Numerical investigations on cold cracking avoidance in fillet welds of high-strength steels

• Published in: Welding in the world 2013-05, Vol.57 (3), p.359-371
• Main Authors: Steppan, E., Mente, T., Böllinghaus, Th
• Format: Article
• Language: English
• Subjects: Chemistry and Materials Science; Materials Science; Metallic Materials; Research Paper; Solid Mechanics; Theoretical and Applied Mechanics
• ISSN: 0043-2288; 1878-6669
• DOI: 10.1007/s40194-013-0036-4

Industry faces a growing demand for high-strength structural steels with yield strengths of up to 1,300 MPa in order to cope with increasingly higher strength requirements in engineering. Higher strength levels are achieved by a special coordinated production process and an adapted chemical composition. Nevertheless, disastrous damage cases with high-strength steels have occurred in the past. The sensitivity to mechanical property degradation by hydrogen increases dramatically with strength. This phenomenon leads to hydrogen-assisted cold cracking. T-joints with fillet welds made from one side with an included angle of 60° were examined for their cold cracking behavior. Based on the T-joint, a modified heat input, even interpass temperature, plate thickness, and length ones were examined. The diffusion behavior and the effectiveness of different post-weld heat treatments in joints were simulated. The results of post-weld heat treatments are illustrated in practical hydrogen removal heat treatment diagrams. It is noticed that the T-joint is subject to a very high risk of hydrogen-assisted cold cracking (HACC). Contrary to other joints, its most critical area for cracking is not the weld metal but the heat-affected zone surrounding area of the root pass. The simulation shows that HACC in the T-joint can only be avoided by applying a sufficient post-weld heat treatment.