steel annealing and magnetic properties 1

[arivel]

Hi everyone .
I would like to know the feasibility of building a field coil speaker.
I talked about it in these links:

https://www.eng-tips.com/viewthread.cfm?qid=502574

https://www.eng-tips.com/viewthread.cfm?qid=504490

https://www.eng-tips.com/viewthread.cfm?qid=504785

I ask you this question:
I read on the net that the magnetic characteristics can be improved by annealing steel with a low carbon content, but by how much?
and what are the magnetic properties that are improved?
saturation ?
permeability ?

 

[MagBen]

Anneal won't increase saturation much but could improve permeability drastically. wet H2 is the most effectively to remove carbon, dry H2 to remove S. both C and S can act as pins to magnetic domain movement so lower permeability.
There exists a commercial low carbon steel, electrical iron, melted in vacuum to knock down as much as impurities. carbon content can be as low as a few ppm.

 

[EdStainless]

Cold work from machining will impact perm, but not saturation.
I have done these extended anneals (18 hrs at 2700F with slow cool) for parts used in measurement equipment.
To maximize properties you really need to go back and reanneal these parts at 1475F.
Non-metallic (C, S, O, N) impurities hurt properties but metallic (P, Ni, Cu, Mn) ones in small amounts do not.
We actually started using 1001ELI (now commonly called EDDS) and it was always less than 0.005%C.
And even though the spec is 0.02%S max it was typically 0.0007%.

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P.E. Metallurgy, consulting work welcomed

 

[arivel]

thanks everyone for the replies

 

[arivel]

I tried searching for 1001ELI (EDDS) but it appears to be a deep drawing metal, produced in sheet metal form only.
I'm in Europe and more precisely in Italy so I think that around here a different nomenclature-classification is used, but knowing it I could facilitate the search. You know something about this ? .

 

[EdStainless]

Find a mill that makes the grade and see if they will sell material at a gage thicker than the final sheet gage.
We used to see this material up to 3-4mm commonly with some even heavier.

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P.E. Metallurgy, consulting work welcomed

 

[arivel]

I'm sorry but I'm Italian and I'm forced to use the automatic translator from which I obtained an incomprehensible text. Would you be so kind as to explain in other words?.
I need it in the form of solid cylindrical bars and tube.

 

[EdStainless]

If the supplier is rolling thin sheet, then they are starting from thick slabs and rolled to plate thicknesses as part of the process.
You may be able to get some of this alloy in gauge that is thicker than the finished sheet.
It would likely be a piece of plate.
And then you would have shape and machine the parts that you want out of it.

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P.E. Metallurgy, consulting work welcomed

 

[arivel]

if I find a small artisan foundry, can I melt EDDS steel starting from sheet metal to obtain the shape I want? .
with the second fusion, do the characteristics of the steel change, such as carbon and gas content?

 

[arivel]

or I could laser cut a package of laminations and then stack them together but is it possible to weld them together?

 

[EdStainless]

This stuff should weld easily.
Use TIG, Ar shield, and no filler.

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P.E. Metallurgy, consulting work welcomed

 

[MagBen]

For a field coil speaker in your case, using laminations possibly won't gain you too much benefit since eddy current losses probably not a big deal. you could simply purchase a low carbon steel, even 1005/1008 if 1001 is not easy to get. If the steel was forged or cold worked, you should at least do a stress relief anneal. If only slightly worked, use as-is may still work.