120 990  60 970  7 10 J1 654 1360 1030 0.07 110 920 110 900 18 11 K1 631 1370 1010 0.06 130 880 130 860 17 12 A1 721 1310 1030 0.08 110 940  90 910 12 13 A1 721 1440 1110 0.09 100 1030  80 1010  5 14 A1 721 1360  960 0.06 130 840 120 820 14 15 A1 721 1370 1090 0.32 120 1020  70 1000 11 16 A1 721 1350 1040 0.08  60 980  60 960  6 17 A1 721 1360 1080 0.10 110 1050  30 1020  9 18 A1 721 1380 1060 0.09 120 940 120 910  1 19 A1 721 1370 1010 0.08 100 920  90 890  6 20 A1 721 1360 1020 0.09 110 970  50 950 13 22 A1 721 1360 1030 0.07 140 900 130 880  8 23 A1 721 1380 1050 0.06 130 910 140 890  7 24 A1 721 1360 1040 0.09 120 910 130 890  6 (Note) An underline represents a condition outside of the range of the present invention.

TABLE-US-00004 TABLE 2-2 Second cooling Coiling Average cooling rate from conditions Temper Galvanization conditions light reduction rolling Coiling rolling Ni pre- Average Heating Alloying Alloying completion temperature to temperature Elongation plating temperature rising temperature temperature time No. 200° C. or lower (° C./s) (° C.) (%) (g/m.sup.2) rate (° C./s) (° C.) (° C.) (sec) Note 1  50  40 0.7 1.0 20 460 520 15 Examples 2  70  30 1.0 1.5 40 460 510 20 3  60  50 0.8 1.1 30 440 530 15 4 110 100 0.9 1.3 20 480 490 35 5  60  60 1.2 1.2 30 460 550 15 6  70  50 0.7 2.1 50 470 530 20 21  60  30 0.3 1.2 25 460 520 15 7  70  60 0.7 1.1 30 450 520 20 Comparative 8  60  80 0.8 1.0 20 460 530 15 examples 9  50  50 1.1 1.2 40 470 500 30 10  60  70 0.9 1.0 30 460 520 20 11  50  60 0.7 1.1 20 450 510 15 12  60  80 0.8 1.0 30 460 540 10 13  50  50 0.9 1.2 20 470 520 15 14  80  60 0.7 1.1 20 460 530 25 15  60  40 1.0 1.5 30 460 510 20 16  50  60 0.8 1.2 20 450 520 15 17  70  30 1.2 1.3 40 470 530 30 18  60 100 1.1 1.0 30 460 540 25 19  30  90 0.8 1.2 20 470 520 20 20  60 200 0.7 1.1 30 460 510 15 22  50  50 0.7 None 20 470 610 30 23  60  40 0.8 1.0 15 460 600 40 24  50  50 1.0 1.2 30 460 520 60 (Note) An underline represents a condition outside of the range of the present invention.

TABLE-US-00005 TABLE 3-1 Sulfides Prior Proportion of Volume fraction of microstructures austenite sulfides having Martensite (%) grains aspect ratio of Texture Fresh Tempered Residual Average more than 3 among Pole martensite martensite Total austenite Ferrite Other aspect sulfides having density of ΔHv No. (%) (%) (%) (%) (%) (%) ratio area of 1 μm.sup.2 {211}<011> (Hv) 1 0  99  99 1 0 0 1.2  0.8 1.7 48 2 0 100 100 0 0 0 1.6  0.6 2.3 45 3 1  99 100 0 0 0 1.3  0.7 1.9 49 4 0  99  99 0 1 0 2.1  0.8 1.8 46 5 2  97  99 1 0 0 1.7  0.7 2.6 47 6 0 100 100 0 0 0 1.5  0.9 1.7 50 21 0 100 100 0 0 0 1.3  0.9 1.8 81 7 0  87  87 0 9 4 1.9  0.8 1.9 118 8 0  77  77 3 14 6 2.3  0.7 3.8 109 9 0  69  69 1 11 19 1.5  0.9 4.7 98 10 0 100 100 0 0 0 2.4 26.2 3.5 95 11 0  96  96 4 0 0 2.2  1.3 2.3 105 12 0  99  99 1 0 0 1.1 14.5 1.6 98 13 0  99  99 1 0 0 1.2  0.7 1.8 89 14 0  99  99 1 0 0 3.2  0.8 5.1 96 15 0  99  99 1 0 0 1.2  4.5 2.5 75 16 0  99  99 1 0 0 1.4  3.7 2.3 89 17 0  99  99 1 0 0 1.3  3.9 2.0 100 18 0  99  99 0 0 0 1.1 14.7 1.3 95 19 0  53  53 3 23 21 1.4  0.7 3.7 129 20 0  94  94 1 2 3 1.3  1.5 3.4 105 22 0  98  98 0 1 1 1.2  0.8 2.0 64 23 0  98  98 0 1 1 1.4  0.7 1.9 63 24 0  98  98 0 1 1 1.3  0.8 1.8 69 (Note) An underline represents failure.

