Brazing Aluminum

[AweMan]

I've been asked to do this article on welding Aluminum so here goes.
The alloys we are going to be dealing with are typically 4043 and possibly 6061-T-6 {Aircraft Aluminum}
NOTE: 700 series Aluminum is Non Weldable Using the T.I.G. process
We all know the very best way to weld Aluminum is to use a T.I.G. welder to accomplish the task.
We all do not have access to a T.I.G welder , so a secondary way to join two pieces of Aluminum is to braze /solder the pieces together using a gas flame heat source IE. Oxy/acetylene torch set.
Some manufacturers claim that an inexpensive propane torch or Mapp gas torch with a turbo tip {obtainable at most hardware sources IE. Lowes, HomeDepot, WallMart etc.} will provide enough heat to accomplish the task using their products.
There are many manufacturers that produce brazing/soldering Aluminum products, which one you choose to use is entirely your choice. My recommendation is to obtain several "Brands" and try them out on scrap material to ascertain which ones are the easiest to use and suit your needs.
Aluminum brazing/soldering product manufacturers all have prescribed tips and techniques for using their product so I recommend you follow their advice on "How To"
Google Aluminum brazing for manufacturers or visit your local welding shop supplier
NOTE: Aluminum brazing/soldering materials are not cheap!
I myself have not used any of these brazing/soldering products, so I can’t recommend one above the other
I do know that these Aluminum brazing/soldering products require a heat source capable of 600 to 900 degrees. Depending on the alloy and manufacturer.
Aluminum typically reaches its melting point at around 1,220F {660ºC} degrees give or take a few. Aluminum oxide melts at around 3,600ºF (1,982ºC. Aluminum comes from the manufacturer with a chemically induced coating {Aluminum Oxide} therefore it is very important to remove any oxide from your Aluminum project before trying to weld it, be it T.I.G. or the braze/solder method. The atmosphere can also create Aluminum Oxide very rapidly on Aluminum {essentially rust although with Aluminum it isn’t red} so, cleaning your pieces one day and welding them later is out of the question. Clean them and then weld A.S.A.P.
The point is, it is essential to have a clean surface before welding any metal, Aluminum or otherwise. Joint fit up and tack welding your pieces into place is critical. Aluminum has a horrendous expansion rate when heated. Heat sinks and fixtures {described in my previous welding threads} may be desirable to help prevent distortion.
To obtain the best results it is essential to practice both technique and joint types on scrap material until you become proficient and satisfied with your weld joint appearance.
REMEMBER: any type of welding/brazing/soldering produces toxic fumes
ALWAYS: work in a well ventilated area.
ALWAYS: use safety equipment
NEVER: weld/braze/solder without eye protection.
PROTECT: your ears wear hearing protection. It’s NOT cool being deaf { Don’t ask me how I know}
BE SAFE NOT SORRY!

 

[GregW]

Re: Braising Aluminum

Hi Kerry,
I don’t know if you recall that air cleaner project I mentioned in another thread of yours, but I finished it a couple of weeks ago. The directions for the rod I used said to tin the base metal using a stainless steel brush to spread the molten braze around. I went through a fair amount of brushes when the braze stuck to them, rendering them useless in short order when they turned into blocks of metal. I didn’t have any luck tacking the pieces together. When the base aluminum gets hot enough, several inches of braze would liquefy. I guess working with larger pieces would be easier, I wound up clamping my parts together. There is a learning curve with this stuff, but I was happy with the outcome in the end.
Here is a photo of 1 ½ of the three filter housings I made. The incomplete one gives a better idea of what was brazed.

