FSW is a method of pushing the rotating tool (FSW tool) between the materials to be joined and joining by moving the tool along the joining line.
The materials to be joined are softened by the friction heat generated between the tool and the materials, are mixed by the rotating tool, and then joined.
The use of this joining method, unlike conventional arc welding, can join materials without melting them, resulting in less deformation after joining, less joining defects, and high quality and low product cost. It is also an energy-saving method compared to conventional joining methods.
Currently, it is widely used as a joining technology for aluminum alloys of low melting point, allowing it to be used in manufacturing railway cars and automobiles.
On the other hand, the steel FSW with a higher melting point has been considered difficult for use as a joining tool because the tip of the tool becomes excessively hot due to frictional heat, severely damaging the tool.
In particular, FSW of austenitic stainless steel with high deformation resistance at high temperature has poor durability and high price, so a durable and inexpensive tool material has been desired. In collaboration with Nippon ITF and Tohoku University, we have developed a tool material for steel FSW and have started selling samples.
By applying a ceramic coating that has excellent wear resistance to a low cost tungsten alloy that does not use expensive elements, we have provided the following characteristics to the tool. Our goal is to achieve price lower than the tool currently considered to be the most reasonable while achieving higher durability and longer service life than the conventional low cost tool materials. We have confirmed that the austenitic stainless steel, the most difficult FSW among steels, is a material capable of wire bonding of 10 m or more with a joining depth of 4 mm.
The tungsten based tool material we have developed is also effective for FSW such as carbon steel, high tensile strength steel, low alloy steel and copper alloy other than stainless steel. It is expected to be incorporated into various industries including electric and chemical plants, railway cars, and semiconductor manufacturing equipment using vacuum containers.