TABLE-US-00006 TABLE 3-2 Mechanical properties Galvanized layer Tensile strength Total elongation vE-40° C.(J/cm.sup.2) Hole Fe Ni Al (TS) (MPa) (EL) (%) vE- expan- TS × con- con- con- L C L C L C 40° C. sion λ tent tent tent direc- direc- TS(L)/ direc- direc- EL(L)/ direc- direc- (L)/vE- ratio (MPa .Math. Bare (mass (mass (mass Adhe- No. tion tion TS(C) tion tion EL(C) tion tion 40° C.(C) (λ) %) spots %) %) %) sion Note 1  994 1006 0.99 13.9 13.7 1.01 87 84 1.04 60 60360 None 11.0 0.5 0.5 OK Ex- 2 1047 1092 0.96 12.5 12.1 1.03 74 72 1.03 55 60060 None 10.3 0.7 0.4 OK am- 3  991 1011 0.98 12.2 12.0 1.02 78 75 1.04 61 61671 None 11.8 0.6 0.5 OK ples 4 1155 1176 0.98 13.3 12.7 1.05 89 86 1.03 52 61152 None 7.9 0.7 0.3 OK 5 1217 1233 0.99 11.8 11.4 1.04 73 70 1.04 47 57951 None 13.6 0.6 0.8 OK 6 1022 1045 0.98 12.6 12.3 1.02 77 76 1.01 58 60610 None 12.8 1.2 0.6 OK 21  990  996 0.99 13.8 13.6 1.01 85 82 1.04 40 39840 None 11.3 0.6 0.5 OK 7  723  780 0.93 11.7 11.0 1.06 77 73 1.05 40 31200 None 11.6 0.6 0.5 OK Com- 8  768  887 0.87 12.3 11.0 1.12 74 60 1.23 37 32819 None 12.3 0.5 0.6 OK par- 9  748  869 0.86 12.5 11.3 1.11 67 59 1.14 35 30415 None 8.6 0.6 0.3 OK ative 10  991 1128 0.88 12.1  9.8 1.23 61 34 1.79 28 31584 None 11.2 0.5 0.5 OK ex- 11 1317 1437 0.92 10.9  9.9 1.10 60 49 1.22 22 31614 None 10.1 0.6 0.4 OK am- 12  995 1005 0.99 13.6 11.9 1.14 82 73 1.12 31 31155 None 12.4 0.5 0.6 OK ples 13  943  960 0.98 13.2 13.1 1.01 42 37 1.14 32 30720 None 11.5 0.6 0.5 OK 14  995 1074 0.93 13.1 11.3 1.16 81 73 1.11 29 31146 None 12.7 0.6 0.6 OK 15  973  994 0.98 13.7 13.0 1.05 64 48 1.33 32 31808 None 10.4 0.8 0.4 OK 16  963  984 0.98 13.3 12.6 1.06 62 49 1.27 31 30504 None 11.1 0.6 0.5 OK 17  973  995 0.98 13.1 12.5 1.05 49 38 1.29 33 32835 None 12.6 0.7 0.6 OK 18  978 1001 0.98 13.7 12.1 1.13 84 59 1.42 31 31031 None 13.2 0.5 0.7 OK 19  681  736 0.93 12.3 11.1 1.11 73 61 1.20 38 27968 None 11.5 0.6 0.5 OK 20  832  891 0.93 11.4 10.3 1.11 74 63 1.17 35 31185 None 10.8 0.5 0.5 OK 22  965  977 0.99 12.3 12.1 1.02 54 50 1.08 38 37126 Present 13.5 0.0 0.7 NG 23  972  979 0.99 12.4 12.2 1.02 53 51 1.04 39 38181 None 12.8 0.5 0.6 OK 24  981  988 0.99 12.1 11.9 1.02 51 50 1.02 38 37544 None 12.5 0.6 0.5 OK (Note) An underline represents failure.

