Characterization of Soft Magnetic Composite Impeders

Induction tube welding is used for the continuous production of metallic tubes. These systems often utilize an internal magnetic flux controller (impeder) to improve process efficiency. This impeder is typically made of ferrites, and in the welding of small tubes (less than 1” OD), these materials can often become saturated, leading to a significant reduction in process efficiency. This provides an opportunity for these systems, in which the ferrite impeder has become saturated, for a material with a higher saturation flux density such as a soft magnetic composite (SMC) to greatly improve process efficiency and make welding of small tubes more energy efficient. Significant energy savings and increased productivity have been demonstrated both theoretically and practically when switching from the traditional ferrite impeder core to one made of an SMC. Typical energy savings for these trials ranged from 20-50%, with additional potential benefits of increasing production speeds and the ability to reduce the impeder size to limit the chances mechanical loss of the impeder.

To utilize the favorable magnetic properties of SMCs in these systems, the greater heat generated in these materials at equivalent magnetic loading needs to be properly managed with the available cooling water supply. A test stand has been constructed to create the conditions impeders ranging from 10-19mm OD would see in production, and trials have been run to fully characterize the levels of loading they can handle provided with sufficient cooling. The end goal of these trials is to be able to accurately determine the loading and required cooling for these impeders to survive in a production environment; reducing the risk of failure, which may stall adoption of this technology and limit the potential energy saving that could be realized given widespread adoption.