Study on the quenching strategies for seamless hydrogen storage vessels made of Cr–Mo steel

Abstract

Seamless hydrogen storage vessels made of Cr–Mo steel are commonly used for hydrogen refueling stations, whereas due to high-pressure storage requirements and the resulting large wall thickness, conventional single-sided quenched vessels usually face poor uniformity of mechanical properties along the wall thickness after heat treatment. In response to this issue, double-sided quenching has been proposed as an improved solution, while single-sided quenching remains a practical option for vessels with thin wall thicknesses due to its simplicity and low cost. To date, there is a lack of systematic research to clearly define the applicable thickness ranges for single-sided and double-sided quenching of such vessels. In this study, seamless hydrogen storage vessels made of Cr–Mo steel with a wall thickness of 44 mm underwent single-sided quenching and double-sided quenching, respectively. Specimens sampled from the cylinder of these vessels along the wall thickness were subjected to hardness tests and Charpy impact tests. Concurrently, the variations in temperature and phase along the wall thickness were analyzed through numerical simulation. Based on this, quenching strategies were developed by simulating the mechanical uniformity of vessels with different wall thicknesses. Results indicate that when subjected to single-sided quenching, both hardness and impact absorbed energy gradually decrease from the outer surface to the inner surface, while double-sided quenching results in a distinct V-shaped distribution of these properties. This difference is primarily attributed to the significant variations in cooling rates and resulting phase distributions between single-sided and double-sided quenching. To meet the maximum permissible hardness deviations specified in GB/T 44457, single-sided quenching is suitable for vessels with wall thicknesses not exceeding 40 mm and double-sided quenching is recommended for vessels with wall thicknesses between 40 mm and 60 mm.