TABLE-US-00007 TABLE 4-1 Light reduction Heating Rolling First cooling rolling Heating Rolling Time from finish Average Cooling Temperature condition temper- finish rolling completion cooling stop decrease Rolling Rolling Steel Ar3 ature temperature temperature to start rate temperature by cooling temperature reduction No. No. (° C.) (° C.) (° C.) of'cooling (s) (° C./s) (° C.) (° C.) (° C.) (%) 25 A1 721 1370 1030 0.07 130 900 130 880  7 26 B1 720 1350 1010 0.05 150 940  70 920 11 27 C1 693 1380 1070 0.09 100 950 120 920  5 28 D1 726 1360 1050 0.07 160 900 150 880 18 29 E1 733 1390 1060 0.10 120 920 140 890 14 30 F1 711 1370 1020 0.08 170 910 110 880  6 45 A1 721 1370 1040 0.08 120 920 120 900  6 31 G1 741 1360 1040 0.09 110 950  90 930  6 32 H1 801 1350 1060 0.08 130 990  70 960  9 33 I1 791 1390 1050 0.10 120 990  60 970  7 34 J1 654 1360 1030 0.07 110 920 110 900 18 35 K1 631 1370 1010 0.06 130 880 130 860 17 36 A1 721 1310 1030 0.08 110 940  90 910 12 37 A1 721 1440 1110 0.09 100 1030  80 1010  5 38 A1 721 1360  960 0.06 130 840 120 820 14 39 A1 721 1370 1090 0.32 120 1020  70 1000 11 40 A1 721 1350 1040 0.08  60 980  60 960  6 41 A1 721 1360 1080 0.10 110 1050  30 1020  9 42 A1 721 1380 1060 0.09 120 940 120 910  1 43 A1 721 1370 1010 0.08 100 920  90 890  6 44 A1 721 1360 1020 0.09 110 970  50 950 13 46 A1 721 1360 1030 0.07 140 900 130 880  8 (Note) An underline represents a condition outside of the range of the present invention.

TABLE-US-00008 TABLE 4-2 Second cooling Coiling Average cooling conditions Galvanization conditions rate from light reduction Coiling Temper Average rolling completion temper- rolling Ni pre- temperature Heating Alloying Alloying temperature to ature Elongation plating rising rate temperature temperature time No. 200° C. or lower (° C./s) (° C.) (%) (g/m.sup.2) (° C./s) (° C.) (° C.) (sec) Note 25  50  40 0.7 1.0 20 460 — — Examples 26  70  30 1.0 1.5 40 460 — — 27  60  50 0.8 1.1 30 440 — — 28 110 100 0.9 1.3 20 480 — — 29  60  60 1.2 1.2 30 460 — — 30  70  50 0.7 2.1 50 470 — — 45  60  30 0.3 1.2 25 460 — — Comparative 31  70  60 0.7 1.1 30 450 — — examples 32  60  80 0.8 1.0 20 460 — — 33  50  50 1.1 1.2 40 470 — — 34  60  70 0.9 1.0 30 460 — — 35  50  60 0.7 1.1 20 450 — — 36  60  80 0.8 1.0 30 460 — — 37  50  50 0.9 1.2 20 470 — — 38  80  60 0.7 1.1 20 460 — — 39  60  40 1.0 1.5 30 460 — — 40  50  60 0.8 1.2 20 450 — — 41  70  30 1.2 1.3 40 470 — — 42  60 100 1.1 1.0 30 460 — — 43  30  90 0.8 1.2 20 470 — — 44  60 200 0.7 1.1 30 460 — — 46  50  50 0.7 None 20 470 — — (Note) An underline represents a condition outside of the range of the present invention.

