How to "Weld" Aluminum Without a Welder

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Introduction: How to "Weld" Aluminum Without a Welder

Welding aluminum is not as hard as you think. Turns out you can weld aluminum without a welder!

This instructable will teach you how to use a propane torch and some aluminum brazing rods as a quick way to bond aluminum without using a welder. It makes for a very strong bond and with a little practice can be done quickly with great looking results.

Step 1: Propane Torch

The blue Bernzomatic will work just fine but I prefer using the yellow premium touch as it's hotter and works much quicker.

Step 2: Brazing Rods

You'll also need some aluminum brazing rods. I purchased all of these things at Home Depot.

Step 3: Cut Aluminum Tubing

What I like about using aluminum is it's soft enough to cut with ordinary woodworking saw blades.

Step 4: Chamfer Edges

I'll then chamfer the edges to allow a channel for the brazing material.

Step 5: Wire Brush Aluminum

Before brazing it's very important that the aluminum is clean.

Step 6: Heat Up Aluminum

Clamp up the tubing and start heating the aluminum with a propane torch. Aluminum will start to melt at 1200deg Fahrenheit but the brazing rod will melt at around 700deg so we want to get the aluminum hot enough to melt the rod without melting the tubing. Getting the tubing hot enough may take 4 to 5 minutes. You'll know when it's hot enough when the rod starts to melt on contact.

Step 7: Braze the Aluminum

Rub the brazing rod along the channel until it's filled in and finish it off with some more heat. If you don't get the aluminum hot enough the brazing rod will just clump up and not stick to the tubing. This takes some patience and practice as my first few tries resulted in failures and ugly joints.

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188 Comments

I am not about being negative and certainly when 3 years or more late to the
discussion, but have my own opinions based on personal experience.

As some have commented there are now actual space age
adhesives which are stronger than brazing with cold joints that do not loose
molecular integrity. Heating to 1200 deg seems pretty extreme for setting
up a braze with dissimilar metals.

I have done much work using 4030 but mostly T6 as a local
Metal Supplier has all metals including DOM coming in 20 foot sheets and once
cut go to bins or sorted areas where the metal is sold by the pound, I believe
a 9 inch thick billet of T6 is originally like a sheet of plywood 4' x 8' heavy
as can be and about $9,000.00. I mostly use scraps from DOM tubing,
Angles and Drawn Shapes. Easily identified by filleted corners instead of
square in the inside, Obviously Tubing has no seams etc.. T6 is about
$2,00 per Lb. They sell a fantastic supply of race care pre-shaped
mounts, for Cage building. The best assortment of welding claiming
working tools ever. Have all kinds of pre-made parts for gates,
ornamental iron and 5lb Arc sticks in every type and thickness for 1/2 of
everyone else. Even perforated metal and honeycomb interior
structure that can be used for light weight aircraft walls or thick enough to
be used as a firewall if backed with material using the previously mentioned
Spacecraft Adhesives.

A note on Loctite, get and use them all in big bottles if you
can, also a silver paste called Anti Seize to be used on threads with
dissimilar metals, Wheel studs, spark plugs and everywhere you are not using
loctite., I had a High Performance Air cooled Baja Desert race bike and
besides flow porting and titanium valves the head was milled with a
groove. It is called O-ringing. No gasket, use Loctite O-ring head
sealing material specifically made for ultra high performance race engineering
at an astonishing price about $30 per oz and lay a bead in the groove.
Let it set and torque the head with the highest confidence, Compression
retention and Heat Transfer.

Back to T6. I am not equipped with gas shield or have
experience with said techniques. But found 4 simple steps to permanently,
solidly join aluminum that I can accomplish.

1. Keep the joint clean, and use a Stainless-steel wire brush that is only
for Aluminum ever, ever!

2. Clean the metal with what seems to be an Acid that sells for $10 at the
same Metal Supply. Clean of impurities joints is the most important.

3. Preheat the joint but not in excess using simple light always moving wide
focus torch to get everything even and not outside temp especially in cold of
winter. Not hot or anything much over 200 F.

4. I am a bad welder but there are white shielded welding electrode
sticks for Arc welders that look kind of like the Brazing rods but actually
penetrate and weld Aluminum. I have used them on 4030 and T6 specifically
to make a fuel tank mount in the bed of my truck that has been off road for 10
years banging around caring a 200 lb load with Zero issues on a 2 foot tall
structure with load factors of that amount of fuel moving against my hand built
frame. The Rods were from next door to Industrial Metal Supply at a
Miller Branded Welding Shop. Not cheap like Metal sticks but permanent.
With only 1 issue, I had not considered there is no real slag, just what
I see as the equivalent of Aluminum Oxide. Did not know until I kept
running into a Pro Chassis Builder Aluminum Oxide is the 2nd hardest material
and you will not be grinding it down with those never anything better on metal
work stacked sanding disks. I have to say with metal work, although they do not
flap and are marketed for use with angle grinders. The same Metal suppliers
have bulk packs made by Metabo. You can take down metal spatter and
unevenness without digging in, basically leaving a pre-finished surface.
Years ago, if I saw someone looking a grinding disks I would exclaim the unreal
benefits and long life of the sanding disks.

