Abstract
In order to investigate the relations between micro-fissure and cooling velocity, welding was done at various preheating temperatures, and it was recognized that micro-fissure did hot appear at all in welding at preheating temperature above 950°C (above A3 transformation polint). Further the relations between micro-fissure and chemical component of core rod were investigated, and it was made clear that carbon content of core rod have a great influence upon micro-fissuring.
In the conclusion several experimental data as to the relations between micro-fissure and mechanical properties of weld were introduced. And as a result of preliminary experiments several preventingg measures against micro-fissuring were proposed.
