超音波接合に関する研究(第1報)

Abstract

The contact face of materials to be joined recieves compression and shearing force under ultrasonic vibration, with becomes hot by friction, and then both the metallic faces are exposed, metallic atoms appreaching mutually; in this way ultrasonic welding is done through mutual attactive force and diffusion of metallic atoms.In this joining method, the joined state sometimes becomes crescent-or ring-shaped, but in order to get perfect (the whole area) joining, it is necessary for to chose the conditions so as to give enough compression and shearing force.There are many factors that influence heat generation at the contact face of materials to be joined, of which particularly effective conditions are described below.1. Ultrasonic power: The greater it is, the higher is temperature rise.2. Tip pressure: The lower it is, the higher becomes temperature rise. But under the same ultraso nic power, tip pressure for the highest temperature at the contact face of materials has some limit, which increases with increase of ultrasonic power.3. Joining time: Temperature immediately rises within 1 to 2 sec., but thereafter becomes almost constant.4. Materials to be joined and sheet thickness: The harder the material is (of cource enough compression and shearing force must be given) and the thinner the sheet is, the higher is temperature rise.5. As the contact face of differently thick materials, the temperature is higher under the condition when a thinner sheet is placed on the tip side than when a thicker sheet is done, and the thinner is the sheet on the tip side, the higher is the temperature rise.Therefors joinability (workability) by ultrasonic welding is almost dependent on materials and their sheet thickness to be placed on the tip side.In this study, we observed a temperature rise over 700°C.The relationship between joining strength and conditions is proportional to the relationship between temperature rise at the contact face of materials to be joined and ultrasonic vibrating conditions which elevate the temperature, and All of 0.08 mm titanium, aluminum and copper were fractured in the base metal around nugget of joining part. The effects of joining conditions on joining properties are as follows:1. Ultrasonic power: The greater it is, the higher is joining strength. But tip or anvil and material to be ioined are often ioined.2. Joining time: Within the limits in which the material to be joined is not joined with tip or anvil, the longer the better.3. Tip pressure: When the joining strength is proportional to the joining area, tip pressure had better be high to the effect that nugget diameter is enlarged.4. Surface condition of the material to be joined: The cleaner the surface, the higher is the joining strength, especially electrolytically polished material is excellent.In joining titanium to titanium or titanium to stainless steel, tip pressure (50 to 60%), ultrasonic power (40 to 70%) and joining time (over 100%) should be increased in comparison with the joining condition of same thickness aluminum sheet. And using of convex anvil is efficient.Joinability (workability) and joining strength by ultrasonic welding were improved by means of electrolytically polishing the material to be joined and using suitably insert.