Method for refining rare earth inclusions in super stainless steel

Abstract

The invention provides a method for refining rare earth inclusions in super stainless steel, and belongs to the technical field of ferrous metallurgy. According to the method, the molten steel of the super stainless steel is subjected to primary refining and refining operation, so that the sizes of rare earth inclusions in the super stainless steel can be effectively refined, and the total oxygen content is remarkably reduced. Wherein during primary refining, the contents of oxygen, sulfur and aluminum in tapping molten steel can be effectively controlled within a proper range; in the refining process, slag adjusting, diffusion deoxidation treatment, precipitation deoxidation treatment, calcium treatment for feeding a silicon-calcium wire and rare earth treatment for feeding a rare earth core-spun yarn are sequentially carried out, the total oxygen content of the molten steel can be further reduced, and the size of rare earth inclusions can be further refined. A calcium treatment process is added before rare earth treatment, and a feeding amount formula of a silicon-calcium line is designed, so that calcium aluminate inclusions are in a semi-liquid state, collision growth of the calcium aluminate inclusions is inhibited, and the situation that the sizes of the rare earth inclusions are too large due to genetic effects is avoided.

Description

technical field [0001] The invention relates to the technical field of iron and steel metallurgy, in particular to a method for refining rare earth inclusions in super stainless steel. Background technique [0002] Super stainless steel mainly includes super duplex stainless steel (such as S32760 and S32707) and super austenitic stainless steel (such as 254SMO), whose alloy content is much higher than ordinary stainless steel, so its strength, toughness and corrosion resistance are significantly better than ordinary stainless steel, widely It is used in petrochemical, chemical tanker manufacturing, nuclear power, pulp and paper, seawater desalination, desulfurization absorption devices and other fields in harsh corrosive environments. The high alloy content makes the cold / hot processing of super stainless steel difficult. The large-sized non-metallic inclusions in the steel will cause stress concentration during processing, resulting in cracks and seriously reducing the yiel...

AI Technical Summary

Problems solved by technology

However, the rare earth oxygen sulfur inclusions generated by rare earth treatment generally have the following three serious problems: (1) The density of rare earth inclusions is relatively high, such as the common Ce 2 o 3 Inclusions, density 6.2g / cm 3

However, traditional calcium treatment often completely denatures alumina inclusions into liquid calcium aluminate inclusions, which is very unfavorable for the refinement of rare earth inclusions

For example, the Chinese patent (patent application number 201810042651.5) provides a "purification method for low-carbon high-alloy steel", in which calcium treatment and rare earth treatment are sequentially performed in the VD / RH refining stage, and the amount of calcium-silicon wire added is 3-5m / per ton of steel, the amount of rare earth added is 30-100 μg / g, the state of calcium-aluminate inclusions after calcium treatment is unknown, and the amount of rare earth added is too low to be suitable for super stainless steel; Chinese patent (patent application number 202010832440.9) discloses "a A low-cost composite rare earth structural steel and its production method", calcium treatment is carried out in the refining stage, and rare earth treatment is carried out in the RH vacuum treatment stage, but this patent only provides the content of calcium and rare earth in the final molten steel, without the specific addition of calcium and rare earth The actual operation cannot be specifically guided; the Chinese patent (patent application number 201511019835.2) discloses "a high-strength steel plate with improved low-temperature impact toughness and its manufacturing method", and the yttrium-based rare earth silicon-calcium alloy core is fed during the refining stage of the LF furnace Line 300~500m

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