MIG 溶接における移行粒子の保有熱量, 温度 : 抵拡発熱の溶滴保有熱量におよぼす影響

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Heat content of the droplet detaching from the wire tip in MIG arc welding is measured calorimetrically under a special electrodes arrangement shown in Fig. 1,2. Ozawa already reported on this problem and we tested further to understand the temperature characteristics for wires of low and high conductivities. Fig. 4 shows the results for copper and aluminum wires and Fig. 6 those for steel and stainless steel wires. For aluminum wire, the heat content Q_m expressed in cal/g increases as the current is increased in globular transfer range and reaches a nearly constant high value. The temperature is estimated to be nearly equal to the boiling point for the spray transfer range. The characteristic curve of Q_m-I under a constant wire extension for steel or stainless steel wire (Fig. 6) is shown in Fig. 7. Q_m increases as the current I is increased for globular transfer range, AB, which is similar to that of aluminum shown in Fig. 8. After reaching a maximum value, Q_m decreases for further current increase (curve BCD). The decrease of Q_m is related to the pencil-like forming of the wire tip, which is the well-known characteristic for wires of low thermal and electric conductivities, and this suggests that the droplet can detach more easily when the wire tip takes the pencil-like form. Q_m-I curves in Fig. 6 (a) can be explained clearly from the above mentioned idea. Fig. 8 shows a Q_m-I curve for aluminum wire for an extraordinarily long wire extension, and the curve shows the same tendency as that of steel wire. Now we understand that the droplet temperature decreases to as low as the melting point of the wire material when the wire is preheated sufficiently by Joule's loss, and it rises to as high as the boiling point when the Joule's heating is negligible and the wire is heated abruptly by arc of sufficiently large current density. Figs. 9,11 show the equivalent melting voltage calculated from Q_m and the specific melting rate m (mg/Amp・sec) shown in Figs. 4-8. From these figures we can clearly estimate the Joule's heating and the anode heating.
1967-10-25

MIG 溶接における移行粒子の保有熱量, 温度 : 抵拡発熱の溶滴保有熱量におよぼす影響

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