Simulation Of Subclad Crystal Steel Continuous Casting Temperature Field And Study On Solidification Characteristics

During the continuous casting process of subclad steel wide slab in a domestic steel plant,there are always cracks in the billet,which leads to the reduction of the qualified rate of steel billet and the increase of production cost of the enterprise.There are many factors that lead to the quality problems such as cracks in the billet,among which the mould taper and the solidification transformation of steel play a key role in controlling the cracks in the billet.Therefore,in this study,whether the mold taper is reasonable or not and the solidification characteristics of steel grades are studied and improved in order to reduce the production of slab cracks and improve the product quality.The mathematical model and geometric model of solidification heat transfer in slab continuous casting are established by using thin strip moving method and Mile algorithm.Based on the production data,the boundary heat transfer conditions of slab are calculated,the simulation software ProCAST is used to simulate the solidification heat transfer.Compared with the measured temperature,the relative error is less than 1.1,which indicates that the solidification heat transfer model has high accuracy.The effects of undercooling and drawing speed on the microstructure of the billet were simulated and analyzed.It was found that the drawing speed had little effect on the microstructure growth.With the decrease of superheat,the number of grains increases,the average radius of grains decreases,and the ratio of equiaxed crystals increases gradually,but the effect of drawing speed on the rate of equiaxed crystals is smaller than that of superheat.In this study,the DSC cooling curve of steel was measured.The results show that the actual peritectic transition temperature is 1345?,and the reaction is rapid.In addition,the actual solidification temperature range is narrow and has the characteristics of layer-by-layer solidification mode.AlN,TiN and TiC do not precipitate in liquid steel.During solidification,the ratio of TiN,formation is 0.000517 and AlN is precipitated in austenite.When the cooling rate is 10?·s-1,the transition temperature range of ??? is 600? to 564?.When the cooling rate is 30? ·s-1,the phase transition temperature range of ??? is from 577? to 509?.Combined with the thermal expansion experiment,the simulation results of the process at a drawing speed of 0.8 m·min-1,1.0m·min-1 and 1.2m·min-1 were analyzed.It was found that the taper should be 0.85 from 0 to 0.3m and 0.96 from 0.3 to 0.82m from the meniscus.