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Old 10-06-2005, 10:17 AM
rudiekazu rudiekazu is offline
Join Date: Oct 2005
Posts: 1
Default Demagnetizing

were having a hard time welding a water catcher out of a de-scale box in the rolling mill at Mittal Steel Riverdale.the de-scale box blast's high pressure water on both sides of the slab before it enters the rolling mill stands, taking all the scale off the slab. the water catcher is made from an astralloy to minimize erosion. what ever happens during operation magnetize's the bagee-bee's out of the water catcher. we can hardly even scarf the crack out with a torch. any insight would be very welcome.
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Old 10-06-2005, 12:47 PM
houlibar's Avatar
houlibar houlibar is offline
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Join Date: Jul 2005
Location: SoCal, most advanced third world country
Posts: 1,893

Welcome to the forum.

I'm assuming the equipment has been magnetized by the high pressure water jets. The friction of the water creates a static electrical charge. (This is why mobile fueling trucks are grounded before fuel delivery. The friction of the tires builds a static charge.) Also minerals in the water will have polarity and water will act as a conductor. You can see what I mean if you borrow a conductivity meter from the boilerhouse water lab and test the water.

I can't really tell you how to fix the problem. But maybe get you going in the right direction. To demagnetize the equipment you will have to reverse the polarity of the magnetic field it generates. You'll have to create a coil around the equipment and induce a polarized charge with a large generator.

You may want to consult with a local outfit that does stress relieving of welding piping. Stress relieving is done by wiring the pipe to a DC generator and shorting it to ground so it builds intense heat. Both the time and temperature are controlled for the desired result. Anyway, those guys are probably very familiar with magnetic objects and certainly have the equipment and experience.

Here's some reading on the subject of unwanted magnetizm:

A ShopFloorTalk thread on demagnetizing

A technical Paper on Demagnetizing

Hope this has been some help.
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