Method for controlling low-melting-point inclusion in high-strength low-alloy steel

Abstract

The invention provides a method for controlling a low-melting-point inclusion in high-strength low-alloy steel, which comprises the following steps: 1, tapping into a ladle, and adding additives into molten steel in the ladle after the start of tapping, wherein the additives include an iron alloy, aluminum deoxidizer, slow release deoxidizer and lime; 2, performing LF (ladle furnace) refinement in the ladle, wherein the basicity range of slag in the refinement process is 3-6; the refining slag subjected to LF slagging comprises the following components in percentage by mass: 50-65% of CaO, 6-12% of MgO, 13-26% of Al2O3, 9-19% of SiO2 and less than 0.5% of (FeO+MnO); 3, after slagging, blowing Ar gas from the bottom of the ladle, and desulfurizing while strongly stirring; and 4, in the strongly stirring process and the subsequent process, reacting the slag, the molten steel and an inclusion. The invention has the following advantages: favorable deoxidization and desulfurization effect is achieved, and simultaneously, the composition of the non-metallic inclusion in the steel is controlled to be in a high-melting-point region of a CaO-MgO-Al2O3(-SiO2) phase diagram, so that the inclusion is less prone to polymerization, and less deformation is caused in the subsequent rolling process, thereby achieving the purpose of controlling the large strip-shaped inclusion in a high-strength low-alloy steel plate.

Description

technical field [0001] The invention belongs to the technical field of steelmaking and refining, and in particular provides a method for controlling low-melting-point inclusions in high-strength low-alloy steel. Background technique [0002] High-strength low-alloy steel (HSLA) is widely used in high-rise buildings, offshore platforms, long-span bridges, pipeline steel plates, etc., and has high requirements for strength, low-temperature impact toughness, and hydrogen-induced cracking (HIC) resistance. Non-metallic inclusions, especially long inclusions have a great influence on its performance. This is mainly because: (1) strip-shaped inclusions have a significant impact on the properties of the steel plate in the non-rolling direction, resulting in anisotropy of the steel; (2) HIC cracks are mostly formed at the strip (or string) inclusions, And this expansion will eventually lead to product failure. [0003] MnS inclusions are easily extended into long strips during rol...

AI Technical Summary

Problems solved by technology

[0005] These calcium aluminates with low melting point will also be extended into long strips in the subsequent rolling, resulting in reduced ductility and HIC resistance of high-strength low-alloy steel sheets, seriously affecting their performance

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