High strength cold rolled steel sheet and plated steel sheet excellent in the balance of strength and workability
View Patent ↗A high-strength cold-rolled steel sheet exhibiting an excellent strength-workability balance, including in percent by mass: 0.10-0.25% of C; 1.0-2.0% of Si; 1.5-3.0% of Mn; 0.01% or less (not including 0%) of P; 0.005% or less (not including 0%) of S; 0.01-3.0% of Al; and remaining part consisting of iron and inevitable impurities, wherein the space factor of bainitic ferrite to the entire structure is 70% or more, the space factor of residual austenite to the entire structure is 5-20%, the hardness (HV) is 270 or greater, and the half-value width of an X-ray diffraction peak on a (200)-surface of α-iron is 0.220 degrees or smaller.
1. A high-strength cold-rolled steel sheet having a matrix comprising bainitic ferrite and residual austenite, wherein said high-strength cold-rolled steel sheet comprises:
0.10-0.25 wt. % C;
1.0-2.0 wt. % Si;
1.5-3.0 wt. % Mn;
0.01 wt. % or less, not including 0 wt. %, P;
0.005 wt. % or less, not including 0 wt. %, S;
0.01-3.0 wt. % Al; and
balance consisting of iron and impurities,
wherein said bainitic ferrite exhibits a space factor within said matrix of 70% or more,
wherein said residual austenite exhibits a space factor within said matrix of 5-20%,
wherein said high-strength cold-rolled steel sheet exhibits a Vickers hardness number of 270 or greater, and
wherein an X-ray diffraction peak on a (200)-surface of α-iron has a half-value width of 0.220 degrees or less.
2. The high-strength cold-rolled steel sheet according to claim 1 , further comprising:
0.3 wt. % or less, not including 0 wt. %, Mo; and/or
0.3 wt. % or less, not including 0 wt. %, Cr.
3. The high-strength cold-rolled steel sheet according to claim 1 , further comprising:
0.1 wt. % or less, not including 0 wt. %, Ti; and/or
0.1 wt. % or less, not including 0 wt. %, Nb.
4. The high-strength cold-rolled steel sheet according to claim 1 , further comprising:
50 mass ppm or less, not including 0 mass ppm, Ca.
5. A plated steel sheet produced by a process comprising plating a surface of said high-strength cold-rolled steel sheet according to claim 1 .
6. The plated steel sheet according to claim 5 , wherein said plating is galvanizing.
7. The high strength cold-rolled steel sheet according to claim 1 , wherein the bainitic ferrite exhibits a space factor within said matrix of 70% to 95%.
8. The high strength cold-rolled steel sheet according to claim 1 , wherein the bainitic ferrite exhibits a space factor within said matrix of 80% to 95%.
9. The high strength cold-rolled steel sheet according to claim 1 , wherein the bainitic ferrite exhibits a space factor within said matrix of 90% to 95%.
10. The high strength cold-rolled steel sheet according to claim 1 , wherein the residual austenite exhibits a space factor within said matrix of 8-20%.
11. The high strength cold-rolled steel sheet according to claim 1 , wherein the residual austenite exhibits a space factor within said matrix of 10-20%.
12. The high strength cold-rolled steel sheet according to claim 1 , wherein the residual austenite exhibits a space factor within said matrix of 15-20%.
13. The high strength cold-rolled steel sheet according to claim 1 , wherein the high-strength cold-rolled steel sheet comprises 0.10-0.23 wt. % C.
14. The high strength cold-rolled steel sheet according to claim 1 , wherein the high-strength cold-rolled steel sheet comprises 0.15-0.23 wt. % C.
15. The high strength cold-rolled steel sheet according to claim 1 , wherein the high-strength cold-rolled steel sheet comprises 0.18-0.23 wt. % C.
16. The high strength cold-rolled steel sheet according to claim 1 , wherein the X-ray diffraction peak on a (200)-surface of α-iron has a half-value width of 0.205 degrees or less.
17. The high strength cold-rolled steel sheet according to claim 1 , wherein the X-ray diffraction peak on a (200)-surface of α-iron has a half-value width of from 0.180 degrees to 0.205 degrees.