The Relationship Study Between Interface Constraints And Joints Quality For Dissimilar Metal Inertia Friction Welding

In the process of practical work, the weldments of turbocharger and shaft mainly bear torque, and have high welding quality requirement on edge regions. However, the inertia friction welding of solid shaft superalloy K418 and alloy steel 40 Cr Ni Mo A whose diameter is the same have many defects such as uneven distribution of interface temperature, serious energy loss and poor welding quality of edge regions. Only by optimizing the process parameters is unable to overcome the above defects. Therefore, it is very urgent to design a reasonable form of interface structure to maximize joint welding quality of edge regions.A new method that uses interface constraints to hinder thermoplastic material of edge regions to spill has not been studied by experts and scholars by far. So the plane constraints program and steps constraints program are designed based on interface constraints. Each program properly increases the shaft diameter for shallow constraints of edge regions, to study the effect on microstructure, plastic flow and mechanical properties of edge regions. The research results show that for the welding joints of plane constraints program and steps constraints program under the same process parameters, with the increase of interface constraints, their axial burn-off lengths reduce gradually, and steps constraints program joints reduce larger; weld lines shapes become more and more curved, lead to the increase of combination area between materials and occlusion degree, helping to improve the welding quality; DRX widths of both sides of interface increase gradually, grains of K418 side become more and more sophisticated, and martensite contents of 40 Cr Ni Mo A side rise guadually, illustrating the increase of element diffusion quantity and helping to interface metallurgical bonding. The tendency of microhardness changes is more similar. and that of DRX and TMAZ microhardness of 40 Cr Ni Mo A side rises on the whole. The microhardness of steps constraints program change larger and their values are higher, and peak points of microhardness are located near the borders of DRX and TMAZ of 40 Cr Ni Mo A side. The tensile strength of edge regions show a rising trend, and that of steps constraints program are slightly higher. At the same time, the tensile strength of core regions of plane constraints program are gradually reduced.At the same time, the Johnson & Cook model is used as constitutive model of alloy steel 40 Cr Ni Mo A and the thermal and mechanical multiple physics fields model of inertia friction welding to simulate the welding process. The error rates of simulate and actual burn-off lengths do not exceed 8%, within the reasonable error range, showing that Johnson & Cook model is correct and the simulation results are accurate and feasible. Simulation results show that with the increase of interface constraints, for the joints of plane constraints program, interface peak temperature decreases continuously before upsetting stage, and it remains unchanged basically when upsetting stage begins. At the same time, the mean pressures of core regions decrease gradually and that of edge regions rise gradually. For the joints of steps constraints program, interface peak temperature decreases on the whole before upsetting stage, and it rises on the whole when upsetting stage begins, and their temperature is higher than plane constraints program. The mean pressures of interface edge regions rise gradually, but generally less than that of friction interface should bear.