Stabilization of weld pool through jet flow argon gas backing in C-Mn steel keyhole TIG welding

Welding tests were carried out to join the 16 Mn steel with three different shielding modes, including no shielding, fully covered Argon gas, and backing jet flow Argon gas. It was found that: (1) it was hard to achieve a stable K-TIG welding process if the backside weld pool was exposed in the air; (2) stable keyhole welding process could be created in the current range of 410A-450A if the backside weld pool was covered with static argon gas; and (3) stable keyhole welding current range was increased to 420A-560A if the argon gas jets directly flowed towards the backside weld pool. The jet flow gas provides additional pressure supplementing gravity to balance the arc gas pressure. Fully penetrated weld could be obtained even though the welding current was beyond the upper threshold point. The welds obtained in higher currents had comparable quality to those obtained at the low threshold point. The results give new solution to stabilize the fully penetrated weld pool.