アーク溶接継手の収縮過程に関する研究(第4報)

Abstract

As the factors which affect the contraction process of a weld joint in arc welding, three factors are considered; (1)t welding heat input (Q), (2) plate thickness (h) and (3)gauge length (l) over which the contrac. tion is measured. Besides, effect of transformation expansion of weld during cooling should also be considered.In the prior works (parts 1-3), keeping welding heat input constant, effects of the other factors on the contraction were investigated. In the present report, effect of welding heat input on contraction was considered. Knowledge on contraction process of a weld joint has advanced to the following point: The quantity of critical plate thickness (hcr) can be taken as a parameter concerning the mutual effect of heat input (Q) and plate thicness (h), and the critical plate thickness (hcr) is proportionate to the square root of heat input (Table 1). Contraction progresses with different processes according to whether plate thickness (h) is larger than the critical phate thickness (hcr) or not (Fig. 6). In the case of h≥hcr contraction progresses to the final value through the first, the second and the third steps. The final contraction is proportionate to hcr (or to √Q) independently of plate thickness (h). In the case of h<hcr, on the contrary, only the third step appears in contraction process. The final contraction is proportionate to the square of hcr (or to Q) and increases with decrease in plate thickness (Fig. 5).Successful agreement was observed between experimental results and calculated ones (Figs. 10-13). However a little difference between them was observed in the effect of moving of heat source which was neglected in the analysis (Fig. 15).