TABLE-US-00009 TABLE 5-1 Prior Sulfides Volume fraction of microstructures austenite Proportion of Martensite (%) grains sulfides having aspect Texture Fresh Tempered Residual Average ratio of more than 3 Pole martensite martensite Total austenite Ferrite Other aspect among sulfides having density of ΔHv No. (%) (%) (%) (%) (%) (%) ratio area of 1 μm.sup.2 {211}<011> (Hv) 25 0 99  99 1 0 0 1.2  0.8 1.7 46 26 0 100 100 0 0 0 1.6  0.6 2.3 42 27 1 99 100 0 0 0 1.3  0.7 1.9 47 28 0 99  99 0 1 0 2.1  0.8 1.8 43 29 2 97  99 1 0 0 1.7  0.7 2.6 45 30 0 100 100 0 0 0 1.5  0.9 1.7 48 45 0 100 100 0 0 0 1.3  0.9 1.8 78 31 0 87  87 0 9 4 1.9  0.8 1.9 115 32 0 77  77 3 14 6 2.3  0.7 3.8 107 33 0 69  69 1 11 19 1.5  0.9 4.7 96 34 0 100 100 0 0 0 2.4 26.2 3.5 92 35 0 96  96 4 0 0 2.2  1.3 2.3 103 36 0 99  99 1 0 0 1.1 14.5 1.6 95 37 0 99  99 1 0 0 1.2  0.7 1.8 87 38 0 99  99 1 0 0 3.2  0.8 5.1 93 39 0 99  99 1 0 0 1.2  4.5 2.5 72 40 0 99  99 1 0 0 1.4  3.7 2.3 88 41 0 99  99 1 0 0 1.3  3.9 2.0 97 42 0 99  99 0 0 0 1.1 14.7 1.3 92 43 0 53  53 3 23 21 1.4  0.7 3.7 127 44 0 94  94 1 2 3 1.3  1.5 3.4 102 46 0 98  98 0 1 1 1.2  0.8 2.0 62 (Note) An underline represents failure.

TABLE-US-00010 TABLE 5-2 Mechanical properties Tensile Strength Total Elongation vE-40° C.(J/cm.sup.2) Hole Galvanized layer (TS) (MPa) (EL) (%) vE- expan- Fe Ni Al L C L C L C 40° C.(L)/ sion TS × λ content content content direc- direc- TS(L)/ direc- direc- EL(L)/ direc- direc- vE- ratio (MPa .Math. Bare (mass (mass (mass Adhe- No. tion tion TS(C) tion tion EL(C) tion tion 40° C.(C) (λ) %) spots %) %) %) sion Note 25 1046 1056 0.99 13.4 13.2 1.02 82 79 1.04 56 59136 None 2.5 0.6 0.5 OK Exam- 26 1088 1133 0.96 12.1 11.7 1.03 70 68 1.03 50 56650 None 1.8 0.8 0.4 OK ples 27 1043 1062 0.98 11.7 11.5 1.02 72 69 1.04 55 58410 None 1.9 0.6 0.6 OK 28 1215 1235 0.98 12.9 12.4 1.04 84 82 1.02 48 59280 None 2.2 0.8 0.3 OK 29 1257 1268 0.99 11.3 11.0 1.03 67 65 1.03 44 55792 None 1.2 0.7 0.8 OK 30 1075 1098 0.98 12.1 11.8 1.03 71 69 1.03 53 58194 None 2.8 1.3 0.5 OK 45 1043 1055 0.99 13.5 13.1 1.03 81 78 1.04 37 39035 None 2.1 0.6 0.5 OK 31  775  835 0.93 11.2 10.6 1.06 73 69 1.06 36 30060 None 2.1 0.7 0.5 OK Com- 32  808  925 0.87 11.9 10.5 1.13 69 55 1.25 32 29600 None 1.8 0.6 0.7 OK par- 33  808  927 0.87 12.1 11.0 1.10 62 55 1.13 31 28737 None 1.5 0.6 0.3 OK ative 34  942 1179 0.80 11.6  9.3 1.25 56 31 1.81 24 28296 None 2.3 0.7 0.5 OK exam- 35 1365 1494 0.91 10.4  9.4 1.11 55 46 1.20 19 28386 None 1.9 0.7 0.4 OK ples 36 1035 1047 0.99 13.1 11.5 1.14 75 67 1.12 28 29316 None 2.7 0.6 0.5 OK 37  993 1010 0.98 12.8 12.7 1.01 38 32 1.19 29 29290 None 1.6 0.7 0.5 OK 38 1053 1121 0.94 12.7 10.9 1.17 75 67 1.12 26 29146 None 2.0 0.8 0.6 OK 39 1013 1032 0.98 13.2 12.6 1.05 59 43 1.37 28 28896 None 1.7 0.9 0.4 OK 40 1013 1024 0.99 12.9 12.1 1.07 58 45 1.29 27 27648 None 2.6 0.7 0.5 OK 41 1021 1047 0.98 12.6 12.0 1.05 45 33 1.36 30 31410 None 1.4 0.8 0.6 OK 42 1035 1059 0.98 13.3 11.7 1.14 78 52 1.50 28 29652 None 1.3 0.6 0.7 OK 43  735  790 0.93 11.9 10.7 1.11 68 55 1.24 33 26070 None 2.9 0.7 0.6 OK 44  881  943 0.93 11.1 10.0 1.11 69 58 1.19 31 29233 None 1.5 0.6 0.5 OK 46 1004 1015 0.99 11.9 11.8 1.01 50 46 1.09 35 35525 None 1.6 0.0 0.7 NG (Note) An underline represents a condition outside of the range of the present invention.

