平板の突合せ溶接進行中の拘束材・仮付け溶接に作用する引裂力について

Abstract

This paper deals with the effect of welding conditions on separating forces produced in restraints like strong backs or tack welds during butt welding.The calculations have been carried out on variations of separating forces during welding under various conditions of heat input, plate length and restraint or tack weld pitch, using the finite element method explained previously. It is assumed that the rigidity of restraints and tack welds is infinite.The main conclusions obtained in the study are summarized as follows:The larger the effective molten pool length on the mechanical point of view (lM) is, the larger is the difference of separating forces between restraints and tack welds. The result depends on the type of restraint: in case of restraint like strong back, the restraint acts as a restraint after heat source passed through it, but in case of tack weld, the tack weld melts and cannot act as a restraint after heat source passed through it.The maximum separating force produced in an end restraint or an end tack weld ((Fy/h)emax) can be characterized as follows.(Fy/h)emax in the end tack weld is smaller than in the end restraint under the following conditions:lp=1200mm 416≤lM≤1663 (mm) 6000≤q/υh≤24000 (cal/cm2)where lp is a restraint or tack weld pitch, lM is an effective molten pool length on the mechanical point of view and q/υh is heat input per unit thickness and unit weld length.(Fy/h)emax increases as the heat input (q/υh) increases under consta-nt lM and decreases as the effective molten pool length (lM) increases under constant q/υh.Effect of plate length (L) on (Fy/h)emax depends on the welding conditions (q/υh, lM) and plate length (L).A restraint pitch has larger effects on (Fy/h)emax than a tack weld pitch.These results can be applied to tow electrodes submerged arc welding under the conditions that distance between leading electrode and trailing electrode (lLT) is small compared to lM.