304 stainless steel screws

[hinged]

I have(2)304 stainless steel screws that are made by different mfr.
One mfr I know how they are formed, the other appears to be formed the same but I can't verify that.

Both are going into situations where they are being required to be non magnetic, or as little as possible.

Both screws are cold formed, have a 1/4-20 thread for 1" , 3/8" dia. x 1/8" thick shoulder and a 9/16" diameter x .100 thick head.

What will cause both to show a different magnetism from each other.

When I touch the end of one with a magnet it reacts as if it is "steel" and the other screw does not react as much.
The magnet i'm using is a neodymium magnet with 3.6 lbs pull.
The screw that acts as if "steel" has been passivated, demagnetized, the Gauss reading showed 0.0 and certified by the vendor that it is indeed 304 st stl.
Even after the demag process it still shows more magentism than the other screw.
I'm not holding the magnet on the part long enough to create a charge inthe screw, just touching the end and they pick up.
I have not yet had this material analyzed, that is the next step.

Any and all thoughts would be very much appreciated.

Regards,
Hinged

 

[Ron]

Cold working can increase magnetic sensitivity. Check the hardness of the two specimens...the harder one probably has higher magnetic response.

 

[hinged]

Ron,

Thank you for the reply, I did forget to indicate we did have the "steel" reacting sample solution annealed and it didn't appear to do anything.
Any other thoughts?

Regards,
Phil

 

[EdStainless]

Annealed? You mean at 2100F for 10 min?
It is either so loaded with martensite that it won't clean up in a simple anneal, or
it is not 304, and it is loaded with ferrite, or carbides, or other trash.
My guess is that it isn't really 304.

Gauss readings mean nothing. that would only tell you if it was magnetized. You need to know if it is ferromagnetic.

You don't really want to use fasteners like this. Have some made in S21904 (21-6-9, Nitronic 40) and don't anneal them.
They will be non-magnetic even as cold formed.



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Plymouth Tube

 

[TVP]

If the parts were properly annealed, and are still ferromagnetic, then I agree with EdStainless: the chemical composition is not Type 304. Did you order these fasteners to a consensus standard, such as ASTM A 193, ISO 3506, etc.?

 

[unclesyd]

If you have an an extra screw a very common way to get rid of the cold work induced magnetic properties is the heat to cherry red (in air is OK) and drop in water. This was part of some acceptance tests for years. To verify SS a quick dip %0/50 vol HNO3 RT will tell.

As stated above if it came from across the ponds there is no telling what it's made of. The majority of small SS fasteners are now from overseas.
To get a 304 SS fastener that is not ferromagnetic normally requires a special order.