Study On The Theory And Technology Of Clad Casting Process Of Aluminum Alloy Cylindric Composite Ingots

A new fabrication process has been developed in this paper.The clad bar and pipe ingots with high metallurgical quality and without defects in interfaces were obtained by investigating the effects of the main technological parameters on metallurgical quality and diffusion in interfaces.First,the methods of numerical simulation and experiment were used to study flow field,temperature field,heat transfer and solidification behaviors during clad casting process of AA4045/AA3003 clad bar.Then the effect of liquid alloy distribution methods,casting speed,casting temperature,contact height,liquid level height of 3003 alloy and clad-layer thickness on the physical field mentioned above,interfacial microstructure,elements diffusion and interface bonding strength were studied in detail.Finally,the optimal technical condition for AA4045/AA3003 cladding bar was obtained.A couple mathematic model of the interaction of multi-physical field to describe the cladding casting process was developed.This model can accurately describe the melt flow,heat transfer and solidification during the cladding casting process of AA4045/AA3003 cladding bar by comparing with the experiment results.The numerical simulation and experimental results showed that blocks in distributor influence the uniformity of interfacial temperature by changing melt flow direction and speed.The more dense and nonuniform the block distributes,the smaller the circumferential temperature difference at the interface is,and the sparse unequal distribution could keep the difference whthin 5 ?.With the increase in casting speed,the sump depth and the temperature of supporting layer increase,the thickness of supporting layer decreases,and a more reheat in the interfacial region promotes elements diffusion,which can improve the bonding strength.However,excessively high casting speed would decreases supporting layer thickness increase its temperature,resulting in interface damage and experiment failure.Casting temperature has a little affect on the temperature field of cladding casting process due to heat caused by the increase of casting temperature is far less than solidification latent heat of the alloy.Contact height directly affects efficient diffusion time of alloying elements at the interface.Increasing the contact height could lengthen the efficient diffusion time,and enhance the reheat in the interface at the same time.Liquid level of 3003 alloy slightly affects flow field during cladding casting process,while it has larger effect on the formation and temperature of supporting layer.The temperature field in the interfacial region is influenced by the thickness of clad layer,as well as the temperature and temperature gradient at solidification front.The optimal cladding casting parameters of AA4045/AA3003 cladding bar with size of?140 mm/?110 mm were obtained based on the investigation on effects of different parameters on the process and interfacial microstructure and properties as follows:sparse unequal distribution of clad alloy and level pour distribution of core alloy are used respectively,casting speed is 100-110 mm/min,liquid level height of core melt is 50-60 mm,contact height is 30 mm.In these conditions,the cladding bar prepared in this study has a planar and clean interface without porosities and inclusions and their tensile strength is about 102 MPa and shear strength approaches 77.2 MPa,higher than that of AA3003.According to the experiments of homogenization,indirect hot-extrusion and cold-drawing,the idea homogenization parameters are 560?+12h.For the clad pipe with size of ?32 mm × 2.0 mm and cladding ratio 10%the clad layer of the ingots before extrusion should be 4 mm.Considering productivity and reducing eccentricity ratio,extrusion parameters are 375? and 1.5 mm/s.Conical die with a angle of 30 degree should be introduced during indirect extrusion to avoid trilaminar clad pipe.The aluminum alloy cladding casting technology is developed to cast AA4XXX/AA6XXX cladding bar and AA4045/AA3003 cladding hollow billet successfully.The technology of the clad casting developed in this paper has been applied in ???? Al fabrication plant to produce clad pipes in volume production.