Influence of Dehydrogenation Heat Treatment on Hydrogen Distribution in Multi-Layer Welds Of Cr-Mo-V Steel

Abstract

Cr-Mo-V steel normally undergoes a dehydrogenation heat treatment (DHT) of 350 °C × 4 h after welding, to minimize the susceptibility to cold cracking due to residual hydrogen in the weld. For low ambient temperatures or failure to sufficiently heat the weld during the DHT holding period, it is sometimes difficult to maintain and guarantee the 350 °C for 4 h. We therefore surmised that lower temperature DHT over a longer time period could be substituted for the standard DHT conditions and still achieve the same dehydrogenation effect. In this paper, using experimental and numerical methods to measure hydrogen diffusivity and the influence of DHT on Cr-Mo-V steel welds, we demonstrate that even at temperatures as low as 280 °C held over longer time periods, there is an equivalent dehydrogenation effect as in the existing conditions.