Influence of pulsed laser beam welding in vacuum on the mechanical properties of non-grain oriented electrical steel sheets

Major components of electrical machines are iron cores made of stacked electrical steel sheets. In this paper, pulsed laser beam welding in vacuum is used to join the individual electrical steel sheets. Three different non-grain-oriented electrical steel alloys are investigated and joined by individual spot welds. The influence of pulsed laser beam welding in atmosphere as well as in vacuum on the welding result and the tensile strength of the welded joint is discussed. The results show that the insulation coating of the electrical sheets has significant effects on the grain structure as well as the hardness of the weld spots. These effects can be reduced with decreased working pressure, which reduces the power loss of iron cores. The reduction of the working pressure and the associated reduction of the vapor plume, which appears to reduce the energy input into the component depending on the material and coating, results in an increase of the melt volume and the joint cross sectional area. The tensile strength of the performed welds was tested and interpreted with respect to the influencing process parameters.