Friction plunge welding is a technique for joining dissimilar materials. One of its simplest forms is shown in the illustration. In this case, a pre-shaped stud of relatively hard material has been joined to a plate made from a relatively soft material.
The stud is rotated and its specially shaped probe forced into the plate. This creates frictional heat and a zone of plasticised material in the softer plate. Plasticised material flows around the probe; the shoulder pushes this material back on to the probe and prevents it being lost from the joint.
After rotation is stopped, the plasticised material cools and locks the stud into the plate. Depending on the materials being joined, a metallurgical bond may also be formed. No part of the stud deforms or is consumed in the process.
The process also works in reverse as it is possible to force a softer material into a hole in a hard material.
Careful consideration must be given to design to ensure optimum joint performance.
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