Choosing a Laser-cutting Technology to be Applied to a Deep-drawn Product

摘要

Residual stresses are an inevitable result of mechanical and heat treatments of steel. The stress field generated at the surface and through the cross section of a product is usually non-uniform, and there can be important stress gradients. In general residual stresses can be defined as self-balanced internal stresses existing in a free body on which no external forces are acting. In the present study the focus was on the residual stresses occurring in a steel deep-drawn product of a complex form. The residual stresses occur mainly because of different degrees of plastic deformation at different locations. The residual stresses occurring in the product as a result of the manufacturing process of deep drawing can be comparatively strong. In slitting or cutting a useful product out of a deep-drawn part by laser cutting, a portion of the residual stresses will get relieved and produce distortion of the deep-drawn product. The studies made showed that the distortion of the deep-drawn product depended on the mode of cutting-out. Also the state of the residual stresses after slitting or cutting-out of the deep-drawn product will depend on the mode of cutting-out, i.e., on the sequence of individual cuts chosen. The product used in the analysis made was a deep-drawn steel mud-guard, which makes a component part of a working machine. The various modes of cutting-out a useful product of 1260x800x370 mm in size were performed with laser cutting using cutting oxygen. The residual stresses in the mud-guard were determined with a semi-destructive hole drilling strain gage method.