Effect of weld penetration depth on hydrogen-assisted cracking of high-strength structural steels

  • The need for steels with highest mechanical properties is a result of the increasing demands for energy and resource efficiency. In this context, high-strength structural (HSS) steels are used in machine, steel and crane construction with yield strength up to 960 MPa. However, welding of HSS steels requires profound knowledge of three factors in terms of avoidance of hydrogen-assisted cracking (HAC): the interaction of (1) microstructure, (2) local stress/strain and (3) local hydrogen concentration. In addition to the three main factors, the used weld-arc process is also important for the performance of the welded joint, especially when using modern arc variants. In the past, the conventional transitional arc process (Conv. A) was mainly used for welding of HSS grades. In the past decade, the so-called modified spray arc process (Mod. SA) has been used increasingly for welding production. This modified process enables reduced seam opening angles with increased deposition rates comparedThe need for steels with highest mechanical properties is a result of the increasing demands for energy and resource efficiency. In this context, high-strength structural (HSS) steels are used in machine, steel and crane construction with yield strength up to 960 MPa. However, welding of HSS steels requires profound knowledge of three factors in terms of avoidance of hydrogen-assisted cracking (HAC): the interaction of (1) microstructure, (2) local stress/strain and (3) local hydrogen concentration. In addition to the three main factors, the used weld-arc process is also important for the performance of the welded joint, especially when using modern arc variants. In the past, the conventional transitional arc process (Conv. A) was mainly used for welding of HSS grades. In the past decade, the so-called modified spray arc process (Mod. SA) has been used increasingly for welding production. This modified process enables reduced seam opening angles with increased deposition rates compared to the conventional process. Economic benefits of using this arc type are: a reduced number of necessary weld beads and a lower weld seam volume, which result in decreased total welding time and costs. Nonetheless, investigations on a high-strength S960QL showed significantly higher hydrogen concentrations in the weld metal at a reduced seam opening angle with Mod. SA. This indicates an increased susceptibility of the welded component to HAC. Hence, existing recommendations on HAC-avoidance cannot be transferred directly to the Mod. SA-process. In the present study, the susceptibility to HAC of the HSS steel S960QL with same type of filler material was investigated. For that purpose, both Conv. A and Mod. SA were used with same heat input at different deposition rates. For assessment of the HAC susceptibility, the externally loaded implant test was used. Both conducted test series with Conv. A and Mod. SA showed similar crack critical stress of about 280 MPa. Below this value, no delayed fracture appeared. The welds with Mod. SA showed higher hydrogen concentrations. The fracture occurred in the heat-affected zone (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 to tests carried out with Conv. A.zeige mehrzeige weniger

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Metadaten
Autor*innen:Thomas SchauppORCiD
Koautor*innen:Hamza Yahyaoui, Michael Rhode, Thomas Kannengießer
Dokumenttyp:Vortrag
Veröffentlichungsform:Präsentation
Sprache:Englisch
Jahr der Erstveröffentlichung:2019
Organisationseinheit der BAM:9 Komponentensicherheit
9 Komponentensicherheit / 9.0 Abteilungsleitung und andere
9 Komponentensicherheit / 9.4 Integrität von Schweißverbindungen
DDC-Klassifikation:Technik, Medizin, angewandte Wissenschaften / Ingenieurwissenschaften / Ingenieurwissenschaften und zugeordnete Tätigkeiten
Freie Schlagwörter:Fractography; High-strength steels; Hydrogen; Implant test
Themenfelder/Aktivitätsfelder der BAM:Material
Material / Degradation von Werkstoffen
Veranstaltung:72nd IIW Annual Assembly and International Conference: Commission II-A
Veranstaltungsort:Bratislava, Slovakia
Beginndatum der Veranstaltung:07.07.2019
Enddatum der Veranstaltung:12.07.2019
Verfügbarkeit des Dokuments:Datei im Netzwerk der BAM verfügbar ("Closed Access")
Datum der Freischaltung:15.07.2019
Referierte Publikation:Nein
Eingeladener Vortrag:Nein
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