Aluminium-Assisted Alloying of Carbon Steel in Submerged Arc Welding: Application of Al-Cr-Ti-Cu Unconstrained Metal Powders

Al assisted alloying of carbon steel in Submerged Arc Welding (SAW) by Al-Cr-Ti-Cu unconstrained metal powders is applied. A base case without metal powder additions is compared to two metal powder addition schedules, Al-Cu-Ti and Al-Cu-Ti-Cr. Al powder is used as a deoxidiser element to control the oxygen partial pressure at the weld pool-molten flux interface to ensure that most of the Ti and Cr metal powder is transferred into the weld pool and that the weld metal ppm O is controlled within acceptable limits of 200 to 500 ppm O. The likely sequence of alloy melt formation is deduced from the relevant alloy phase diagrams. The effect of Fe addition into the initial Al-Cu-Ti and Al-Cu-Ti-Cr alloy melt is illustrated in thermochemical calculations. Increased metal deposition productivity with metal powder addition in SAW is confirmed. The metal deposition rates increased by 19% and 40% when Al-Cu-Ti and Al-Cu-Ti-Cr powders were applied at the same weld heat input used in the absence of metal powder additions.

Automated summary

Al-Cr-Ti-Cu unconstrained metal powders are used to assist the alloying of carbon steel in Submerged Arc Welding (SAW). The addition of Al-Cu-Ti and Al-Cu-Ti-Cr metal powders increases the metal deposition rates by 19% and 40% respectively, compared to the base case without metal powder additions. Using Al powder as a deoxidiser allows for control of oxygen partial pressure and ensures the transfer of Ti and Cr metal powder into the weld pool while keeping the oxygen content in acceptable limits. The likely sequence of alloy melt formation is deduced from the alloy phase diagrams and the effect of Fe addition is illustrated in thermochemical calculations.