Uncertainty analysis of a water flow calorimeter while welding in short-circuit and spray transfer regimes

Abstract

The thermal efficiency of arc welding influences the cooling rate, peak temperature, and microstructures of a weld, which affects the material properties of the welded joint. This work quantifies the uncertainty of thermal efficiency measurements on gas metal arc welds using low (2.5 kW) and high (9.5 kW) arc powers. In order to understand the effect of calorimeter parameters on the measured efficiency, a two-factor, two-level full factorial design was carried out for each arc power condition. In this study, the factors are flow rate (2 l/min and 5 l/min) and plate thickness (0.25 in. [6.35 mm] and 0.375 in. [9.53 mm]). The results show that the uncertainty in the thermal efficiency measurements increases when both higher flow rates and plate thickness are used. Moreover, the use of a thick plate causes the heat transfer regime to change, increasing the cooling rate and decreasing the observed thermal efficiency. Uncertainty is also influenced by the metal transfer mode during welding.