How to "Weld" Aluminum Without a Welder

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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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    190 Discussions

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    FredH65

    1 year ago

    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,

    1 reply
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    TCSC47FredH65

    Reply 6 months ago

    Cheers Fred. I found your comments very interesting. I learnt how to weld aluminium many many years ago as an apprentice and I found it quite hard. I would prefer using glue of some sort but having seen it used in car manufacture what worries me is its toxicity. There were quite a lot of precautions taken to keep the toxic fumes away from the workers. The other thing is the need to make sure the surfaces are extremely clean (toxic cleaners again?). You deal with that well, but I have to admit as an amateur nowadays,it is the fault of many of my gluing attempts. Some times my joints work well and sometimes they don't and I put it down to poor preparation as much as buying a cheap glue.

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    Jerrylee1966

    Question 7 months ago on Introduction

    I'm working on a aluminum valve cover that's polished up , I've had to take an oil fill bung off of another cover so I need to put it on this polished up a very shinny valve cover. My question is how do I solder or weld this on without turning the aluminum blue from the heat? If it can't be helped, is there a way to take out the blue color?

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    Nyxius

    2 years ago

    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.

    7 replies
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    imakeembetterNyxius

    Reply 2 years ago

    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.

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    Nyxiusimakeembetter

    Reply 2 years ago

    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.

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    skysentinel.Nyxius

    Reply 1 year ago

    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.

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    imakeembetterNyxius

    Reply 2 years ago

    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)

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    imakeembetterimakeembetter

    Reply 2 years ago

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

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    hydraniximakeembetter

    Reply 2 years ago

    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.

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    hydranixNyxius

    Reply 2 years ago

    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.

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    hydranix

    2 years ago

    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.

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    amiir

    2 years ago

    does butan torch works too? or we should use just propane?

    thanks

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    dnorobo

    2 years ago

    This is great - THANKS.

    For alternative methods of metal joinery (and those looking for DIY/home tech aluminum joining options) I suggest the following (my experience includes exterior grade aluminum sign fabrication in a hurricane zone):

    - acrylic adhesives (industrial grades are best - Lord Adhesives and 3M in the USA)

    - double stick tapes (same)

    - epoxies (various including above)

    - mechanical fasteners (nut/bolt, angle iron, etc.). Also, thicker gauge aluminum can be tapped / threaded very nicely, allowing for mechanical screws to be mounted directly into the metal. The right hardware can be attractive.

    - wire welding (equipment can be rented - ridiculously easy with right equipment)

    Obviously, make sure you match your product's performance expectations to the fastening method's capacity. Make sure to read technical sheets, MSDS and fabrication guidelines, in order to make sure you use a product properly and to its fullest potential - most of that can be found online. If you are building something load bearing, that has moving parts, is for exterior use, etc. - you may want to consider consulting an engineer or accessing that knowledge.

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    imcp1024

    2 years ago

    good job, don't be afraid of cutting angles. gives wider bonding area, and looks nice. doesn't that cutting dull your blade?

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    Nightshade

    2 years ago

    I for one appreciate your instructable. Don't let answering perfectionist keep you from doing what you do!! Keep it up Rick Morty would be proud.

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    Technoaussie

    2 years ago

    Although I've always had a policy That if you can't say something nice about someone, say nothing, I feel the need to point out that a lot has changed since 'Aluminum solder first came on the market, soldering aluminum is not and never will be in any shape of form 'welding' aluminum. It is just a heat joining process that weakens the tensile strength of aluminum.

    Many years ago I was one of the first professional boat builders in Australia to build a 15 ft boat completely free of any welding or riveting. It was 'glued' together and was rated to handle 65 horsepower outboards.

    I was not the only builder converting to chemical joints but the size of the ovens needed and the unique jigs you had to build to hold it altogether during curing made them quite expensive.

    Back to my reason for commenting... I supplied a 'kit' that would allow cold repairs to be made. This is what I'm writing about now. Soldering aluminum requires very accurate heat. How do you get this using a propane blow torch? With a crayon stick designed for the temperature specified to melt the solder. You put a crayon line near the solder point. when it disappears, you've reached the temperature.

    Many aluminum suppliers and more advanced hardware outlets will sell you the low temperature 'solder' and heat indicating crayon in a package.

    The bad part of using heat on aluminum is loss of tensile strength! The slower you cool it, the more strength it will retain but once heated to the point where you solder it, all sorts of often dramatic things can happen.

    A much stronger and distortion free way to join aluminum is to 'glue' it together. The thermal setting adhesive used to equal the strength of aluminum itself is hard to find in DIY amounts and I doubt Mum would be very happy to find letterbox being bonded in her oven but there are plenty of 'cold bond' 2 pack adhesives on the shelves that will (when properly used) give you greater strength bonds with no likely hood of separation as solder joints provide.

    2 replies
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    TigerTomTechnoaussie

    Reply 2 years ago

    Which is the best "cold bond" 2 pack adhesives do you suggest to give me a greater strength bond with the aluminum i am bonding for a fence gate outdoors?

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    TechnoaussieTigerTom

    Reply 2 years ago

    Hi Tom,
    If you can you tell me where in the universe you live it will help determine what is most suitable and where you can get it. The summer and winter temperature will help too. The people who supply me, tailor mixes to suit climates but they also have mixes for exterior use that can be mixed to be secure in below freezing or extreme humidity but unfortunately not one single mix for both climates.

    I've got plenty myself I can probably give you some if you live in Australia. Sending it overseas can be a problem sometimes but I believe its available in most countries.

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    KROKKENOSTER

    2 years ago

    This is what I looked for for longer that I care to remember Excellent!!