Forming Behaviour of Steel Sheets after Mechanical and Laser Beam Forming

摘要

This paper reports the influencing factors and the characteristic behaviour of steel plates during both the mechanical forming and laser beam forming processes. Samples of the steel sheets were mechanically bent to 120 mm curvatures using a 20 ton capacity eccentric mechanical press at room temperature and also with the laser beam using a 4.4 kW Nd: YAG laser system at a scan speed of 1.9 m/min, beam diameter of 12 mm, laser power of 1.7kW at 25% beam overlap using argon for cooling the irradiated surfaces. The chemical composition of both the as-received material and the formed samples were analysed by emission spectroscopy to quantify the changes in the elemental composition. The result shows a percentage increase in the carbon after the mechanical and laser forming processes when compared to the parent material. This can be attributed to the enhancement resulting from the forming processes. The formed samples were further characterized through microstructure, microhardness and tensile tests. The microstructural characterisation of the samples revealed that the grains of the mechanically formed and laser formed components are elongated, it was also observed that there is an increase in the pearlite grains of the laser formed components resulting from the thermal heating during the laser process. The microhardness profiles of the formed components showed that there is a significant percentage increase in the Vickers microhardness values of the laser formed samples when compared to the mechanically formed samples and with respect to the parent material. The laser beam forming process can be considered a more appropriate forming process in terms of the resulting material properties in this regard.