Casting 'Super Invar' 1

[KENAT]

Does anyone know, or can anyone point me to resources that might address, Casting super Invar?

As back ground, we use a large cast Invar 36 component as a major structural piece on one of our microscopes, in order to minimize thermal drift.

I've been wondering for a while now, given that we're casting it anyway, whether casting it out of super Invar might give us even better drift performance without too much of a cost impact.

I don't want to propose it until I have at least a vague notion that it's a realistic option.

I've done various Google searches about it but haven't found much definitive. I know that the composition of Super Invar Alloy is 32% Nickel, 5.5% Cobalt and the remaining balance Iron but I'm not sure what that Cobalt does to it's casting properties.

I believe our current casting vendor mixes the invar themselves rather than melting down invar ingots, though I'm not 100% sure.

Thanks.

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[cloa]

Why not ask Carpenter?

http://www.cartech.com/techcenter.aspx?id=1692

 

[arunmrao]

kenat from GD&T to casting Invar,you are travelling a long way. It is possible to cast Super Invar and one can prepare their own alloy,instead of buying ingots. Only care is pick up of gases during melting and pouring. hey could add Nickel oxide or Iron Oxide and possibly purge with Argon gas. It will be wonderful,if they have vacuum melting facility.

For heat treatment adopt the water quench route and followed by stress relieving.

If you need more details,I shall share whatever little I know.
Good Luck!

_____________________________________
"The richer we have become materially, the poorer we have become morally and spiritually." Martin Luther King Jr

 

[mw1st]

Cobalt, and other element are added to Fe-Ni alloys to alter/change expansion coefficient.
Below link to a book (p.587) and other material that you may find usefull.

 

[mw1st]

Sorry, failed to click "insert file" while posting original reply.

 

[KENAT]

Thanks all,

The obvious thing would be to speak to our vendor but we have new purchasing staff and the whole thing's got a bit political so I just wanted to do some research without upsetting our supply chain;-).

I wanted to get a feel for if casting super invar instead of invar 36 is likely to be significantly more difficult/expensive.

Arunmrao, I won't actually be doing the casting myself though so don't be too impressed!

cloa, stupid as it sounds my initial attempts at Google searches didn't turn up anything of much help from Carpenter, however via your link I've found some useful stuff, thanks.

(My next pet project is to see how much it would cost to replace the big slabs of Granite our stuff sits on with Zerodur or something!;-))

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[arunmrao]

Kenat you may also contact NiDI,they have excellent reports on the subject and will gladly share. You may also directly place your questions to a panel of experts with them. I learnt my Invar metallurgy from them.

_____________________________________
"The richer we have become materially, the poorer we have become morally and spiritually." Martin Luther King Jr

 

[KENAT]

Thanks Arunmrao, by nidi NiDI do you mean the Nickel Institute? I tried a link to nidi.com but it's a virus risk apparently.

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[arunmrao]

http://www.nickelinstitute.org/index.cfm?ci_id=15786&la_id=1&method=1&search_keyword=invar

The name is changed now to Nickel Institute. Sorry about the confusion. I have provided a search link for Invar.Please refer to them.Hope you find it useful.

_____________________________________
"The richer we have become materially, the poorer we have become morally and spiritually." Martin Luther King Jr

 

[EdStainless]

I presume that this equipment operates near room temp. This becomes a special case for TC. Super Nilvar should not be any harder to cast than Invar 36.

Is there any Ti or Al in your castings? Often these are added for deoxidation. You might be better off with Nb to tie up O, N, and C.

You anneal, water quench, and then bake at 400F for a few cycles? I am going from memory but that is what I think we used to use.

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Plymouth Tube

 

[KENAT]

Yes, this product operates at room temperature, though with some customers that can mean a good bit more than 20°C apparently.

I can't remember what heat treat we do on this cast part but we've built nearly 200 and I don't think we've had any issues.

I know on some other machined Invar parts we do major machining, then do heat treat then do light finish machining per this note.

"AFTER MAJOR MACHINING IS COMPLETE, STRESS RELIEVE AS FOLLOWS: HEAT
TO 1500F (815C), HOLD FOR 30 MINUTES, WATER QUENCH. REHEAT TO 600F
(315C), HOLD FOR ONE HOUR, AIR COOL. FINISH MACHINING IS PERMISSIBLE
AFTER HEAT TREAT, .030 MAXIMUM MATERIAL REMOVAL FROM ANY SURFACE."

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