Ultra-high strength strip steel and its production process

Abstract

The ultra-high strength strip steel consists of C 0.10-0.20 wt%, Si<0.6 wt%, Mn not more than 2.6 wt%, Al 0.020-0.080 wt%, Cr 0.35-0.90 wt%, Nb 0.015-0.050 wt%, Ti 0.015-0.050 wt%, and B 0.0005-0.0030 wt%, except Fe and inevitable impurities. Its production process includes the following steps: smelting and casting; hot rolling, acid pickling and cold rolling; continuous annealing and complex roller cooling and gas jetting cooling or high speed gas jetting cooling; and flattening and trimming. It has simplified production process and low production cost.

Description

technical field [0001] The invention relates to an ultra-high-strength strip steel and a production method thereof, in particular to a 1180Mpa ultra-high-strength strip steel and a production method thereof. Background technique [0002] In recent years, in order to protect the global environment and save energy, it is necessary to reduce the fuel consumption of automobiles, which requires lightweight automobiles. Therefore, steel mills have put forward the demand for the development of high-strength and high-formability cold-rolled steel sheets. At the same time, bumpers, door reinforcements, The demand for ultra-high-strength steel of 1180Mpa or more is also increasing for various automotive reinforcement components such as beams. [0003] So far, the main processes for the commercial production of most ultra-high-strength strip steel with a strength grade exceeding 1180Mpa are: [0004] Steelmaking→hot rolling of continuous casting slab→pickling and cold rolling→continuo...

AI Technical Summary

Problems solved by technology

In order to ensure the strength, the austenite formed in the two-phase region will not undergo pearlite transformation and directly enter the bainite transformation region after the cooling rate of the fast cooling section is controlled. The cooling section is longer and there is no slow cooling section. In addition, the cooling rate of the patented steel is too slow in the fast cooling section (1-30°C / S) and the composition does not contain Cr, Nb, Ti and other elements that are beneficial to strengthening, so it is impossible to obtain the main For dual-phase steel containing ferrite and martensite, due to the low cooling rate, this technology is likely to obtain a dual-phase structure containing ferrite and bainite, or containing ferrite, bainite and residual The multi-phase structure of austenite, because there is no martensitic transformation strengthening and carbonitride dispersion strengthening, so the strength level is difficult to exceed 1180Mpa. Finally, the invention has no smoothing process after annealing, which has no effect on the strip shape and subsequent processing. is unfavorable