Microstructure and shearing strength of stainless steel/low carbon steel joints produced by resistance spot welding

Abstract

The present research utilized the resistance spot welding process on stainless steel and low carbon steel. The diameters of joint and nugget, microstructure and shearing strength of joints were examined. When increasing the welding current, welding time or clamping force, the diameters of welding joints and nuggets became larger due to the higher heat input and normal load. The shearing strength of joints increased and then decreased with increasing welding current or welding time and decreased with increasing clamping force. For the metallurgical evaluation, it was found that there were five regions around the joint, which consisted of the nugget (austenite and martensite with dendritic structures), coarse heat-affected zone (martensite and pro-eutectoid ferrite), fine heat-affected zone (ferrite and pearlite), base material (ferrite and pearlite) for low carbon steel, and base material (austenite) for stainless steel. In orthogonal tests, it was found that the welding current had the most significant influences on shearing strength, and then welding time and clamping force. Finally, an artificial neural network was established to predict the shearing strength of joints under various welding conditions. The results showed that the shearing strengths predicted by the artificial neural network had good correlation with experimental values. A shearing strength higher than 10000 N could be achieved when welding current was higher than 12.5 kA and welding time was longer than 85 ms. The artificial neural network model has applicable values for predicting the shearing strengths of joints between dissimilar steel plates.

Keywords

• Dissimilar steels
• Microstructure characterization
• Mechanical behavior
• Welding parameters