In recent years, in order to reduce the costs of transportation and construction of pipelines, which are often constructed using multiple-electrode submerged arc welding (SAW), higher joint performance is required. Therefore, there has arisen the need to understand theoretically and control appropriately metallurgical and mechanical characteristics in Heat Affected Zone (HAZ), which has a significant influence on the strength and toughness of welded joints.
Commonly, metallurgical phenomena in HAZ are evaluated based on the highest temperature and the cooling rate. Therefore, in order to control metallurgical and mechanical characteristics in HAZ by means of the welding conditions, evaluating the temperature distribution and the temperature history near the melted zone is essential. However, a detailed investigation of the temperature distribution for multiple-electrode submerged arc welding has not yet been performed enough.
In present study, in order to investigate the temperature distribution and histories during multiple-electrode submerged arc welding, the experimental results are compared with the theoretical results. In the theoretical analysis, the temperature rise equation in multiple heat sources welding is developed using the method of summation. Furthermore, on temperature distribution during welding, the effects of multiple heat sources, such as the number of heat sources and the distance between each electrodes, are considered quantitatively through the thermal conduction theoretical analysis. As the result, the distance between lead heat source and final heat source primally influences the area with the difference between a single heat source welding and multiple heat sources welding. Based on the results, it is expected to control temperature distribution near melted zone by more appropriate heat input characteristics, which is depended on heat source arrangement.