Appx wattage needed for solding aluminum tubing with soldering iron?

[coppercone2]

I don't see the scarf joint in the picture looking substantially different then a lap joint, maybe you mean a more advanced scarf joint that was not in the picture

[beanflying]

There was no 'scarf' joint in the picture on my post a few back as it is NOT a joint used in sheetmetal.

A more appropriate joint prep for brazing or welding is done like this in the case of bar or tube. The longer surface area (length of joint) does make it stronger than the 90 degree butted version with the same prep but sitting the filler in the case of a brazed joint on the surface will get you a rubbish joint. Straight up 90 degree butt joints are done in the majority as a compromise in simplicity of prep and welding.

[mag_therm]

Comments about my interpretaion of posts by Copper and Bean.

A single bevel butt is a mainstream structural joint probably referenced in all the structural welding standards -reliable because it is done from only one side, and because there is less step in the cross section.
A lap joint has about 2 * step in area at the weld which becomes a stress concentration in bending and tension.

The term " Brazing" defined by AWS is fuzzy and wide, extending to the wicked/sweated plumbing joints Copper has done, to a joint made with filler rod.
"The Oxy Acetylene Handbook" by Linde differentiates  "brazing" as a thin film of filler drawn into a joint.
Then "bronze welding" as having  joint design the same as if it would be fusion welded, but the parent is not melted. After "tinning" (now called alloying), the joint is proceeds with filler rod and "the results are fully compatible to those obtained through fusion welding"
Chapter 19 covers "Principles of Bronze Welding"

I would classify the Harris solder wire 1 ounce and flux as linked by CopperCone, as "brazing" and the Alumiweld which comes in 3mm rods , half pound tubes,as being more like "bronze welding".
The big difference is that Alumiweld has almost no plastic or "mush" zone between solid and liquid.
And  gas torch, due to the high thermal conductivity of Aluminum, does not allow a close control of the melt that TIG can do.
Therefore gas torch joints can not be made close together. So many of the fusion weld joints shown in the posts become difficult, unreliable and impossible, as I have experienced and I think also 2 others on this thread have experienced.

[beanflying]

Both single and double bevels are used in welding including a double v groove (grooved both sides) to reduce buckling during welding plate as an example. Single Bevel is just one option and not a solution for all cases, used in the wrong place and a single bevel causes material to twist and bend. We were not however talking about 'welding' in this case as 'brazing' is a different animal having effectively zero penetration of the base metal.

The point to v-grooving a brazed joint is to increase the weld metal thickness and hence get more strength in that joint, the V will also get increased surface area for the braze to bond to. There is no mixing or penetration of the filler into the parent metal so this is a braze and there is no ambiguity here at all regardless of the Snake Oil consumable used.

[CatalinaWOW]

Something you might consider would be to make (or buy) an expander to allow you allow you to slip the end of your square tubes together by a few millimeters.  I don't know the temper of the 6013 tube you are buying, but the numbers say that it will allow that much expansion for most if not all tempers.  Doing this would increase the braze surface and also greatly simplify alignment during assembly.  With a little thought you can see how to accomplish this overlap when making corners also.  I don't see much chance of bending this tube into reasonable size arcs though.

Doing such joints would make epoxies much more practical.  I know you had a bad experience, but JB Weld is certainly not the apex of epoxy performance and lapping joints dramatically reduces the strength requirements.  Also note that there are mechanisms for brazed joints to pass a pressure test and then fail under use.  Flux inclusions being the most obvious example.

None of this has to preclude you buying the welder you want.  The welder will find its uses however you make your heat exchangers.

[mag_therm]

I did a trial Al chassis braze test piece when  oxy acet torch was used today.
https://app.box.com/s/1bjr3mnt9x80n8bdzmfpfnbm6bywkhns
https://app.box.com/s/rt91tmfrxzpmc4da87ypfxlws09qc93p

This is 1/8, 3.2 mm 6061 with Forney 46111 filler rod.
Photos are as welded before smoothing.
The joint is a single bevel butt brazed from one side.
The joint was half filled then repeatedly dragged under the melt, with a sharpened tool steel bit to scarify the parent metal.
Then filled up to slightly high.
I have experience now that this method  makes a stronger neater joint.
If the filler appears gray-white when cooling, not shiny,, I think it is indication that  at least some of the oxide floated out.

The filler metal has gone through to back as shown, but any attempt to turn the piece over and reheat the back side will just result in the filler running out.

Happy welding day, waiting for my new scope to arrive.

[coppercone2]

keep graphs like this in mind when brazing


thats strength vs distance between surfaces.
.
https://blog.lucasmilhaupt.com/en-us/about/blog/joint-clearance-and-joint-strength

that has values for aluminum braze I think. its a precise process

[beanflying]

keep graphs like this in mind when brazing


thats strength vs distance between surfaces.
.
https://blog.lucasmilhaupt.com/en-us/about/blog/joint-clearance-and-joint-strength

that has values for aluminum braze I think. its a precise process

That chart is clearly labelled as for Stainless Steel and has zero to do with Aluminium. The 'EzyFlo' mentioned there is a Silver Solder. There is two passing mentions of Aluminium on the entire page and again nothing specific as far as prep, method or joints. At least read the content you find when searching Google 

[coppercone2]

at least read the table on the second link where I said it had constants for aluminum

real eager to be a pain in the ass aint ya

[beanflying]

Hardly you posted off topic garbage!

Either because YOU DIDN'T READ the googled page you posted a chart that has NOTHING at all to do with Aluminium Brazing. OR it is completely an attempt at deliberately misleading or you or just you went looking for data to prove your lack of idea on what joints are actually possible with Aluminium filler. Silver Solder behaves very very differently to Aluminum.

'Ideal' thickness mentioned in that second link is a hypothetical theoretical fantasy from someone invested in selling a product. Aluminium filler will not flow into a gap of that width without additional preparation it will pool on top of that width gap and likely cause a porous result.

Lastly apart from mouthing off about Aluminium Brazing in every thread it is discussed in have you actually done much of it?

[coppercone2]

at least I got a number you got nothing. there is no mention of any kind of measurement. whats your deal. you can see from that number that the ball park strenght comes from something small, not as small as silver but its still small. They ain't write quarter inch there did they, they expect 2-3 pieces of printer paper developing the strength of the joint.

point is its a damn small number that makes the strength in the case of all brazing. you can surmise if its more then a few pieces of paper its bad. thats what brazing and soldering is about, a real small amount of material being really strong and making light weight high strength very neat and compact joints.

maybe this is a discussion about anchoring aluminum with brute force or something. there are alot of ways to use it but if you want that legendary performance thats the number you got to work with. you might actually be able to do some structural mathematics if you meet those joint criterion

[beanflying]

What I have is multiple decades of Gas welding on a range of gear and materials for a start.

The point is is that that 'damn small number' is a FRAUD and cannot be achieved. It simply will not flow into a narrow crack or close fitting surface. If you had done any level of Aluminium with Gas or even Brazing in general (not silver soldering) then you would have a clue about joint prep!

Lastly apart from mouthing off about Aluminium Brazing in every thread it is discussed in have you actually done much of it?

So?

[coppercone2]

thats because most of the alloys they sell are optimized for radiator crater fillers. I worked with testing large surface area stuff that was brazed gas tight aluminum around complex geometry

youtube aluminum braze-offs show that there is plenty of alloys that have a semblance of flow to them, but thats why I recommend the solder, it actually flows, and you can get the strenght from it, rather then falsified crater goo, without having to consult industrial manufacturing experts

[coppercone2]

I think they optimize alot of them as not to fuck up a car radiator with a clog.