High-strength steel with resistance to delayed fracture with yield ratio ≤ 0.5 and production method

Abstract

The invention provides high-strength anti-delayed fracture steel with a yield ratio of no more than 0.5. The steel comprises, by weight, 0.11 to 0.25% of C, 15.5 to 17.5% of Mn, 0.030 to 0.050% of Mo, 0.005 to 0.02% of Co, 0.005 to 0.009% of B, 0.009 to 0.011% of N and 0.011 to 0.025% of La+Ce+Nd. A production method for the steel comprises the following steps: desulphurization of molten iron; converter smelting; RH vacuum treatment; continuous casting; hot rolling, wherein finish rolling temperature is in a range of 755 to 790 DEG C; cold rolling, wherein a reduction rate is 51 to 54%; and continuous annealing. According to the invention, the problems of low elongation percentage, a high yield ratio and poor welding performance of high-strength steel of a same grade are overcome, and the phenomenon of delayed fracture is avoided; an automobile crash-proof part manufactured from the steel has better formability, welding performance and energy absorption performance compared with other cold-rolled high-strength steel, and use security, weight reduction performance and energy saving performance of a product are substantially improved; B, Mo, Co and N are employed, so refined crystalline strengthening and precipitation strengthening are realized, and a low yield ratio, heat resistance and corrosion resistance are guaranteed; a steel plate has double effects and a low yield ratio, and good forming capability, good bearing performance and anti-fracture performance of a material are guaranteed.

Description

technical field [0001] The invention relates to a cold-rolled high-strength steel and a production method thereof, in particular to a high-strength steel with a yield ratio ≤ 0.5 and anti-delayed fracture and a production method thereof. Background technique [0002] The lightweight technology of automobiles, especially cars, continues to develop. Steel materials such as anti-collision parts and important beams, longitudinal beams, wheel covers and floors are required to have high strength and high plasticity, as well as good formability and good weldability. Martensitic steel is guaranteed At the same time of high strength, its formability cannot meet the requirements, its carbon equivalent is significantly increased, and its weldability is difficult to meet the requirements. [0003] After searching, the Chinese patent application number is CN201210012636.9, which discloses a low-cost high expansion rate expansion pipe TWIP steel and a steel pipe preparation method. Althou...

AI Technical Summary

Problems solved by technology

However, automobiles, especially car structural parts, mostly use cold-rolled or galvanized products, with a thickness of 0.6~2.0mm. Hot-rolled steel cannot meet this thickness requirement, and it has a single TWIP effect, which will greatly increase the cost. Moreover, its single Austenitic The body must have a manganese content of more than 20 to achieve, and at the same time, it needs to contain a high carbon content and a high silicon and aluminum content.

In this way, it brings great difficulty to the smelting, the manganese content is too high and it is difficult to realize the converter steelmaking production, at the same time, high silicon or high aluminum will cause the crystallizer nozzle to be blocked and the cast slab will have cracks

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