Method for controlling non-metallic impurities in structural alloy steel

Abstract

A method for controlling non-metallic impurities in structural alloy steel includes the following steps of: step one: pre-smelting molten steel: (1) batching; (2) slagging in advance in the melting stage; (3) tapping, tapping conditions: (P) is less than or equal to 0.005 percent; (S) is less than or equal to 0.005 percent; and tapping temperature is 1640 DEG C to 1660 DEG C; step two: external refining: at the time of one third of the tapping of a primary smelting furnace, fluxing medium is added into ladles; the heating station of an external refining furnace adopts Si-Fe powder and SiC powder to conduct diffusive deoxidation; oxygen is determined before the ladles enter vacuum degassing, and deoxidizing agent is added; step three: vacuum refining: the vacuum process is kept for longer than or equal to 20min under less than or equal to 66.7Pa; the post-vacuum soft argon blowing time is longer than or equal to 15min; the soft argon blowing intensity is less than or equal to 0.10Mpa; and the post-vacuum crane ladle temperature is 1530 DEG C to 1540 DEG C; and step four: continuous casting. The method improves the purity of steel by improving the composition and size of the non-metallic impurities in steel so as to further meet the requirement on pure steel under high dynamic stress and high cycle fatigue loading.

Description

technical field [0001] The invention relates to alloy structural steel smelting technology, in particular to the control technology of the form of non-metallic inclusions in alloy structural steel. Background technique [0002] With the continuous expansion of the application field of alloy structural steel, the quality demand level of products is constantly developing towards high, refined and sharp fields, such as railway spring steel, railway bearing steel, rolls, valve springs, suspension springs, steel cords, tire wires , steel strands and other steel types are subject to high dynamic stress and high fatigue cycle load under actual application conditions; therefore, high-strength steel with high dynamic stress requires ultra-clean product intrinsic quality. The shape and size of non-metallic inclusions, residual element content, etc., as key indicators of purity, have attracted the attention of people in the metallurgical industry. The content of residual elements depe...

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Problems solved by technology

[0003] The traditional smelting of alloy structural steel adopts aluminum deoxidation and high-basic slag vacuum refining technology; its disadvantage is that the inclusions in the steel exist in the form of oxides, sulfides, silicate inclusions, and point-like non-deformable inclusions. In steel; due to the high alkalinity of the slag system and the large steel-slag interfacial tension, the adsorption capacity of the inclusions in the steel is weak, so that the inclusions in the steel are not easy to float up and remove; due to the high viscosity of the slag system, the gas in the steel during the vacuum process It is not easy to diffuse up and overflow, so that the gas content in the steel is relatively high; and the inclusions in the steel exist in the form of oxides and point-like non-deformable inclusions. This type of inclusions is mainly brittle inclusions Al2O3 inclusions, high For high-strength steel under dynamic stress, during engineering use, brittle inclusions will generate a harmful tension field around the steel, which will lead to the generation and expansion of fatigue cracks and reduce the fatigue life of the steel

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