Chemical Interaction of Cr-Al-Cu Metal Powders in Aluminum-Assisted Transfer of Chromium in Submerged Arc Welding of Carbon Steel

Abstract

In submerged arc welding (SAW) of chromium containing steels, the chromium in the weld metal is usually sourced from weld wire. Manufacturing of precise weld wire compositions for alloying of the weld metal is expensive. In addition, alloying of weld metal with high levels of copper via weld wire is hindered by work hardening of the weld wire. In the SAW process, a large quantity of oxygen is added to the weld pool. Because chromium has a high affinity for oxygen, the oxygen partial pressure at the weld pool-molten flux interface must be controlled to ensure high recovery of chromium to the weld metal. This study illustrates the application of copper as stabilizer, in conjunction with aluminum, to enhance chromium transfer to the weld pool. The stabilizer effect occurs because the Cr-Al-Cu alloy liquidus temperatures are much lower than the pure Cr liquidus temperature. The result is an increase in the total quantity of Cr, Al, and Cu powder melted into the weld pool. The application of Al powder additions to control the partial oxygen pressure at the molten flux-weld pool interface is confirmed in the presence of Cr and Cu metal powders to ensure the weld metal ppm O content is maintained at the acceptable level of 300 ppm.