Theoretical And Experimental Research On Micro-amplitude Twin Roll Casting

Twin roll strip casting technology is regarded as the most revolutionary technology of metallurgy industry in the 21st century.Its craft combines with the rapid solidification technology and the thermal forming technology,makes the short process successful However the twin roll strip casting process is a highly coupled complicated problem,Involving the flow field,temperature field,solidification,thermal deformation and so on.Subtle change of process parameters are likely to lead to serious defect of casting strip.To promote the industrialization of twin roll strip casting technology,the flow field,temperature field distribution,process parameter control technology also need further research.This paper based on the twin roll strip casting’s characteristics,surface of the roller heat transfer mode was studied,and further to determine the reasonable casting process.Developmented Φ500×350 twin roll strip casting machine,studied the flow field,solute field and temperature field distribution.Combinate with the casting strip experiments,crack problem,center segregation problem,vibration fine-grain problem have carried on the corresponding research.This article researched innovations and the main research contents are as follows:1.Combined with the twin roll strip roll casting and welding pool crystallization roller contact heat transfer characteristics,the flexible contact area and the rigid contact area were separated by the Kiss point.Based on the heat transfer experiments,the heat transfer rule of flexible contact area and rigid contact area were researched,the distribution of heat flow was "peaky" or "double peak" curve.The craft software was developed to compute the reseasonable casting process,rolling force,include the location of Kiss point,temperature of outlet,providing the theoretical basis for design rolling machine process parameters.2.Designed and developed the Φ500×350 micro amplitude twin roll strip casting machine.The machine is 3.7m high,30T weighs,adopt tundish metallurgy technology,float roll gap control technology,vibration fine crystal technology,etc.,can product stainless steel,carbon steel,silicon steel,composite board,non-ferrous metal and so on This paper also researched the cooling water channel,thermal stress and thermal deformation,the amount of interference and vibration dynamics of the casting rollers and analyzes the other design problems.The 2mm low carbom steel strip have been producted by the casting mill,and the casting strip structure was been analyzed.3.Equal scale water model experiment platform was developed,and discovered the core pool backflow phenomenon.The backflow is due to the liquid viscous force and crystallization roller extrusion effect.Bluid the mathematical model of twin roll casting strip,study on the roll casting speed,casting temperature,pool high and roll gap width on the influence of the outlet temperature further.4.Established the VOF three-dimensional flow field model by considering the air layer’s affect,analyzed the flow field of traditional feeding system.The roll gap export zones temperature distribution problems were discovered,especially the edge area temperature drop.Therefore this paper developed a new "ship shape" feeding system,and verified its superiority by hot-water model experiments and mathematical simulation model.5.Based on the results of simulation and rolling experiments,this paper analyzed the mechanism of the casting strip’s inclined crack.Due to the molten pool temperature and Kiss point location distribution unevenly,the deformation at different region were discrepant,and the shear force produced by metal material of lateral movement parallel to the crack cause dynamic sliding along the crack surface extension,produced through slip crack,belongs to the X type crack.6.A mathematical model based on Scheil model had been developed by considering the distribution of solute elements.The redistribution of solute elements in solidification process was studied.This paper also explained the centerline segregation mechanism.Based on the mathematical model to study the different roll casting speed,roll gap width on the core of the effect of segregation,explained the Kiss point location is the main factors influencing the segregation,provide the basis for cast-rolling strip industrial production.7.Based on the solidification principles of dendrite fusing and cavity theory,the nucleation rate of vibration model was established,combining KGT dendrite growth model established CAFE model used to predict the vibration solidification organization Based on the vibration solidification experiments verified the correctness of the CAFE model.The vibration can increase the nucleation rate and refine the solidification organization effectively.Introduction of the technique of vibration fine-grain technology to twin roll strip roll casting process,the results showed that vibration casting can improve the strip core nucleation rate,refine the solidification organization,and the influence of different frequency of welding pool was studied.