In-Situ Temperature Monitoring and Feedback Control in the Gas Tungsten Arc Welding Process

Abstract

An approach has been developed to automate the gas tungsten arc welding (GTAW) process. The process temperature was monitored in-situ and employed to implement feedback control using the infrared ratio pyrometer. The automation of the process was achieved by replacing the foot pedal of the GTAW power source with an in-house developed control system consisting of a data acquisition system and a relay. The GTAW current was made variable automatically to achieve the desired or setpoint temperature. The temperature control is demonstrated for a broad range of 400–1600 °C for both stationary and moving heat source (GTAW torch). The standard deviation from the setpoint temperature was found to be within ± 25 °C for all the cases. It was also implemented for the single-pass bead deposition by feeding a low alloy steel wire to control the bead temperature in the range of 1200–1400 °C at different deposition speeds. The bead geometrical and mechanical properties could be altered by controlling the deposition temperature. The maximum bead width increased, and height decreased with the increase of the deposition temperature at a constant deposition speed. The microhardness was found to decrease by ~ 12% with the increase in deposition temperature from 1200 to 1400 °C, while the deposition speed had a marginal effect. © 2022, The Author(s), under exclusive licence to Korean Society for Precision Engineering.