TABLE-US-00011 TABLE 6-1 Light reduction Heating Rolling First cooling rolling Heating Rolling Time from finish Average Cooling Temperature condition temper- finish rolling completion cooling stop decrease Rolling Rolling Steel Ar3 ature temperature temperature to rate temperature by cooling temperature reduction No. No. (° C.) (° C.) (° C.) start of cooling (s) (° C./s) (° C.) (° C.) (° C.) (%) 47 A1 721 1370 1030 0.07 130  900 130  880 7 48 B1 720 1350 1010 0.05 150  940  70  920 11 49 C1 693 1380 1070 0.09 100  950 120  920 5 50 D1 726 1360 1050 0.07 160  900 150  880 18 51 E1 733 1390 1060 0.10 120  920 140  890 14 52 F1 711 1370 1020 0.08 170  910 110  880 6 53 G1 741 1360 1040 0.09 110  950  90  930 6 54 H1 801 1350 1060 0.08 130  990  70  960 9 55 I1 791 1390 1050 0.10 120  990  60  970 7 56 J1 654 1360 1030 0.07 110  920 110  900 18 57 K1 631 1370 1010 0.06 130  880 130  860 17 58 A1 721 1310 1030 0.08 110  940  90  910 12 59 A1 721 1440 1110 0.09 100 1030  80 1010 5 60 A1 721 1360  960 0.06 130  840 120  820 14 61 A1 721 1370 1090 0.32 120 1020  70 1000 11 62 A1 721 1350 1040 0.08  60  980  60  960 6 63 A1 721 1360 1080 0.10 110 1050  30 1020 9 64 A1 721 1380 1060 0.09 120  940 120  910 1 65 A1 721 1370 1010 0.08 100  920  90  890 6 66 A1 721 1360 1020 0.09 110  970  50  950 13 67 A1 721 1370 1040 0.08 120  920 120  900 6 68 A1 721 1360 1030 0.07 140  900 130  880 8 (Note) An underline represents a condition outside of the range of the present invention.

