HOT-ROLLED STEEL SHEET

Abstract

This hot-rolled steel sheet has a predetermined chemical composition, in a microstructure at a 1/4 position of a sheet thickness in a sheet thickness direction from a surface, by area ratios, a primary phase is 95.00% to 98.00% of bainite, a secondary phase is 2.00% to 5.00% of tempered martensite, an average grain size of the secondary phase is 1.5 μm or less, a pole density in a (110)<112> orientation is 3.0 or less, an average grain size of an iron-based carbide is 0.100 μm or less, in a microstructure from the surface to a 1/16 position of the sheet thickness in the sheet thickness direction from the surface, a pole density in a (110)<1-11> orientation is 3.0 or less, and a tensile, strength TS is 980 MPa or more.

Claims

1. A hot-rolled steel sheet comprising, as a chemical composition, by mass %: C: 0.040% to 0.150%; Si: 0.50% to 1.50%; Mn: 1.00% to 2.50%; P: 0.100% or less; S: 0.010% or less; Al: 0.010% to 0.100%; N: 0.0100% or less; Ti: 0.005% to 0.150%; B: 0.0005% to 0.0050%; Cr: 0.10% to 1.00%; Nb: 0% to 0.06%; V: 0% to 0.50%; Mo: 0% to 0.50%; Cu: 0% to 0.50%; Ni: 0% to 0.50%; Sb: 0% to 0.020%; Ca: 0% to 0.010%; REM: 0% to 0.010%; Mg: 0% to 0.010%; and a remainder including iron and impurities, wherein, in a microstructure at a ¼ position of a sheet thickness in a sheet thickness direction from a surface, by area ratios, a primary phase is 95.00% to 98.00% of bainite, a secondary phase is 2.00% to 5.00% of tempered martensite, an average grain size of the secondary phase is 1.5 μm or less, a pole density in a (110)<112> orientation is 3.0 or less, an average grain size of an iron-based carbide is 0.100 μm or less, in a microstructure from the surface to a 1/16 position of the sheet thickness in the sheet thickness direction from the surface, a pole density in a (110)<1-11> orientation is 3.0 or less, and a tensile strength TS is 980 MPa or more.

2. The hot-rolled steel sheet according to claim 1, comprising, as the chemical composition, by mass %, one or more selected from the group of: Nb: 0.005% to 0.06%; V: 0.05% to 0.50%; Mo: 0.05% to 0.50%; Cu: 0.01% to 0.50%; Ni: 0.01% to 0.50%; Sb: 0.0002% to 0.020%; Ca: 0.0002% to 0.010%; REM: 0.0002% to 0.010%; and Mg: 0.0002% to 0.010%.

Description

EXAMPLES

[0213] Next, examples of the present invention will be described. Conditions in the examples are examples of the conditions adopted to confirm the feasibility and effect of the present invention. The present invention is not limited to these examples of the conditions. The present invention is capable of adopting a variety of conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.

[0214] Steels having a chemical composition shown for Steel Nos. 1 to 36 in Tables 1 and 2 were made from melting, and slabs having a thickness of 240 to 300 mm were manufactured by continuous casting. Hot-rolled steel sheets were obtained under manufacturing conditions shown in Tables 3 and 4 using the obtained slabs. The “average cooling rate between FT and CT” in Tables 3 and 4 indicates the average cooling rate from the start of cooling after hot rolling to coiling (stop of cooling). In addition, tempering was performed under conditions of 350° C. to 600° C. and 30 seconds to 12 hours so as to obtain the values of “tempering parameter LMP” shown in Table 3 and Table 4. In addition, before finish rolling, descaling was performed by a normal method (the collision pressure of water to be sprayed was less than 3.0 MPa). Only for No. 42, descaling was performed such that the collision pressure of water to be sprayed became 3.5 MPa.