 

[AweMan]

Re: Braising Aluminum

Greg:
Hey guy! Those Air Cleaners turned out nicely. Great job.
Yea, as I said I have Not used these type rods or this process, although I have done considerable reading on the subject. Some of the techniques seemed completely foreign to me. I guess because I`m an "Old School" welder haha. I can see where the tinning process using a stainless steel brush to spread the aluminum braze around could be a bit cumbersome to say the least. I would think there might be some easier way.
I read where some manufacturers of these rods say to tin the joint, where as others claimed it was not necessary. One manufacturer even claimed thier product could "wet" the parent material even though the Aluminum oxide was not removed. Some even mentioned getting a good wetting action through dirt and paint. {foriegn thoughts going through my mind here i`ll tell ya} I think I would stick to what I know, clean, clean, and clean then weld.
I can see where reading every thing you can get your hands on about the rod maunfacturer tips and techniques then pratice and more practice would be benneficial. Mabe make the next pair of Air Cleaners out of brass. Hehehehehe They sure would look purtty sittin on a pair of H-6`s

 

[Roger]

Re: Braising Aluminum

You can braise it, roast it, boil it, grill it, whatever.
It's still tough and doesn't taste good.

Sorry - couldn't resist.

 

[Steve_S]

Re: Braising Aluminum

Not to hijack the thread but... Wow Greg, those look great!

 

[beaulieu]

Re: Braising Aluminum

How strong is the "brazing" rod which has a high zinc content so it will melt lower ,
the guys at the swap meet make it look so easy !

say compared to a gas welding rod of the same material / alloy you are working with ?

Thanks

Beaulieu

 

[AweMan]

Re: Braising Aluminum

Beaulieu
Here is a Quote from one manufacturer!




" Lets you do it yourself – Regardless of your experience anyone can easily learn how to braze aluminum.


Does the impossible! – Accomplishes many repairs even after a welder says it can't be done stronger than welding and even repairs oily or oxidized metals.

Imagine getting stronger, better results than welding, by using our high-strength brazing rods and just a torch—the kind of propane or mapp gas torch you probably already have or can easily pick up at your local hardware store.



Stronger – More tensile strength plus more elongation. with our {deleted} brazing rod.


Easier – No flux or mixes. No special brush needed like other inferior brazing alloys.


Better Penetrating – Penetrates past impurities like antifreeze, oil, and corrosion. Even repair metals you just cannot weld or repair with conventional Mig or Tig welders."

DISCLAIMER: I have NO affiliate with any manufacturer of Aluminum brazing alloys NOR do I promote any of thier products for profit.

 

[beaulieu]

Re: Braising Aluminum

Want to buy some swamp land . /bcforum/images/%%GRAEMLIN_URL%%/smile.gif /bcforum/images/%%GRAEMLIN_URL%%/smile.gif /bcforum/images/%%GRAEMLIN_URL%%/smile.gif

I am sure it will "weld" that too .

Yeah I see these ads but wonder if it works ,

I did find an old ad from the 1930s using the same stuff /bcforum/images/%%GRAEMLIN_URL%%/smile.gif

Beaulieu

 

[Biff]

Re: Braising Aluminum

Well I can't speak for all those 'glowing' claims, I can say I have used those rods for many projects and have used them successfully.

I have repaired a chipped blade on my boats prop, made a portable deer tree stand, a base for the windblocker on my Bugeye, and a few other minor repairs.

I clean the aluminum, clean again, and then brush the joining areas with a stainless steel brush, clamp the pieces together and then immediately solder/braze/weld them together.

Before I was convinced of the rods worth I took two pieces of 1/4" x 1" aluminum about 6"s long and butt joined them together. After it had cooled I clamped one end in a vise and began bending, pulling, and twisting the piece from the opposite end. The 1/4" x 1" aluminum strip failed/gave before the joint. That convinced me that it was strong enough to use. That's my story and I'm 'sticking' to it.

