Superconducting Magrid IRL

30 09 2009

WOW. Check out this part we just got from prometal:

IMG_4116

There is some slight warping, so the lid doesn’t fit as tightly with some of the faces. This can be corrected with machining, but some extra material would need to be built in.

IMG_4127

It really helps to hold the shape in your hands. Amazingly this process is inexpensive. These two pieces cost ~$110. So we can afford to do about 10 iterations, more if necessary. Pretty cool.

Previously we used the 420 Stainless Steel +Bronze, which is magnetic. This time we used the 316 Stainless Steel + Bronze hoping it would be non-magnetic –  but unfortunately it is magnetic.

With superconducting cable:

IMG_4134

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22 responses

30 09 2009
Schrödinger

Excellent!Much better than my amateur welding attempt, and a lot cheaper than buying all the tools. I thought about going that route, but I want to learn to work with metal as well.

1 10 2009
Giorgio

The magnetic feature is indicating clearly that the structure of the metal is Ferritic instead of Austenitic. You should get the proper metal composition and consider a thermal treatment to transform the Ferritic (magnetic) structure into an Austenitic (non magnetic) one.

Here you can get some more details:

http://www.imoa.info/moly_uses/moly_grade_stainless_steels/metallurgy_of_Mo_in_stainless_steel.html

Giorgio.

1 10 2009
FAMULUS

Unfortunately, Prometal only offers 2 stainless steel alloys:

http://www.exone.com/eng/technology/x1-prometal/materials_prometal.html

So we’d have to switch fabrication techniques to use a austenitic alloy.

1 10 2009
FAMULUS

Prometal has a sister company that can 3D print sand resin molds for casting. I think you can use most casting metals.

http://www.prometal-rct.com/en/home.html

1 10 2009
FAMULUS

Great article on casting stainless steel… talks about magnetic properties.

http://steel.keytometals.com/Articles/Art67.htm

Quote:

In the cast stainless steels structures may be austenitic, ferritic, martensitic, or ferric-austenitic (duplex). The structure of a particular grade is primarily determined by composition. Chromium, molybdenum, and silicon promote the formation of ferrite (magnetic), while carbon, nickel, nitrogen, and manganese favor the formation of austenite (non-magnetic).

Chromium (a ferrite and martensite promoter), nickel, and carbon (austenite promoters) are particularly important in determining microstructure. In general, straight chromium grades of high-alloy cast steel are either martensitic or ferritic, the chromium-nickel grades are either duplex or austenitic, and the nickel-chromium steels are fully austenitic.

Cast austenitic alloys usually have from 5 to 20% ferrite distributed in discontinuous pools throughout the matrix, the percent of ferrite depending on the nickel, chromium, and carbon contents. The presence of ferrite in austenite may be beneficial or detrimental, depending on the application.

1 10 2009
Giorgio

To be more clear, I mean that you should get from the manufacturer the “exact” composition of the metal that was usen in the manufacture of the piece, and than consider a thermal treatment.

Giorgio.

2 10 2009
FAMULUS

How much more exact can you get than 316 Stainless Steel?

The liquid bronze is then infused into the pores of the steel by capillary action.

1 10 2009
2 10 2009
Giorgio

Mould casting will probably increase of one order of magnitude your costs, if you can get the exact chemical composition of the meta used in the manufacturing process you can consider to contact a foundry to apply a thermal treatment to the manufactured pieces to transform the Ferritic structure in a non magnetic austenitic structure:

http://www.osti.gov/bridge/servlets/purl/188630-sPsuuO/webviewable/188630.pdf

This will be probably be much cheaper and quicker than making a sand mould and casting the pieces (at least here in my country).

Giorgio.

2 10 2009
Schrödinger

Nice one Giorgio. I wasn’t aware you could even do that to iron.

From wiki:
“As it cools further its crystal structure changes to face centred cubic (FCC) at 1394°C, when it is known as gamma-iron, or austenite. At 912°C the crystal structure again becomes BCC as alpha-iron also known as ferrite, is formed, and at 770°C (the Curie point, Tc ) the iron becomes magnetic as alpha-iron, which is also BCC, is formed.”

If you heat it hot enough, then quench it, it should retain most of it’s austenite structure and be non-magnetic, correct?

2 10 2009
Giorgio

Exactly, this is a very common process used in all foundries to give the metal the desired crystal structure according the end use of the product.
Heating temperatures and holding times are strictly connected to the metal chemical composition. Also the residual % of the Ferritic phase is connected to the starting chemical composition of the metal.

Giorgio.

2 10 2009
FAMULUS

So let’s treat it like typical 316 stainless…. heat it above 1394°C, then quench it.

Right? Pretty simple to test.

3 10 2009
ike

too bad the expansion differential between the two materials could blow the whole shebang apart. unless bronze is ductile enough. could be worth a try, youll need a new one where the pieces connecting the faces protrude to be out of the way anyway (talk-polywell wisdom, look at wb7)

5 10 2009
FAMULUS

“one where the pieces connecting the faces protrude to be out of the way anyway”

Ike, can you explain this further, or provide a link?

The bronze would melt before the curie point of the steel.

5 10 2009
ike

hm, dunno which thread it was, but check talk polywell for “funny cusps”

5 10 2009
Giorgio

The bronze inside might as well prevent the ferritic-austenitic transformation at all.
Help from an exprienced mettalurgist sould be seeked in case the manufacturer of the material is unable to give support with this issue.

Giorgio.

6 10 2009
FAMULUS

I’m getting a quote today from PrometalRTC for the same shape made with a casting process.

6 10 2009
Giorgio

I am curious to know the quotation, just to make a comparison with the costs in my country.

Giorgio.

17 11 2009
Hello Internets! « Prometheus Fusion Perfection

[...] we build the Fusor, we are also building the Bussard Reactor. We have the first prototype of the magrid, and we are testing the superconducting [...]

10 12 2009
Dielectric Test « Prometheus Fusion Perfection

[...] The machine would have 2 turns of superconducting YBCO and be made using the inexpensive prometal process as before. [...]

21 07 2010
Marty

Since we are talking about much improved capacity to manufacture these things why not go the next step and design a dodecahedron? Bussard himself talked about some of the other platonic solids.

I’m guessing that the cusp loss problems could well be significantly reduced compared to the cube.

But then, maybe I’m getting ahead of things.

Neat ideas though.

21 07 2010
FAMULUS

I already did:

http://prometheusfusionperfection.com/2009/02/03/decawell-moon-shot/

I ended up going with the truncated cube for the sake of simplicity.

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