You haven't provided too much info to go on, but low-carbon annealed steel/iron is usually a good choice.

I commonly use machined 1215 Low Carbon Steel for this type of application.  It's low carbon content, low cost, ease of machining, combined with being readily available make it a good choice. Have it annealed once all machining is complete for the best properties, although it generally works fine without annealing.

-Tony Staples
www.tscombustion.com

If these are small and the forces are low they you can look at lower C steels.  The deep drawing grades that are used for appliances are variations of 1004-1005 with lower inclusion contents.

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I assume your suggestions the best materials are low carbon steel followed by an annealing process. The forces during operation are rather high for this type of micro- motor.

Thank you Tony & Ed for your response!

MMPD

You don't really tell us much about your requirements.  What is "best" to you?  Low cost, easy to fabricate, high permeability, high flux density, high resistivity, high strength or good corrosion resistance?  12L14 or 1215 is a good low cost option & may be good enough but you say this is a "high performance" application.  The lower carbon steels like 1005 may be a bit better magnetically will be harder to machine and so soft they yield easily.  It is conceivable that you might want to use silicon iron for higher electrical resistivity.  Or you might want to look at ferritic stainless like 430FR if you need corrosion resistance.  If you need really high flux density you want 50% iron cobalt.  

Requirements:

High permeability, high flux density, high resistivity, good strength, and good machining characteristics. Cost is not a real concern since the housing OD is under one inch.

Looking for the best material with the best magnetic properties as described above.

Thanks,

MMPD  

Ah, now we have a clearer picture.  In order to satisfy all of those requirements, and cost and corrosion not being much of a concern, then I would recommend Carpenter Silicon Core Iron B-FM.  It is a great for permeability, flux density, resistivity, strength, and the FM variety is a free machining grade.  It has only one drawback; It's available in bar form, but it can be a real pain to find.  You need to call Carpenter and find out what diameter bars they may have available.

In lieu of that, if you can live with lower resistivity, I would use 1215, which you can get from McMaster-Carr all day long.

-Tony Staples
www.tscombustion.com

Tony:

I have been looking at the Carpenter "magnetic steels" including Carpenter Electricla Iron. Your suggestion of Carpenter Silicon Core Iron B-FM is right in line with Carpenters information as listed on the Carpenter web site. Bar form is fine; my OD requierements are <.750".

Thanks,

MMPD

MMPD,

I know they make it in .875" diameter, because that's how one of my suppliers purchased it when I was at a previous employer! They may be willing to sell you some if they keep any in inventory, or else, the next time they do a mill run for my former supplier.

-Tony Staples
www.tscombustion.com

Tony:

I have a call in to Carpenter Steel and will know shortly what is available and when. Carpenter's vast selection of "magnetic or electrical steels" should yield positive results.

Thanks again,

MMPD