METHOD OF PRODUCING ALLOY WITH FREE AND FIXED CARBON Russian patent published in 2003 - IPC

FIELD: metallurgy, particularly, methods of production of alloys based on iron and carbon. SUBSTANCE: method includes smelting of low-carbon semiproduct with use of iron charge in the form of direct-process iron and/or pig iron in amount of 75-100%, its overheating in excess of liquidus temperature by 20-70 C; tapping of melt; carburizing of melt with carbon black particles sizing 10^-5-10^-7 cm introduced into melt in amount of 0.01-2.14%; oxidizing in tapping and/or refining, and/or casting; deoxidizing with elements whose affinity to oxygen is equal to or higher than aluminum affinity to oxygen in amount of 0.05-3%; refining, crystallization and working of alloy by pressure. Cooling of melt in the course of casting and crystallization to temperature of 1147 C is carried out at rate of not more than 10 C per minute. Further cooling to temperature equal to and/or higher than 723 C is effected at rate equal to and/or lower than 5 C per minute. In the course of melt cooling, it is held at solidus temperature for 0.5-60 min. Technical result of the invention consists in preservation in the course of casting and crystallization of constant content of carbon particles and ratio of amounts of free and fixed carbon in melt due to prevention of dissolving of carbon particles in liquid alloy and formation of cementite in solid metal after cooling down to solidus temperature. The method is used in manufacture of articles combining high strength and ductility and capable of changing of physico-mechanical properties after completion of molding or manufacture of structural members and articles. EFFECT: higher efficiency. 2 cl, 1 tbl, 1 ex