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Brass TIG Welding - Black Oxide around welds - Help!

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Plastic
Joined
May 6, 2016
Hello everyone,

I'm currently working on some brass parts which need to be welded together. The welds are strong but are covered in a black oxide/soot/dust after each weld, some of it comes off easily while the rest is needs to be ground off.

My setup is as follows:

DC Kemppi TIG
Cup Size 6
100% Argon
1.6 mm Tungsten (CK 2% Lanthanated)
1.6 SIFphosphor bronze no.82

Could anyone offer some advice for avoiding/reducing the amount of this black stuff? :)
 
I can't offer specifics on the soot, except to wonder what your pre-weld cleaning method is and whether the Argon is contaminated, but I'm going to "health and safety" by hoping that you're well vented from the fumes - zinc and lead vapor are both bad to breathe.
 
Ditch the tig pick up the gas torch. Simple fact is how ever clean it still is only a partial success, the zinc simply vaporises at the heat of the plasma. some of it forms a white smoke some of it condenses back on the part and thats only going to come of mechanically im affraid!

Bronze welds whilst not as clean with the tig as say a stainless job it does not seam to suffer the same issue, even though you would expect the tin to vaporise much the same it seams to be way less of a issue than the zinc is.
 
The brass is cleaned well before each weld using acetone, and I'm using an air filtered mask plus an extraction unit just to be safe..

Here is a photograph which should explain things better than I can....

IMG_3673.jpg
 
Ditch the tig pick up the gas torch. Simple fact is how ever clean it still is only a partial success, the zinc simply vaporises at the heat of the plasma. some of it forms a white smoke some of it condenses back on the part and thats only going to come of mechanically im affraid!

Bronze welds whilst not as clean with the tig as say a stainless job it does not seam to suffer the same issue, even though you would expect the tin to vaporise much the same it seams to be way less of a issue than the zinc is.


why would you expect the tin to vaporize? melting point and boiling point are non linear. (oh, and good luck finding a bronze that is a tin bronze).

plasma is around 10,000C, so, zinc boils a little below " heat of the plasma"
Zinc boils at 900C (dull red)
Tin boils at 2600C way above steel melting range, ("white" heat)

I don't like to TIG brass for that reason, if I do, knowing the boiling point of zinc, I will use as low a amperage as possible and keep the filler coming to cool the weld, and as soon as the hissing, boiling, white haze starts, back off the current. I use a silicon bronze rod, if I can get away with the color mis-match. you mostly heat the filler rod and puddle, basically, violating the "rules" of how one would do it normally.
 
I can't offer specifics on the soot, except to wonder what your pre-weld cleaning method is and whether the Argon is contaminated, but I'm going to "health and safety" by hoping that you're well vented from the fumes - zinc and lead vapor are both bad to breathe.

no, not a pre-cleaning issue. yes, don't breathe.
 
why would you expect the tin to vaporize? melting point and boiling point are non linear. (oh, and good luck finding a bronze that is a tin bronze).

plasma is around 10,000C, so, zinc boils a little below " heat of the plasma"
Zinc boils at 900C (dull red)
Tin boils at 2600C way above steel melting range, ("white" heat)

I don't like to TIG brass for that reason, if I do, knowing the boiling point of zinc, I will use as low a amperage as possible and keep the filler coming to cool the weld, and as soon as the hissing, boiling, white haze starts, back off the current. I use a silicon bronze rod, if I can get away with the color mis-match. you mostly heat the filler rod and puddle, basically, violating the "rules" of how one would do it normally.

Had not realised boiling point did not at least vaguely follow melting point, should know not to make assumptions like that especially on here!!!!

FYI if tin is not the main alloying element with copper i was kinda assuming it would not be a bronze? All of the bronzes i have encountered are something like 80-90% copper a good 5%+ tin then other stuff. I know aluminium bronze is a exception to that, but std yellow bronze or even the red phosphorous bronze tins still the main non copper alloying element is it not?

Like you say, your very much more melting it on the work, not so much feeding a puddle type approach. Brass joints i will generally always silver braze given the choice here. Done right there very strong and also very very clean. I just have never really found anything in what i do were tig brazed or the brazed welded type joint would be advantageous. I played with it a while back on some cast iron repair jobs, but generally for them i still much prefer a either fully preheat and post heat welded joint or if the metals clean and the joins good a silver braze repair. Because the silver braze flows through out the whole joint when done right you have vast area to gain strength, fillet of braze has nothing like the strength of a typical weld.
 
there is brass, and there is brass. as in, a bunch of different alloys that are all called "brass".

the only way to know what you are really working with it to know the alloy number.

