High-strength and high-toughness steel plate with yield strength of 700 MPa and method of manufacturing the same

Patent metadata

Field	Value
Publication number	US-9771639-B2
Application number	US-201214129103-A
Country	US
Kind code	B2
Filing date	May 25, 2012
Priority date	Sep 26, 2011
Publication date	Sep 26, 2017
Grant date	Sep 26, 2017

Abstract

The present invention relates to a high-strength high-toughness steel plate and a method of manufacturing the steel plate. The steel plate contains the following chemical compositions, by weight, C: 0.03-0.06%, Si≦0.30%, Mn: 1.0-1.5%, P≦0.020%, S≦0.010%, Al: 0.02-0.05%, Ti: 0.005-0.025%, N≦0.006%, Ca≦0.005%, and more than one of Cr≦0.75%, Ni≦0.40%, Mo≦0.30%, other compositions being Ferrum and unavoidable impurities. The finished steel plate, with a thickness of 6-25 mm, has a yield strength of ≧700 MPa, an elongation A50 of ≧18%, Akv at −60° C. of ≧150 J and good cool bending property.

First claim

The invention claimed is:

1. A high-strength high-toughness steel plate, comprising the following chemical compositions, by weight, C: 0.03-0.06%, Si≦0.30%, Mn: 1.0-1.5%, P≦0.020%, S≦0.010%, Al: 0.02-0.05%, Ti: 0.005-0.025%, N≦0.006%, Ca≦0.005%, and more than one of Cr, Ni and Mo, wherein Cr≦0.75%, Ni≦0.40%, and Mo≦0.30%, other compositions being Ferrum and unavoidable impurities, wherein the high-strength high-toughness steel plate has a thickness of 6-25 mm, a yield strength of ≧700MPa, an elongation A 50 of ≧18%, and an Akv at −60° C. of ≧150J, and wherein the high-strength high-toughness steel plate structure comprises mainly tempered martensite and dispersed carbides and with no bainite structure.

2. The high-strength high-toughness steel plate according to claim 1 , characterized in that C is 0.031-0.059% by weight.

3. The high-strength high-toughness steel plate according to claim 1 , characterized in that Si is 0.03-0.30% by weight.

4. The high-strength high-toughness steel plate according to claim 1 , characterized in that Mn is 1.02-1.5% by weight.

5. The high-strength high-toughness steel plate according to claim 1 , characterized in that P is ≦0.015% by weight.

6. The high-strength high-toughness steel plate according to claim 1 , characterized in that S is ≦0.005% by weight.

7. The high-strength high-toughness steel plate according to claim 1 , characterized in that Al is 0.02-0.046% by weight.

8. The high-strength high-toughness steel plate according to claim 1 , characterized in that Ni is 0.10-0.40%.

9. The high-strength high-toughness steel plate according to claim 1 , characterized in that Cr is 0.3-0.75%.

10. The high-strength high-toughness steel plate according to claim 1 , characterized in that Mo is 0.10-0.30%.

11. The high-strength high-toughness steel plate according to claim 1 , characterized in that Ti is 0.01-0.025% by weight.

12. The high-strength high-toughness steel plate according to claim 1 , characterized in that N is ≦0.005% by weight.

13. A manufacturing method of the high-strength high-toughness steel plate according to claim 1 , comprising:
after vacuum degassing treatment, continuous-casting or die-casting molten steel, and if the molten steel is die-casted, blooming it into a billet;
heating the continuous casting slab or billet at temperature of 1100-1250° C., then one-pass or multi-pass rolling it in austenite recrystallization zone, with the total reduction ratio being ≧70% and the rolling finishing temperature being ≧860° C.;
water-cooling rapidly the rolled steel plate at a rate of 15-50° C./s to the temperature range 200-300° C., then air-cooling it for 5-60 s;
after the cooled steel plate entering an online heating furnace, rapidly heating it at a rate of 1-10° C./s to 450-550° C., tempering it for 15-45 s, then air-cooling it outside the furnace.

14. The method according to claim 13 , characterized in that the rolling finishing temperature is 860-900° C.

15. The method according to claim 13 , characterized in that after the cooled steel plate entering an online heating furnace, rapidly heating it at a rate of 1-10° C./s to 450-500° C., tempering it for 15-45 s, then air-cooling it outside the furnace.

16. The method according to claim 13 , characterized in that the online heating furnace is an induction heating furnace.

17. The high-strength high-toughness steel plate according to claim 1 , characterized in that Ni is 0.13-0.36% by weight.

18. The high-strength high-toughness steel plate according to claim 1 , characterized in that Cr is 0.32-0.75% by weight.

19. The high-strength high-toughness steel plate according to claim 1 , characterized in that Mo is 0.13-0.26% by weight.

20. The high-strength high-toughness steel plate according to claim 1 , wherein the structure consists of tempered martensite and dispersed carbides with no bainite structure.

21. The high-strength high-toughness steel plate according to claim 1 , wherein the steel plate was cooled at a rate of no less than 15° C./s to avoid bainite formation.

Assignees

• Zhang Aiwen
• Jiao Sihai
• Zhang Qingfeng
• Baoshan Iron & Steel

Inventors

• Zhang Aiwen
• Jiao Sihai
• Zhang Qingfeng

Classifications

• C21D1/28

  Normalising · CPC title

• C22C38/06

  containing aluminium · CPC title

• C22C38/02

  containing silicon · CPC title

• C21D8/0263

  following hot rolling · CPC title

• C21D8/0226

  Hot rolling · CPC title