A method for reducing cracks at the corners of low-carbon boron-containing steel billets

Abstract

The invention discloses a method for reducing corner cracks of a small low-carbon boron-containing steel square billet. The method includes primary cooling and secondary cooling. A reasonable primary cooling water amount and secondary cooling water amount governing equation during continuous casting is given out on the basis that the crystallizer water inlet temperature, season or environmental temperature change influences are fully considered, the proper secondary cooling water distribution ratio of all areas is adjusted on this basis, the first area accounts for 35%-40%, the intermediate area apart from the first area and the tail area accounts for 52%-60%, the tail area accounts for 5%-8%, and therefore the corner temperature of a casting blank at a bent straightened area can be controlled more stably, and a third brittleness temperature interval of low-carbon boron-containing steel is reasonably evaded. By the adoption of the method, through optimized control over a continuous casting cooling technology of the small low-carbon boron-containing steel square billet, the corner crack defect of the casting blank can be greatly reduced, the crack occurrence rate is lowered to be within 0.5% from 6.67% before, surface quality of the casting blank can be stably controlled, and the quality of final products is improved.

Description

technical field [0001] The invention belongs to the technical field of billet continuous casting. Specifically, the invention relates to a method for reducing cracks at the corners of low-carbon boron-containing steel billets. Background technique [0002] Low-carbon boron-added steel is one of the typical billet continuous casting steels, and has a wide range of uses in national production. One of its main features is that 5-50ppm of boron is added to the steel. Boron is one of the elements that can significantly improve the hardenability of steel. Since boron is easy to segregate at the austenite grain boundary, it inhibits pro-eutectoid ferrite. The nucleation at the austenite grain boundary promotes the formation of bainite and martensite, which can greatly increase the strength of the steel. [0003] In the continuous casting process of low-carbon boron-added steel, corner cracks are more likely to occur on the surface of the slab, including corner star cracks, claw c...

AI Technical Summary

Problems solved by technology

[0005] (1) The continuous casting cooling process fails to fully consider the influence of mold inlet water temperature, seasonal or ambient temperature changes on the cooling effect, resulting in the occurrence of corner cracks during the production of low-carbon boron-containing steel, and sometimes the corner crack defects are well controlled Better, but sometimes the process is the same, but the incidence of corner cracks is high, and it is difficult to control stably;

[0006] (2) In order to increase the temperature at the corner of the slab as much as possible, the existing technology often excessively reduces the water volume of the mold, which will lead to a thinning of the shell thickness of the mold exiting the mold. Unreasonable, the strength of the billet shell will be difficult to resist the hydrostatic pressure, increasing the possibility of steel breakout and bringing serious consequences to production

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