Type 4130 magnetic ?

It's mostly iron and plenty magnetic. Steel-tubed fuselages can absorb magnetic fields and cause compass correction problems.

Why?

Dan

I would like to fabricate a set of modified, hollow plungers for electrical solenoids. I need to start off with tubing, which are readily available from a 4130 source.

Well the plunger is spring loaded, so it will retract back when the solenoid is not energized. Though I would prefer something that is poor at retaining magnetism. Do you have a type off the top of your head ?

Carbon not only pins the iron crystalline structure in place mechanically, it also does so magnetically -- so high strength steels tend to be magnetically 'hard' as well.

Silicon stiffens up steel but makes it brittle -- however, it does so without affecting the magnetic properties much. So the laminations in transformer cores and motor armatures are generally made with silicon steel.

Look for silicon steel, magnet steel, or lamination iron. I have never seen this available in anything other than flat sheet -- I don't know if it's because the stuff is used for laminations, or if it is really only workable in flat sheets. IIRC it is bendable enough that you should be able to roll it, however.

In the end you may not have that much problem with the residual magnetism. I suspect that your solenoid core will pick up iron filings but won't 'stick'. You'll have to give it a try.

How about 416 Stainless?

416 is a strong alloy, often used in firearms, and stainless is normally non-magnetic.

BK

Armco iron, which is carbon free. Same stuff used in laminations for motors. Don't know if it's available as tubing, however. Otherwise, just plain low carbon steel tubing.

Harold

Wrong. 416 *IS* magnetic.

Harold

Ok, then 316 is the non-magnetic alloy

BK

The magnetic stainless used in solenoid valves is 430.

Ordinary mild steel will work fine for DC solenoids. The higher saturation flux density and permeability of "magnetic" silicon steel won't make much difference in a solenoid because the magnetic properties will be largely dominated by the airgap.

For AC solenoids you'll want laminations to avoid eddy current heating and loss.

I think remanence might be an issue. I hacked together a solenoid out of mild steel and found that it wouldn't let go after the current was removed.

Good point about the heating. There's a lot to solenoid design. It that plunger is going to have something soft on one end, for a seal, you definitely have to deal with heat. And particualarly it the solenoid, when energized is going to STOP a fluid flow. That heat may have no where to go.

Pete Stanaitis

-------------------

D> >

Yep! All of the 300 series is non-magnetic, assuming it's not work hardened, at which time it is mildly magnetic.

Harold

The carbon in 416 is to high - you want 316L or 304L or 317L.

You want an austenitic stainless steel - essentially non-magnetic in the annealed condition. Can be hardened only by work hardening.

Martin Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder

Harold and Susan Vordos wrote:

annealed condition.

I don't think non-magnetic material would work real well for solenoid plungers.

Why not use a 18/10 stainless steel like 316 or

304. They aren't magnetic at all.

Wouldn't do much good, Tom. It has to have magnetic properties without having *residual* magnetic properties.

Harold

According to Don Foreman :

annealed condition.

I thought that he was asking about a material for making the tube in which the plunger travels, and if so, a magnetic material will shunt most of the field away from the plunger, requiring a much stronger field.

Enjoy, DoN.