TABLE-US-00012 TABLE 6-2 Second cooling Average cooling rate from light reduction rolling Coiling Tempering completion conditions Temper conditions temperature Coiling rolling Heating to 200° C. temperature Elongation temperature No. or lower (° C./s) (° C.) (%) (° C.) Note 47  50  40 0.7 520 Examples 48  70  30 1.0 510 49  60  50 0.8 530 50 110 100 0.9 490 51  60  60 1.2 550 52  70  50 0.7 530 53  70  60 0.7 520 Compar- 54  60  80 0.8 530 ative 55  50  50 1.1 500 examples 56  60  70 0.9 520 57  50  60 0.7 510 58  60  80 0.8 540 59  50  50 0.9 520 60  80  60 0.7 530 61  60  40 1.0 510 62  50  60 0.8 520 63  70  30 1.2 530 64  60 100 1.1 540 65  30  90 0.8 520 66  60 200 0.7 510 67  60  30 0.3 520 68  50  50 0.7 610 (Note) An underline represents a condition outside of the range of the present invention.

TABLE-US-00013 TABLE 6-3 Heating Rolling First cooling Light reduction Heating Rolling Time from finish Average Cooling rolling condition temper- finish rolling completion cooling stop Temperature Rolling Rolling Steel Ar3 ature temperature temperature to rate temperature decrease by temperature reduction No. No. (° C.) (° C.) (° C.) start of cooling (s) (° C./s) (° C.) cooling (° C.) (° C.) (%) 69 A2 731 1360 1020 0.06 150 900 120 880  5 70 B2 733 1370 1000 0.08 100 920  80 900 10 71 C2 696 1360 1050 0.10 120 930 120 910  7 72 D2 759 1390 1030 0.07 170 870 160 850 16 73 E2 729 1360 1060 0.09 130 910 150 880 12 74 F2 731 1350 1010 0.10 140 890 120 870  8 75 G2 750 1370 1020 0.08 100 920 100 900  5 76 H2 820 1380 1050 0.10 120 970  80 950 10 77 I2 804 1360 1030 0.09 110 950  80 930  5 78 J2 667 1350 1010 0.08 100 910 100 890 15 79 K2 652 1350 1040 0.08 120 900 140 860 20 80 A2 731 1320 1020 0.09 100 920 100 900 10 81 A2 731 1430 1100 0.10 110 1020  80 1000  5 82 A2 731 1350  970 0.05 150 870 100 840 15 83 A2 731 1360 1080 0.30 100 1040  60 1020 10 84 A2 731 1350 1060 0.10  70 1010  50 990  8 85 A2 731 1370 1070 0.09 100 1050  20 1030 10 86 A2 731 1370 1050 0.10 100 950 100 930  2 87 A2 731 1350 1020 0.09 120 910 110 890  5 88 A2 731 1350 1000 0.10 100 950  50 920 15 (Note) An underline represents a condition outside of the range of the present invention.

TABLE-US-00014 TABLE 6-4 Second cooling Average cooling rate from light reduction rolling Coiling Tempering completion conditions Temper conditions temperature Coiling rolling Heating to 200° C. temperature Elongation temperature No. or lower (° C./s) (° C.) (%) (° C.) Note 69  60  50 — — Examples 70  50  30 — — 71  70  70 — — 72 100 100 — — 73  80  50 — — 74  60  40 — — 75  60  50 — — Compar- 76  50  70 — — ative 77  70  60 — — examples 78  50  80 — — 79  50  50 — — 80  50  70 — — 81  60  60 — — 82  70  50 — — 83  50  30 — — 84  60  50 — — 85  50  40 — — 86  60  50 — — 87  20 100 — — 88  50 200 — — (Note) An underline represents a condition outside of the range of the present invention.