360 is the common leaded brass you get in the USA- and it has lead and zinc in it.
It is possible to tig weld it, but it will pop a bit from the lead and zinc.
I use a silicon bronze filler when I have to do this, and usually it takes a second pass or sometimes a third, to fill all the bubbles.
So I only do this when I am going to sand out the welds.
There is a color difference between the filler and the brass, too.

Some ornamental iron guys silver solder brass railings- they go for as tight a fitup as humanly possible, then use silver solder and a gas torch.

Me, I just tig it, and sand it.
It will work, structurally.

I prefer to work with bronzes with no, or low, lead and zinc composition if I possibly can.
I use Silicon Bronze, or sometimes Naval Bronze for ornamental- both forge, and weld, much better than "brass".
 
I've had decent luck with welding brass sheet and tube (c260 and c272/c330). I found welding on AC with the balance set all the way up to 99%. This allows for the most heat input but you still get some cleaning. The welds are never good enough to be left as is and end up getting ground and polished

I would agree with the others that this is a small enough joint that silver solder would be a better bet. What's the wall thickness of the tube? I guessing 1/16" or so as you did not bevel the joint.

d56c5aa8235987da68725620c017671b.jpg
 
hah! yes, on here ya gotta be on yer toes!!

the whole "bronze" moniker is really just a mess, and I'm not sure exactly why, but there is almost NO bronze that is a traditional tin bronze on the commercial metal market. I can speculate that it is a result of the "secondary market", I. E. , scrap market, starting in 1870 or so, when machines started cutting all the little bits and pieces that we know and love on wood planes, locks, keys, plumbing, etc. (a lot of them in Connecticut, Watertown, New Briton, etc.). the copper-zinc-lead alloys cut so much better that the tonnage of them completely overwhelmed other alloy systems when look-alike yellow metal scrap got melted together.

that is probably why it is almost impossible to find a lead free brass as well.

the "true bronzes" ( NOT primarily Zinc as an alloying element), as opposed to the brass alloys that are called "bronze" such as "architectural bronze" CDA 385, are now mostly silicon, aluminum, or phosphor, I think. at one point beryllium was common, but it turned out to be so dam toxic, it has mostly disappeared, I hope!

yes, I "silver solder" (capillary braze) these alloys whenever possible also myself...
 
The brass is cleaned well before each weld using acetone, and I'm using an air filtered mask plus an extraction unit just to be safe..

Here is a photograph which should explain things better than I can....

View attachment 182913

Is that a siegmond welding table? How do you like it. I've been looking at that as a nice in between step between a $4000 build pro and a $20000 bluco. I saw one in person at imts, and it looked quite a bit nicer than the build pro but not nearly as nice as a he bluco a few booths down.
 
Thanks everyone for your help, the realisation that it cannot be avoided leads me to my next question, what is the best way to remove it? Is there a chemical I can use to remove it??

Whetstone, yes its a Siegmund table, we bought it recently and its been good so far. There are a few issues that we are speaking with Siegmund about, mainly a few of the accessory squares are not square....which is was totally unexpected! I think i'll write up a small review once this project is over.
 
...there is almost NO bronze that is a traditional tin bronze on the commercial metal market

'almost NO'? I can understand wanting to deny the label of 'traditional' to C932/SAE 660.

Even so, it surely ain't the only 'high-Tin' Bronze alloy out there, and nooo, they are lot all 'leaded'.

Bill
 
Thanks everyone for your help, the realisation that it cannot be avoided leads me to my next question, what is the best way to remove it? Is there a chemical I can use to remove it??

JM2CW, but "mechanically", AND NOT chemically.

The components of Brass - Zinc more than most - are too often eager to play-house 'independently' with strong reagents. By the time you get a nice clean-looking surface, you can easily have started a serious degradation of the very structure of the Brass around and under it.

If you MUST use a Brass at all rather than a Bronze, I'd start over and use a solder/braze technique at lower temps.

Bill
 
I use scotchbrite to clean up stuff like this.
I have scotchbrite pads that I cut to fit rubber hand sanding blocks, or my old Porter Cable Speed Bloc pad sander, round scotchbrite pads with velcro backs that fit a backing pad for my 4 1/2" grinder, scotchbrite belts, from Klingspor, for my 1 1/4" x28" Makita detail belt sander, and scotchbrite wheels I can use in air die grinders.

One of em usually fits.
 








 
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