厚鋼板の隅肉溶接における微小欠陥の発生機構およびそれに対する施行法の研究(第1報)

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In construction of hulls, the most of weld crackings are originated in fillet joints, and also many toe crackings which are remained almost unknown on their initiating process, are frequently included in them.In this respect, author has studied on the cause and effect of the toe crack initiation in a full penetrated T type fillet joint of thick plates and obtained the conclusions as follows : -1. The cracking of this kind was prevailing on the toe of the backingpass-side weld and originated from the notch root suffered large weld strain by the thermal and strain cycles in the finishing-pass-side welding.2. In these thermal and strain cycles, above 90% of the strain were proceeded below 550℃ and the strain cycles worked mostly as contraction on the notch root.3. In the case of the sum of the absolute value of the weld strain on the notch root exceeding 12%, the toe cracking initiated in further straining.On this critical value of the strain, same results are obtained as retained ductility of the mechanical prestrained specimen in bending.4. As factors increasing the weld strain, there were the depth of back-chipping, the larger diameter of welding electrode and the sharpness of the notch root. On this account, for the prevention of the cracking, the welding should be carried out in controlled conditions on these factors.
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