Hydrogen-assisted cracking in GMA welding of high-strength structural steels using the modified spray arc process

Abstract

High-strength structural steels are used in machine, steel, and crane construction with yield strength up to 960 MPa. However, welding of these steels requires profound knowledge of three factors in terms of avoidance of hydrogen-assisted cracking (HAC): the interaction of microstructure, local stress/strain, and local hydrogen concentration. In addition to the three main factors, the used arc process is also important for the performance of the welded joint. In the past, the conventional transitional arc process (Conv. A) was mainly used for welding of high-strength steel grades. In the past decade, the so-called modified spray arc process (Mod. SA) has been increasingly used for welding production. This modified process enables reduced seam opening angles with increased deposition rates compared with the Conv. A. Economic benefits of using this arc type are a reduction of necessary weld beads and required filler material. In the present study, the susceptibility to HAC in the heat-affected zone (HAZ) of the high-strength structural steel S960QL was investigated with the externally loaded implant test. For that purpose, both Conv. A and Mod. SA were used with same heat input at different deposition rates. Both conducted test series showed same embrittlement index “EI” of 0.21 at diffusible hydrogen concentrations of 1.3 to 1.6 ml/100 g of arc weld metal. The fracture occurred in the HAZ or in the weld metal (WM). However, the test series with Mod. SA showed a significant extension of the time to failure of several hours compared with tests carried out with Conv. A.

Re-Melting Behaviour and Wear Resistance of Vanadium Carbide Precipitating Cr27.5Co14Fe22Mo22Ni11.65V2.85 High Entropy Alloy

“… Cold-cracking Cold cracking occurs due to high hardness and/or low toughness of the material [ 24 ]. This can be intensified due to external restraints or other phenomena like the hydrogen assisted cracking [ 25 , 26 ]. Stress relief cracking Cracking which occurs due to high strength and low ductility during post weld heat treatment [ 27 , 28 , 29 ].…”

“…Cold cracking occurs due to high hardness and/or low toughness of the material [ 24 ]. This can be intensified due to external restraints or other phenomena like the hydrogen assisted cracking [ 25 , 26 ].…”

Hydrogen-Assisted Cracking in GMA Welding of High-Strength Structural Steel—A New Look into This Issue at Narrow Groove

“…Investigations carried out using the Mod. SA in the implant test showed that the deeper weld penetration profile and the increased welding current result in higher diffusible hydrogen concentrations and longer time-to-failure of the specimens until fracture [39]. However, the critical implant stress for crack initiation was not affected.…”

“…For the investigations, the quenched and tempered high-strength structural steel S960QL (BM) according to EN 10025-6 [44] with a plate thickness of 20 mm was chosen. This steel is typically used in mobile crane construction and shows high susceptibility to HAC in GMAW [37,39]. The welds were carried out with micro-alloyed filler materials of the same type.…”

Application of Macro-Instrumented Indentation Test for Superficial Residual Stress and Mechanical Properties Measurement for HY Steel Welded T-Joints

“…They provide superior strength per weight than conventional structural steels and yield cost savings by simplifying or eliminating heat treatment processes [3][4][5][6]. Hydrogen embrittlement was investigated due to the offshore application of these steels [7][8][9]. The effect of welding on the mechanical properties of these steels has been studied with conventional uniaxial tensile testing, the Charpy V-notch impact test, and a hardness test [3,6,10,11], and optimum welding parameters for gas metal arc welding have been proposed [11].…”