抄録
The arc rotation velocity in the magnetically impelled arc butt welding of a steel pipe was measured using the probe method and a high speed camera and the condition of arc plasma inside the pipe was photographed. The following is the conclusion thus obtained.
(1) The arc rotation velocity and arc angle were measured by the probe at each position on the pipe circumference immediately after an arc is ignited and the relationship between these and the method of supplying power was analyzed. With the steel pipe (60.5 mm in OD, 3.8 mm in wall thickness) used for the experiment, it was necessary to supply power at least two or more points to prevent ex- cessive local fusion or arc extinction.
(2) The arc rotation velocity was measured using a high speed camera, and the arc rotation velocity was classified into three regions of the low velocity region, high velocity region and speed fluctuation region.
(3) It was surmised that both the time th and tf that divide the above three regions are physical property values, and the time th is the time required for the area 1.0 mm from the pipe end exceeds the Curie temperature and the time tf is the time required for the entire surface of the pipe end to reach the melting temperature.
(4) Changes in the arc rotation velocity in the high velocity region and the velocity fluctuation region were analyzed by using the equation of motion to surmise the virtual mass, saturation magnetic flux density, and drive force.
