Effect of heat-affected zone microstructure and alloyage line of welded joint in low-alloy steel on the delayed destruction

The microstructure of a heat-affected zone and alloyage line of welded joint in low-alloy steel is researched at welding by various filler materials. It is established, that the heat-affected zone (HAZ) of austenitic and mart-ensitic welds has a disperse structure and less sharp transition of structure from base metal to weld metal, than ferrite-perlite weld. If consider, that hydrogen diffuses mainly at the grain boundaries, the large-grain structure HAZ of ferrite-perlite weld, being a barrier, will promote of its accumulation at the grain boundaries, that will lead to the delayed destruction.