Abstract: A water vapor shielded metal-arc welding is mainly used for repairing process．Low cost is prominently its advantage，moreover the welds made with water vapor as shielding gas were significantly more of free porosity，so investigations of hydrogen content in weld metal with this process is stimu-lated．In the present work the diffusible hydrogen content in steel welds made with this process is determined．The dissociation of the water vapor in arc and energy absorbed by dissociating reaction are analyzed．The temperature distribution of arc and partial pressure of hydrogen are estimated by the numerical method．The hydrogen absorption mechanism during water vapor shielded arc welding process is approached．The reason for not high hydrogen content and free porosity in welds with this process is explained．

Key words: Diffusion hydrogen content, Arc temperature distribution, Metal-arc welding, Water vapor shielded