In this paper, the effectiveness of in-process control welding by additional cooling, which is one technique to reduce welding distortion, is investigated through experiments. The temperature distribution control during welding is performed by water-cooling. To reduce welding distortion more effectively, it is necessary to set the watercooling torch at an appropriate position behind the welding torch. Weldability is not affected by this additional cooling and welded material is not more hardened by rapid cooling. It is expected that inprocess control welding by additional cooling can be a useful technique for reducing welding distortion in practical applications.
It is well known that welding distortion has a negative influence on material properties, structural fabricability, and structural integrity. There are many methods to control or reduce welding distortion, but most methods involve costly processes in additions to welding. When manufacturing efficiency is considered, in-process control of welding distortion is more preferable than post-welding process or other methods. In-process control of welding distortion has been performed by using a restraint system, elastic pre-straining, pre-heating, or temperature distribution control by heating or cooling. In recent years, methods of temperature distribution control for reducing welding distortion have been studied. In these studies, temperature distribution during welding is controlled by another torch for heating or cooling, but not by a welding torch. An example of temperature distribution control by heating is back heating to reduce angular distortion. In-process control welding by back heating has been studied by the current authors (Mochizuki, Ohata, Takeno and Toyoda, 2000.) (Okano, Mochizuki and Toyoda, 2007.) and Zhang (Zhang, Zhang and Wu, 2007). Temperature distribution control by cooling has been studied by Guan (Guan, Guo, Li and Leggatt, 1994.) (Guan, Zhang and Guo, 1994.) and the current authors (Mochizuki, Yamasaki, Okano and Toyoda, 2005). In-process control welding by additional cooling has already been partially applied for thin plate structure in practical.
