Weld Metal Toughness of Autogenous Laser-Welded Joints of High-Strength Steel Domex 960

• Published in: Materials performance and characterization 2019-11, Vol.8 (6), p.1226-1236
• Main Authors: Kurc-Lisiecka, Agnieszka, Lisiecki, Aleksander
• Format: Article
• Language: English
• ISSN: 2379-1365; 2165-3992
• DOI: 10.1520/MPC20190071

The results of investigations on autogenous laser welding of 5.0-mm-thick high-strength steel Domex 960 are presented in this article. The experimental plates delivered directly from the steel manufacturer were used for butt joint welding. The disk laser with maximum output power (maximum capacity of the laser generator) of 3.3 kW, emitting at 1.03 μm, and with the beam spot diameter of 200 μm was used for the trails of welding. Initially, the bead-on-plate welding tests were carried out, and then the test butt joints were laser welded. The influences of basic technological welding parameters, especially the energy input of laser welding on the shape of the fusion zone, the microstructure of weld metal and heat affected zone, and the impact toughness were analyzed. Laser welding trials were conducted in a wide range of energy input from 100 to 400 J/mm. Despite the low energy input of the laser welding process and also the short cooling times t8/5, tendency to cold crack was found neither in the weld metal nor in the heat affected zone. The carbon equivalent (CET), determined by the chemical analysis of the experimental melt, was just 0.341, indicating moderate tendency to increase hardness after welding because of martensitic transformation. It was found that the energy input has a clear influence on the microstructure and the impact toughness of the weld metal. The weld metal of the test butt joint welded at the energy input of 198 J/mm showed the average impact toughness at approximately 80 % of the base metal, whereas the weld metal of the test butt joint welded at a lower energy input of 132 J/mm showed the average impact toughness at the level of just 60 % of the base metal of Domex 960 steel.