Hcat Contents and Temperaturc of Metal Droplets in Pulsed MIG Welding

Study on Pulsed Arc Welding (Report 2)

Abstract

Heat contents of metal droplets in MIG welding are investigated for both cases, pulsed and constant current, using analogue transistor power source. From the measurement of heat content of metal droplets temperature of metal droplets is also evaluated taking account of heat loss due to radiative and conductive heat transfer between droplets and surrounding atmosphere during their flight into the calorimeter. Results obtained are summarized as follows;
(1) Among the electrode materials, used in this experiment, mild steel, stainless steel and copper alloy, heat contents of mild steel is observed to be highest, copper alloy lowest. In case of constant current MIG arc, heat contents of any materials increase as the current become higher, so far as globular transfer mode occurred. But when spray transfer mode is established, heat contents become almost constant.
(2) Heat contents of metal droplets in pulsed current type are slightly higher than those in constant current one, and are dependent on the average current used. Under such condition that spray transfer occurs syncronously with the current pulse, heat contents of droplets are nearly equal to that in constant current of peak current level.
(3) In MIG welding of mild steel, stainless steel and copper alloy, temperature of metal droplets in low current level of 30 amp. are estimated to be little higher above melting point of each material, but reach about 2000°C in current range higher than 200 amp.