Induction Heating causing Magnetized Bearings

[dArsonval]

An old topic among those who have forgotten half or all of what they've learned
along the way... and I'll plead guilty for not fully knowing much about this topic before posting
the following question. My modest search has proved no useful info... so I've landed back here.

Electrical Apparatus Repair has long involved the process of heating components to meet
various "fits" during the assembly process... as well as getting "things" dismantled.

The process of heating "Bearings" to expand their dimensional fit for a particular installation or removal
is achieved numerous ways. Most all of us here know this.

In using an Alternating Current Induction method... it's long been known... this process
magnetizes the component being heated... and some additional procedure is necessary for the
heated item to be "rid of" any (magnetized [component] attributes).

Is it achieved by "ramping-down" the alternating current to a [zero value]...
before removing the component/bearing from the inductive environment?

How is a bearing removed from an induction heating process... to avoid being magnetized?

John

 

[MikeHalloran]

The simplest way is to withdraw the assembly/component axially from the field, slowly.

Slowly in this context can mean a time from from seconds to minutes.

You can tell when you're far enough away from the field by holding a screwdriver.



Related fun fact: One easy way to magnetize a screwdriver is to turn off the field while the screwdriver is within the aperture of a degaussing coil (or the field assembly of a shaded pole motor). It may take a couple of tries to get it really strong, but the odds of switching off the coil on a zero crossing are pretty small.



Mike Halloran
Pembroke Pines, FL, USA