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Old 01-28-2019, 08:09 PM
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Default Stainless question

I made two knurled nuts out of non magnetic stainless and after I knurled them the knurled part is magnetic I can only think that I have used the knurling tool on plain old steel that the stainless is now impregnated with steel. What do we think about that?
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Old 01-28-2019, 08:37 PM
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Your knurling must have disrupted some electrons. It's all magic that I know little about.
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Last edited by Tim KS; 01-28-2019 at 08:43 PM.
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Old 01-28-2019, 09:09 PM
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I am not sure this is correct, but I thought some stainless steels will work harden and become slightly magnetic. It might have some steel transferred from the knurling. One way to test that is to get them wet and see if they rust up.


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Old 01-28-2019, 09:13 PM
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I do not know about how they got magnetized, however, I will say they are very good looking parts.

Do you want to make them non or less magnetic?

Scott
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Old 01-28-2019, 10:02 PM
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I think Brian nailed it. I have had that happen to me once.
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Old 01-28-2019, 10:27 PM
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Perhaps it is not magntic, but due to the compression it has undergone is developing it's own gravitational pull..

The difference between magnetic(ferritic) and non magnetic (austentic) is primarily the crystalline structure. Any cold working can begin to change the stucture from austentic to ferritic. I'm sure there are better explanations online, and I take no blame for any spelling errors.
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Old 01-29-2019, 01:52 AM
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Quote:
Originally Posted by Walker View Post
Perhaps it is not magntic, but due to the compression it has undergone is developing it's own gravitational pull..

The difference between magnetic(ferritic) and non magnetic (austentic) is primarily the crystalline structure. Any cold working can begin to change the stucture from austentic to ferritic. I'm sure there are better explanations online, and I take no blame for any spelling errors.
I believe you are closer to right, I have read about this before and it would have to do with the piece being in a high-speed motion under pressure and temperature change as the metal does warm and cool very fast may not be of high temps but I think that is where the speed of turning and pressure come in... IDK but maybe kind of like rubbing a needle on something to magnetize it to make an emergency campus

Not saying I understood or fully understood what I was reading at the time but it seemed plausible...

Buy Hey, what do I know...
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Old 01-29-2019, 10:44 AM
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Quote:
Originally Posted by Walker View Post
The difference between magnetic(ferritic) and non magnetic (austentic) is
primarily the crystalline structure. Any cold working can begin to change
the stucture from austentic to ferritic. I'm sure there are better explanations
online, and I take no blame for any spelling errors.
Yup, you got it, by working the steel you have changed the structure enough
that it is magnetic. BTW you never mentioned what alloy of SS you were
using.

Annealing the parts now will likely get them back to non-magnetic.
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Old 01-29-2019, 11:58 AM
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Quote:
Originally Posted by Shade Tree Welder View Post
Yup, you got it, by working the steel you have changed the structure enough
that it is magnetic. BTW you never mentioned what alloy of SS you were
using.

Annealing the parts now will likely get them back to non-magnetic.
I have no idea what kind of stainless it was a drive shaft for a pump off of a lawn truck sprayer
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Old 01-30-2019, 10:31 AM
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A few bits of info:

Wrought, austenitic stainless steels, such as 304 and 316, are generally regarded as non-magnetic in the annealed condition, ie they are not attracted significantly by a magnet. However, if they are cold worked they will be attracted to a permanent magnet.
---
It is possible for the magnetic permeability of austenitic steels to be changed during processing. For example, cold work and welding are liable to increase the amount of martensite and ferrite respectively in the steel. A familiar example is in a stainless steel sink where the flat drainer has little magnetic response whereas the pressed bowl has a higher response due to the formation of martensite particularly in the corners.
---
https://www.finishing.com/454/35.shtml
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