Hydrogen-assisted cracking in GMA welding of high-strength structural steels using the modified spray arc process
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RESEARCH PAPER
Hydrogen-assisted cracking in GMA welding of high-strength structural steels using the modified spray arc process Thomas Schaupp 1
&
Michael Rhode 1,2
&
Hamza Yahyaoui 1 & Thomas Kannengiesser 1,2
Received: 13 January 2020 / Accepted: 4 August 2020 # The Author(s) 2020
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 highstrength 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. Keywords High-strength steel . GMA welding . Diffusible hydrogen . Implant test . Fractography
1 Introduction To achieve the climate goals and the associated reductions in CO2 emissions, modern steel constructions require the use of high-strength structural steels with yield strengths of 690 MPa and more. High-strength structural steel grades have been used for several decades, particularly in mobile crane construction [1, 2]. The field of application is currently being extended to wind turbine and bridge construction. Manufacturers offer numerous base and filler materials for this Recommended for publication by Commission II - Arc Welding and Filler Metals. * Thomas Schaupp [email protected] 1
Bundesanstalt für Materialforschung und -prüfung (BAM), Unter den Eichen 87, 12205 Berlin, Germany
2
Otto-von-Guericke-University, Universitätsplatz 2, 39106 Magdeburg, Germany
purpose. However, the increasing strengths require significantly higher demands on the welding processing. In order to guarantee the mechanical properties of the base materials also in the welded joint, narrow process limits must be considered during the welding production [3–6]. Incorr
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