Laser Forming of Mild Steel Sheets Using Different Surface Coatings

Abstract

Laser forming is a comparatively recent technique which has been developed to shape metal components. It has also been applied to the forming of composite materials. In this process, thermal stresses are produced in the sheet metal by irradiating the surface of the sheet using a controlled defocused laser beam. This causes the sheet to bend, usually, towards the side of the sheet which is exposed to laser irradiation. The laser beam power, scan speed, beam size, and number of laser passes determine the shape of the final product. Laser forming is different when compared to the traditional forming techniques like bending, drawing, pressing, stamping, etc. in the sense that it is a non-contact technique. Hence, the advantage of the laser forming process for a small batch of components is its flexibility and reduction in cost and time. Research to-date on laser forming has been done theoretically, experimentally, and numerically. Effect of almost all the parameters—geometric, material and energy—affecting the shape of final product have been studied at length. Some experimental studies have been carried out using surface coating like graphite on the face of the sheet where the laser is passed. However, there are limited studies on the effect of different surface coatings on laser forming of sheets. Hence, the objective of the present work is to investigate the effect of different surface coatings on the laser forming of metal sheets. In the present work, mild steel is selected as the work material. Two different coatings, viz., commercial lime and cement are selected. First, the effect of the coatings is studied on simple line bending operation. The experiments are carried out at different values of laser power and laser scan speed for each coating. The results are compared with the results obtained from line bending of uncoated specimen. It is found that the cement coating performs better than the lime coating. Next, the effect of coatings is investigated on laser forming of complex shapes like dome and bowl shaped surfaces. For each coating the experiments are carried out at different values of laser power. It is found that the cement coated specimens can undergo more deformation than the lime coated specimens.