Effect of oscillation frequency on the mechanical properties and failure behaviors of laser beam welded 22MnB5 weld

Abstract

Al–Si coated 22MnB5 steel is a lightweight material that helps significantly reduce vehicle weight and fuel consumption. In this article, the effect of different oscillation frequencies on the fraction of α-ferrite, the cross-sectional shape, microstructure and mechanical properties of laser welded Al–Si coated 22MnB5 steel was investigated. The results showed that after stamping, the fraction of α-ferrite in the fusion zone can be significantly reduced from 47.9% to 2.2% by oscillating laser beam welding compared to static laser beam welding with oscillation frequency and amplitude equal to zero. When the oscillating frequency was increased from 0 to 320 Hz, the cross-sectional shape of the weld changed from “X'' to “Y'', and the tensile strength and elongation of the welded joint was firstly increased and then decreased from the minimum value of (426.45HV, 1159.92 MPa, 1.14%) to the maximum value of (476.98HV, 1521.39 MPa and 2.76%). The formation of α-ferrite along the strip distribution near the upper surface of the fusion zone of static laser beam welding and oscillating laser beam welding after hot stamping, which led to stress concentration and eventual failure. Under the tensile-shear load, the cracks in the weld of static laser beam welding and oscillating laser beam welding were initiated on the massive α-ferrite location in the top surface of the fusion zone and expanded to the bottom of the weld.

Keywords

• Al–Si coating
• Press-hardened steels
• Oscillation laser beam
• Microstructure
• Mechanical property