Design of molds for electroslag remelting

Abstract

669.154.9 The metallurgical equipment repair shop at the Magnitogorsk Metallurgical Combine uses ESP-1.25 -11 furnaces to make rollers for continuous casters. The copper ingot molds of the crystallizing tanks (CMTs) undergo rapid wear during service, which has made the method used to obtain the molds an important concern. To provide the shop with serviceable crystallizing tanks, first the combine mastered a technology for refining copper by electroslag remelting (ESR) and using the copper to make the CMT. A modification was subsequently proposed for the method used to calculate the thickness of the walls of the CMT.One method used to design CMTs and check their quality is based on the critical heat flux and the temperature of the inside working surface of the ingot mold (which should not exceed 500~ [1]. The shop successfully introduced this method and proposed an algorithm for designing CMTs that were to be made in the shop. However, the calculation of the critical heat flux in the method in [1] is based on the sampling of a large number of process parameters, which complicates the design process. As a result, well-known relations [2, 3] were used to simplify the heat-flux calculation in the design of CMTs.The calculation and design are based on determination of the necessary dischm~e of coolant water and the temperature on the inside surtace of the CMT. This temperature should be lower than the allowable value. The method used to pertbrm the thermal calculations for the CMT is described below.We determined the amount of heat released into the slag bath:where G is the productivity of the remelting operation, kg/h; Qt is the theoretical amount of heat needed to melt 1 kg of metal (for most grades of steel, at the initial moment of time we take Q ---1210 kJ/kg); qs is the fraction of the heat of the slag bath which is lost through the wall of the CMT, this fraction depending on the ratio of the area of the contact surface between the molten slag and the wall to the surface area of the metal bath [2]; Tlrdn is the fraction of heat radiation lost from the surface of the slag (assumed to be equal to 0.06).We determined the average heat flux reaching the wall of the CMT:where Ff t is the area of contact of the slag with the wall of the CMT, m2:where Dot is the working diameter of the CMT, m; h is the height of the slag bath, m.We determined the ratio FS/Fmb (Fmb = 3.14D2t/4 is the area of the metal bath). We then used the method in [2] to determine qs and we calculated Q from Eq. (1).Magnitogorsk State Technical University; Magnitogorsk Metallurgical Combine.