Layman needs help finding the right material...

[gnarbro]

hello all, hopefully you can help me. i'm wanting to wind some small electromagnet coils. the coil cores are .375" in diameter. i need a really soft steel as well low carbon content. will it be hard for me to find 1008 rod? should i then have the rod annealed? basically, i would like to know the most available type of steel that is closest to what i need and where i could find it. any help is greatly appreciated. if you need more info to understand what i need let me know. thanks!

 

[EdStainless]

How long are the cores? I am thinking that you might want to punch slugs from sheet. I have used 1002EIL for cores. This is the stuff that the appliance companies use for deep forming appliance cases.

In either case, yes you should Hydrogen anneal after the cores are cut and/or formed.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[gnarbro]

thanks for the reply. the cores will vary in lengths but mainly around an inch. is 1002eil easily obtained? what does EIL stand for? i've heard of silicon or relay steel, has anyone used this for cores? is it available in the size i need? thanks again.

 

[sreid]

If this is just a DC,say, electromagnet then 1018 steel shoud work fine.

For 60 Hz AC, silicon steel is used to increase the resistance to eddy currents. The core is built up from thin sheets also to minimize eddy current losses. The laminations must be electrically insulated from each other usually by converting the lamination surfaces to black iron oxide. Search for Tempel steel.

 

[EdStainless]

ELI is extra low interstitial, these are high formability or deap draw steels. No, My plan wouldn't work for 1" long parts.
If this is DC, and switching speed isn't important, then any low carbon steel that has been annealed should be fine. Stay away from free machining grades.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[gnarbro]

thanks all. these coils are for tattoo machines.it is DC powered by a AC to DC power supply and the voltage will be changed all the time. it's basically the same mechanics as an old doorbell or alarm. make and brake relay. i need the material really soft so the armature and front coil will kind of flatten themselves into position after the machine has been run a while. the machines are usually run a few hours at a time so heat is a concern also. the coils are insulated with a piece of masking tape and are wound with 24 gauge insulated magnet wire. usually 6 to 10 layers. 1018 has been used a lot but some are finding out lately that 1010 works better. i will try to find 1002 or 1010 rod then cut to length. does this steel sound best for my application? does anyone have any good methods for annealing at home? thanks again for the help!

 

[sreid]

Here's a link to 1010 steel that tells how to anneal.

http://www.suppliersonline.com/research/property/metals/809.asp

The lower the impurities in steel, the higher the magnetic flux can go before saturation. To reduce the eddy current iron losses (heat), however, you would be much better off using laminated silcon steel. A softer button made from your choice could be attached to the end for the "softness" you require.

 

[EdStainless]

This would work better if you used a long pin, shaped like a nail, and stacked thin lamination pieces on it. The smal end could be peened over like a rivet head to hold the stack tight. The use of laminations will greatly reduce the heating.
The laminations dont need to be special electrical steel in order to help. If you want to make one on the cheep and see how it works get a chunk of a junk refrigerator. Then you are going to need a way to punch your 3/8" diameter discs, with a small hole in the center.
The stack will need to be very tightly compressed, no gaps allowed. You may need to even remove the burrs from the edges and center hole in order to get them to stack tightly. You would porbably want to press the stack tight before you fasten it.
One more thought, instead of using masking tape try to find some mylar or Kapton tape. I have some Kapton film (no adhesive). They are much stronger and will resist wear better.
It would also help (reduce noise, increase life, improve cooling) if you glued the windings together. An epoxy would be a good choice. Coat the core with a thin layer and start winding. Add a thin layer of adhesive over each layer of windings. Make sure that it is all cured before you power it.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[gnarbro]

thanks alot for the help. for tradition's sake i think i'm going to stick with a plain piece of annealed steel for the core. will i be able to find cold rolled 1002(or 1010 if need be) in 3/8" rod? is it even made? any pointers on where to find this would be greatly appreciated. i'll ask in the steel uses and processes forum also. thanks again for the input.