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2016
Journal Article
Titel
Laser beam weldability of high-manganese austenitic and duplex stainless steel sheets
Abstract
Manganese alloyed stainless steels represent a cost-effective alternative to conventional CrNi stainless steels due to strong fluctuations of the nickel prices during the last years. In CrM-nNi-steels, nickel is replaced by lower-cost manganese and partially nitrogen for stabilization of the austenitic phase. This also brings benefits regarding the mechanical properties, as it results in an increased material strength. Laser beam welding of such materials was investigated for direct comparison with standard CrNi-steels. Main emphasis was laid on finding adequate process parameters to achieve a stable welding process and obtain a good weld quality. Two different laser sources, a 4.4 kW Nd:YAG- and a 6 kW C02-laser, were used to weld 1.5 mm stainless steel sheets in continuous wave mode. A Mn-austenitic (1.4376) and a lean duplex (1.4162) steel, as well as the standard austenitic (1.4301) and duplex (1.4362) steels were selected as test materials. Both butt and overlap joint configurations were studied. Experiments were carried out systematically, varying the welding speed, laser power and focal point position in order to determine adequate process windows. The influence of the shielding gas type and flow rate on the process stability and the weld quality were investigated. The effects of weld edge preparation on the weld appearance and quality levels attained were also considered. The obtained welded joints were subjected to radiographic tests for detection of internal imperfections. Also a metallurgical characterisation of the samples regarding the resulting phase composition or balance and hardness in dependence of the welding process parameters was conducted. Furthermore, tensile and potentiodynamic tests were performed to evaluate the mechanical and corrosion properties, respectively. 1he results provide an insight into the advantages and limitations of the laser beam welding process for joining high-manganese alloyed stainless steels. Conditions for the production of defect free and corrosion resistant welds having good mechanical properties could be determined.