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Best stainless material to replace laminations in brushless stator

Best stainless material to replace laminations in brushless stator

Best stainless material to replace laminations in brushless stator

(OP)
I am planning to use magnetic stainless instead of laminations in a brushless motor. Of course the Eddy currents will be higher than with laminations but at low speed it should be fine.
I as wondering what kind of SS would be most appropriate for such application. High saturation is a must, as well as high resistivity. But what about hysteresis losses? What is the difference between the following materials for resistivity, saturation and hysteresis losses (coercivity)? Also, there is certainly a difference between annealed and hardened conditions, or annealed and cold-worked condition, etc.

304
316
430F
446
416
410
420
440B
17-4
etc

Or maybe easier to answer, what stainless material is typically used in brushless motor rotors (on which the magnets are glued)?
I need solid bars of about 2 inches diameter.
Thanks for your help!

RE: Best stainless material to replace laminations in brushless stator

If the permeability of the stainless is much less than the permeability of the laminations you will see a corresponding reduction in the magnetic field strength.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Best stainless material to replace laminations in brushless stator

I believe Carpenter specializes in producing these stainless alloys with specific magnetic properties. IE; you can get AISI 304 from Carpenter guaranteed with low permeability or guaranteed with a certain level of permeability.
https://www.cartech.com/en/product-solutions/

STF

RE: Best stainless material to replace laminations in brushless stator

Well you can rule out all 300 series alloys since they are not ferromagnetic.
There are a few 400 series alloys that are made with controlled magnetic properties.
But usually it is just initial perm and saturation.
Cartech is one of the largest suppliers of these, they are usually used in DC applications such as relays and solenoids.
The hysteresis losses at anything above a few Hz will be >10x that of Si steels.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Best stainless material to replace laminations in brushless stator

Skip 300 that are faint ferromagnetic at RT even at cold worked condition

Avoid 400 martensitic SS (410, 416, 420, 440), and PH grades (17-4), the mircostructure can pin the magnetic domain leading to high hysteresis losses.

The only choice is ferrite SS among which there is a trade-off. High Cr offers better corrosion, higher resitivity, but lower saturation, sometimes higher coercivity.

Annealed vs. cold-worked condition vs. hardened: annealed only.

And yes, bulk ferrite stainless can be used in brushless motor rotors (low frequency/speed). check with Carpenter for low Cr ferrite stainless alloys, e.g. Chrome core 8, 12,13, 430 etc. which are designed for solenoid and fuel injectors applications.

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