Effect of melting procedure on the quality of steel 12KhN3MA
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Ingots of structural steel 12KhN3MA obtained by ESR, VAR, and EBR have a dense defect-free macrostructure.
The dispersity of the dendritic structure of ESR, VAR, and EBR ingots melted at similar rates in molds of similar size is practically the same. The somewhat larger interaxial intervals of the dendrites in ESR and VAR ingots as compared with the EBR ingot is due to the less perfect dendritic structure of these ingots.
Impurities of nonferrous metals are effectively removed from the steel only by vacuum remelting processes.
Sulfur is removed only by the ESR process, while phosphorus is not removed by any of these remelting processes. The cleanness of the metal (atomic parts per million) more than doubles after remelting as compared with open melting (∼1500 at. ppm for open melting, ∼675–750 at. ppm after remelting). The lowest total concentration of nonmetallic inclusions and most even distribution of nonmetallic inclusions occur in the EBR ingot.
The work of crack propagation (dynamic bending tests) is highest for the EBR ingot.
KeywordsSulfur Phosphorus Mold Total Concentration Similar Rate
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