TABLE-US-00001 TABLE 1 Steel Chemical composition, mass % (remainder: Fe and impurities) No. C Si Mn P S Al N Ti B Cr Nb V 1 0.068 0.80 1.92 0.082 0.003 0.032 0.0023 0.109 0.0015 0.67 2 0.095 1.15 1.65 0.048 0.009 0.034 0.0032 0.115 0.0012 0.91 3 0.121 1.05 1.52 0.059 0.008 0.030 0.0039 0.132 0.0017 0.98 4 0.047 1.40 2.21 0.055 0.007 0.033 0.0024 0.081 0.0023 0.14 5 0.145 1.45 1.42 0.051 0.002 0.032 0.0034 0.115 0.0019 0.81 6 0.062 0.75 1.71 0.048 0.002 0.032 0.0036 0.108 0.0015 0.67 7 0.132 0.60 2.10 0.063 0.008 0.034 0.0015 0.097 0.0015 0.34 8 0.080 1.32 1.80 0.034 0.002 0.030 0.0027 0.011 0.0017 0.71 0.02 9 0.088 0.77 1.71 0.066 0.007 0.026 0.0039 0.109 0.0017 0.65 0.05 10 0.091 0.79 1.66 0.063 0.010 0.032 0.0029 0.086 0.0023 0.77 0.02 0.05 11 0.098 1.14 1.92 0.081 0.001 0.027 0.0040 0.130 0.0020 0.70 12 0.099 0.95 2.19 0.060 0.009 0.030 0.0025 0.114 0.0018 0.63 13 0.083 1.04 2.20 0.025 0.009 0.033 0.0019 0.124 0.0020 0.25 14 0.085 0.97 2.00 0.078 0.003 0.034 0.0034 0.130 0.0021 0.87 15 0.085 1.03 1.92 0.063 0.006 0.029 0.0022 0.106 0.0016 0.45 16 0.084 0.73 1.77 0.065 0.004 0.029 0.0036 0.110 0.0024 0.62 17 0.086 0.96 1.66 0.038 0.009 0.026 0.0019 0.115 0.0019 0.47 0.02 18 0.098 0.79 2.04 0.027 0.002 0.029 0.0017 0.080 0.0018 0.77 0.05 19 0.092 0.84 1.93 0.094 0.004 0.031 0.0022 0.110 0.0018 0.35 20 0.093 0.76 1.84 0.054 0.008 0.031 0.0034 0.115 0.0015 0.24 Steel Chemical composition, mass % (remainder: Fe and impurities) No. Mo Cu Ni Sb Ca REM Mg Note 1 Present Invention Steel 2 Present Invention Steel 3 Present Invention Steel 4 Present Invention Steel 5 Present Invention Steel 6 Present Invention Steel 7 Present Invention Steel 8 Present Invention Steel 9 Present Invention Steel 10 Present Invention Steel 11 0.10 Present Invention Steel 12 0.10 0.05 Present Invention Steel 13 0.008 Present Invention Steel 14 0.002 Present Invention Steel 15 0.004 Present Invention Steel 16 0.003 Present Invention Steel 17 0.10 Present Invention Steel 18 0.10 0.10 Present Invention Steel 19 Present Invention Steel 20 Present Invention Steel

TABLE-US-00002 TABLE 2 Steel Chemical composition, mass % (remainder: Fe and impurities) No. C Si Mn P S Al N Ti B Cr Nb V Mo 21 0.085 0.97 2.02 0.023 0.002 0.030 0.0037 0.082 0.0021 0.44 22 0.088 1.19 1.51 0.058 0.004 0.032 0.0030 0.124 0.0024 0.52 0.02 23 0.091 0.80 1.87 0.055 0.002 0.026 0.0021 0.112 0.0021 0.57 0.02 0.10 24 0.035 1.32 2.31 0.074 0.003 0.031 0.0021 0.112 0.0021 0.33 25 0.161 1.32 2.42 0.028 0.002 0.027 0.0038 0.130 0.0021 0.59 26 0.110 0.41 2.21 0.021 0.007 0.034 0.0032 0.098 0.0021 0.42 27 0.090 1.61 1.62 0.076 0.009 0.033 0.0027 0.102 0.0023 0.92 28 0.080 1.20 0.90 0.051 0.002 0.034 0.0032 0.070 0.0021 0.98 29 0.082 0.80 2.61 0.029 0.007 0.025 0.0016 0.091 0.0024 0.34 30 0.071 0.72 1.91 0.045 0.005 0.028 0.0026 0.000 0.0021 0.42 31 0.075 0.75 1.82 0.085 0.003 0.027 0.0015 0.160 0.0023 0.55 32 0.082 0.90 1.75 0.036 0.009 0.033 0.0024 0.080 0.0000 0.38 33 0.087 0.75 1.65 0.066 0.002 0.027 0.0037 0.111 0.0015 0.00 34 0.091 0.80 1.80 0.057 0.010 0.025 0.0020 0.121 0.0017 1.30 35 0.071 0.71 1.82 0.051 0.002 0.030 0.0036 0.042 0.0021 0.71 36 0.055 1.20 1.85 0.007 0.005 0.030 0.0021 0.120 0.0015 0.65 Steel Chemical composition, mass % (remainder: Fe and impurities) No. Cu Ni Sb Ca REM Mg Note 21 Present Invention Steel 22 Present Invention Steel 23 Present Invention Steel 24 Comparative Steel 25 Comparative Steel 26 Comparative Steel 27 Comparative Steel 28 Comparative Steel 29 Comparative Steel 30 Comparative Steel 31 Comparative Steel 32 Comparative Steel 33 Comparative Steel 34 Comparative Steel 35 Present Invention Steel 36 Present Invention Steel Underlines indicate that values are outside the scope of the present invention.

