Brazing with "Milk of Magnesia"

mfgbydesign · Dec 12, 2011

We have a process specification written several years ago that calls for coating fixure locating surfaces with "Milk of Magnesia." No $h!t.
Well I'm a bit uncomfortable with that statement especially since we are trying to get nuclear certified. I recently worked to pass Nadcap Accreditation for brazing & welding (aerospace) & believe me we didn't put anything like that in the WPS's.
The only thing I can figure is it's so the operator doesn't braze the part to the fixture.

Is this an old school technique for "braze stop?"

Ferrous Antiquos · Dec 12, 2011

Bottoms up!

I have absolutely no insight into your question.

But I do know that when you mix vodka with milk of magnesia, you've made a Phillips Screwdriver !!

GregSY · Dec 12, 2011

I've hear of it used as an anti-sieze compund for threads.

John Garner · Dec 12, 2011

mfgbydesign --

Plain (unflavored) Milk of Magnesia is a water-borne suspension of powdered magnesium hydroxide. When Milk of Magnesia is heated, the suspension water boils away, leaving the solid magnesium hydroxide; continued heating -- to just above 600 F, IIRC -- releases the water from the magnesium hydroxide crystal structure, leaving plain magnesium oxide.

A painted-on coating of Milk of Magnesia that has been dried and dehydrated essentially becomes a coating of magnesium oxide powder that can, as you speculate, be a "braze stop", or, as GregSY mentions, a high-temperature anti-seize.

John

jim rozen · Dec 12, 2011

I thought it was mag citrate. But no matter I've heard tell of using it as stop-off
for braze process.

One *can* purchase commercially available (aerospace qualified??) stop off from
braze manufacturers. I'd start with Eutectic.

mfgbydesign · Dec 12, 2011

Thanks to all

for taking the time to read & respond. Humor appreciated!
I am recommending revising the spec to use commercially available "stop-off" as the operator tells me the MOM doesn't really work that well. It tends to burn off & dissipate in the first 1/2 hour. This large assembly takes 2-3 hours to get up to temp. with 12 rosebud torches on it and the brazing operation itself takes about an hour. Then 3-4 hours to cool down enough to crane lift it out of the fixture. I watched it the other day & it's pretty intense.

jonfritch · Dec 12, 2011

cokctailes

Ferrous Antiquos said:
I have absolutely no insight into your question.

But I do know that when you mix vodka with milk of magnesia, you've made a Phillips Screwdriver !!

Yes, and if you use prune juice you'll get a pile driver.

Zonko · Dec 12, 2011

I gotta see that

......

2-3 hours.....what kind a and HOW MUCH flux do you use. Like a gallon per part

.

Gotta love that kind of stuff

cash · Dec 12, 2011

GregSY said:
I've hear of it used as an anti-sieze compund for threads.

This is exactly what we use for when parts are bolted together and we heat treat them and we need to get apart after heat treat.

casement · Dec 12, 2011

MOM was standard anti-seize for many high-temp USAF jet engine components for many years. Also used on aircraft igniter plugs.

Works quite nicely.

Link with some references:

Unusual anti-seize compound - Bob Is The Oil Guy

dkmc · Dec 13, 2011

jonfritch said:
Yes, and if you use prune juice you'll get a pile driver.

How about Vodka + Mother in Law = Back Seat Driver
...loud & obnoxious one to boot!

mfgbydesign · Dec 15, 2011

Zonko said:
I gotta see that ......

2-3 hours.....what kind a and HOW MUCH flux do you use. Like a gallon per part .

Gotta love that kind of stuff

Handy Harmon white flux. Don't think I'm giving up any secrets there.

The joints (dozens of them) are relatively small compared to the size of the part, but the pockets are deep. Takes awhile for everything to come up to temp., then soak, then cool down. Sorry can't share any images, you know, can't have the competition see how it's done. It's basically too big for induction and too expensive for a furnace braze.
Take a look at the "simulated rotor bars" on page two:
http://www.electricmachinery.com/brochures/1300-PRD-400A.pdf

Cyclotronguy · Dec 15, 2011

Milk of Magnesia

Back in the day when I was still doing certified Nuclear Research, milk of mag was not uncommon. As for example when you rebuilt the mass spec on a Veeco vacuum test station, the factory manual specified milk of mag for various micro-welds in the accelerator assy.

It was pretty common in high vac work too.

Being a quasi medical product Milk of Mag was at least USP and other than paperwork likely close to AR grade (Analytical Reagent).

But like all things Rad-Safe.... it's the document chain of responsibilty that counts.

Supplies from Handy & Harmon were always a good choice..... frequently Eutectic Castolin got "black-listed" because they were just too proud to publish full disclosure of what was in their alloys and fluxes....... at least historically.

Keep in mind this is at this point decade old experience.

Cyclotronguy

Search

Largest Manufacturing Technology Community on the Web

Search

Brazing with "Milk of Magnesia"

mfgbydesign

Aluminum

Ferrous Antiquos

Titanium

GregSY

Diamond

John Garner

Titanium

jim rozen

Diamond

mfgbydesign

Aluminum

jonfritch

Aluminum

Zonko

Stainless

cash

Titanium

casement

Aluminum

dkmc

Diamond

mfgbydesign

Aluminum

Cyclotronguy

Stainless

Similar threads