Study On Secondary Dendritic Spacing Of High Manganese Steel For Continuous Casting

Mn13 steel is a typical wear-resistant high-manganese steel,and it is also a wear-resistant material that is commonly used in the world.Serious microsegregation and cracks are more likely to occur in Mn13 continuous cast slab due to its high carbon and manganese element content,low thermal conductivity,strong thermal sensitivity and wide mushy zone,therefore,high manganese steel is mostly produced by ingot casting process.However,continuous casting process is better than ingot casting process,which means that product high manganese steel by continuous casting process will become a future trend.Nowadays,research on the quality of high manganese steel continuous casting slab has aroused widespread concern.Among these researches,the dendrite and dendrite spacing,especially the secondary dendrite spacing are the important parameters to characterize the solidification structure of continuous casting slab.It means that the study on the distribution and variation of the secondary dendrite spacing of high manganese steel continuous casting slab have important guiding significance for improving the quality of continuous casting slab of high manganese steel.In this paper,micro structure of Mn13 steel continuous casting slab was studied to determine related variation of secondary dendrite spacing,based on the experimental results,the distribution of secondary dendrite spacing and the effect of different casting speeds on secondary dendrite spacing of Mn13 steel continuous casting slab were clarified.At the same time,the solidification heat transfer behavior of Mn13 steel was simulated and its correlation with the secondary dendrite spacing was confirmed,finally,the functional relation between the secondary dendrite spacing and the cooling rate was established.Under experimental conditions,the conclusions are as follows:(1)When the casting speeds of Mn13 steel were 0.7m/min,0.9m/min,1.0m/min and 1.1m/min,the relations between the secondary dendrite spacing and related distance from the surface of the continuous slab were confirmed to be λ2=9.42×x0.63，λ2=10.1×x0.63,λ2=11.59×x0.6,λ2=13.77×x0.56,respectively.(2)Based on the on-site conditions of Mn13 steel continuous casting process,a continuous casting solidification heat transfer model was established.Based on this model,the temperature distribution characteristics,growth rule of solidified shell and liquid core length of Mn13 steel continuous casting billet under different process conditions can be predicted.(3)The influence of the casting speed on the center temperature of the wide surface of the slab was obvious.With the increase of the casting speed,the center temperature of the slab surface increases,and the thickness of the solidified shell decreases.When the casting speed increased from 0.7m/min to 1.1m/min,liquid core length of the cast slab increased from 10.5m to 17.8m.(4)By combing the solidification heat transfer model and the secondary dendrite spacing experimental results of the Mn13 steel continuous casting slab,the relation between the secondary dendrite spacing and related the cooling rate was determination as λ2=77.46×v-0.38.This relation can provide important guidance for the optimization of the Mn13 steel continuous casting secondary cooling process.