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De-magnetizing AISI 304 fasteners without spoiling surface finish

sir,
we have a quantity of ss 304 grade bolts which got magnetized due to cold working. for customers specs, we need to de-magnetize these, but are afraid that stress relieving will spoil the surface finish. Is it possible to do it electrically or any other way so as the surface finish is maintained?

Sumeer Aggarwal
alloy steel wire and products manufacturer - New Delhi, India
June 21, 2011

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Hi, Sumeer.

To my limited knowledge you can easily remove any magnetism with an electrical degausser, but you cannot remove ferromagnetism with a degausser. That is, you can make the item not attract an iron nail, but you can't make it not attract a magnet.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
June 24, 2011

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When we want to get rid of the ferromagnetic characteristic of 300 series stainless steel that comes with cold working, we stress relieve at 900 degrees C or anneal at 1066 degrees C. If done properly in a protective atmosphere, the surface finish will not change. A complication is that to avoid sensitization of the stainless steel, a fast cool is required. We use small loads within our vacuum furnaces, and a forced gas quench (the small loads assist the cooling rate).

Good luck!

Lee Gearhart
metallurgist - E. Aurora, New York
June 26, 2011