 

[AweMan]

Re: Braising Aluminum

Beaulieu:
I know this technology and technique goes back a ways. Back in the fifties I watched my father repair an Aluminum screen door using a Oxy/Acetylene Aluminum brazing process of some sort. {I was young} I do remember there was a pretty colored blue flux he used along with some sort of solid Aluminum looking filler rod. I also remember that same door holding up for some years after the repair. When I was employed as an Aircraft Welder, welding supply salesmen would ocasionaly come into our shop and do demonstrations on this Aluminum process, among others. We, as Aircraft Welders were NOT allowed to use anything except the T.I.G. welding process and A specific welding proceedure for each Aluminum part we repaired. We were bound by F.F.A. regulations to STRICKTLY adhere to these proceedures. Then the part would go to inspection, either visual {Non critical parts} or die penatrant or magnaflux or all three and critical parts would go to ultrasound and or xray before they were accepted for reassembly on an engine. There was an extensive paper trail documenting each step of each repair {if a part failed they would know when the repair was made, whom made it, and how long it was in service before it failed}. The point is, during my welding career I never had the chance to experiance using these Aluminum braising products. I make NO claims as to thier ease of use, stregnth or longevity.

Side Note: I have seen some of these briazed joints after they were produced on various items {Not aircraft related} after a time {I can`t say how long} The brazed joint`s have had a dark aperance {the braze it`s self}, I surmise from the high zink content used in the alloy. {much like a 43 zink penny will turn black}. Other than discoloration I can`t say if tensil stregnth is compromised.

 

[DrEntropy]

Re: Braising Aluminum

I've always given the non-TIG aluminum "knitting kit" the jaundiced eye. But I'm an old NDT type, rust-belt native. Level-II Nuke tubing... Now I'm curious. Seems the only real problem with it (for our purposes) would be possible inclusions. I'd love to have access to a tensile test machine about now.

 

[foxtrapper]

Re: Braising Aluminum

TIG is nice, but not the only way to weld aluminum.

MIG welding of aluminum is quite common as well, and works well, particularly on thicker pieces.

Torches work also, with a carburizing flame. This isn't particularly easy, but can be learned with some practice.

There are some stick arc aluminum rods out there as well. I've no experience with them, so I can't comment. I have heard they worked adequately.

 

[AweMan]

Re: Braising Aluminum

I did at one point during my welding experiance use some Aluminum arc welding rod to fix some parts on military Gama Goats {A type of two pieced articulating 4x4 jeep substitute} To see a pic of this "Critter" go here https://www.gamagoat.com/

I can say this about Aluminum Arc welding. Spatter Spatter and more Spatter. It did however "Get er done". It seemed to work better by using it as a flux coated Oxy/Acetylene welding rod than with the arc, especially on thinner sections.

Another type Aluminum arc welding rod one of my co-workers used once was called alumabronze {I watched cause I was very curious about it} This rod was supposed to be capable of welding aluminum to brass and or stainless steel. It did work however the apperance was horrific and you have NEVER seen Spatter until you`ve seen this rod in action. The weld turned out to be very brittle and wouldn`t suit our purposes.

I have done extensive M.I.G. welding of Aluminum {One project lasted almost two years} There is a lot more to M.I.G. welding than just "Squirting wire". Fine tuning the voltage amperage and wire speed ratios into a spray arc process is a feat in itself. {and NO your typical M.I.G. welding machine can not accomplish this process} But once you get there you can do some beautiful work. If done properly the welds can be as good quality as T.I.G. welds
The machines we were using were Linde 450 digipulse M.I.G.. As the name implies digitaly controlled. One of the finest M.I.G.`s I have ever encountered. To buy one you need a bunch of Money! Some of the "old School" welders in our group refused to use them because of the digital readouts and complicated control features. {THEY MISSED OUT!!}
The learning curve wasn`t all that bad, however it did take some effort.

 

[beaulieu]

Re: Braising Aluminum

I know guys that weld aluminum cylinder heads ,

They tig weld them

But first they put the head in an oven and heat to 400-500 degrees,

reasoning is there is less thermal shock to the head and it will weld easier.

Thanks for all your thoughts, you would think after all these years someone would have done a real world test /bcforum/images/%%GRAEMLIN_URL%%/smile.gif

Beaulieu

Beaulieu