2017 Volume 35 Issue 2 Pages 9s-12s
In the current standard, diameters of upset weldable steel bar are restricted 16mm or less. In this study, we visualized the changes of welded part and the changes of temperature in the upset welding by using a high-speed camera. The specimens used in the experiment are SD390 steels with diameters of 19mm or more. Thus, in the upset welding of shear reinforcement with diameter of 32mm, it is possible to achieve a 100% joint efficiency by ensuring the optimum Joule heat by adjusting the welding pressure and the electric current. The two-color thermometry revealed that ensuring the joining temperature range (1300°C-1400°C) is important to secure the safe welding.