TABLE-US-00015 TABLE 7-1 Prior Volume fraction of microstructures austenite Sulfides Martensite (%) grains Proportion of sulfides Texture Fresh Tempered Residual Average having aspect ratio Pole martensite martensite Total austenite Ferrite Other aspect of more than 3 among density of ΔHv No. (%) (%) (%) (%) (%) (%) ratio sulfides having area of 1 μm.sup.2 {211}<011> (Hv) 47 0 99  99 1 0 0 1.2  0.8 1.7 45 48 0 100 100 0 0 0 1.6  0.6 2.3 43 49 1 99 100 0 0 0 1.3  0.7 1.9 46 50 0 99  99 0 1 0 2.1  0.8 1.8 45 51 2 97  99 1 0 0 1.7  0.7 2.6 44 52 0 100 100 0 0 0 1.5  0.9 1.7 47 53 0 87  87 0 9 4 1.9  0.8 1.9 112 54 0 77  77 3 14 6 2.3  0.7 3.8 109 55 0 69  69 1 11 19 1.5  0.9 4.7 95 56 0 100 100 0 0 0 2.4 26.2 3.5 93 57 0 96  96 4 0 0 2.2  1.3 2.3 106 58 0 99  99 1 0 0 1.1 14.5 1.6 92 59 0 99  99 1 0 0 1.2  0.7 1.8 85 60 0 99  99 1 0 0 3.2  0.8 5.1 96 61 0 99  99 1 0 0 1.2  4.5 2.5 75 62 0 99  99 1 0 0 1.4  3.7 2.3 83 63 0 99  99 1 0 0 1.3  3.9 2.0 92 64 0 99  99 0 0 0 1.1 14.7 1.3 95 65 0 53  53 3 23 21 1.4  0.7 3.7 118 66 0 94  94 1 2 3 1.3  1.5 3.4 106 67 0 100 100 0 0 0 1.3  0.9 1.8 82 68 0 98  98 0 1 1 1.2  0.8 2.0 65 (Note) An underline represents a condition outside of the range of the present invention.

TABLE-US-00016 TABLE 7-2 Sulfides Volume fraction of microstructures Prior austenite Proportion of sulfides Martensite (%) grains having aspect Texture Fresh Tempered Residual Average ratio of more than Pole martensite martensite Total austenite Ferrite Other aspect 3 among sulfides density of ΔHv No. (%) (%) (%) (%) (%) (%) ratio having area of 1 μm.sup.2 {211}<011> (Hv) 69 100 0 100 0 0 0 1.1  0.7 1.5 57 70 99 1 100 0 0 0 1.5  0.5 1.8 53 71 100 0 100 0 0 0 1.3  0.8 2.1 62 72 98 2 100 0 0 0 2.0  0.6 1.7 55 73 99 0  99 1 0 0 1.8  0.9 2.3 55 74 100 0 100 0 0 0 1.4  0.8 1.6 65 75 79 6  85 0 10 5 1.8  0.7 1.8 123 76 68 7  75 3 15 7 2.1  0.9 3.5 121 77 54 12  66 2 12 20 1.6  0.8 4.2 105 78 100 0 100 0 0 0 2.5 23.5 3.7 105 79 92 5  97 3 0 0 2.3  1.2 2.5 116 80 100 0 100 0 0 0 1.2 12.6 1.7 103 81 98 2 100 0 0 0 1.3  0.8 1.6 95 82 100 0 100 0 0 0 3.1  0.9 4.8 107 83 100 0 100 0 0 0 1.3  3.2 2.3 87 84 100 0 100 0 0 0 1.4  3.5 2.1 94 85 99 1 100 0 0 0 1.2  3.3 2.2 104 86 100 0 100 0 0 0 1.2 13.6 1.4 105 87 35 18  53 2 25 20 1.2  0.8 3.2 130 88 77 15  92 2 3 3 1.5  1.7 3.5 116 (Note) An underline represents a condition outside of the range of the present invention.