TABLE-US-00003 TABLE 3 Finish rolling Heating Rolling start completion Cooling start Average cooling rate Test Steel temperature temperature temperature time between FT and CT No. No. ° C. ° C. ° C. Seconds ° C./sec 1 1 1264 1137 974 0.6 104 2 2 1295 1113 963 0.3 117 3 3 1250 1186 1025 0.9 90 4 4 1287 1108 971 0.3 102 5 5 1285 1130 964 0.6 120 6 6 1277 1160 1006 0.8 82 7 7 1264 1122 1023 0.4 98 8 8 1291 1186 965 0.4 117 9 9 1253 1101 1004 0.9 85 10 10 1292 1186 967 0.7 90 11 11 1300 1133 961 0.1 85 12 12 1288 1104 1025 1.0 82 13 13 1279 1188 1002 0.1 83 14 14 1287 1143 1001 0.4 115 15 15 1273 1164 1026 1.0 87 16 16 1265 1176 984 0.3 81 17 17 1275 1136 991 0.1 95 18 18 1275 1166 1018 1.0 93 19 19 1261 1129 998 0.2 85 20 20 1295 1157 988 0.3 115 21 21 1287 1159 973 1.0 103 Coiling Coil cooling Tempering Test Steel temperature rate parameter No. No. ° C. ° C./hour LMP Note 1 1 589 38 14480 Present Invention Example 2 2 554 31 13820 Present Invention Example 3 3 519 32 15080 Present Invention Example 4 4 581 39 14900 Present Invention Example 5 5 515 36 15300 Present Invention Example 6 6 585 32 13760 Present Invention Example 7 7 523 36 15181 Present Invention Example 8 8 588 32 15296 Present Invention Example 9 9 557 37 15282 Present Invention Example 10 10 531 40 12945 Present Invention Example 11 11 548 37 13860 Present Invention Example 12 12 518 39 14640 Present Invention Example 13 13 553 33 13820 Present Invention Example 14 14 556 30 14460 Present Invention Example 15 15 569 32 15340 Present Invention Example 16 16 583 37 15340 Present Invention Example 17 17 510 38 13700 Present Invention Example 18 18 587 36 14860 Present Invention Example 19 19 586 30 13700 Present Invention Example 20 20 586 38 14200 Present Invention Example 21 21 589 38 15100 Present Invention Example

