Study On Solidification Structure And Properties Of Continuous Casting Ag-28Cu Alloy

Continuous casting technology is a kind of near net shape technology,its advantages include that increasing the practical rate of metal,saving energy,increasing the quality of casting,improving working conditions,etc.But in the process of continuous casting,the process parameters(such as heat transfer condition,pouring temperature and casting speed,etc.)have a serious impact on the quality of slab,and its cost is very high for precious metals that through the experiment to find the best process parameters.While the computer simulation is a kind of low cost and high efficient way for improving the processes.In this paper,the ProCAST software was used to simulate the temperature field and micro structures in solidification of Ag-28Cu alloy continuous casting,and the effect of the different process parameters of continuous casting on solidification structure was studied.The results show that:The lager the surface coefficient of heat transfer or the slower the casting speed,the larger the columnar grains ratio and the smaller the equiaxed grains ratio.And the effect of pouring temperature on the ratio of columnar grains and equiaxed grains is small.By increasing the surface coefficient of heat transfer,reducing the pouring temperature and improving the casting speed,can have the effect of grain refinement.By comparing the simulation results of micro structure under 7 kinds of process condition,the best process conditions is that:the surface coefficient of heat transfer is 1800W/(m2.K),the pouring temperature is 830?,the casting speed is 1.5m/min.In this paper,Ag-28Cu alloy samples were produced respectively based on the continuous casting method,water-cooled copper casting method and directional solidification method.At the same time,Ag-28Cu-Ni alloy samples that Ni content are 0.75 wt%,lwt%and 2wt%respectively were produced by continuous casting,and then rolling and drawing.The effect of different ways of solidification and Ni element on the micro structure and mechanical properties of Ag-28Cu alloy were studied.The results show that:Micro structure of Ag-28Cu alloy sample was produced by continuous casting method is all rules eutectic organization,eutectic spacing of a single grain within water-cooled copper casting sample have obvious changes,and there is segregation phenomenon in it.Ag-28Cu alloy samples was produced by directional solidification method and Ag-28Cu-Ni alloy samples were produced by continuous casting method have obvious segregation phenomenon,its micro structure is three-phase coupling structure include rich Cu phase,rich Ag phase and eutectic phase.After Ni element is added in Ag-28Cu alloy continuous casting samples,the fracture mechanism of Ag-28Cu-Ni alloy are dimple fracture,transgranular fracture and cleavage fracture.And it show that its brittleness increased.The fibrous tissue was produced in Ag-28Cu-Ni alloy after processing,it can increase elongation of the alloy.But after true strain increases to 4.30,the enhancing effect begin to abate.Under the same deformation,when Ni content is 0.75wt%,tensile strength of Ag-28Cu-Ni alloy is largest,when Ni content is lwt%,the elongation of Ag-28Cu-Ni alloy is maximum.