Production method of formable high-strength medium-thickness steel plate

Abstract

The invention relates to a production method of a formable high-strength medium-thickness steel plate, which comprises the following steps: converter steelmaking, ladle furnace refinement, vacuum treatment, continuous casting, heating, rolling, pre-straightening, on-line quenching, and tempering heat treatment. The steel comprises the following components in percentage by mass: 0.07-0.09% of C, 0.15-0.30% of Si, 1.55-1.60% of Mn, at most 0.010% of P, at most 0.005% of S, at most 0.10% of Nb+V+Ti, at most 0.5% of Cr+Mo, at least 0.020% of Alt and at most 0.21% of Pcm. The Q690D steel plate produced by the method is still in good condition when being subjected to 200mm-wide cold bending; the cold bending property of the real steel plate satisfies the requirement of the consumer for formability; the yield ratio of the steel plate is less than 0.92, and the uniform elongation is greater than 8%, thereby satisfying the operational requirements of related design; the product of strength and elongation is enhanced by more than 35%, the dynamic loading resistance of the high-strength steel plate is enhanced, and the safety of equipment is improved; the hot charging and on-line quenching of the continuous casting billet lower the production cost; and the composition design of less than 0.21% of Pcm enhances the weldability of the high-strength steel plate.

Description

technical field [0001] The invention belongs to steelmaking technology, and is a production method of easy-to-form high-strength medium-thick steel plate. Background technique [0002] With the development of the metallurgical industry, the production of high-strength steel plates with a yield of more than 550MPa has undergone tremendous changes, from the traditional reheating quenching + tempering (ie RQ+T) process to TMCP, TMCP+T, DQ+T, Q+ P, Q+P+T, especially in recent years, the on-line direct quenching (Direct Quenching, DQ for short) process after rolling has made great progress and is widely used in the production of high-strength steel plates. [0003] Compared with the high-strength structural steel produced by other processes, the high-strength structural steel produced by the DQ process can greatly reduce the content of alloy elements and reduce the carbon equivalent under the condition of equivalent mechanical properties, improve the performance of welding and ot...

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Problems solved by technology

[0011] In short, the high-strength steel plate produced by the traditional direct quenching + tempering process (DQ+T) has the following disadvantages: the steel plate contains B elements, the hardenability of the steel plate is good, and the steel plate produced has high strength, high impact and low elongation. High, but the uniform elongation 0.96; the high yield ratio of the steel plate, it is difficult to meet the actual use requirements of the design; There is delamination in the steel plate; the steel plate is sampled according to the standard and the cold bending is qualified, but most of the wide cold bending and the actual steel plate are cracked, that is, the cold forming performance is poor; the cooling rate in the traditional DQ process after rolling the steel plate is > 35 ℃ / s, resulting in an uncontrolled yield-to-strength ratio

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