Looking for advice on permaible metals

[magnasanti]

I need a decently permeable metal that is at least as good as 1018 steel or stainless 416. There is a metallurgical worker who had a special blend
of stainless called AL631-17CR 7NI. Here is the analysis C .072; MN .74; P.019; S.001; SI .480; CR 16.59; NI 7.22; AL .810; MO .280; CU .440; TI .04. I need to know if this stainless steel can be used. FEMM Does not have it in the library.

 

[dgallup]

That looks like Carpenter Custom 631 (17Cr-7Ni) Stainless which is described as "semi-austenitic, precipitation-hardening stainless steel that provides high strength when sufficiently cold drawn and then aged. Corrosion resistance is similar to Type 304. Carpenter Custom 631 (17Cr-7Ni) is designed to provide an austenitic structure in the annealed condition with excellent cold drawability. To achieve age-hardening properties, Carpenter Custom 631 (17Cr-7Ni) must be cold drawn."

So in the annealed case the permeability would be very low. Hardened it will go up but probably not as much as you want. I have no mag prop data for it, try contacting Carpenter, they could at least test it for you if you promise to buy 20,000 lbs.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[MagBen]

Do you mean magnetic permeability? and you wanted to have as high as possbile permeability? The composition listed fits Carpenter's "Custom 631 AISI Type 631", but it is a semi-austenic SS including austentic, martensic and maybe a small amount of ferrite as well. The permeability is expected to be lower than 416, 1018. solution treatment could get 100% austentic with a permeabiltiy of close to 1, like air or 3xx SS.
"Custom 631 AISI Type 631" was not designed for magnetic applications.

 

[EdStainless]

Actually 17-7PH is used in a lot of magnetic applications.
When you age it it becomes very ferromagnetic.
So if you need an assemble that is both magnetic and non-magnetic (think two cores on a common shaft) you can machine the part, age it, then induction anneal a ring in the center and you end up with two solenoid cores attached to each other and magnetically isolated without and brazing to mechanical fasteners.

But it is crap for a non-magnetic material.

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Plymouth Tube

 

[MagBen]

Ed, sounds an interesting application. people may use its magnetic proeprties. Austenite condition, max DC permeability=1.4-3.6 , marentsite: max perm=134-208.
Carpenter makes ferritic Stainless steels specially for magnetic applicaitons: Chrome Core 8, 12, 13, 18 (Cr content) and 430F for solenoids and Fuel injectors applications. max permeability can be as high as 3,000 (8 and 12Ni). 18Ni Chrome core has a max perm 1,500.