My new pickup magnetizer

[Joe Gwinn]

1010 is perfect. ... In fact 1010 is hard to get by, being so despised (for its mechanical properties) so in practice 1018 is an acceptable substitute if you can get nothing milder.

I agree, and would add only that one can if necessary improve 1018 magnetically by completely annealing it, which is easily done.

[David King]

What about "CL-40" cast iron rod? Rod Cast Iron CL 40 1 in Dia x 3 ft L G1232533 | eBay
Zoro is actually a great place to deal with. Good prices and free almost overnight UPS shipping +20% off coupons in the mail. They are somewhere between McMaster Carr and Graingers

*Edit -this is "grey iron" which has a magnetic permeability of 125 vs 150 for mild steel. I have a feeling that a "Malleable Iron" would be better. See: http://www.ductile.org/didata/Sectio...c%20Properties

[Joe Gwinn]

What about "CL-40" cast iron rod? Rod Cast Iron CL 40 1 in Dia x 3 ft L G1232533 | eBay
Zoro is actually a great place to deal with. Good prices and free almost overnight UPS shipping +20% off coupons in the mail. They are somewhere between McMaster Carr and Graingers

*Edit -this is "grey iron" which has a magnetic permeability of 125 vs 150 for mild steel. I have a feeling that a "Malleable Iron" would be better. See: Ductile Iron Data - Section 5

Cast iron isn't very good magnetically compared with mild steel.

[Claus H]

Cast iron isn't very good magnetically compared with mild steel.

I think any mild steel will work fine.. Have not tried anything other then that we have now, not sure of the exact alloy, will try to find out, what it is.. Cast iron will not be good..

[David King]

Thanks, 1018 is available everywhere and can be annealed in hydrogen (1600ºF for 1 hour) to improve magnetic properties.
This place specializes in low carbon magnetic alloys in case anyone wants to do better. CMI Specialty Products, Inc. |
They are located in CT...
I read through this thread which explains all about what we are wanting to know.
Any low carbone steel dealer in USA - Magnetic engineering - Eng-Tips

[Joe Gwinn]

Thanks, 1018 is available everywhere and can be annealed in hydrogen (1600ºF for 1 hour) to improve magnetic properties.

For most purposes, any full anneal will do - the hydrogen isn't needed. Protect the piece from excessive oxidation by wrapping it in heat treating stainless steel foil, with a bit of paper inside the foil packet. Put packet in furnace, heat to a good red heat, allow to cool slowly. People used to do this in a charcoal fire. The workpiece will change shape in annealing as the strains are relieved. Anneal the raw stock, and then machine the resulting annealed piece as needed.

For the record, the hydrogen is provided in the form of ammonia vapor fed into the furnace. The heat disassociates the ammonia into hydrogen and nitrogen.

[David King]

I got a price from CMI Specialty iron today. A 10 foot, 1" rod costs $263+ shipping. I'd say that was a deal stopper for a few percent improvement in efficiency over CRS which runs about 1/20th that much.
I live close to Stack Annealing, I'll call them and see what a small load of CRS pieces would cost to heat treat.

Perhaps there would be interest in making up a kit? It would include rough machined metal parts and perhaps the electronic components. Folks can go out and buy their own coil wire, wind and assemble at home and stuff it all in a box or in the back of a Variac's case.

Would a 1kVA variac cover this application? http://www.ebay.com/itm/1KVA-Power-T...-/321290437553

[the great waldo]

Hi Klaus

Could you upgrade the circuit diagram with the specifications for the the bridge rectifier and wattage ratings of the resistors for dummies like me.

Cheers

Andrew

[Joe Gwinn]

I got a price from CMI Specialty iron today. A 10 foot, 1" rod costs $263+ shipping. I'd say that was a deal stopper for a few percent improvement in efficiency over CRS which runs about 1/20th that much.
I live close to Stack Annealing, I'll call them and see what a small load of CRS pieces would cost to heat treat.

I'd also determine if annealing is needed, or is it cheaper to use a slightly larger polepiece made of as-received 1018.

[Chasin' Note]

It's two coils wired in series, two coils of 4000 turns of 0.4mm wire, on a 150mm long, 25mm diameter, soft iron core, powered from a full-wave rectifier bridge of the variac, a few tricks to get the digital readout working. Schematic comming up.. It's all build into variac case..

What's the value for the rectifier & which variac did you used?

[Claus H]

I used a 750watt variac, and a 1000v 10A rectifier..

[Chasin' Note]

I used a 750watt variac, and a 1000v 10A rectifier..

Thanks Claus

[Chasin' Note]

Schematic [ATTACH=CONFIG]29114[/ATTACH]

Are there 2 full wave bridge rectifiers?

[eschertron]

Are there 2 full wave bridge rectifiers?

Looks like 1 for the control circuit and one for the coil. This eliminates the "trying to switch D.C." problem mentioned earlier.

[Helmholtz]

Here's my homemade magnetizer:



It is built from a 1.5kVA, 400V/230V transformer having a U/I core. A had to rearrange the laminations to have all the U shaped ones on one side and wired the coils in series. It is powered from a 30V/10A regulated power supply (seen at left). For demagnetizing I connect it to a variac.

Works great for all alnicos.