Project nominated for the Innovation of the Year Steelie Award 2022
Arc welding is a necessary and indispensable technology for manufacturing steel structures in the construction, steel frame, construction machinery and shipbuilding fields, but there is a chronic shortage of welding engineers engaged in welding work throughout Japan.
In the past, it had been proposed that the shortening of welding time can be realised by “ultra-narrow groove welding,” which can substantially reduce the amount of welding.
However, because it is extremely difficult to perform sound welding in ultra-narrow groove welding due to the generation of spatter (scattered molten metal) and lack of penetration, it was not possible to solve these problems with the existing technology.
JFE Steel developed a high-efficiency ultra-narrow groove welding system that can solve the above-mentioned problems, thereby reducing welding time considerably.
The world’s first optimum CO2 gas-shielded arc welding method in ultra-narrow groove welding with both ultra-low spatter welding and strong and stable arc directivity with deep penetration was developed by adding an appropriate amount of REM (rare earth metal) to the welding wire and setting the polarity to “wire negative,” which is the opposite of the conventional technology.
A novel ultra-narrow groove welding system, which combines a slightly bent contact tip (the part which supplies electricity to the wire) and a welding torch capable of 180° reversal, was also developed. Utilising the strong directivity of the arc, a deep penetration depth was secured by promoting melting in the weld and optimising the deposition method. As a result, this technology achieved ultra-narrow groove welding with absolutely no lack of penetration, which had been the greatest challenge.
By realising ultra-narrow groove welding, the amount of welding was significantly reduced to 1/3 of the conventional level. In addition, a further shortening of work time has also become possible by the omission of spatter removal work by ultra-low spatter welding and the omission of post-welding straightening work by reduction of welding heat distortion.
As a result of the high evaluation of the merits of the developed technology, it has been applied in the construction of an office building in the Tokyo Metropolitan area, jackets at Haneda International Airport, and the welding of tunnel segments and a large-scale oil tanker.
It has also contributed to the early restoration of Kumamoto Castle, which was severely damaged in a series of giant earthquakes in 2016.