Adaptive penetration control using infrared measured temperature gradients

In this paper, the effects of shielding gases on weld penetration were studied using infrared sensors. Argon, helium and mixtures of these gases were used in the experiments. Autogenous bead-on-plate welds were made keeping all welding variables except the shielding gas composition constant. Dynamic changes in the shielding gas composition were then introduced and corresponding changes in the thermal distribution of the molten pool and surrounding region monitored. After the fact metallography was used to determine puddle dimensions. These results were then compared to the infrared surface temperature measurements. Gradients in the molten metal pool were found to dramatically change as the puddle shape changed when a different shielding gas composition was introduced. This behavior was used in implementing dynamic weld penetration control.