Simultaneous Joining and Forming of Dissimilar Steels by Electrically Assisted Pressure Joining

Abstract

In the present study, simultaneous joining and forming of dissimilar steels Q235B (ball) and SCM435 (stud) by electrically assisted pressure joining (EAPJ) are experimentally investigated. The target product is intended with a dust-cover ring in the stud head, then the electrodes and the stud head are designed accordingly so that the deformed stud head can fill the electrode cavity. In EAPJ, compressive deformation and pulsed electric current are simultaneously applied to the workpieces to create diffusion bonding. As a result, the sound solid-state joints are successfully fabricated by EAPJ, while a target geometry is also successfully formed. In the bending test, the fabricated ball stud is broken through the ball, and the maximum bending load is higher than the target value for commercial applications. The microstructure analysis and hardness test show that the progress suggested in the present study can cause grain refinement, induce tempered martensite, and increase the portion of polygonal ferrite in the deformed zone (DZ), the joining zone (JZ), and the thermal-mechanically affected zone (TMAZ), respectively. The results of the present study confirm that the concept of EAPJ is applicable to the simultaneous joining and forming of dissimilar steels.