Abstract
Modern arc processes, such as the modified spray arc (Mod. SA), have been developed for gas metal arc welding of high-strength structural steels with which even narrow weld seams can be welded. High-strength joints are subjected to increasingly stringent requirements in terms of welding processing and the resulting component performance. In the present work, this challenge is to be met by clarifying the influences on hydrogen-assisted cracking (HAC) in a high-strength structural steel S960QL. Adapted samples analogous to the self-restraint TEKKEN test are used and analyzed with respect to crack formation, microstructure, diffusible hydrogen concentration and residual stresses. The variation of the seam opening angle of the test seams is between 30° and 60°. To prevent HAC, the effectiveness of a dehydrogenation heat treatment (DHT) from the welding heat is investigated. As a result, the weld metals produced at reduced weld opening angle show slightly higher hydrogen concentrations on average. In addition, increased micro- as well as macro-crack formation can be observed on these weld metal samples. On all samples without DHT, cracks in the root notch occur due to HAC, which can be prevented by DHT immediately after welding.
Highlights
Lightweight design in steel constructions require an increasing use of high-strength structural steels with yield strengths ≥ 690 MPa [1,2]
Ever, attention must be paid to the fact that higher diffusible hydrogen are present when flux cored wires are used compared with solid wires [11 plicable guidelines for welding high-strength structural steels [16,17], a su preheat and interpass temperatures is recommended to minimize the risk these inhomogeneous heat inputs can lead to increased we
In addition the prevention ofsteels formation, welding process and interpass temperatures is recommended to minimize the risk against hydrogen-assisted cracking (HAC)
Summary
Lightweight design in steel constructions require an increasing use of high-strength structural steels with yield strengths ≥ 690 MPa [1,2]. These steels are mainly used in building, plant and crane construction. Their use is currently being extended to the offshore sector [3]. The joining of these steel grades by welding is mainly carried out by gas metal arc welding (GMAW). Base materials with yield strengths of up to 1300 MPa [4] and filler materials of up to 930 MPa [5] are commercially available
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