Theramal Stress Analysis And Microstrusture Simulation Of Continious Casting Slab Solidification Process

The China's steel industry and continuous casting technology are developing at an unprecedented rate,how to improve the quality of continuous casting billet has become one of the main issues that metallurgists pay attention to and research.The quality problem of continuous casting billet not only restricts the rapid and efficient development of continuous casting technology,but also has a considerable impact on the quality and performance of subsequent steel products.The quality problem of continuous casting billet is caused by the solidification of the billet in different cooling sections.The process is closely related to the solidification structure.Therefore,it is very meaningful to study the solidification process and structure of the cast slab under different continuous casting processes.In this dissertation,the numerical simulation method is used to simulate the continuous casting process of a 150mm×250mm 50# steel rectangular billet produced by a steel plant in Tangshan.The casting simulation software Pro CAST is used to complete the thermal stress simulation of the rectangular billet in the mold,steady state simulation of rectangular billet continuous casting process and simulation of rectangular billet solidification structure.Through the unsteady state simulation of the cooling process of the rectangular billet in the mold,and the non-steady state model is established based on Mi LE algorithm,the distribution law of the temperature,stress and air gap of the rectangular billet is obtained.During the cooling and solidification process of the casting billet in the mold,the corners receive the greatest cooling strength and solidify first,and the stress is also the largest.At the same time,the corners have the first and the largest air gap.The effects of different processes(pouring temperature,casting speed)on the surface temperature and stress of the slab are simulated,and it is found that changing the casting speed has a more significant effect on the temperature and stress of the casting slab.When the pouring temperature and casting speed are increased,the temperature at each position on the surface increases,while the stress at each position on the surface of the cast slab decreases.Through steady-state simulation,the change law of the temperature field and solid phase ratio of the slab during the whole continuous casting process under different casting temperatures,casting speeds,and secondary cooling strengths was obtained.The position and size of the mushy zone under different processes were studied and the liquid was determined.The higher the pouring temperature is,the higher the steady state temperature of the slab center is,the greater the length of the liquid cavity is,but the length of the mushy zone is almost unchanged,and the starting and ending positions are far away from the meniscus;the higher the casting speed is,the higher the steady state temperature of the slab center is,the longer the length of the liquid cavity and the mushy zone is,and the starting and ending positions are far away from the meniscus;the greater the strength of the secondary cooling is,the lower the temperature at the center of the cast slab in the steady state is,and the shorter length of the liquid cavity and the mushy zone is,and the smaller the distance between the mushy zone and the meniscus is.The slab solidification structure under different nucleation parameters and process parameters was simulated and observed.The results showed that: With the increasing of the average nucleation undercooling,the proportion of equiaxed crystals becomes smaller and the grain size becomes larger.When the maximum nucleation density is increased,the proportion of equiaxed crystals becomes larger and the grain size becomes smaller.Increasing the casting temperature,the number of equiaxed crystals decreases and the average size of crystal grains increases.Increasing the casting speed,the number of equiaxed crystals increases and the average grain size decreases.Increasing the secondary cooling strength,the number of equiaxed crystals decreases and the average grain size increases.