A Study of Thickening Phenomenon in Laser Bending Zone of a Metal Laminated Plate

A metal laminated plate, taking stainless steel/carbon steel laminated plate (SCLP) for example, is being increasingly used in the aircraft, ship, car and automotive industries. Based on the temperature gradient and thickening mechanisms, the thickening phenomenon was investigated for the SCLP forming and application widely. The bending zone thickness increases after laser bending of the SCLP. Then, an IPP image processing software was used to evaluate the grain size and thickness changes in laser bending zone. There are three areas they are stainless steel squeezed layer on the top, carbon steel extended layer at the middle and the bottom layer of stainless steel. The research results show that the grain size increases bigger in laser bending process which means thermal expansion thickening (TET) on one hand. In the positive bending process, grains extended by laser heating are squeezed through the bending stress and extrusion thickening (ET) on the other hand. The sizes of both stainless steel at upper layer and carbon steel layer at middle get thicker, but the bottom stainless layer changed little. The research outcomes also show the thickening size consists of TET and ET, where TET effect accounts for great proportion in the range of bending angle 5-20 degree. While ET effect increases in the range of bending angle 30-60 degree, the thickening ratio of TET and ET reaches 2 to 3 at bigger angles. The researches of the thickening phenomenon provide a deeper understand on laser bending theory and technology.