NLMK DanSteel, Frederiksverk, Denmark:

E. A. Goli-Oglu, Cand. Eng., Chief Technologist, e-mail: Egoli-Oglu@yandex.com
A. N. Filatov, Metallurgical Engineer

The relevance of investigating the quality of thick-walled welded joints is explained by the increased technological complexity of manufacturing and the consistent increase in the requirements for reliability and operational durability of welded structures for critical purposes. Microstructure and mechanical properties of 122 mm thick-walled welded joints after submerged arc welding (SAW) with heat inputs of 15 and 50 kJ/cm are under investigations. The microstructural condition of critical heat-affected zones, hardness, impact energy and resistance to fatigue strength are identified, described and tested. The microalloyed steel with СEQ ≤ 0.33% used for the welded joint and produced by thermomechanical controlled process with accelerated cooling, is showing a high level of resistance to static and dynamic loads in the welded joint and is recommended for use when manufacturing critical structures with high level of reliability. The results of the study were used in the course of certification testing of VL E36 / S420ML heavy plates according to the international rules DNV-OS-B101 and TUV 305/2011/EU: System 2+ and ABS Rules Materials and Welding.

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