A MULTI-TRACK LASER BEAM PROCESS OF SURFACE HARDENING OF A FULL SIZE STEEL BLANK OF LOW-CARBON STEEL FOR PRODUCING AUTOMOTIVE COMPONENTS

摘要

The invention relates to a multi-track laser beam process of surface hardening of a full size steel blank of low-carbon steel for producing automotive components with improved strength and fatigue life, the process comprising the steps of: providing a hot rolled low carbon steel blank in the form of flat sheet having a chemical composition by weight percentage, C,Mn,S,P,Si,Al,V,Nb,and Ti respectively of 0.08, 1.4, 0.005,0.014, 0.005, 0.04, 0.001, 0.001, and 0.002; optimizing laser processing variables to produce a temperature capable for phase transformation of the initial microstructure of the steel sheet; selecting a laser track profile for surface hardening of the steel sheet; applying the selected laser processing variables in the form of laser power (1200W) and scanning speed (10mm/s) combinations on the surface of the steel sheet; selecting and adapting associated laser optics to operate the laser beam such that an impingement laser spot size on the sheet is of rectangular shape, wherein a 6-axis robot employed to carry the laser through a fiber fixed on 6th axis enabling an movement of the laser beam under the specimen along a short axis of the rectangular beam controlling the surface temperature of the specimen to eliminate any possibility of melting the sheet based on on-line surface temperature effect and comparing with pre-stored data representing surface temperature effect; and periodically reviewing the development of desired microstructure of the sample, including measuring hardness level and fraction of different phases.