CO/sub 2/ short arc weldability of rare earth treated pipeline steels in circumferential welds

The CO/sub 2/ short arc weldability of rare earth treated steels was investigated. The effect of chemical compositions in steels of 23 heats on arc instability was investigated with the welding condition close to circumferential welding. Experimental results described in terms of Ts (a short circuiting period at one event) examined by multiple regression analysis, revealed that Ts depends strongly on rare earths. The arc instability results in step-like defects on a bead in CO/sub 2/ welding of steels containing 0.02% and over of rare earths. The defect is interpreted in terms of the transfer of an excessively large drop generated by extended intervals between short circuitings. To prevent the defect, increased welding current, decreased welding speed, and a DCSP source are recommended.