Structure and properties control of carbon alloys cast blanks produced by aluminothermic method with following heat treatment

Abstract

Abstract Casting production with aluminothermic method is one of the mainstream lines of production process designing and improvement in foundry practices. Cast blanks production methods based on thermite mixtures application provide economic benefits due to machinery and steel production plants waste (ferrous and non-ferrous chip scrap and scale) usage. Alloys resulting from exothermal reaction are used for cast blanks production. For minimization of expenses coming from power consumption, the oncoming cast blanks properties correction is conducted at initial stages to put them into operation immediately after production, which is achieved by adding fillers in charge materials to decrease reaction’s heating effect or by external heat supply. In some cases reaction’s high intensity and temperature lead to difficulties in final properties foreseeing therefore affecting the formation of repairable and irrepairable defects. Cast blanks with irrepairable defects are used as charge materials in further recasting in traditional melting units, which increases metal waste processing efficiency and non-wastefulness. Cast blanks with repairable defects are a subject to further processing. E.g., in case of chemical and structural inhomogeneity, high-rate internal stress, cast blanks are a subject to complex heat treatment, that allows bringing properties to the required level. Annealing is applied to achieve better homogeneity compared to as-cast condition. After heat treatment cast blanks contain granular pearlite or ferrite with various inclusions. It’s been established that high rates of alloying aluminium increase the high-carbon steels hardening temperature. After 1000°C hardening the samples have martensite structure with hardness index up to 628 HBW.