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Flux Mixing [Jan. 25th, 2005|09:32 pm]
Doug Ayen
Having drunk too much tea yesterday, I spent the evening into the morning mixing up four fluxes to test. The ingredients I ordered were anhydrous borax, boric acid, and fluorspar. The borax is a fine white granular, sort of like sugar; the boric acid is a fine white powder, and the fluorspar is a brownish-grey fine powder. The borax and boric acid, as supplied, were rather lumpy, requiring me to use a mortar and pestle to break it down. I made up two stainless steel forge welding fluxes, and two carbon steel fluxes.

The fluxes will be tested, probably this Saturday, when I have a good block of time available. The two stainless steel fluxes will be tested on ATS34, one of the more popular steels out there, and the high carbon fluxes will be tested on 1050, of which I have an abundant supply. The standard against which the fluxes will be tested is straight, laundry-style hydrous borax, which is what I've been using up until now.

The four mixes I've prepared are:

Stainless 1:

2 parts fluorspar
5 parts usp boric acid powder.
20 parts anhydrous borax.

Stainless 2:

5 parts Anhydrous Borax
2 parts powder Boric Acid
2 parts Fluorspar (calcium fluoride)
1 1/2 parts powdered iron oxide
1/2 part powdered Sal Amoniac
1/2 part non iodized Salt

High Carbon 1 is straight borax

High Carbon 2:

20 parts anhydrous borax
1 part sal amoniac

High Carbon 3:

10 parts boric acid
10 parts anhydrous borax
1 part sal amoniac

I'll be using the 3 burner NC Tool propane forge, and the 50 lb power hammer for the tests. Each piece of steel will first have the mill scale removed, then two 4" pieces will be wired together. Each bundle will be stamped with an identifier so that I don't lose track of which bundle is which. Following a suggestion of Jim Hrisoulas's, each bundle will first be soaked in a saturated solution of borax to provide a surface flux, then heated in the forge until just glowing, fluxed with the flux mixture for that test, then heated to welding temperature at one end. That end will be hammered under the power hammer for a few blows, reheated, and upset to check the quality of the weld. Lastly, the piece will be put on a hardy and the two pieces separated until either it fails, or it's obvious the weld is as strong as the original steel. There will be five tests of the high carbon, one for each flux, and two of the stainless.

If someone is interested in showing up, I'll see if I can convince them to take photos of the different tests, and of course I'll post the results here.


[User Picture]From: cz_unit
2005-01-25 06:46 pm (UTC)
I'm interested in the results, working with flux/braizing rods and oxyacetelyne here. Question for you though: I managed to bend a mounting bar on my tractor weight box the other day (twisted). Should I heat it red hot before bending straight, or bend straight, then heat it to anneal?

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[User Picture]From: blackanvil
2005-01-26 10:10 am (UTC)
If it bent cold, it's probably low-carbon steel. You may be able to cold-bend it back, no annealing necessary -- but without knowing what kind of steel it is, it's hard to say for sure. I would probably heat, straighten, then air cool to normalize, followed by a heat-and-quench to harden if the part needs some springiness. A 450F temper in the oven for an hour afterward would remove any residual brittleness.

But in all honesty, if the piece bent cold, take a good look at it, and if you don't see any cracks or obvious defects, you may just be able to straighten it cold and use. Use a low-impact method, such as using a couple of bricks and standing on it, instead of hammering, though. Hammering will cause all sorts of problems unless you do it just right.

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[User Picture]From: cz_unit
2005-01-26 10:21 am (UTC)
*nod* I'll look at it tonight and probably just use the bench vise to straighten it out. Thanks!

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[User Picture]From: cjpetherick
2005-01-26 06:32 am (UTC)
Chris here: Where are you located. I'm in Brandywine, Md., just West of the Patuxent River in Northern Charles County -- about 40 minutes outside Washington.
(Reply) (Thread)
[User Picture]From: blackanvil
2005-01-26 10:10 am (UTC)
Berryville, VA, about 65 miles outside DC, head west on 7.
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