Summary
- The low-temperature friction stir welding technology enables joining at temperatures below the A1 point, where the heat of friction on the joining surface does not cause transformation of the crystalline state, by applying the appropriate pressure using a joining tool.
- By suppressing thermal effects, strength degradation does not occur and the strength of the joined material remains the same as that of the base material.
- We propose patent licenses for this technology to manufacturers of joining equipment and to companies in the automotive, railroad, and infrastructure industries that use joining equipment.
Technology Overview & Background
Friction stir welding (FSW) is a joining technique in which a cylindrical welding tool is pressed against a plate-shaped joining material while rotating to soften the joining material by frictional heat generated by the tool, and then the joint is stirred. Compared with conventional fusion welding, this method is widely used because it reduces the deterioration of the joint strength, but it does not completely prevent the deterioration of the joint strength.
Professor Fujii of Osaka University has developed a method to reduce the strength degradation of the bonded area to zero. By applying sufficient pressure while keeping the rotation speed low, this method can join materials in the solid state at a temperature lower than the crystal transformation point (A1 point) of the joining surface. This allows joining without any degradation of the joined area and without heat affected zones, and joints with tensile strength equal to or greater than that of the base metal are achieved with medium to high carbon steels.
Data
In a lap joint of two S45C plates 1 mm thick, a WC-Ni cemented carbide tool was used under conventional conditions (tool rotation speed: 200-1200 rpm, tool pressure: 4.5 tons) and low heat input conditions (low rotation type, tool rotation speed: 30,50 rpm, tool pressure: 12,15 tons). The results of tensile tests afterwards showed that the joints broke under the conventional conditions, but not under the low heat input conditions.
Patent(s)
Patent 6579596 in Japan
Principal Investigator & Academic Institution
Prof. Hidetoshi Fujii Osaka University, Joining and Welding Research Institute
Expectations
- If any company is interested in developing a joining device that incorporates this technology, we propose to develop the device in collaboration with Osaka University. We can also provide technical guidance for practical application.
- If your company is in need of joining equipment using this technology, please contact us. We will propose a joint research and development system with Osaka University to see if it is possible to join the metals used by your company.
- We are also available for direct meetings with researchers regarding this invention/project.
Project No.DA-01264a