Abstract: There is plenty of dissimilar steel welding and overlay welding in hydrogenation reaction system. Dissimilar steel welding has the defects of unbalanced material properties and uneven thermal expansion. Interfacial stress, interface H concentration and carbon migration during surfacing are the key factors leading to hydrogen-induced disbanding of the hydrogenation equipment surfacing layer. The overlay welding method will affect the interface metallographic structure and the tendency of hydrogen-induced disbanding. Such issues as how to understand the characteristics of dissimilar steel welding correctly, how to select welding materials accurately and how to select more reasonable use of welding methods are worthy of discussion. Experiences have shown that for hydrogenation equipment, it is reasonable and feasible to adopt submerged arc overlay welding for single-layer overlay welding and adopt automatic submerged arc overlay welding plus automatic electro slag overlay welding for two-layer overlay welding.

Key words: dissimilar steel, hydrogen-induced disbanding, overlay welding, single-layer overlay welding, two-layer overlay welding