Reducing potential errors in the calculation of cooling rates for typical arc welding processes

To reach the goal of weight reduction, modern thermo-mechanically processed micro-alloy steels are increasingly used to replace carbon-manganese structural steels. The processing window for welding these newer materials is much smaller, so it is important to accurately determine the rate of heat input, the t8/5-value (cooling rate) and also to ensure that the desired cooling rate is achieved in production. Variations in the welding process, welding parameters welded joint configuration, welding position, and layer structure change the rate of heat input into the component. At the same time, the arcing efficiency is affected by configuration and position. In combination, these parameters can affect the cooling behavior by more than 60%. Various welding processes and parameters are analyzed and the potential errors are discussed. Following this, the impact of these errors is illustrated with reference to practical measurements. The summation of the possible errors shows that it is difficult in practice to achieve the desired mechanical and metallurgical characteristics, as well as theoretically predicting these values, and also calculating or simulating properties such as distortion, microstructure, or residual stresses. The work presented here, together with recommendations for adjustment of published efficiency values as well form factors to calculate the t8/5-value (cooling rate), is expected to make a significant contribution to improve the quality of welded joints.