TABLE-US-00004 TABLE 4 Finish rolling Heating Rolling start completion Cooling start Average cooling rate Test Steel temperature temperature temperature time between FT and CT No. No. ° C. ° C. ° C. Seconds ° C./sec 22 22 1273 1143 960 0.6 83 23 23 1267 1102 984 0.9 93 24 24 1290 1101 1018  0.1 106  25 25 1264 1139 1001  0.8 85 26 26 1286 1185 1025  0.7 101  27 27 1265 1110 957 0.2 89 28 28 1256 1174 975 0.9 112  29 29 1277 1100 959 0.5 82 30 30 1287 1196 968 0.2 82 31 31 1273 1175 997 0.9 81 32 32 1271 1123 975 0.8 80 33 33 1278 1175 989 0.2 93 34 34 1297 1123 969 0.4 100  35  2 1273 1175 910 0.8 120  36  2 1291 1123 979 1.5 87 37 20 1282 1175 1026  0.6 25 38  2 1256 1123 983 0.9 107  39  2 1287 1175 964 0.4 108  40  2 1277 1123 977 0.8 97 41  2 1262 1134 995 0.4 96 42 35 1287 1130 980 0.7 51 43 36 1273 1176 950 0.4 83 Coiling Coil cooling Tempering Test Steel temperature rate parameter No. No. ° C. ° C./hour LMP Note 22 22 560 32 14960 Present Invention Example 23 23 585 36 14980 Present Invention Example 24 24 594 34 15100 Comparative Example 25 25 524 40 15320 Comparative Example 26 26 538 31 15306 Comparative Example 27 27 550 35 15100 Comparative Example 28 28 522 31 14880 Comparative Example 29 29 539 40 15465 Comparative Example 30 30 516 39 15426 Comparative Example 31 31 556 40 15352 Comparative Example 32 32 505 35 14140 Comparative Example 33 33 517 33 15466 Comparative Example 34 34 589 37 14420 Comparative Example 35  2 531 34 14600 Comparative Example 36  2 506 31 13600 Comparative Example 37 20 525 32 15420 Comparative Example 38  2 630 34 15192 Comparative Example 39  2 510 20 14660 Comparative Example 40  2 587 41 12460 Comparative Example 41  2 573 32 16587 Comparative Example 42 35 542 33 15296 Comparative Example 43 36 551 73 13700 Comparative Example Underlines indicate that values are outside the scope of the present invention.

[0215] For the obtained hot-rolled steel sheets, the microstructural fraction at the 1/4 position of the sheet thickness in the sheet thickness direction from the surface, the average grain size of the secondary phase, the pole density in the (110)<112> orientation, the average grain size of the iron-based carbide, and the pole density in the (110)<1-11> orientation in the microstructure from the surface to the 1/16 position of the sheet thickness in the sheet thickness direction from the surface were obtained by the above-described methods.

[0216] The obtained results are shown in Tables 5 and 6. In examples where the total of the area ratios of bainite and the secondary phase did not reach 100%, the remainder of the microstructure was ferrite.

TABLE-US-00005 TABLE 5 Pole density in (110)<112> Pole density in (110)<1-11> Secondary Average grain size of orientation at sheet thickness orientation from surface to sheet Test Steel Bainite phase secondary phase ¼ position from surface thickness 1/16 position from surface No. No. Area % Area % μm — — 1 1 97.90 2.10 1.4 1.8 2.1 2 2 96.92 3.08 1.3 2.7 2.8 3 3 96.07 3.93 1.4 2.0 2.1 4 4 97.80 2.20 1.3 1.9 2.2 5 5 96.45 3.55 1.4 2.3 2.6 6 6 97.95 2.05 1.4 1.9 2.2 7 7 96.19 3.81 1.4 1.4 1.9 8 8 97.64 2.36 1.3 2.2 2.3 9 9 97.21 2.79 1.4 2.4 2.6 10 10 96.33 3.67 1.3 2.0 2.3 11 11 97.24 2.76 1.3 2.7 2.9 12 12 96.34 3.66 1.3 2.0 2.4 13 13 96.59 3.41 1.3 1.5 1.7 14 14 96.78 3.22 1.4 2.4 2.8 15 15 97.97 2.03 1.3 1.9 2.3 16 16 97.49 2.51 1.4 2.6 2.8 17 17 95.40 4.60 1.4 2.1 2.2 18 18 97.81 2.19 1.4 1.4 1.7 19 19 97.70 2.30 1.4 2.0 2.2 20 20 97.98 2.02 1.4 2.6 2.7 21 21 97.97 2.03 1.3 2.2 2.6 Average grain size of iron-based Test Steel carbide No. No. μm Note 1 1 0.061 Present Invention Example 2 2 0.048 Present Invention Example 3 3 0.086 Present Invention Example 4 4 0.081 Present Invention Example 5 5 0.097 Present Invention Example 6 6 0.041 Present Invention Example 7 7 0.092 Present Invention Example 8 8 0.098 Present Invention Example 9 9 0.096 Present Invention Example 10 10 0.029 Present Invention Example 11 11 0.045 Present Invention Example 12 12 0.070 Present Invention Example 13 13 0.045 Present Invention Example 14 14 0.063 Present Invention Example 15 15 0.098 Present Invention Example 16 16 0.098 Present Invention Example 17 17 0.044 Present Invention Example 18 18 0.075 Present Invention Example 19 19 0.040 Present Invention Example 20 20 0.054 Present Invention Example 21 21 0.085 Present Invention Example

