TY - CONF A1 - Schaupp, Thomas A1 - Yahyaoui, Hamza A1 - Rhode, Michael A1 - Kannengießer, Thomas T1 - Effect of weld penetration depth on hydrogen-assisted cracking of high-strength structural steels N2 - 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 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. T2 - 72nd IIW Annual Assembly and International Conference: Commission II-A CY - Bratislava, Slovakia DA - 07.07.2019 KW - Hydrogen KW - Implant test KW - High-strength steels KW - Fractography PY - 2019 AN - OPUS4-48462 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael A1 - Kannengießer, Thomas A1 - Schaupp, Thomas A1 - Mente, Tobias T1 - Hydrogen in weld joints - An underestimated risk? - Utilization potential of gas analytics versus safety of welded components N2 - Hydrogen was once called “the versatile embrittler” [1], which summarizes very well the effect on reduction of ductility and/or toughness in technical alloys like steel. In that connection, welding is one of the most important component fabrication technologies. During welding, hydrogen can be transferred to the weld pool from manifold sources (like contaminations, residuals at the surface, etc.). As hydrogen embrittles a material, the safety of welded components with hydrogen is always a critical issue. Weld heat input causes additional changes in the microstructure like grain growth or partial dissolution of precipitates and many more. All these things influence the mechanical properties and also represent hydrogen traps. These traps decrease the hydrogen diffusion compared to the ideal lattice. The result can be so-called delayed hydrogen assisted cracking (HAC) of the weld joint due to the significantly decreased diffusivity by trapped hydrogen. This is often an underestimated risk as those cracks can appear in the weld joint even after some days! It is essential to know about hydrogen ingress during welding and the microstructure specific hydrogen diffusion. Both are depended on weld parameter influence and the chemical composition of the base material and weld metal. For that purpose, gas analytic methods like solid-state carrier gas hot extraction (CGHE) are useful tools to: (1) identify detrimental hydrogen concentrations from weld joints, (2) binding energies from hydrogen traps by thermal desorption analysis or (3) high-temperature diffusion coefficients. Those values are extremely important for welding practice in terms of recommendations on realistic hydrogen removal heat treatment (HRHT) after welding. Considering the increasing use of “digital” experiments, the data is also needed for reliable numerical simulations of HAC process or HRHT-effectiveness. The present contribution gives an overview on the influence of hydrogen on weld joints, the necessity, methods and standards for hydrogen determination (CGHE) with the aim of fabrication of safe welded and crack-free components. [1] R. A. Oriani (1987), Corrosion 43(7):390-397. doi: 10.5006/1.3583875 T2 - 20. Tagung Festkörperanalyse - FKA20 CY - Vienna, Austria DA - 01.07.2019 KW - Hydrogen KW - Welding KW - Gas analytic PY - 2019 AN - OPUS4-48402 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rhode, Michael A1 - Schaupp, Thomas A1 - Münster, C. A1 - Mente, Tobias A1 - Kannengießer, Thomas A1 - Böllinghaus, Thomas T1 - Hydrogen determination in welded specimens by carrier gas hot extraction - a review on the main parameters and their effects on hydrogen measurement JF - Welding in the World N2 - Carrier gas hot extraction (CGHE) is a commonly applied technique for determination of hydrogen in weld joints using a thermal conductivity detector (TCD) for hydrogen measurement. The CGHE is based on the accelerated hydrogen effusion due to thermal activation at elevated temperatures. The ISO 3690 standard suggests different specimen geometries as well as necessary minimum extraction time vs. temperature. They have the biggest influence on precise hydrogen determination. The present study summarizes the results and experience of numerous test runs with different specimen temperatures, geometries (ISO 3690 type B and small cylindrical samples), and factors that additionally influence hydrogen determination. They are namely specimen surface (polished/as-welded), limited TCD sensitivity vs. specimen volume, temperature measurement vs. effects of PI-furnace controller, as well as errors due to insufficient data assessment. Summarized, the temperature is the driving force of the CGHE. Two different methods are suggested to increase the heating rate up to the desired extraction temperature without changing the experimental equipment. Suggestions are made to improve the reliability of hydrogen determination depended on the hydrogen signal stability during extraction accompanied by Evaluation of the recorded data. Generally, independent temperature measurement with dummy specimens is useful for further data analysis, especially if this data is used for calculation of trapping kinetics by thermal desorption analysis (TDA). KW - Hydrogen KW - Carrier gas hot extraction KW - Experimental design KW - Thermal conductivity device PY - 2019 DO - https://doi.org/10.1007/s40194-018-0664-9 SN - 0043-2288 VL - 63 IS - 2 SP - 511 EP - 526 PB - Springer CY - Berlin, Heidelberg AN - OPUS4-47603 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schaupp, Thomas A1 - Rhode, Michael A1 - Yahyaoui, Hamza A1 - Kannengießer, Thomas ED - Lippold, J. ED - Boellinghaus, Thomas ED - Richardson, I. T1 - Influence of heat control on hydrogen distribution in high-strength multi-layer welds with narrow groove JF - Welding in the World N2 - High-strength low-alloyed (HSLA) steels with yield strength ≥ 690 MPa are gaining popularity in civil engineering and construction of heavy vehicles. With increasing yield strength, the susceptibility for degradation of the mechanical properties in the presence of diffusible hydrogen, i.e., hydrogen-assisted cracking (HAC), generally increases. HAC is a result of the critical interaction between local microstructure, mechanical load, and hydrogen concentration. In existing standards for welding of HSLA-steels, recommendations including working temperatures and dehydrogenation heat treatment (DHT) are given to Limit the amount of introduced hydrogen during welding. These recommendations are based on investigations into conventional arc welding processes. In the past decade, modern weld technologies were developed to enable welding of narrower weld seams with V-grooves of 30°, e.g., the modified spray arc process. In that connection, a reduced number of weld runs and weld volume are important technical and, economic benefits. In the present study, the hydrogen distribution in S960QL multi-layer welds with thickness of 20 mm was analyzed. The influence of different weld seam opening angles, heat input, working temperature and DHT were investigated. The results show that weldments with narrow grooves contained an increased amount of diffusible hydrogen. Hydrogen concentration has been reduced by decreasing both the heat input and working temperature. Hydrogen-free weldments were only achieved via subsequent DHT after welding. Furthermore, hydrogen distribution was experimentally determined across the weld seam thickness in HSLA gas metal arc welded multi-layer welds for the first time. KW - Hydrogen KW - GMAW KW - High-strength steels KW - Heat control KW - Heat treatment PY - 2019 DO - https://doi.org/10.1007/s40194-018-00682-0 SN - 0043-2288 SN - 1878-6669 VL - 63 IS - 3 SP - 607 EP - 616 PB - Springer CY - Berlin Heidelberg AN - OPUS4-47878 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -