proper application of powder flux to aluminum welding? storage req

[coppercone2]

So I have seen a few methods of doing it. I have seen people just get the rod hot and dip it in the flux to melt it on, and I have seen people make a paste with water, distilled water or even rubbing alcohol.

I found when I tried it with rubbing alcohol a long time ago, it did not really make a good slurry.

I have even seen this


Can you mix this stuff up and keep it stored as a slurry in a glass jar (like a good chemistry one), or does it need to be prepared before use?

https://www.specialisedwelding.co.uk/downloads/chemicals-data-sheets/SDS%20-%207520%20ALUMINIUM%20WELDING%20FLUX.pdf

I have heard conflicting things from the welding store. Aluminum always gives me a problem, and I want to keep my process as good as possible.

I know with traditional brazing flux you can just add water to it, because its like vetted heavily, but the one for aluminum is a bit weird. Bunch of flourides. I don't know how those behave.


I want to put it in a glass jar, drip some water in it carefully while stirring to make a slurry, and keep that around for a long time ready for use. Is this acceptable?
]

To give some background, this flux, that is popular, is capable of being stored wet
https://superiorflux.com/sds/AB_8.pdf

But, it does not have weird chemicals in it (cryolate). It says this chemical is basically a rock ore that dissolves aluminum oxide at high temperatures, maybe making this flux good. It won't react with lithium or sodium flouride will it?

[vk6zgo]

Years ago we had a demonstration at my work of a particular brand of aluminium welding consumables.
We all had a try on a sample piece-------- mine was pretty cruddy, but it did weld.

We didn't really have the need for it, so didn't follow it up, but I was intrigued.
A few years on, I noticed that the normal welding shop had aluminium rods & flux, so bought some.

The flux was already mixed with water, but looked a lot like the stuff in the video.
The powder part had settled to the bottom of the jar, with a layer of water on top, so I assumed that the stuff at rhe bottom was the active flux, & the water layer was just protective, & stuck the rod into the bottom part.

My joints were horrible-----now I know why!

[coppercone2]

Do you mean you think you should have stirred it to become uniform, or do you think the water did something to it (unclear from your post)? This is what happened with my aluminum brazing flux, with denatured alcohol.

I managed to make VERY strong aluminum welds that impressed me in terms of ductility, basically inverted a piece like 8 times before it started to rip, and not only across the weld zone, but it looked GNARLY. Seriously I never seen metal so disgusting.

I am not actually sure you had a flux problem. It really could be the alloy I think, the welding store sells different rods for different alloys (2 common types), with one being predominant, but I suspect home depot might have been selling some shady shit.

No one like gas welding it lol, the information is sparse, most of the time people yell to buy a tig.

I almost have a vendetta against this, I am probably going to source the correct alloys and rods to actually see if it CAN work nice with what I have. Feels like a god damn global conspiracy. In terms of youtube results not occurring in my shop, anything aluminum brazing, welding or soldering is #1. Usually I can get pretty close results with a few tries, but aluminum has been a fucking perpetual disaster. I trust epoxy to do a better job (if you do some calculations, and have a decent surface area, you can actually get something like 1/2+ the strength of an aluminum weld around a plate fixed to another plate with epoxy, just doing the PSI calculations based on area, on something moderately sized, or exceed the strength of a weld on something big as far as I can tell.

[SilverSolder]

Aluminum is really hard to weld with gas.  The filler rod melting point is so close to the item you're welding that it is only too easy to cause the workpiece to sag or even go "splat" with little prior warning...

[T3sl4co1l]

Well, yeah.  It's just physics.  Metallurgy more specifically; the chemistry of metals.  Aluminum doesn't make useful alloys with anything that depresses its melting point much, save for exactly two: zinc and tin.  Neither of which are all that strong, so you have your choice of soldering, brazing and welding.  Invest in TIG: doesn't need any toxic hell fluxes.

Tim

[KL27x]

Alloying is a red herring when it comes to welding, though, right? We don't need to alloy steels to weld them. We can weld elemental iron. The difficulty in welding aluminum is the electrically insulating oxide layer that forms on aluminum AND the very high thermal conductivity that gives a smaller margin of error before the entire piece melts into a puddle. So wait, yeah, alloying it to make the weld take without melting the rest of the piece would be good, but the difference is that aluminum is so much higher in thermal conductivity.

Same reason welding stainless is easier process to control (laying down a weld, anyhow; keeping it stainless is a different matter) than carbon steel, due to lower thermal conductivity.

[coppercone2]

well this super 6 flux kicks ass, my skill is terrible (maybe I should not use so much fire bricks because it ended up making a 'scarab' out of my two test aluminum pieces rather then a bead line, but it actually blends into the metal good and looks like a over heated weld rather then the abominations I was getting with brazing aluminum flux. No ratty edges etc, looks like dunes in a desert

I guess it pays to use the correct substance. Beware though, the flux gets hot when you dilute it, like ferric chloride. I can try to get better without that wild card now.

I think the welding store was selling gold myers flower before

[coppercone2]

me after aluminum weld attempt

[T3sl4co1l]

Alloying is a red herring when it comes to welding, though, right? We don't need to alloy steels to weld them. We can weld elemental iron. The difficulty in welding aluminum is the electrically insulating oxide layer that forms on aluminum AND the very high thermal conductivity that gives a smaller margin of error before the entire piece melts into a puddle. So wait, yeah, alloying it to make the weld take without melting the rest of the piece would be good, but the difference is that aluminum is so much higher in thermal conductivity.

Yeah, conductivity is the big deal.  If it had a substantial mushy range, like off-alloy solders (think of what 50/50 or 40/60 feels like, compared to near-eutectic 60/40), you'd be able to deal with that -- the metal matrix doesn't instantly melt when it crosses solidus, it can hold some shape before turning into a useless slump.  But that range is so narrow, and the conductivity high, that you don't have much choice, and that goes for almost all alloys of aluminum.

Contrast with copper alloys, where elemental copper is even worse to weld (or so I understand), but the lower conductivity and much wider mushy range of many bronzes makes them quite easy to weld.

Same reason welding stainless is easier process to control (laying down a weld, anyhow; keeping it stainless is a different matter) than carbon steel, due to lower thermal conductivity.

Yup, both the mushy (liquidus-solidus) range and the conductivity work against you.  Seems to suggests a kind of ratio between a bulk thermal time constant* and the desirable power density.  Doing some materials with torch is easy, doing some even with arc welding is hard!

*Which depends on geometry: cross section, also ambient heat flow to a lesser extent.

Is laser or e-beam welding of copper a thing?  I'd guess with the power density being another step higher again, it'd be pretty reasonable...  Could also just be that, if you're breaking out such sophistication for a job, you're probably not going to mind putting in the extra thought to optimize fitment, preparation and process...

Wonder if... physics apparatus needs that much?  Wouldn't think there are all that many industrially important assemblies, in copper, that couldn't be 1. direct cast, 2. machined, 3. furnace brazed (or other brazing processes), or other options, with laser and e-beam welding being fairly distant except for something that absolutely needs the e.g. chemical purity of a welded joint...

But I digress

Tim

[coppercone2]

i noticed sometimes if you heat it wrong, an entire section kind of suddenly melts in a split second on thin materials, i think it is being held together as pseudoslush and then suddenly totally collapses (maybe slush layer on top and solid on the bottom being eroded, its hard to tell if its molten )

when you braze it I thought it was solid before and I poked it, and it turned out to be molten, once its dirty from flux

very frustrating, fortunately extremely cheap 'mod'. I only like this because its cheap with what I have. Steel is fine.

[KL27x]

I can't weld aluminum, at all, with stick. I tried with the special rods.

Best I can figure it's about getting the piece super-clean, pre-heating it just right, then getting it welded on the first try without fouling it, while the stick burns like a fast-fuse.

The main reason I ever want to use aluminum is because you can buy it in accurately extruded shapes to begin with. If the thing gets completely deformed during welding, then stick-welding it is not very good, for that.

I'm a hack, though. All the videos I have watched on welding, I have so far boiled down, in my own experience, as 6013 for thin sheet metal. 7018 is easiest if you are making long welds, but it is difficult to restart it once you stop. So if your welder blows the breaker on welds longer than 5 seconds, anyhow, forget it.  In that case, it's 6010/11 for everything other than thin sheet metal. 

[coppercone2]

I have a few of those rods but I have not used them yet, I saw chucke use them before for doing nasty low worth repairs like on cheap trailers owned by cheap people that want cheap repairs IIRC, I just bought them out of curiosity and to be nice to the store (new store)

The alumiprep is really good for cleaning I think, bubbles a little and the part turns a kind of white color

I really don't spend that much time and effort on welding, its there as a side hobby really, as far as I am concerned doing it proper is like getting a college degree

[vk6zgo]

Do you mean you think you should have stirred it to become uniform, or do you think the water did something to it (unclear from your post)? This is what happened with my aluminum brazing flux, with denatured alcohol.

I managed to make VERY strong aluminum welds that impressed me in terms of ductility, basically inverted a piece like 8 times before it started to rip, and not only across the weld zone, but it looked GNARLY. Seriously I never seen metal so disgusting.

I am not actually sure you had a flux problem. It really could be the alloy I think, the welding store sells different rods for different alloys (2 common types), with one being predominant, but I suspect home depot might have been selling some shady shit.

