Ultra-clean rare earth steel and occluded foreign substance modification control method

Abstract

The invention provides ultra-clean earth steel and an occluded foreign substance modification control method. 10-200 ppm of rare earth elements are included in the steel, and 50% or more occluded foreign substances in the steel are dispersed RE-oxygen-sulfide with the average equivalent diameter Dmean ranging from 1 micrometer to 5 micrometers in a spherical shape or a spheroidal shape or a granular shape. According to the method, at least 80%, preferably at least 90%, of Al2O3 occluded foreign substances in the steel are modified into RE-oxygen-sulfide, compared with steel with the same components without rare earth, the total amount of the occluded foreign substances in the steel is reduced by 18% or higher, the cracking probability caused by occluded foreign substances such as Al2O3 intraditional pure steel is reduced, the mechanical and chemical performance such as the fatigue life of the steel is remarkably improved, precise control over the modification type, distribution and dimension of the occluded foreign substances in the steel is achieved, and the method is suitable for researching and producing of high-performance steel in more varieties.

Description

technical field [0001] The invention belongs to the field of alloys, and relates to an ultra-clean rare earth steel and a modification control method for inclusions. Background technique [0002] In the past ten years, after the double hypoxia technology, that is, the simultaneous control of the initial oxygen content of the rare earth metal itself and the total oxygen content of the steel melt, has been applied, the effect of the rare earth has become extremely stable and prominent. Many previous applications of the inventor have been Related technologies are presented, including: CN201610265575.5, which involves the preparation method of high-purity rare earth metals, which can avoid the occurrence of coarse inclusions, fluctuations in material properties, and blockage of nozzles during production. The impact has not been studied; CN201611144005.7 relates to an ultra-low oxygen rare earth alloy and its use, using high-purity rare earth alloys to treat steel, and gives a co...

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Problems solved by technology

However, although this document mentions REM oxysulfide, the purpose of controlling the amount of REM added is to target the formation of REM oxide inclusions, and the influence of the change of O content in the steel caused by the addition of REM on inclusions, as well as the impact of impurities The influence of elements such as S on inclusions, the rolling fatigue life of the obtained pure bearing steel containing rare earth inclusions is 3.2-9.2 times that without adding REM

[0004] In the invention application 201811319185.7 of Cheng Guoguang et al. of Beijing University of Science and Technology, it is pointed out that the rare earth Ce has the opposite effect on MgAl 2 o 4 It has a good modification effect, but only when the rare earth content in the bearing steel is controlled to 0.002% (ie 20ppm), CeAlO is obtained 3 Composite inclusions wrapped with TiN, when the rare earth content in the bearing steel reaches 0.004% (ie 40ppm), the main type of inclusions in the bearing steel is Ce 2 o 3 And separate TiN inclusions, when the rare earth increases to 0.007% (ie 70ppm), the type of main inclusions in bearing steel is also represented by separate Ce 2 o 3 and TiN, with the further increase of rare earth content in steel, Ce 2 o 3 Stable in the steel, although the TiN content of the inclusions in the steel is reduced, but the Ce 2 o 3 The lattice matching with TiN inclusions is not good, and the formation of a large number of rare earth oxides degrades the mechanical properties of steel

[0005] At present, the effect of rare earth addition on the modification of inclusions in steel is not yet clear. After the addition of rare earths, the controllability is poor, and there is a lack of systematic and in-depth research, which leads to the difficulty and poor stability of the production control process of inclusion denaturation, which greatly restricts the production of low-cost rare earths. High-performance steel, such as bearings, gears, molds, stainless steel, steel for nuclear power, steel for automobiles, etc., and the promotion and application of various key components

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