Now a little rub in although it has ended abruptly a few years ago,
with sale of the facility. There was a metal supply that dealt in scrap
near Temecula, I used to watch people complain about how little they were paid
for recycle beverage aluminum cans. All the while I am in the same room
buying Brand New Condition, Military Surplus hardware by the pound, $1.00 for
up to 25lbs. $0.75 to 50 lbs and continuing to $0.25 for 100 pounds (the
same cost as 25 pounds) for unlimited amounts of $68.00 Grease cups for spindle
lubrication at about $1.50 for 5 sets. Military Spec with data
sheets Stainless Steel hardware (at $0.25 per lb.) Bolts that are in
Cardboard Tubes. Screws that when ran into sheet metal of any type provided a
threaded connection grade 10 hardness, but had a reverse course thread pitch
under the head so the bolt can never back out without actually
tightening. Packaged Thrust Ball Bearings and seats, great for a windmill
to turn on. They had 12 mill poly Bags to keep all groups of hardware
sorted and unlimited 5 gallon pails to transport and keep forever.
While the Can people bitched, I was buying perforated steel sheet scrap for
$0.50 per lb. if you price it what I paid $12 for should have been just under
$200.00 and almost the same if I wanted less but made a cut at the Industrial
supplier. Originally this place sold scrap steel for $0.20 and $0.25
galvanized, but the all-time high ended up $0.40 and $0.50 for galvanized metal
in the non-Military area (this was actual scrap or remnants. I
purchased used largest shelving clearly from Home Depot and another set from
Lowe's which sold for $2.50 per foot for the uprights. My $16' tall 8'
wide shelves with locking supports was $120 and $140 respectively. Only
buying the triangular cross braces being lighter and sold at $0.40 by the lb.
made them $8 per, opting out of the heavy grids for platforms. That's my
unsolicited diatribe and I am attesting it is from personal experience and my
slanted perspective,

I'd be worried about Bimetallic potentials and what that would do to corrode the aluminum. Anyone ever see what happens when you put aluminum and copper in contact with each other in water? I don't know what is in those soldering rods, but I'd feel pretty safe betting that it isn't aluminum.

it's an aluminum zick alloy. there's no interatction, and the alloy actually dissolves some of the base al when brazing, it's an actual weld.

If that is indeed the case, then it still is not a weld. No, it is a eutectic mixture. You are causing the aluminum to melt cooler by weakening the crystal matrix with the zinc. Not a weld. A true weld uses similar materials to yield a semi-continuous grain structure. Brazing ~= welding. Brazing == mechanical locking between differing grain structures. Welding is just a distortion of a continuous grain structure.

The application of the finished joint/connection (environment, stress, load, temperature, etc.) is a primary consideration with this technique. That being said, I will respectfully summit in my humble opinion: If this process functions as intended, then the issue of whether it is a true weld or not, is of little concern to the average person, myself included.

that's debatable, as the metallurgy of many weldments often different then the base structure, when filler is used, or a filler of a lower melting temperature is recommended or strongest, because of that debate welds are commonly defined as any process that melts, dissolves, or mechanically forms the base of two materials and joins them as one continuous material (with no mention of alloy) that is equal to or stronger then the base, thus making allowance for forge welding, friction stir welding(a process that can weld ti to fe), bimetal weldments(like this one), and plastic welding to be used in the same category and more importantly to allow all of the above to use the same set of standards with iso and astm, although the lower heat in this method does allow overlap with brazing and soldering, making this process notable, and largely debatable, however aluminum zinc alloys as a welding medium are compatible with many welding processes and are an excellent way to minimize distortion, and to create a stronger joint then the base structure, at the expense of ductility, therefore and considering the primary skill level this instructable seem to be catering to its a weld, and a good skill to have as well, because of the lower temps and therefore higher accuracy. fair warning however, don't use on a bicycle frame, the lower ductility will eventually cause failure. (although I believe firmly that any process that dissolves the base matrix should have its own category but it doesn't)

oh and welds have to be tempered to create a continuous crystalline structure.

In sorta layman's terms, a weld molecularly bonds the metals into a single joined piece. Melting a dissimilar metal between the two pieces is just a simple solder joint.

Galvanic corrosion. A tiny piece of less noble metal, a sacrificial strip so-to-speak, in electrical contact with the metals you intend to protect will do just fine.

Butane can work but will be more expensive as you'll (quite a bit) use more gas to get the aluminum to melt.

Propane works and will be cheaper than butane, but still will require quite a bit of gas, unless you have an oxygen fed torch or a powerful air blown torch,

For a torch like in the picture (no oxygen or blower) you'll want to use MAPP gas (yellow can) as it burns much hotter and will melt the aluminum using far less gas and cost much less despite being a more expensive by weight.