Numerical Analysis Of Influence Factors On Solidification End Point Of Thick Slab Continuous Casting

At present,the conventional continuous casting process has a certain metallurgical length,and the complete solidification of the slab is realized before the flame cutting.However,for the thick slab,with the increase of slab thickness,the internal metallurgical defects such as central segregation and shrinkage cavity are often formed at the end of continuous casting near the solidification end point,and the serious macro defects are difficult to be effectively eliminated in the subsequent heating and rolling process.Referring to the rolling process with liquid core after cold capping of die casting ingot,if a certain proportion of liquid core can be retained in the center of the slab during the continuous casting stage,it can obviously effectively solve the internal defects such as central segregation and shrinkage cavity of the thick slab during the rolling process.In this thesis,a three-dimensional model is established based on the thick slab with a section size of 300 mm×2300 mm in a domestic steel plant.The conventional continuous casting process of thick slab and the continuous casting process(with liquid core)for liquid core rolling are calculated by ANSYS software.On this basis,the effects of different casting superheat and casting speed on the solidification process and stress distribution of thick slab during conventional continuous casting and liquid core rolling were compared.The main conclusions of this thesis are as follows :(1)For the conventional continuous casting process,when the casting speed is increased by 0.1 m/min,the center temperature and corner temperature of the wide surface of the slab are increased by about 15 ℃,the shell thickness of the slab mold outlet is reduced by about 0.575 mm,and the solidification end point position is extended along the casting direction by about 2.8 m.The superheat has little effect on the surface temperature and center temperature of the slab.When the superheat increases by 5 ℃,the center temperature of the wide surface and the core temperature of the slab increase by about 4 ℃,the shell thickness at the mold outlet decreases by about 0.1 mm,and the solidification end point of the slab extends about 0.12 m along the casting direction.(2)Compared with the conventional continuous casting process,the continuous casting process for liquid core rolling can keep the central liquid rate of the slab out of the air cooling zone at about 5.0% under the condition of superheat of 20.0 ℃ and casting speed of 1.0 m/min.Under the condition of superheat of 20.0 ℃ and casting speed of 1.1 m/min,the central liquid rate of the slab in the air cooling zone is maintained at 10.0%.The change of casting speed has little effect on the surface temperature of thick slab in the mold,but has great influence in the secondary cooling zone and air cooling zone.(3)For the continuous casting process for liquid core rolling,the equivalent stress value of the slab surface(especially the corner)in the continuous casting bending straightening section is the largest,which is easy to produce a large stress concentration area.Through calculation,the equivalent stress value in the straightening area of continuous casting is within the safe range,and it is not easy to cause cracks in the slab under the action of thermal stress;it is proved that the continuous casting method of retaining a part of the liquid core ratio in the slab and entering the rolling process is theoretically feasible.