Induction assisted GMA-laser hybrid welding of high-strength fine-grain structural steels

Abstract

The huge range of application for high-strength fine- grain structural steels is increasing because of the advantages concerning the mechanical properties and welding suitability for this material. Thick sheets up to 10 mm are used e.g. for offshore applications, mobile crane-, concrete pump-, pipeline- and shipbuilding. Conventionally, fine-grain structural steels are joined using arc welding methods in multi-layer processes, and at a comparatively low welding speed. Edge pretreatment time and high consumption of additional materials are typical for arc welding methods. Induction assisted GMA-laser hybrid welding is more efficient because of the advantages in terms of the high welding speed, a reduction of the edge pretreatment with lower flank angles and a smaller heat affected zone (HAZ). In the course of this research, a process has been developed for a single-layer seam for fine- grain structural steels with the grades S700MC, X70 and S690QL in a thickness range from 10 to 15 mm. For this configuration, a reproducible process has been achieved. The high quality welding seams were characterized by metallographic analyses, tensile tests, notched-bar impact tests and hardness tests. In addition, the use of inductive preheating provides advantages regarding the process and the metallurgy. It is possible to increase the welding speed, and to obtain homogeneous mechanical properties around and in the welding seam. A simulation model was developed for both the preheating process and the GMA-laser hybrid welding process, to accompany the experimental research.The huge range of application for high-strength fine- grain structural steels is increasing because of the advantages concerning the mechanical properties and welding suitability for this material. Thick sheets up to 10 mm are used e.g. for offshore applications, mobile crane-, concrete pump-, pipeline- and shipbuilding. Conventionally, fine-grain structural steels are joined using arc welding methods in multi-layer processes, and at a comparatively low welding speed. Edge pretreatment time and high consumption of additional materials are typical for arc welding methods. Induction assisted GMA-laser hybrid welding is more efficient because of the advantages in terms of the high welding speed, a reduction of the edge pretreatment with lower flank angles and a smaller heat affected zone (HAZ). In the course of this research, a process has been developed for a single-layer seam for fine- grain structural steels with the grades S700MC, X70 and S690QL in a thickness range from 10 to 15 mm. For this configurati...