Abstract: A constantly growing market for corrosion-resistant steels requires new, innovative and economical joining processes. For laser beam welding of thin-walled structures, joining technologies are required that cause minimal energy input into the component and thus reduce thermal distortion. Highly brilliant beam sources that meet these requirements are suitable . With decreasing beam diameter in the welding process, however, the heating and cooling rates increase. This leads to large temperature gradients and minimal holding times between heating and cooling. When welding “thin” duplex stainless steel sheets, this leads to less austenite in the ferrite matrix. However, these ferritic austenitic alloys require a balanced phase ratio of ferrite and austenite for optimum mechanical properties and corrosion resistance. This paper addresses the effect of process parameters on the cooling rate and thus directly on the phase balance between austenite and ferrite in 2205 (EN 1.4462/UNS S32205) duplex stainless weldments. Welded samples were metallographically examined with X-ray diffractometer and light optical microscopy Conclusions drawn from the analyses, are used to create a meta-model. This model in the field of thin-walled structures made of duplex steel is intended to improve the predictability in order to be able to estimate the phase ratio in the weld by means of process parameters. By means of a correlation analysis, the individual characteristics of the process parameters are to be shown on the phase ratio.
Authors: S. Ulrich, F. Gemse, S. Jahn, and P. Schaaf
Keywords: duplex stainless steels, laser welding, austenite content, microstructure