Magnetic Permeability of stressed SS 4

[Ron07663]

I am designing a deep drawn SS can to be a shield for a magnetic sensor. We need the relative permeability of the shield to be as close to 1 as possible so as to not interfere with the sensor. Annealed 304 or 316 SS should be on the order of 1.0 to 1.02. What can I expect the permeability value to be for stressed 304 and 316?

 

[mcguire]

Thanks very much for the information.

 

[mcguire]

If I were doing hulls I would want more austenite stability and pitting resistance than 304 has to make sure no SCC or perforation. What thicknesses are such hulls, if you can say without violating the "secrets act"?

 

[Ron07663]

It is a big issue for ships and submarines! See these references:

http://asm.confex.com/asm/ms2004/techprogram/paper_5090.htm

http://www.nidi.org/nickel/0999/5-0999n.shtml

Ron

 

[EdStainless]

There have been large scale tests looking at using AL-6XN for ship hulls for mine sweepers.
Resists corrosion
very non-magnetic
strong
high ductility = high damage tolerance

But not at todays prices.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[unclesyd]

The Navy did make two SS mine sweepers during WWII but they had cracking problems so they went back to wood.
The Calypso was a ex wooden mine sweeper.

As posted above its an ongoing thing of who is the better at hiding, finding, or blowing up the other, with this work being carried out not far from me. They don't kill as many fish as they use to as electronics have taken over.

 

[vantveen]

Does anyone know the permeability of stainless steel at ambient and at cryogenic (4 Kelvin)temperature?

 

[mcguire]

Vanteen
This topic is worth a separate thread. It of course depends upon which grade of stainless, but so are actually anti-ferromagnetic near 0 K.

As far as AL6XN for naval vessels, I understand they are getting some major attention because of their superior resistance to explosions ( as distinct from projectile penetration ) and their better acoustic signature than other non-magnetic materials. This alloy beats titanium and HSS armor plate materials.

 

[Ron07663]

FYI:
I found this reference on the magnetic effects of Stainless. It is a good summary with Cold Work vs. Permeability chart. It is written for the non-metallurgist.

http://www.assda.asn.au/data/portal/00007704/content/52067001080540743296.pdf

Ron

 

[Ron07663]

I thought I would follow up on this thread and basicly close it out.
We ran sample parts out of our deep draw tool of both 316 SS and 305 SS. The 305 was selected for Ni content of 12% or greater.
The 316 parts had a measured permeability of 1.15 right out of the tool and 1.0003 after solution anneal.
The 305 parts measured 1.003 right out of the tool.
Our specification required 1.05 MAX. So, if 316 were used, we would require a post draw anneal.

Thanks again for everyones help with this.

 

[unclesyd]

Thanks for the follow up on a successful resolution of your problem as it doesn't happen very.