Study on Hydrogen Distribution in Multi-layer Weld of Cr-Mo-V Steel

It has developed the numerical simulation method of hydrogen diffusion for multi-layer weld on Cr-Mo-V steel. The developed simulation method can estimate the distribution of hydrogen concentration on weld metal and predict reduction of hydrogen by various dehydrogenation heat treatment conditions. The accuracy of calculation is practically enough for selecting the condition to prevent a cold cracking. In order to improve the accuracy of the calculation of hydrogen diffusion on weld, it is necessary to input the actual thermal history and initial hydrogen concentration into the calculation model. Also, it is important to model the hydrogen diffusion corresponding to the real phenomenon. It has found that the hydrogen degassing rate of Cr-Mo-V steel was slower than the conventional steel from measured data by gas chromatography. The hydrogen concentration was the maximum at the position of slightly inside from surface of last weld side. If it was compared the reduction of hydrogen concentration of 623K 4 hours and 553K 6 hours, the 623K 4 hours is much effected. However, when the longer time at 553K DHT is applied, it is expected further reduction of hydrogen concentration.