TY  - CONF
A1  - Fey, Gero
T1  - Thermophysically Simulated Weld HAZ and CCT Diagram of High Strength Low Alloy Pipeline Steel
N2  - Green produced Hydrogen is considered as a key energy carrier for the transition to a more sustainable energy supply. Large-scale infrastructure projects, such as the European Hydrogen Backbone, aim to establish a hydrogen pipeline network connecting production and consumption regions. To enable this distribution, existing and newly build pipeline networks play a crucial role. High-strength low-alloy (HSLA) pipeline steels such as L485ME (X70) are therefore faced to challenges associated with hydrogen transportation.
One critical challenge in hydrogen transportation is hydrogen-assisted cracking (HAC), which is influenced by mechanical loading, hydrogen content, and the material itself. The microstructure of the steel has a significant impact on its resistance to HAC. Since pipeline tube sections are commonly joined by welding, the weld metal and heat-affected zone (HAZ) reveal different microstructures compared to the base material. In particular, the coarse grain heat affected zone (CGHAZ) is considered to be a critical zone for HAC. Therefore, the understanding of the resulting microstructure in the HAZ is essential to assess the material’s performance under hydrogen exposure. 
A quenching dilatometer was used to simulate the weld HAZ of an HSLA L485ME pipeline steel. The influence of cooling on the CGHAZ was investigated at a peak temperature of 1250°C using varying t8/5-cooling times (from 2 s up to 500 s), focusing on microstructural evolution and hardness. Based on these experiments, a continuous cooling transformation (CCT) diagram was constructed. 
Additionally, other regions of the weld HAZ were thermophysically simulated using two different t8/5-cooling times, namely 6 s and 15 s, while varying the peak temperature between 1250°C and 800°C. The resulting microstructures and hardness values were analyzed and compared.
T2  - IIW Intermediate Meeting
CY  - Trollhättan, Sweden
DA  - 10.03.2025
KW  - L485ME
KW  - Pipeline steel
KW  - CCT
KW  - Heat-affected zone
KW  - Dilatometry
PY  - 2025
AN  - OPUS4-63102
LA  - eng
AD  - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER  -