Method for controlling fine cracks on surface of sub-peritectic steel bar

Abstract

The invention relates to a method for controlling fine cracks on the surface of a sub-peritectic steel bar. The method is characterized in that the relation between a peritectic reaction body shrinkage rare (Gamma) and the carbon content of molten steel at a brittleness temperature zone (LIT-ZDT) is calculated and analyzed through a phase diagram, the carbon content with the shrinkage rate of a peritectic reaction body being less than 0.004 is preferentially selected to be the component control range during smelting of sub-peritectic steel, and the content of sulfur in the molten steel is controlled to be less than 0.005%; the superheat degree of the molten steel during continuous casting is controlled to be 15-25 DEG C through strict refining temperature control; in the case of continuouscasting protective slag, the protective slag which is high in alkalinity, high in viscosity, high in melting temperature, high in melting speed and high in crystallization rate is adopted; the continuous casting pulling speed control is determined according to the peritectic reaction intensity, wherein the pulling speed is less than or equal to 0.002 / Gamma(m / min); a weak cooling mode is adoptedfor cooling and secondary cooling of a crystallizer; the conicity of the crystallizer is controlled to be 1.15-1.25% / m; and the vibration of the crystallizer adopts a non-sinusoidal vibration mode. According to the method, the fine cracks on the surface of the sub-peritectic steel bar can be successfully controlled, the quality and percent of pass of the surface of the sub-peritectic steel bar areremarkably improved, and the production cost is reduced.

Description

technical field [0001] The invention belongs to the field of iron and steel production, and relates to a method for controlling fine cracks on the surface of hypoperitectic steel rods. Background technique [0002] Bars are widely used in construction, machinery, automobiles, ships and other industrial fields, and have always been an indispensable product for various iron and steel enterprises, and have good economic benefits. However, there have always been problems with the surface quality of the bar, especially in the hypoperitectic steel with a carbon content of 0.09-0.17wt%, which has serious fine cracks on the surface of the bar. [0003] The hypoperitectic steel will undergo peritectic reaction L+δ→γ and peritectic transformation δ→γ near the solidus temperature during solidification, resulting in large volume shrinkage and linear shrinkage, resulting in uneven growth of the primary shell, plus The thermal stress and phase transformation stress generated by the perit...

AI Technical Summary

Problems solved by technology

However, there have always been problems with the surface quality of the bar, especially in the hypoperitectic steel with a carbon content of 0.09-0.17wt%, and the fine cracks on the bar surface are serious

In order to meet the requirements of users, various enterprises need to peel off the surface of the bar, and serious cracks will cause the product to be scrapped, which seriously affects the production quality and reduces the production efficiency.

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