In the building structure field, welding robots have been used since the latter half of the 1980s. Today, a large number of robots are used mainly for in-factory welding of column components.
As for steel frames of buildings, the welding of single bevel T-joints with steel backing is usually used. Recently, there have been some experimental reports concerning a 25-degree groove welding by semi-automatic arc welding.
In the report, the authors demonstrated the relationship between groove angles and welding conditions from the viewpoint of hot crack occurrence, penetration and shrinkage in the first layer welding, using steel frames welding specimens of straight-line welding joints. In particular, these various experiments showed that though the groove angles and welding conditions were similar, there were differences in hot crack occurrence due to the binding forces.
In this actual study, based on the experimental results in the above, we were able to demonstrate the relationship between groove angles and welding conditions of the first layer in specimens where square steel tubes and diaphragm were joined together. And, we also performed full-layer welding using a 30-degree angle groove. The results were successful and the probability of using welding robots for such columns was confirmed on a 30-degree angle groove.
Shortening the welding time leads to a reduction of greenhouse gas emissions. Therefore, as this is an environmental improvement, we expect this welding process in the steel frames of buildings to become attractive.