Improved Titanium Transfer in Submerged Arc Welding of Carbon Steel through Aluminum Addition

Abstract

ABSTRACT In Submerged Arc Welding of carbon steel, element transfer of Titanium from the molten flux to the weld metal is limited to small quantities as reported in literature, 310 ppm maximum. This limitation is due to the high oxygen potential prevailing at the molten flux-weld pool interface. The results presented here illustrate the use of Al powder in combination with Ti powder to improve Ti transfer into the weld metal to 4% Ti, and still maintain high oxygen content in the weld metal at 509 ppm to form inclusions. This is important in SAW because, in addition to higher Ti in the weld pool, high ppm O is required in the weld pool to form Ti-oxide inclusions in the weld metal to induce acicular ferrite (AF) formation. Oxide inclusions in the weld metal form possible nucleation sites for acicular ferrite formation to improve weld metal strength and toughness. The results confirm that the oxygen potential at the flux-weld pool interface may be lowered by Al powder addition to increase Ti powder transfer into the weld pool, without interfering with oxygen transfer from the plasma arc to the weld pool. Results from welding tests made in the absence of Al and Ti metal powder are used as a base case comparison to explain the process reactions in Submerged Arc Welding in the presence of Ti and Al metal powder.