抄録
A high strength chain is manufactured by bending steel bars, flash welding and subsequent heat treatment. The defects in the flash welded zone have been investigated.
1. The defects are detected in the flash welded zone by UST of 20 MHz. The defects are oxide clusters generated by welding.
2. The defects are found more in the outer area than in the inner of the transverse section of a chain link. This is because the molten steel flows to the inner area from the outer by the electromagnetic force generated during welding, thus the molten steel layer becomes thin in the outer area, where oxide clusters are not ejected together with the molten steel and remain there.
3. The defects can be eliminated by an increase of upsetting length in the weld process ; this is the most of the defect can be removed by cutting off the flash and oxide clusters are finely dispersed.
4. With increasing the upsetting length, the average impact value of the welded zone decreases but the scatter of the value is improved.
