Liquid Metal Embrittlement of Resistance Spot Welded 1180 TRIP Steel: Effect of Electrode Force on Cracking Behavior

Liquid metal embrittlement (LME) caused cracking of Galvanized transformation induced plasticity steels was investigated during resistance spot welding(RSW). Effect of electrode force (3-5kN) for a weld time of 400, and 800ms on crack resistance of TRIP steel was examined in relation to LME phenomenon. The microstructural characteristics of spot weld joints and LME cracking tendency were investigated using dye penetration tests, optical microscopy, scanning electron microscopy together with energy dispersive X-ray spectroscopy. It was found that as the electrode force increases, the crack size decreases due to a fast increase in crack tip temperature which rises further with more holding time up to 800ms in high temperature zone. Least amount of crack size was observed at 5kN electrode force and 400ms of welding time. Finally, the experimental results have also been simulated by finite element modeling(FEM) to find suitable mechanism of crack formation, and a combination of 4kN and 400ms was suggested for the crack free and less thermal deformation in the spot welded TRIP steel.