Determination of melting temperature of slagmaking mixtures for billet CCM mold by differential thermal analysis method

Abstract

At PJSC “Izhstal” continuously casted billets with sections of 125*125 and 140*180 mm are produced at a CCM of radial type, manufactured by STS firm, Italy. At the casting by a closed stream it is recommended to use import Steelin ML/P-280, Steelin ML/LM-280, Steelin ML/HC-230 slag-making mixtures (SMM) in the mold. At present within the import substitution program, pilot-industrial test are carried out at the plant to use SMM of domestic production. To ensure a stable process of casting and obtain quality continuously casted billet it is important to know the operation properties of SMM, including the range of melting, which is characterized by temperatures of SMM softening and melting. The value of the characteristics influences the thickness of the liquid slag layer on the surface of liquid steel in CCM mold. The properties mentioned above were determined by a differential thermal analysis at a automated facility ВТА-983. The difference of temperatures between the sample and the standard, measured during heating and cooling with continuous speed, was the registered parameter. By application the differential thermal analysis method the temperatures of softening and melting of granulated SMM of Intoflux GB 1040/H and Intoflux GB 1220/A grades were determined. Based on the results of the analysis, the softening temperature of the Intoflux GB 1040/H grade SMM was determined as 755 °C, the softening of Intoflux GB 1220/A grade SMM takes place in the temperature interval of 645-803 °C. The temperatures of commencing of crystal phases melting of the mixtures studied were 825 and 925°С for Intoflux GB 1040/H grade SMM, 1097 and 1206 °C for Intoflux GB 1220/A grade SMM. Based on the results of pilot-industrial tests, the Intoflux GB 1040/H grade SMM was recommended for usage at casting medium-carbon and high-carbon steels as a substitution of import SMM of Steelin ML/HC-230 grade.