Decarburization and the Influence of Laser Cutting on Steel Structure

Abstract

By microscopic analysis of 20, 30, 45, У7A, and У8A steel samples obtained by laser cutting in different conditions, the structure of the surface thermal-influence zone is studied. This zone includes a dendritic layer (samples of У8A steel); a region with martensite structure; and an intermediate ferrite or ferrite–pearlite layer, indicating complete (20, 30, 35, or У7A steel) or partial (У8A steel) decarburization of deep regions in laser cutting. The microhardness distribution from the surface into the depth of the samples is studied, and the extent of the thermal-influence zone after laser cutting is determined. A mathematical model is developed and used to analyze the influence of the laser-cutting parameters, the sheet thickness, and the carbon content on the extent of the thermal-influence zone.