Stainless Steel Lugs and Magnetism?

I have some old stainless steel lugs from Henry James. I noticed that some of them are magnetic,
and some aren’t. Pretty strongly magnetic, not barely magnetic. They most definitely are stainless - I soaked them overnight in salt water and they did not show any corrosion.

I was pretty sure that these were made of 304 or 316 stainless, which I thought was non-magnetic ?

Maybe the Foundry used 430 or (eek) 17-4 ?
Does the casting or polishing process induce magnetism ?

This stuff is confusing !

Thanks for any help or thoughts regarding this.

MF in SF

Here’s some info re. magnetism & corrosion resistance in stainless steels:

TLDR:
Not all stainless steels are non-magnetic.
Even ‘non-magnetic’ grades such as 304 and 316 can be magnetic if cold-worked or cast (unless they’re heat treated afterwards).

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I’ve seen 304 sheet become magnetic after getting sheared into smaller pieces. The parts I made with that material was still magnetic after machining. Frustrating to try to explain to the customer haha. That’s a really cool article JMY posted ^ good explanation. I bet those lugs are 304 and have been cold worked at some point in process.

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