TABLE-US-00006 TABLE 6 Pole density in (110)<112> Pole density in (110)<1-11> Secondary Average grain size of orientation at sheet thickness orientation from surface to sheet Test Steel Bainite phase secondary phase ¼ position from surface thickness 1/16 position from surface No. No. Area % Area % μm — — 22 22 96.80 3.20 1.3 2.5 2.7 23 23 97.90 2.10 1.4 2.2 2.5 24 24 97.90 2.10 1.3 1.6 1.7 25 25  0.00 100.00  1.4 1.9 2.4 26 26 98.10 1.80 1.3 1.6 2.0 27 27 85.00 1.90 1.4 2.1 2.4 28 28 82.00 1.60 1.3 2.8 2.9 29 29  0.00 — 1.4 2.7 3.0 30 30 20.00 80.00  1.3 1.9 2.0 31 31 97.30 2.70 1.4 3.5 4.3 32 32 84.00 1.60 1.4 2.0 2.2 33 33 65.00 1.10 1.5 2.1 2.4 34 34 93.70 6.30 1.3 2.1 2.5 35  2 97.10 2.90 1.4 4.0 4.2 36  2 98.50 1.50 1.6 2.7 2.9 37 20 90.00 4.00 1.3 1.3 1.7 38  2 50.00 3.00 1.3 2.2 2.4 39  2 94.00 1.50 1.3 2.8 2.9 40  2 94.50 5.50 1.4 2.0 2.1 41  2 97.60 2.40 1.4 2.6 2.7 42 35 91.20 8.80 1.4 1.9 3.5 43 36 93.10 6.90 1.3 3.2 3.4 Average grain size of iron-based Test Steel carbide No. No. μm Note 22 22 0.080 Present Invention Example 23 23 0.085 Present Invention Example 24 24 0.087 Comparative Example 25 25 0.099 Comparative Example 26 26 0.121 Comparative Example 27 27 0.090 Comparative Example 28 28 0.080 Comparative Example 29 29 0.099 Comparative Example 30 30 0.097 Comparative Example 31 31 0.099 Comparative Example 32 32 0.052 Comparative Example 33 33 0.098 Comparative Example 34 34 0.063 Comparative Example 35  2 0.068 Comparative Example 36  2 0.041 Comparative Example 37 20 0.097 Comparative Example 38  2 0.091 Comparative Example 39  2 0.070 Comparative Example 40  2 0.045 Comparative Example 41  2 0.193 Comparative Example 42 35 0.071 Comparative Example 43 36 0.082 Compaiative Example Underlines indicate that values are outside the scope of the present invention.

[0217] For the obtained hot-rolled steel sheets, the tensile strengths TS, the total elongations El, the hole expansion rates λ, and the limit bend radii R were obtained by the following methods.

[0218] Tensile strength TS and total elongation El

[0219] The tensile strength TS and the total elongation El were obtained by performing a tensile test using a JIS No. 5 test piece in accordance with JIS Z 2241: 2011. The cross-head speed was set to 10 mm/min. Cases where the tensile strength TS was 980 MPa or more were regarded as being excellent in terms of strength and determined as pass, and cases where the tensile strength was less than 980 MPa were regarded as being poor in strength and determined as fail. Cases where the total elongation El was 13.0% or more were regarded as being excellent in terms of ductility and determined as pass, and cases where the total elongation El was less than 13.0% were regarded as being poor in ductility and determined as fail.

[0220] Hole expansion rate λ

[0221] The hole expansibility was evaluated with the hole expansion rate λ that was obtained by punching a circular hole with a diameter of 10 mm using a 60° conical punch under a condition there the clearance became 12.5% and performing a hole expansion test such that burrs were formed on the die side. For each test number, a hole expansion test was performed five times, and the average value thereof was calculated, thereby obtaining the hole expansion rate Cases where the hole expansion rate was 60% or more were regarded as being excellent in terms of hole expansibility and determined as pass, and cases where the hole expansion rate was less than 60% were regarded as being poor in hole expansibility and determined as fail.

