Winding a strong electromagnet

[Xaverius]

Well - ferrite sucks as an EM core........

Wound a quick coil - has like 1/4 the holding power of the hex bolt.

Guess that's why that make filters out of the stuff - it's high permeability sucks up flux great - and doesn't transmit it well?

Oh well - only cost me $20.........

Maybe I'll see if I can get some electrical steel from a junkyard - an old car alternator or microwave or something this weekend.  (actually - I have a junk riding mower - maybe it's got something)

- - -

As to the discrepancy of the holding power of line 1 in the chart - turns out I was testing the hold on a much smaller coil - 40' of #22 - not 125'...... DOH 

Sorry about your results CapNhook, I lament the same effect, however I feel you have vindicated my effort, it isn't just me that thinks ferrite is a loser.  I think you're on to something, ferrite as well as GIron(which I've tried before, ur=100,000) absorbs lots of flux but does not transmit it.  Good observation

Please let me know how your salvage operation goes on used alternators, microwaves, etc.  That may be my next avenue.  Contacted ScientificAlloy.net the other day.  The technician told me at $100.00 minimum order I could obtain a two feet long/one inch diameter electrical steel rod.  The catch is, once I receive the material I will have to send it off to a foundry for heat treating/annealing which is what give it it's magnetic properties.  The material they have there is raw, untreated.  The heat process can easily cost another $100.00++

Oh well, I'm out $20.00 too, live and learn.  Keep on truckin', Rome wasn't built in a day!

[Xaverius]

May have finally found a US supplier for premium EM core material:
"CMI specializes in ultra low carbon electromagnetic iron, not merely low carbon steel."

http://www.cmispecialty.com/products.cfm

"CMI-C Magnetic Core Iron Cold Drawn Rod and Bar per ASTM A-848-01
Diameters:  .2500, .3125, .3750, .4375, .5000, .5620, .6875, .7500, .8750, 1.000, 1.250, 1.500, 1.750, 2.000, 2.250, 2.500, 2.750, 3.000, 3.250, 4.125, 4.500,  6.000"

"PRODUCT DESCRIPTION
CMI-C Electromagnetic Iron Rod is specially processed with a critical strain for optimum uniformity. Maximum magnetic properties are achieved following suggested final anneal applied to fabricated parts.

• BENEFITS
Hi-permeability, low coercivity. Low loss provides highest force/watt input."

Will call tommorrow for prices etc......sounds expensive and like it comes in 6' sections min.

Nice catch,  will investigate further.................

[capthook]

Update:

Sourcing EM core material is a PAIN in the A$$!!

Haven't had time for the junk yard or the visit to the University (going Sunday).......

Carpenter Steel offers some great (expensive) stuff and good info. 
This is a great read on core materials:
http://www.cartech.com/techarticles.aspx?id=1624
Sound like their Vacumet Core Iron or the Silicon Core Iron C would be EXCELLENT cores.
(if one could get a small quantity AND it was fully annealed  )
They only offer large orders directly and all the materials need further final annealing.
edfagan.com and frysteel.com were offered as small suppliers when I spoke to them, but they don't offer the premimum em core materials and still not annealed.
Frysteel: $30 per ft. plus $40 packing cost plus $9 per cut (1' to 6' rods) plus shipping
(maybe I'll call Carpenter Steel again........)

Surepure offers .5" x 1' rods of 99.9% iron at $96
http://www.surepure.com/products.php?ID=7&meas1_ID=41&subCat=23

CMI (from my last post: http://www.cmispecialty.com/index.cfm )
Their min. order is $250 (50 lbs) plus shipping (alot for 50 lbs.) and all their stuff then needs to be further annealed to realize it's full magnetic properties....... (yeeessh  )
And getting them on the phone or their material spec. sheets is like pulling teeth!

I guess the visit to junkyard for some microwave laminations to hack apart is on the list for next week......

[capthook]

An EM core of the highest iron content (lowest carbon) available that is easily sourced and inexpensive should suffice (I'm thinking at this point)

1006 Steel:
Iron, Fe 99.43 - 99.75 %  
Carbon, C <= 0.0800
Manganese, Mn <= 0.450 %
Phosphorous, P <= 0.0400 %
Sulfur, S <= 0.0500 %

1018 Steel:  99% iron
1215 steel: 98.5% Iron

Even a small change in the % of iron content can make a large difference in permeability.

A great Material Properties Database:
http://www.matweb.com/index.aspx

And a great source for just about anything - but the only easy source I've found for 1006 steel:

http://www.mcmaster.com

1/2" x 36" 1006 steel rod: $10.07
(also in strips/sheet form to make laminations if desired)

Should be an improvement over a hex bolt anyway?

As to annealing - X, you mentioned annealing price of over $100 - where to find a resource?

What about blasting the material with a propane torch until it turns (as close as you can get to) red hot and then stick it in the oven for awhile?
Would this help 'anneal' it and improve it's magnetic/permeability properties?

?

[Xaverius]

An EM core of the highest iron content (lowest carbon) available that is easily sourced and inexpensive should suffice (I'm thinking at this point)

1006 Steel:
Iron, Fe 99.43 - 99.75 %  
Carbon, C <= 0.0800
Manganese, Mn <= 0.450 %
Phosphorous, P <= 0.0400 %
Sulfur, S <= 0.0500 %

1018 Steel:  99% iron
1215 steel: 98.5% Iron

Even a small change in the % of iron content can make a large difference in permeability.

A great Material Properties Database:
http://www.matweb.com/index.aspx

And a great source for just about anything - but the only easy source I've found for 1006 steel:

http://www.mcmaster.com

1/2" x 36" 1006 steel rod: $10.07
(also in strips/sheet form to make laminations if desired)

Should be an improvement over a hex bolt anyway?

As to annealing - X, you mentioned annealing price of over $100 - where to find a resource?

What about blasting the material with a propane torch until it turns (as close as you can get to) red hot and then stick it in the oven for awhile?
Would this help 'anneal' it and improve it's magnetic/permeability properties?

?

Pain in the A$$?!?  You're right, I've been there too.  Seems your steel source ideas have some merit.  I'll be checking into some of these materials.

I've never really inquired as to who/where to get annealing done, although I'm sure a search would suffice.   As I am a physicist and not a metallurgist, I cannot tell you if a propane torch would provide the needed annealing.  Some annealing techniques require a hydrogen atmosphere to be effective, also.  You would have to know what temperature propane burns at and also the amount of time for heat exposure, and if the material should be cooled slowly or quenched.(cooled rapidly).  This is an area that needs further research.  If I find out anything I will pass it along.