52539

300 series SS fasteners are affecting compass

July 6, 2009

We have some bolts that we purchased from a local distributor. We have molded them into plastic (ABS) and shipped to our customer. Our customers product has a compass in it and we are now being advised that the bolts are magnetic and affecting the compass.

We can de-magnetize but customer feels this not solve problem. They want us to re-run using 18-8 SS. We thought 18-8 was 300 series already ? What gives? Can the 302HQ SS become magnetic ? If so, how ? If we demagnetize, can it become magnetized again ?

Bob Baer
Fastener Dist. / Mfg - Wheeling, Illinois

Find a shop that does mag particle inspection and have them run the boxes thru the degaussing system until they will not deflect a compass. It works. In war II they degaussed entire ships.
The 302 is essentially 18-8, but not quite. 300 SS can be work hardened and become slightly magnetic, because nickel is "paramagnetic".

Don't use the word "demagnetized" and you will be fine.

The only way that it can be remagnetized is to subject the box to a strong magnetic field.

James Watts
- FL

Bob's use of the word "magnetic" might be meant simply to indicate that they are attracted to a magnet, not necessarily that they are themselves acting as magnets.

Many 300 series stainless steels, which are not attracted to a magnet when in the fully soft solution-annealed condition, become ferromagnetic (attracted to a magnet) when cold-worked.
If this is what Bob means, then too bad as it is an inherent property of the material. You could change to bolts made from K-500 Monel, which is totally non-ferromagnetic.

Bill Reynolds    consultant metallurgist Ballarat, Victoria, Australia