Abstract
It is known that stress concentration and strain concentrtion occure at the root of welded joints with backing strip. Root radius is very important in relation to fatigue strength of the welded joints with backing strip. In this paper, statical equilibrium equation was derived from interfacial tension phenomena of molten metal in the welded joints with backing strip which was fabricated by flat welding or overhead welding. Influencing factors on root radius were studied from the statical equilibrium equation. Influence of torch angle on root radius was experimentally investigated.
The results obtained in this report are as follows;
1) The root radius became larger when misalignment was smaller at the welded joints with backing strip.
2) The root radius was larger when horizontal length between upper and lower fusion penetration point was larger for the welded joints with constant misalignment.
3) The root radius in overhead position was smaller than flat position due to the term of influence of gravity in the statical equilibrium equation.
4) The root shape was convex with solid wire and concave with flux cored wire. Accordingly, is is considered that root shape was influenced by slag.
5) The root radius was largest when torch angle was 90°C for flat position and 70°C for overhead position.
