Purpose. To slow down the processes of formation of chemical heterogeneity and level the crystallization front of the alloy along the height of the ingot, plasma processing of the melt is used during hardening of steel ingots, as well as processing of liquid metal during hardening using pressure, vibration, vacuum and pulsating mixing.
Specifications. Endogenous vibration processing of the melt in the plum cream ensures significant grain refinement and uniformity of the structure; reducing the width of the axial segregation zone, reducing contamination with non-metallic inclusions by 1.5 – 2 times, increasing the impact strength of the metal by 30 – 40%. Deep processing of the melt by plasma of the solidifying ingot reduces the likelihood of the formation of Λ-shaped segregation, aligns the crystallization front of the alloy along the height of the ingots, reduces the structural and chemical heterogeneity and anisotropy of their properties. The structure of a large (142 t) ingot of 25KhNZMFA steel, cast in vacuum, is more uniform, and the density of the metal in the central and bottom parts of the ingot is almost the same. Additionally, the concentration of low-melting impurities in steel in horizontal sections along the entire height of the ingot is reduced. In evacuated metal, the number of non-metallic inclusions is 2.7 – 5.5 times less than in ingots obtained under normal conditions.
Application area. Metallurgical and mechanical engineering industry.
Advantages. New technical solutions have no analogues in foreign practice and make it possible to improve the performance characteristics of massive products that are made from large ingots by significantly reducing the area of structural and chemical heterogeneity, segregation defects and the uniform distribution of non-metallic inclusions in the cast metal.
Technical and economic effect. New technological solutions make it possible to obtain high-quality products for critical purposes with improved performance characteristics for nuclear, chemical, energy and other industries. For example, contamination by non-metallic inclusions is reduced by 1.5 – 2 times, the impact strength of the metal increases by 30 – 40%.
Description. Technical solutions for improving the quality of steel ingots weighing from 7.6 tons to 142 tons with controlled processes of crystallization and structure formation are substantiated; the regularities of crystallization processes and the formation of structural and segregation zones in ingots under different conditions of heat removal and the intensity of convective and capillary mass transfer in the interdendritic channels of the alloys have been established; the dependence of the intensity of the liquid flow on the rate of crystallization of the ingot was determined; the content of gases, the morphology of non-metallic inclusions and their distribution in sections at different horizons of an ingot weighing 142 tons, obtained in vacuum, were determined.