Control method for corner cracks of boron-containing steel plate slabs

Abstract

The invention belongs to the technical field of metallurgy, and particularly relates to a control method for corner cracks of boron-containing steel plate slabs. The production procedure of a boron-containing steel plate sequentially comprises molten iron pre-treatment, converter smelting, secondary refining and plate slab continuous casting. In the continuous casting process, the ratio of the water amount of a crystallizer to the product of the casting blank section size and the pulling speed is controlled to be 0.02-0.03; meanwhile, the ratio of the wide face water amount / wide face size of the crystallizer to the narrow face water amount / narrow face size is controlled to be 1-1.5; a full-width coverage spraying manner is adopted as a secondary cooling manner, and the ratio of the total water amount of secondary cooling to the product of the casting blank section size and the pulling speed is controlled to be smaller than or equal to 0.0075; and according to the proportion of the water amount of each segment in the total water amount, the foot roller area accounts for 10%-15%, the zero segment area accounts for 35%-45%, the arc-shaped segment area accounts for 25%-35%, and the straightening area accounts for 5%-10%. According to the control method for the corner cracks of the boron-containing steel plate slabs, the straightening temperature rises, the corner cross cracks are eliminated, and the hot-rolled coiled plate edge portion surface warping defect occurrence rate caused by the corner cross cracks of the plate slabs is reduced to 0.2% or below from 3%.

Description

technical field [0001] The invention belongs to the technical field of metallurgy, in particular to a control method for corner cracks of boron-containing steel slabs. Background technique [0002] A small amount of boron (5×10 -6 ~50×10 -6 ) can significantly improve the hardenability of steel, obtain excellent mechanical properties such as high strength, high toughness, and high hardness after heat treatment, and save a lot of precious and rare metal elements. However, since the trace element boron is added to the steel, the crack sensitivity of the steel is increased, and it is easy to cause transverse cracks at the corners of the continuous casting billet, which in turn causes warped skin defects at the edge of the hot-rolled coil, resulting in the degradation of the coil or the direct rejection of the coil . [0003] Most of the cracks at the corners of the continuous casting slab start from the mold, where the positive segregation area at the bottom of the vibration...

AI Technical Summary

Problems solved by technology

At present, in the production of boron-containing steel slabs, the method of controlling the N content of molten steel and adding titanium to reduce the transverse cracks at the corner of the slab is widely adopted, but the N content needs to be strengthened from the whole process of steelmaking-refining-continuous casting, which is affected by alloying elements and process flow It is difficult to control stably. Adding titanium to boron-containing steel can reduce the occurrence of cracks at the corner of the slab to a certain extent, but it increases the cost of smelting.

Due to the unsatisfactory control of the precipitation behavior of boron nitride in the casting process of the boron-containing steel slab, the above methods have a poor control effect on the corner crack defects of the boron-containing steel slab.