Production method for controlling large-sized hard inclusions in spring steel wire rods

Abstract

The invention discloses a production method capable of controlling large hard inclusions in a spring steel wire rod. The method comprises procedures of converter smelting, LF refining, continuous casting and heating cogging-down, wherein in the converter smelting procedure, carbon deoxidization and Mn-Si composite deoxidization are adopted sequentially in a deoxidization and alloying process of converter tapping, and a weight ratio of Mn to Si in alloy added in Mn-Si composite deoxidization is larger than or equal to 5.0; in the LF refining procedure, slag is formed by premelting and refiningsynthetic slag, target alkalinity w(CaO) / w(SiO2) is 0.80-1.2, w(Al2O3) in the slag is less than or equal to 3%, w(MnO)+w(MgO) is less than or equal to 10%, and the balance accounts for 5% or less. According to the spring steel hot-rolled wire rod produced with the method, diameter of oxide inclusions on a cross section of the wire rod is reduced effectively; after drawing, heat treatment and shotblasting of the wire rod, rotating and bending fatigue life of a spring wire reaches 1*10<7> or longer, and the fatigue life of a processed high-strength automotive suspension spring reaches 1*10<6> or longer.

Description

technical field [0001] The invention relates to a production method of a steel wire rod, in particular to a production method for controlling large-sized hard inclusions in a spring steel wire rod. Background technique [0002] The higher the strength of the metal material, the more significant the impact of inclusions on its fatigue properties. Non-metallic inclusions form a mosaic structure with the matrix in the steel. During the heating or cooling process of steel, mosaic stress will be generated around the inclusions due to the difference in expansion coefficient. If the number of inclusions is large and the diameter is large, the mosaic stress field will increase. Superposition, the stress of the workpiece during service and the mosaic stress are superimposed, so that the stress around the inclusion exceeds the yield limit of the steel, resulting in cracks and the formation of fatigue sources. With the development of high-strength steel for springs, fatigue fracture w...

AI Technical Summary

Problems solved by technology

The above two patent applications did not pay attention to the reasonable control of the composition of oxide inclusions, and the plastic deformation of the inclusions during the rolling process cannot be guaranteed, and the fatigue life requirements of high-strength springs cannot be guaranteed.

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