Utilising laser forming as a novel way of forming dual phase steel for automotive components

Abstract

Dual phase steel is commonly used in the manufacture of automotive components. The component under consideration for this paper is the centre disc of a pressed wheel. It has been proved by previous research that the reduction in fatigue life of samples machined from the various production stages of the pressed wheel, is as great as 83%. The maximum reduction occurred during the first production stage (production of a bulge shape). This paper covers experimental work on two dimensional samples shaped by various laser parameters to similar radii of curvature as those produced by the first draw production stage of the mechanical forming operation. A CO2 Trumpf laser system was used for the production of laser formed specimens. The heat generated during the laser forming process affected the dual phase (ferrite and ± 25% islands of martensite) microstructure at the surface being irradiated. Laser powers as high as 5kW was employed in the production of two dimensional samples. Fatigue testing revealed that there is a wide range of results obtained from the samples formed to the same radius of curvature and then tested by the bend fatigue test. This paper will give a brief outline of the effect of laser parameters (laser power, laser scanning velocity, and number of laser scans, beam diameter and interval spacing) on the bend and fatigue characteristics of automotive dual phase steel.Dual phase steel is commonly used in the manufacture of automotive components. The component under consideration for this paper is the centre disc of a pressed wheel. It has been proved by previous research that the reduction in fatigue life of samples machined from the various production stages of the pressed wheel, is as great as 83%. The maximum reduction occurred during the first production stage (production of a bulge shape). This paper covers experimental work on two dimensional samples shaped by various laser parameters to similar radii of curvature as those produced by the first draw production stage of the mechanical forming operation. A CO2 Trumpf laser system was used for the production of laser formed specimens. The heat generated during the laser forming process affected the dual phase (ferrite and ± 25% islands of martensite) microstructure at the surface being irradiated. Laser powers as high as 5kW was employed in the production of two dimensional samples. Fatigue testing revealed that the...