Numerical Simulation On The Continuous Extrusion Cladding And Synchronous Drawing Process And Study On Microstructure And Properties Of Aluminum-clad Steel Wire

Aluminum-clad steel wire is a new type of bimetallic composite material which combines the high strength performance of steel with the excellent conductivity and corrosion resistance of pure aluminum,and because of its low manufacturing cost and excellent comprehensive performance,it is widely used in the fields of transmission wires and overhead ground wires.In this paper,in view of the LB40 aluminum-clad steel wire,the continuous extrusion cladding and synchronous drawing forming process of the aluminum-clad steel wire were numerically simulated with the help of Deform software,and the influence law of each process parameter on forming process was studied.And the microstructure and properties of aluminum-clad steel wire under different deformation were researched.The main results and conclusions are as follows:(1)A three-dimensional analysis model was established for the continuous extrusion cladding process of LB40 aluminum-clad steel wire,and the numerical simulation of the continuous extrusion cladding process under the process parameters of different extrusion wheel speed,spillway clearance,friction coefficient and mold gap was carried out.The results show that with the increase of extrusion wheel speed,the temperature of aluminum billet increases,and its deformation resistance decreases,so the torque of extrusion wheel decreases.When the extrusion wheel speed is increased from 10 r/min to 18 r/min,the extrusion wheel torque is gradually reduced from8.2×10~6 N·mm to 6.0×10~6 N·mm,so that increasing the extrusion wheel speed is beneficial to improve the efficiency of the extrusion cladding.When the spillway gap between the cavity and the extrusion wheel is 0.5mm,the overflow result is ideal.If the gap of the spillway is too small,the two will grind each other in the forming process;and if the gap is too large,it will produce a large amount of overflow,and even the billet all flow out of the spillway,resulting in the failure of cladding.With the increase of the friction factor between the mold cavity and the aluminum billet,the torque of the extrusion wheel increases.With the increase of the gap between the guide mode and the extrusion mode,the torque of the extrusion wheel gradually decreases.(2)A Two-dimensional analysis model was established for the synchronous drawing process of LB40 aluminum-clad steel wire,and the numerical simulation of the synchronous drawing process under the process parameters of different modular angle,deformation amount,friction coefficient and drawing speed was carried out.The results indicate that with the increase of the modular angle,the stress value of the Z-axis direction decreases first and then increases,and the maximum value of effective strain is transferred to the interface,which is conducive to improving the strength of interface combination,so the optimal value of the modular angle is 7°.With the increase of the drawing deformation,the Z-axis stress value also increases,but when the deformation amount is greater than 1.08,the Z-axis stress increases substantially,so the deformation amount should be controlled within 1.08.When the coefficient of friction is 0.03-0.09,the change of coefficient of friction has no significant effect on drawing stress,and the appropriate coefficient of friction is about 0.05.When the drawing speed is 5.0m/s,the effective stress and effective strain can be relatively smaller than that at other drawing speed,and the damage factor of steel core and aluminum layer is reduced,so the optimum selection value of drawing speed is 5.0m/s.In addition,through the analysis of mold stress,it is found that the addition of transition fillet at the fixed diameter band and work area connection of the mold can reduce the effective stress and effective strain,thus reduces mold wear.(3)The effects of drawing deformation on microstructure,elements distribute of interfaces,electrical property and mechanical properties of aluminum-clad steel wire are investigated using optical microscopy,scanning electron microscopy,X-ray diffraction,etc.testing methods.The results show that with the increase of drawing deformation,(1)the grains of the steel core of aluminum-clad steel wire transform gradually from equiaxed grain with obvious grain boundaries of as-clad state to irregularly grains with blurred grain boundaries parallel to the drawing direction;(2)the degree of mechanical integration at the aluminum/steel interface of aluminum-clad steel wires is deepening,and the thickness of the mutual diffusion layer is gradually increasing,and Al Ni and Al Fe phases are formed at the interface;(3)the micro-hardness and tensile strength of the aluminum-clad steel wire increase,however its elongation rate decreases;(4)the resistivity of aluminum-clad steel wire increases linearly,and the physical calculation model of the resistivity of aluminum-clad steel wire was established,and the theoretical calculation of its resistivity was obtained.The value of the resistance to electrochemical corrosion of aluminum-clad steel wire from surface to core is as:aluminum layer<interface<steel core.The influence law of temperature on the coefficient of thermal expansion of aluminum-clad steel wire was studied,and the coefficient of thermal expansion increases with the increase of temperature.