The only way I would join the two would be to use a

polymethylmethacrylate composite. This stuff is used on airplane structures to join parts where drilling and riveting would lessen the strength of a subassembly. Be careful though the the stuff is toxic. Wear respirator rubber gloves etc. It is tough as hell strong bond product name Equilox sold by Centaur forge

John Dach
john@MLCE.net
web site: http://www.MLCE.net
I have seen "kits" at boat shows for sale that will "weld" just about any metal to just about any other type of metal. Different rods for different metal combinations. Not cheap but not bank breaking either.

The other thing that MAY work, depending on how much stress si going to be put on the bond area, is using a product called LEXOR (I think that is the name, I know it starts with an L and has an X in it). It is a caulking compound for windows and other needs, is water clear, is a solvent base and is TOUGH. If you ever use it to put in a car windshield, you will destroy the car getting the stuff off. VERY sticky, not terribly expensive and available at your local hardware store.

John Dach

There are some very limited methods for actually welding ferrous to non-ferrous alloys. Unfortunately though, these processes do not lend themselves to the hobbyist or even most welding professionals as they typically require very specialized tooling and equipment. The most effective method that I have used involves a GMAW type process with AL wire and a dabber type wire feeder cycling at about 40 cycles per second with the welding current and voltage tuned to compliment the dabber cycle. Heat shunting is very important to limit the size of the heat affected zone and control cooling contraction in the dissimilar metals. I use water cooled copper bars on both sides of the work-pieces and joint.
Fronius, a welding equipment supplier, has at least one dabber style GMAW gun on the market, so perhaps in the future these technologies will be more readily available.

Go with cool bolts!

This is a school project usually meaning low bucks and low experience, I would go with bolting the pieces together. A robot is a work in progress, and expect to take it apart and do it again, and again. I have often built at least three robots before getting a working version, and even then it was a work in progress.

Lots of good inputs, but many are beyond student level.

Don

Hello there,

yes you can Al-Ss joint very easily.

you have to a brazing alloy of composition Zn98Al2 and a flux paste - Al Flux 028 Cs/D (of company Flux GmbH).

Regards,

Eyup Karaca.
Istanbul-Turkey

The only two ways I could see to join aluminum to steel would be either by friction stir welding FSW or by using a Bi-Metallic explosion welding (piece are generally already joined by explosion and sold as is). Bi-Metalic has been very popular in the marine fields to attach the steel shell to aluminum superstructures.

Alex, P.E.

www.maadigroup.com

I have a millermatic 210 mig welder and a spool gun and I used silicon bronze wire and it work great for welding aluminum to steel

What type of gases and dia. of wire are you using? How many amps and volts are being used? How thick is the material.

Please send me a response to: phil.fockler@morbark.com

Thanks

i would also like to know your wire size, and voltage used with this silicon bronze wire. i have a project i need to complete and i need to weld and aluminum bracket onto some mild steel for a customer of mine... is the same mixture of argon and carbon dioxide ok to use in this application? Please e-mail me back at techryan112@hotmail.com

Hello, my name is Terry and I am trying to get more information on Explosion Welding. Do you have any more information or resources where I can get more information on this subject? Please email me at kassandraromine@yahoo.com. Thanks!

It's called Data-clad and has been made by Dupont for years.
We use it in ship building with a 100% success rate.
I believe you can get almost any combination of ferrous to non-ferrous.
If you only need a relitively small amount and expense is an issue I imagine you could buy scrap from a steel hull-Al superstructure builder quite reasonably.
They have a very informative web-site as well. Dupont/data-clad.

My grandfather showed this to me a few times as a kid and it is part of the reason that im now a professional welder myself. In his 40+ years as a welder in Texaco oil refinery plants he learned that by using an oxy-fuel torch he could sucessfully bond a GALVANIZED STEEL nut onto a piece of Aluminum sheetmetal. Now, i will admit it is still a bit of a grey area in metallurgy since they are dissimilar metals However you can look this up on wiki in the 1950's to the 1970's they developed Aluminum/Zinc alloys and last time I checked...galvanized coatings are mostly Zinc. Well, thats what I know on the matter. I hope it helps....do with this info as you like hehe

Hello there,

I'm very interested of thermal expansion behavior of such a joint-being it welded, glued or brazed. The linear thermal expansion coefficient of aluminum is just twice as high as those of steel. Any shared experience will be greatly appreciated!
twice

Teodor Ganev, Bulgaria

In my experience the biggest problems with the steel/aluminum bond was with corrosion rather than expansion and de-lamination.I was involved in projects that used this material for things ranging from bending long strips of it to weld curved aluminum pilot houses to a steel decks on Coast Guard vessels to include ice breakers and tugs to using smaller pieces as feet to attach aluminum false decks to steel decks on Navy destroyers.I built the gun rooms on 5 destroyers that were directly below the forward deck guns and we never heard of any failures in the bi-metal anywhere on the ships and one would think that the gun room would be one of the higher stress areas as far as shock and vibration goes.
The salt water in direct contact with the dis-similar metals would cause accelerated corrosion if not sealed and coated properly but beyond that we neither saw nor heard of any problems.Navy and CG specs are some of the toughest around and they use it extensively.This material also meets ABS specs for off shore use as well.
You would think if differences in expansion rate were to be a problem it would show up as failure and de-lamination either during or soon after welding during installation.After all you are applying localized heating to each metal separately and to a high heat(obviously up to the melting point of each metal) during the process.Many times we were welding very close to or directly next to the join line with no problems.

In theory there is no difference between theory and practice.
In practice there is.

This is one of those cases where statistics get in the way of reason, I think.

Sure, the two metals have different coefficients of thermal expansion - but while one has twice the expansion of the other, neither of them are moving more than a few millionths of an inch at normal temperatures and both of them have sufficient elasticity to handle that without disassociation.

As you noted, the real issue is going to be galvanic corrosion if not sealed from moisture. That is going to occur in areas where the two metals are in close contact but not molecularly bonded, I'd think. In solid-state diffusion bonding of dissimilar metals the transition zone seems somehow to diminish the galvanic action, whereas two different metals that just touch but are not bonded corrode rapidly. That's just my experience, I don't know the physics to back that statement up. (grin)

Rich

There are many areas of the new automobiles where the steel is laminated with aluminum. Not sure of the process but the crash repair shops have to replace the whole area or send the car to the scrap yard if enough damage.

www Metalrecipes -- heat and beat to the desired shape, repeat as necessary.
warren

You can weld aluminum to steel using GTAW w/AC current, Argon cover gas, and Silicon Bronze filler.
Having said that, I have never tried a guided bend test, but after having used this method, I was unable to knock the two pieces apart with a hammer.
MHO

today, 24/9/11, i successfully welded 40mm x 25mm x1.2mm steel box tubing to 40mm x 24mm x 1.0mm aluminium box tubbing using nothing but 0.9mm gas-less flux cored mild steel wire through a DC current portable MIG welder. my voltage was around 18-19 volts and my amperage was around 100 amps. i have been a boilermaker welder for 20+ yrs and have 20/20 vision and a very steady hand. i have always been told it is impossible to weld these two metals together without special tools and environments.
with what i saw today, you can deposit a pool of molten steel onto the molten surface of aluminium and then build upon that molten pool of steel. when finished and cleaned up, the metals look fused together, you can see the distinct colours but there seems to be a molecular bonding.
help this helps.