TABLE-US-00017 TABLE 7-3 Mechanical properties Tensile strength Total elongation (TS) (MPa) (EL) (%) vE-40° C.(J/cm.sup.2) L C L C L C Hole TS × λ direc- direc- TS(L)/ direc- direc- EL(L)/ direc- direc- vE-40° C.(L)/ expansion (MPa .Math. No. tion tion TS(C) tion tion EL(C) tion tion vE-40° C.(C) ratio (λ) %) Note 47 1002 1012 0.99 14.2 13.9 1.02 90 87 1.03 60 60720 Examples 48 1052 1105 0.95 12.6 12.2 1.03 76 73 1.04 56 61880 49  997 1016 0.98 12.4 12.1 1.02 75 72 1.04 60 60960 50 1140 1161 0.98 13 5 12.9 1.05 84 80 1.05 53 61533 51 1212 1225 0.99 11.9 11.6 1.03 75 71 1.06 49 60025 52 1017 1039 0.98 12.7 12.4 1.02 79 77 1.03 59 61301 53  738  792 0.93 11.8 11.1 1.06 72 68 1.06 41 32472 Comparative 54  756  875 0.86 12.5 11.1 1.13 71 57 1.25 36 31500 examples 55  758  867 0.87 12.6 11.4 1.11 69 61 1.13 34 29478 56  876 1112 0.79 12.3  9.9 1.24 57 30 1.90 29 32248 57 1322 1441 0.92 10.8  9.8 1.10 62 49 1.27 24 34584 58  984  992 0.99 13.5 11.8 1.14 79 70 1.13 29 28768 59  938  953 0.98 13.1 12.9 1.02 44 39 1.13 33 31449 60  985 1061 0.93 13.2 11.9 1.11 76 68 1.12 30 31830 61  958  980 0.98 13.5 12.9 1.05 60 45 1.33 31 30380 62  943  962 0.98 13.4 12.7 1.06 58 44 1.32 32 30784 63  961  982 0.98 13.2 12.7 1.04 46 35 1.31 34 33388 64  963  986 0.98 13.5 12.0 1.13 83 57 1.46 32 31552 65  702  752 0.93 12.4 11.2 1.11 70 59 1.19 39 29328 66  845  903 0.94 11.5 10.4 1.11 71 60 1.18 37 33411 67  885  992 0.89 13.6 13.4 1.01 87 84 1.04 39 38688 68  960  971 0.99 12.1 11.9 1.02 54 50 1.08 38 36898 (Note) An underline represents a condition outside of the range of the present invention.

TABLE-US-00018 TABLE 7-4 Mechanical properties Tensile strength Total elongation (TS) (MPa) (EL) (%) vE-40° C.(J/cm.sup.2) L C L C L C Hole TS × λ direc- direc- TS(L)/ direc- direc- EL(L)/ direc- direc- vE-40° C.(L)/ expansion (MPa .Math. No. tion tion TS(C) tion tion EL(C) tion tion vE-40° C.(C) ratio (λ) %) Note 69 1189 1200 0.99 12.9 12.7 1.02 75 72 1.04 41 49200 Examples 70 1232 1277 0.96 11.4 110 1.04 63 60 1.05 38 48526 71 1185 1204 0.98 11.3 11.2 1.01 65 63 1.03 40 48160 72 1339 1360 0.98 12.4 11.8 1.05 80 76 1.05 35 47600 73 1470 1485 0.99 10.8 10.4 1.04 62 60 1.03 30 44550 74 1205 1228 0.98 11.4 11.1 1.03 67 64 1.05 39 47892 75  918  976 0.94 10.8 10.1 1.07 69 65 1.06 28 27328 Comparative 76  953 1072 0.89 11.5 10.1 1.14 65 52 1.25 21 22512 examples 77  935 1057 0.88 11.8 10.5 1.12 59 51 1.16 20 21140 78 1186 1326 0.89 11.2 9.2 1.22 52 25 2.08 16 21216 79 1532 1652 0.93 10.1 9.2 1.10 51 45 1.13 14 23128 80 1180 1192 0.99 12.8 11.0 1.16 74 64 1.16 15 17880 81 1136 1152 0.99 12.3 12.4 0.99 31 27 1.15 19 21888 82 1192 1272 0.94 12.1 10.5 1.15 72 65 1.11 15 19080 83 1172 1193 0.98 12.6 11.9 1.06 56 45 1.24 18 21474 84 1165 1187 0.98 12.4 11.8 1.05 55 47 1.17 18 21366 85 1179 1197 0.98 12.2 11.6 1.05 48 42 1.14 19 22743 86 1176 1197 0.98 12.9 11.3 1.14 75 51 1.47 18 21546 87  876  932 0.94 11.4 10.2 1.12 62 52 1.19 31 28892 88 1026 1085 0.95 10.3 9.3 1.11 65 54 1.20 27 29295 (Note) An underline represents a condition outside of the range of the present invention.

[0199] It can be seen from Tables 1-1 to 7-4 that, in all of the steel sheets according to the examples, the desired properties were able to be obtained. On the other hand, it can be seen that, in the comparative examples where the chemical composition or the manufacturing method was outside of the range of the present invention, one or more properties were poor.