[0222] Limit bend radius R

[0223] The bendability was evaluated with the limit bend radius R that was obtained by performing a V-bending test. The limit bend radius R was obtained by performing a V-bending test using a No. 1 test piece in accordance with JIS Z 2248: 2014 such that a direction perpendicular to a rolling direction became the longitudinal direction (the bend ridge line coincided with the rolling direction). The V-bending test was performed by setting the angle between a die and a punch to 60° and changing the tip radii of the punches in 0.1 mm increments, and the maximum value of the tip radii of the punches that could be bent without cracking was obtained. The maximum value of the tip radii of the punches that could be bent without crack was regarded as the limit bend radius R. In a case where value (R/t) obtained by dividing the limit bend radius R by the sheet thickness t of the test piece was 1.0 or less, the bendability was regarded as being excellent, determined as pass, and expressed as “Good” in Tables 7 and 8. On the other hand, in a case where a value (R/t) obtained by dividing the limit bend radius R by the sheet thickness t of the test piece was more than 1.0, the bendability was regarded as being poor, determined as fail, and expressed as “Bad” in Tables 7 and 8.

[0224] The above-described test results are shown in Tables 7 and 8.

TABLE-US-00007 TABLE 7 Tensile strength Total elongation Hole expansion rate Test Steel TS EI λ No. No. MPa % % Bendability Note 1 1 1021 14.5 80 Good Present Invention Example 2 2 1067 14.8 69 Good Present Invention Example 3 3 1141 14.4 80 Good Present Invention Example 4 4 998 15.7 78 Good Present Invention Example 5 5 1146 14.8 72 Good Present Invention Example 6 6 993 15.0 77 Good Present Invention Example 7 7 1082 14.2 78 Good Present Invention Example 8 8 1024 15.8 73 Good Present Invention Example 9 9 1047 15.7 74 Good Present Invention Example 10 10 1055 14.4 80 Good Present Invention Example 11 11 1075 15.2 71 Good Present Invention Example 12 12 1078 15.6 79 Good Present Invention Example 13 13 1032 14.8 88 Good Present invention Example 14 14 1038 15.5 76 Good Present Invention Example 15 15 1038 15.7 81 Good Present Invention Example 16 16 1035 15.9 70 Good Present Invention Example 17 17 1041 15.0 74 Good Present Invention Example 18 18 1075 15.7 85 Good Present Invention Example 19 19 1058 14.4 79 Good Present invention Example 20 20 1061 15.2 73 Good Present Invention Example

TABLE-US-00008 TABLE 8 Tensile strength Total elongation Hole expansion rate Test Steel TS EI λ No. No. MPa % % Bendability Note 21 21 1038 15.6 75 Good Present Invention Example 22 22 1047 16.0 70 Good Present Invention Example 23 23 1055 15.5 78 Good Present Invention Example 24 24  895 16.1 55 Bad Comparative Example 25 25 1255 10.3 80 Bad Comparative Example 26 26 1109 13.5 45 Bad Comparative Example 27 27  965 14.3 34 Bad Comparative Example 28 28  975 14.2 32 Bad Comparative Example 29 29 1029 10.5 76 Bad Comparative Example 30 30  843 17.3 35 Good Comparative Example 31 31 1009 16.5 45 Bad Comparative Example 32 32  951 14.5 43 Bad Comparative Example 33 33  941 14.6 42 Good Comparative Example 34 34 1055  9.8 78 Good Comparative Example 35  2 1019 14.3 67 Bad Comparative Example 36  2 1013 14.5 58 Good Comparative Example 37 20  961 14.5 55 Bad Comparative Example 38  2  943 14.3 62 Bad Comparative Example 39  2  975 14.0 55 Good Comparative Example 40  2 1081 12.3 35 Good Comparative Example 41  2  991 15.3 45 Bad Comparative Example 42 35 1011 14.2 72 Bad Comparative Example 43 36  989 15.1 64 Bad Comparative Example Underlines indicate that values are outside the scope of the present invention.

[0225] From Tables 5 to 8, it is found that the present invention examples are excellent in terms of strength, ductility bendability, and hole expansibility On the other hand, it is found that the comparative examples are poor in one or more of strength, ductility, bendability and hole expansibility.

INDUSTRIAL APPLICABILITY

[0226] According to the present invention, it is possible to provide a hot-rolled steel sheet being excellent in terms of strength, ductility, bendability, and hole expansibility and a manufacturing method thereof.