No one like gas welding it lol, the information is sparse, most of the time people yell to buy a tig.

I almost have a vendetta against this, I am probably going to source the correct alloys and rods to actually see if it CAN work nice with what I have. Feels like a god damn global conspiracy. In terms of youtube results not occurring in my shop, anything aluminum brazing, welding or soldering is #1. Usually I can get pretty close results with a few tries, but aluminum has been a fucking perpetual disaster. I trust epoxy to do a better job (if you do some calculations, and have a decent surface area, you can actually get something like 1/2+ the strength of an aluminum weld around a plate fixed to another plate with epoxy, just doing the PSI calculations based on area, on something moderately sized, or exceed the strength of a weld on something big as far as I can tell.

Yeah, I think I should have stirred it to become uniform, as then it would have been close to the consistency of the flux mixture in the video.

The guys who demonstrated their stuff at work could consistently make nice neat joints, & those of our staff with many years experience with gas welding & brazing also could, after several tries, bur as a Noob at the time, mine were pretty dire.

I gave up on the aluminium rods after a while, & ended up using them as antenna elements.

Epoxy is really good, & probably sufficient for any job where you don't need conductivity between the pieces, although, in many cases, a couple of aluminium bolts would probably make good enough electrical contact, & also hold the parts together while the expoxy cured.

[coppercone2]

if your frequency is low enough, but keep in mind that is a slot antenna between the bolts, and you have corrosion/lifetime issues with metal contacts, even if you use alnox etc.

The most heavy shielded ultra low noise phyiscs things actually use welded steel cans, not aluminum, from what I read. I would imagine that would be cryogenic stuff

Fortunately, while we might be able to afford the equipment to detect this level of stuff sometimes, its not really going to effect us because we don't have legions of data processor physicists to actually be irritated by it, so its just a side hobby. I think some program has to act up before they do all that.

then when you think about it, all that happens in the end, is some electronic version of a mechanical scale (comparator) is jiggling in one direction rather then the other direction slightly more often, so take it easy

Electronics gets WAY more expensive if you want to do nice chassis work, and being EE we want nasa

[KL27x]

Epoxy is really good, & probably sufficient for any job where you don't need conductivity between the pieces, although, in many cases, a couple of aluminium bolts would probably make good enough electrical contact, & also hold the parts together while the expoxy cured.

Luckily, yeah. This is enough for a lot of the things I use it for. I also pin or rivet aluminum, a lot. Drilling aluminum is great. Tapping it sucks.

[coppercone2]

you can also solder fairly thick sheet metal boxes as far as a hakko soldering iron goes with the right solder. I recommend that method if someone wants a steel enclosure on a budget

then there is no drilling or rivets and you can do it on a lab bench indoors so long you have good fume extractor. Maybe add like 1 bracket if you are worried about it falling apart if a component over heats. You don't need to bend the steel even, it puts playing cards together strong. With rivets unfortunately you need to bend, or alot of brackets, which can be hard.

[vk6zgo]

I have a few of those rods but I have not used them yet, I saw chucke use them before for doing nasty low worth repairs like on cheap trailers owned by cheap people that want cheap repairs IIRC, I just bought them out of curiosity and to be nice to the store (new store)

The alumiprep is really good for cleaning I think, bubbles a little and the part turns a kind of white color

I really don't spend that much time and effort on welding, its there as a side hobby really, as far as I am concerned doing it proper is like getting a college degree

Yeah, like a lot of things that skilled tradesmen do!

A lot of snooty people look down their noses at such folk, but when you see what they can do, it is humbling.
I once heard some twat with an Economics Degree refer to Boilermakers as  "semi-skilled!"
Hell, As a Technician/Tech Officer, I was just a "Tradesman", myself!

[KL27x]

A lot of snooty people look down their noses at such folk

That shoe fits on the other foot, just as well. 

[coppercone2]

I have a few of those rods but I have not used them yet, I saw chucke use them before for doing nasty low worth repairs like on cheap trailers owned by cheap people that want cheap repairs IIRC, I just bought them out of curiosity and to be nice to the store (new store)

The alumiprep is really good for cleaning I think, bubbles a little and the part turns a kind of white color

I really don't spend that much time and effort on welding, its there as a side hobby really, as far as I am concerned doing it proper is like getting a college degree

Yeah, like a lot of things that skilled tradesmen do!

A lot of snooty people look down their noses at such folk, but when you see what they can do, it is humbling.
I once heard some twat with an Economics Degree refer to Boilermakers as  "semi-skilled!"
Hell, As a Technician/Tech Officer, I was just a "Tradesman", myself!

bit scary to use that designation because if its really a boiler, it can go off like a barrel of dynamite and take out a building