The Paton Welding Journal, 2024, №04



2024 №04 (07)

DOI of Article 10.37434/tpwj2024.04.01

2024 №04 (02)

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The Paton Welding Journal, 2024, #4, 3-10 pages

Parameters and challenges for reliable hydrogen determination in welded joints by carrier gas hot extraction

M. Rhode^1,2, T. Mente¹, T. Kannengiesser^1,2

¹Bundesanstalt für Materialforschung und -prüfung (BAM), Department 9 - Component Safety, Berlin, Germany
²Otto-von-Guericke-University, Institute for Materials Testing and Research, Magdeburg, Germany

Abstract
For the hydrogen-based energy economy of tomorrow, the construction of the necessary infrastructure will play a central role. Most materials used to date, such as welded steels, can be prone to hydrogen embrittlement under certain conditions. This includes the classic delayed cold cracking during welding as well as degradation phenomena during service of components in hydrogen-containing environment. For the evaluation of any hydrogen effect, for example, on the mechanical properties of a welded metallic material, the hydrogen content must be precisely determined. In the case of weld seams, the carrier gas hot extraction (CGHE) according to ISO 3690 is meanwhile state-of-the-art. CGHE is based on accelerated hydrogen degassing due to the thermal activation of hydrogen at elevated temperatures. In addition to the quantification of hydrogen, thermal desorption analysis (TDA) with varying heating rates can be used to determine and evaluate the hydrogen trapping at microstructural defects in the material. For both techniques, experimental and metrological influences must be considered, which have a major effect on the result. For example, ISO 3690 suggests different sample geometries and minimum extraction times for CGHE. This study summarizes the results and experiences of numerous investigations at the Federal Institute for Materials Research and Testing (BAM) with different sample temperatures and geometries (ISO 3690 type B and cylindrical TDA samples) regarding the influence of the sample surface (polished/welded), measurement accuracy depending on the sample volume and the insufficient monitoring of the effect of PI control on the extraction temperature. A deviating extraction temperature from the target temperature can significantly falsify the measurement results. Based on the results, methods are shown which allow the desired extraction temperature to be reached quickly without physically interfering with the measuring equipment. This serves to significantly improve the reliability of the hydrogen measurement through increased signal stability and accelerated hydrogen desorption. In general, an independent temperature measurement with dummy samples is recommended for the heating procedure of choice to exclude possible undesired temperature influences before the measurement. The methods described can be transferred directly to industrial applications.
Keywords: welding, hydrogen measurement, carrier gas hot extraction, ISO 3690, thermal desorption analysis

Received: 14.03.2024
Received in revised form: 09.04.2024
Accepted: 13.05.2024

References

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