Distribution and Segregation of Sulphur in Mild Steel Weld Metals

Abstract

The author investigated the distribution and segregation of sulphur in mild steel weld-metals, using radioisotope S35 and autoradiograph. 5 mC of S 35 is introduced into the coatings or the core wires of arc electrodes or the core wire of unionmelt welding. One pass or multi pass weld-metals were produced using these materials. Autoradiographs on the sections of these specimens were obtained after 15 to 120 days of exposure. From these experiments, the following results were obtained.
(1) In the case of hand welding, the striped patterns perpendicular to the dentritic structure were found on the autoradiographs, but there was no such a remarkable segregation of the top area or the boundaries of dendrite as usually found in steel ingot.
(2) Similar striped patterns were found in the bottom area but striped patterns parallel to the dendritic structure were found in the middle or top area of weld-metals, in the case of unionmelt welding.
(3) These results show that sulphur segregates to the boundaries of dendrite in the case of rapid cooling rate, but does in stripes parallel to the locus of the solidification line of weld-bead in the case of slower cooling rate.