A discussion of the relationship between heat input parameter and angular distortion by considering moving heat source effect

Abstract

In recent years, it has become much more necessary to control or reduce weld distortion, which has negative influences on structural integrity, without loss of manufacturing efficiency. Higher accurate prediction of weld distortion brings in one of the contributions for improvement of manufacturing efficiency. Commonly, angular distortion, which is controlled by temperature distribution along the direction of plate thickness, is controlled by heat input parameter (Q_net/h²). However, it is also known that there are several concerns against applicability of conventional heat input parameter for prediction of angular distortion. One of the concerns is the effect of welding speed. This is because the conventional heat input parameter is derived from welding thermal conduction theory without considering moving of the weld heat source. Actually, a pre-study by experiment about the effect of welding conditions, including welding speed, on angular distortion has shown that angular distortion is not always controlled by heat input parameter in the case of different welding speed. Then, in order to clarify the effect of welding speed on that, more detailed study is further required. In this paper, a numerical study on the effect of welding speed on the relationship between heat input parameter and angular distortion is performed based on the past experimental results. In addition, the reason why the relationship between heat input parameter and angular distortion is affected by welding speed is discussed from a viewpoint of distribution of the maximum temperature rise and residual plastic strain. It is concluded that the effect of welding speed on the relationship between heat input parameter and angular distortion is understood by the difference in distribution of mechanical melting temperature, which identifies the distribution of residual plastic strain for angular distortion, in plate thickness section.

Keywords::

• angular distortion
• heat input parameter
• welding speed
• temperature distribution
• TIG welding

Acknowledgements

We should like to express our profound gratitude to Professor Murakawa Hidekazu of the Joining and Welding Research Institute, Osaka University, and Professor Terasaki Toshio of Kyushu University for their valuable advice during this study.