Studies on the laser spot welding of steel/magnet dissimiliar materials

The paper studies the laser spot welding of SPCC steel and NdFeB permanent magnet. Results show that during welding process the two metals quickly melt, mix and then solidify to form a weld that joins two specimens together. The hardness in the joint is not uniform: the heat affected zone (HAZ) has a lower hardness than NdFeB base metal; within the nugget, the region adjacent to the fusion line has the highest hardness while the middle part of nugget has the lowest hardness in the joint. Hot cracks are apt to occur at the interface between nugget and magnet base metal, whereat the cracks propagate and lead to joint failure during shear tests. The fracture is intergrannular and is a typical brittle fracture. To increase the joint strength and prolong the service life of welded components, it is necessary to take some metallurgical and technological measures to improve the bonding quality between nugget and magnet base metal.