Study Of Steel Flow And Solidification Heat Transfer Behavior In Thin Slab Mold Of Medium Manganese Steel

At present,the production of medium-manganese steel by traditional process mainly has problems such as long production process,high energy consumption,cold cracking of casting slab,etc.Although the production of medium-manganese steel by thin slab continuous casting technology can solve the above problems,due to the large linear expansion coefficient,low thermal conductivity,large thermal stress,and shrinkage stress of medium-manganese steel,it is easy to produce cracks in the mold,resulting in low quality,Therefore,the stable flow of molten steel in the thin slab mold area and the efficient solidification and heat transfer control are the keys to realize the industrialization of the thin slab continuous casting technology of medium manganese steel.This paper adopts the numerical simulation method and takes a thin slab continuous casting mold as the research object,by establishing the mathematical model of a thin slab continuous casting mold with a section size of 1500 mm×90 mm for medium manganese steel,First,the flow behavior of steel in thin slab mold is studied,and the effects of casting speed(4 m/min,5 m/min,6 m/min),immersion depth(250mm,300 mm,350 mm)and inclination angle(10°,20°,30°)on the flow field are compared and analyzed.Secondly,in order to clarify the influence of manganese content on heat transfer,the difference in solidification behavior between medium manganese steel and low carbon steel is compared and analyzed based on the parameters derived from the stable flow field,and the influence of superheat and casting speed on the coupling behavior of liquid steel flow and heat transfer in the mold area of a thin slab of medium manganese steel is studied,which provides theoretical guidance for the industrialization of the thin slab continuous casting process of medium manganese steel.Theoretical guidance is provided for the industrialization of the thin slab continuous casting process for medium manganese steel,and the following conclusions are drawn from the study.(1)By analyzing the one-half three-dimensional mold flow field,it is concluded that the steel flow in the mold shows asymmetry and the asymmetric behavior has a random nature.Changing the immersion depth,casting speed,and the inclination angle of the water spout,it was found that the immersion depth had the greatest influence on the liquid surface flow rate,followed by the inclination angle of the water spout,and the casting speed had the least influence,finally considering the disturbance of the protective slag layer,it was concluded that when the pulling speed was 5 m/min,the immersion depth of the water spout was 300 mm and the inclination angle of the water spout was 30°,the overall flow of steel in the mold was more stable.(2)Under the above parameters and superheat degree 25 K,the temperature at the longitudinal exit of manganese steel in the center of the narrow side of the mold is higher than that of low carbon steel,which is about 19 K,while the highest lateral temperature of low carbon steel near the exit of the mold is higher than that of middle manganese steel,which is about 10 K.The lateral temperature difference on the exit surface of low carbon steel is about 48 K,and the lateral temperature difference on the exit surface of manganese steel is about 57 K.This temperature inhomogeneity is the main reason for surface cracking.(3)For every 0.5 m/min increase in casting speed,the narrow surface center billet shell will be thinned by 6.6% to 10%,and the wide surface center billet shell will be thinned by 3.43% to 6.94%.Changing the superheat degree has little effect on the heat transfer of middle manganese steel,and when the casting speed is 4 m/min,the immersion depth is 300 mm and the reasonable superheat degree range,the thickness of middle manganese steel export billet shell can reach more than 9 mm,which can prevent the occurrence of steel leakage accident.