Control Of Shrinkage Porosity And Solidification Structure Of 25MnSiV Continuous Casting Billet

The central shrinkage cavity and solidification structure of continuous casting billet have important influence on the performance of the billet and the final product.The shrinkage cavity and porosity will reduce the fatigue strength and tensile strength of the steel.The solidification structure of the billet determines the performance of the casting and the use of the product.It is an important task to use mathematical simulation to study the influence of continuous casting process parameters on the central porosity and solidification structure,and to guide the production practice accordingly.In this paper,a mathematical model of solidification heat transfer and microstructure of 25 Mn Si V steel continuous casting was established according to the existing 160 mm×220 mm billet continuous casting process conditions in a steel plant.On the basis of verifying the accuracy of the model,the influences of drawing speed,superheat and water supply in secondary cooling zone on the central porosity and shrinkage cavity of the billet and the microstructure of the billet were studied.The temperature field of solidification end of billet,the change of surface and central temperature of billet during continuous casting and the change of solid phase ratio were discussed.Based on the simulation results,field production experiments were carried out.The results show that: The shrinkage area of the casting slab at a drawing speed of 1.2 m/min is 4.90% larger than that of 1 m/min,and the area of shrinkage cavities at a drawing speed of 1.6 m/min is 96.26% larger than that of 1.2 m/min.For every increase of 0.1 m/min in the drawing speed,the length of the slab liquid core increases by 2.25 m.The porosity area of 40? superheat slab is 2.40% higher than that of 20?,and that of 50?superheat slab is 25.00% higher than that of 40?.The porosity area of 80% secondary cooling zone is 37.93% higher than that of 40%,and the maximum water supply of secondary cooling zone is 11.11% higher than that of80%.The linear relationship between CET conversion position and pulling speed is y=-13.33x+59.33;And the superheat satisfies y=0.17x+43.01.The production experiment was carried out with the casting speed,superheat and secondary cooling water supply of 1.2 m/min,40? and 80% respectively,and the control effect of porosity and shrinkage is improved.