MAG welding of 960QL quenched and tempered steel

The article presents research of the welding technology of S960QL quenched and tempered steel with the thickness of 10 mm. The main problem during welding heat-treated fine-grained steels is cold cracking. The aim of the research was to develop welding technology of tested steel to obtain high ductility and strength properties of the joint and to avoid the problem of crack formation after welding process. For the test the butt joint was welded. For this it was used MAG process in the flat position. Welding process was carried out based on preliminary tests and pre-prepared Welding Procedure Specification according to ISO 15609-1 standard. During welding the M21 mixture was used as the shielding gas. As the filler metal a solid wire G Mn4Ni2.5CrMo was used. The welded joint was tested in accordance with the ISO 15614 standard requirements. The research included non-destructive tests and destructive tests. The non-destructive tests included visual, magnetic particle and radiographic tests. The destructive tests included transverse tensile, root and face bend, impact, macroscopic, microscopic and hardness. Impact test was carried out in the temperature of - 20°C. Hardness measurements were made using the Vickers method and the load of 9.80 N. All of the tests ended with the positive result. The results of research show that tested welding technology and pre-heating temperature equal to 80°C allow to obtain a welded joint meeting the high quality requirements and the international standards requirements.