Best steel for DC electromagnet

[Sgalb]

All,

I've read a number of threads that indicate 1018 steel annealed and 430 stainless are commonly used for solonoids.

My design problem is to pick the best material for a DC electromagnet. Would sombody please recommend a material, either one of the two I mentioned or something different?

Thank you.

 

[BobM3]

"Best" in terms of what? There are materials with higher permeabilities than the two you mentioned but at added cost.

 

[Sgalb]

BobM3,

Good point. I'm looking for high permeability so I can get the strongest flux density for a given number of turns and current. Environment is not important because the part will be encapsulated. I'm not sure about saturation though. I'd probably start with permeability as the metric then compare saturations.

 

[Sgalb]

Also, cost is not important but availability for prototype and research activities is.

 

[Sgalb]

Sorry for the jumbled thread here, the material also needs to be machinable from 2-3" bar stock.

 

[remetaper]

Time ago, I found a very interesting technical paper about this subject. Now, I don't know if this paper is completely available ( fully !!! ) in web. However, this paper appeared in Hong Kong ( MAGIVAL, Shangay 2000,November) and it was a good tool for people who is neither metallurgists nor magnetic experts. Moreover , this paper was a usefull general info for machinability.
About your questioms, I think there is no difficulties if you explaine what you pretend in terms of:
1) magnetic properties ( Max. Permeability, Hc, Br )
2) how much is important machinability ?
3) Stainless or not ?
4) Is material easy available in stock ?
5) it is more easy to find a 3"bar stock of mild steel, Carbon or alloy steel than 430( free machined or not ) stainless grades. This depends on how many pound ( kg ) or tons you need for your design.
6) there is a lot of magnetic data available about 430 and similar grade : what do you want ?
7) Do you use the part as delivered and machined ( after turning , drilling and so on ...)or machined and annealed( stress relieved ) ? Vacuum or annealed and then machined in order to take away the stock remooving?
8) what is the final dimension ( thickness and leghth ) ?
9) Do you obtained Hollow or solid state blanks ?
10 What about magnetic testing ? Costs ? DC o AC ? How much it cost for a single sample?
Let me know if you need more info !

 

[dgallup]

12L14 is commonly used because of the good machineability. It's magnetic properties are usually "good enough" but it all depends on how sensitive your application is to various properties.

 

[BobM3]

Maybe the following will get you going:

http://www.matweb.com/search/datasheettext.aspx?matguid=86447df267114df98eadcc6df3b7f2f5

 

[dgallup]

While the nickel-irons offer the highest permeability, the saturation flux density is low. I'd be surprised if you can find it in 2-3" bar stock.

You will have to register but this is a link to an article on selecting soft magnetic alloys:

http://www.cartech.com/techarticles.aspx?id=1624

 

[Sgalb]

Thanks all

remetaper: Do you have a title for the paper? I can't locate it.

BobM3: Good link, will consider the material.

dgallup: Thanks for the 12L14 suggestion. My test house reccommended that also.

Steve

 

[sreid]

Use 1018 or 12L14. Roughly speaking the permiability will be about 1000 but can vary since the magnetic propertities are not controlled. Nickel [or Chrome plate] so they don't rust]. The more exotic magnetic material usually have higher saturation flux densities [not necessarilly higher permiability] at much greater cost.

 

[EdStainless]

If this is a DC application who would care about the perm?
Saturation is all that matters.
Any low carbon steel grade with less than 0.2%C that has been annealed at 1400-1475F with a slow cool should give very nice high saturation levels.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[remetaper]

SQALB: This is the link

http://www.valbruna-stainless-steel.com/magival.html

but I am noting that cutting data about machinability are disappeared compared to Magival Shangay,2000. I don't know the reason why.However these links ( Cartech and Valbruna ) are useful for beginners and students giving an idea about Magnetism and the choice of right steel grade.

SREID: In my opinion 1018 and 12L14 give permeability more than 1000 when annealed and slow cooled. Nevertheless, consider that Ni or Cr plating process ( after magnetic annealing)reduces permeability due to Hydrogen adsorbation. Several test of Silicon -Iron alloy confirm this problem . However a simple baking (390-400 F) after plating restores magnetic properties.
EDSTAINLESS: you are right : I fully agree !

 

[Sgalb]

Thanks guys,

My application is A-C and I'm looking to create a high Q sensor coil. I need to machine the metal to a particular size so standard cup-core ferrite is out of the question.

 

[Sgalb]

EdStainless,

Actually I have two projects. One is A-C the other is D-C.