Induction shrink-fitting is used for insertion of one metal part into a second metal part. The second metal part is heated just enough that the metal slightly expands, allowing easy insertion of the first part. Once cooled, the parts cannot be separated without significant force, or by reheating and reversing the process.
The induction shrink fitting process requires little or no pressure for assembly and is preferred in mechanical assembly of delicate parts where you can not apply mechanical pressure.
The main advantages of thermal shrink fitting are the reduction of stresses and residual deformations. It is also a quick and effortless process with less risk of mechanical damage to the component.
Typically the lower temperature range is used on metals such as aluminum and higher temperatures are used on metals such as low/medium carbon steels. The low temperature avoids degrading of mechanical properties
Metals typically expand in response to heating and contract on cooling; this dimensional response to temperature change is expressed as a coefficient of thermal expansion.

Advantages/Benefits of Shrink fitting:

The induction heater heats only the part not the atmosphere around it, making the process energy efficient and fast Process consistency and repeatability.

The induction heating process produces a highly uniform and consistent heat.

This often allows less heat to be used for a given process. Easy reversibility of the process for removal.