Welding brass and aluminum

[aurfalien]

Hi all,

I've been getting into building frames etc... and have been using crazy glue to stick em together.

I tried using solder but I had the wrong type as it wouldn't stick to the metals.

Is there a solder I can use as a type of weld?

Should I get a mini butane torch?

[Ace-Garageguy]

"Soldering" and "welding" are two entirely different processes...soldering uses a low-temperature filler material as a metallic 'glue' to join parts, while welding actually melts and fuses the base metals together, usually with a filler too, but at a much higher temperature...and you're not likely to be hobby-bench-welding aluminum alloys. Straight aluminum (non-alloyed) can be welded with hydrogen / oxygen and a small torch...this is how real aluminum bodies were constructed early on...but it's best to learn oxy-acetylene welding on steel first, as you get some color-change of the metals to help you judge heat. You don't get any such warning when gas-welding aluminum...just a big hole.

There are several solders made for joining aluminum alloys that should be suitable for model work, and they work with a propane, butane or mapp-gas torch, but I haven't experimented with enough of them to make any useful recommendations. Here's one...   http://durafix.com/index.html

Soldering brass to brass is fairly straightforward, so long as you have the right tools and materials. The train and slotcar guys were doing it routinely (me too) 50 years ago. Get the right acid-core flux, the right lead/tin solder, and a decent iron or gun and you're golden. You don't need anything magic. There's tons of info on specific solders and fluxes on the model RR forums, and even tricks like using different heat-range solders to join detail parts to a brass model without melting adjacent work.

Sticking aluminum to brass is trickier and requires different solders and fluxes. Just Google "solder aluminum to brass" and research it. As usual, you'll find a lot of "advice" from people who haven't actually DONE it, but little in actual practical repeatable (and verifiable) information. Some say Alumiweld will do it, and supposedly this will too... http://www.harrisproductsgroup.com/en/Products/Alloys/Soldering/Lead-Free-Solders/Al-Solder-500.aspx          Here's another one...   http://muggyweld.com/aluminum-to-brass-solder

There's always epoxy for joining dissimilar metals, but even then, aluminum resists working happily with most glues, and because of this, exotic and expensive adhesives have been developed just for gluing aluminum in the aircraft industry.

The number one rule when trying to solder anything is to have the joint area CLEAN and free of any surface oxidation.

 

 

Edited December 21, 2015 by Ace-Garageguy

[aurfalien]

Darn, I was hoping for an easy answer like; "use this so and so solder etc for doing it".

As usual, many thanks for the reply.

[Crazy Ed]

   Brian, It'd go a long way to tell us what metals you're trying to Solder together and working from there for an answer.

[aurfalien]

Well, I got these brass and aluminum rods from a hobby shop.  They are about the diamteter of what a 1/24 axle would be.  A quick Goog search (there is no such thing as a quick Goog search when one doesn't know subject matter) yeilds gobs of info.   Most of which involves a butane torch.

I prefer solder.

Edited December 21, 2015 by aurfalien

[aurfalien]

/Alloys/Soldering/Lead-Free-Solders/Al-Solder-500.aspx

After re reading your post, this stuff may actually be perfect.  Thanks man!

Thing is is requires to scrub the resin off when done which will damage the delicate parts.  Hmm I'll have to call em for more info.

Edited December 21, 2015 by aurfalien

[10thumbs]

Brian, I've played around with soldering brass and aluminum together.  I ordered a special flux for the aluminum that also works for the brass.  Mind you, these were thin sheets, read heat was conducted easily and quick.  It's a mess!  Flux everywhere, and it was difficult to remove.  It's really tough to get a small and precise joint.  If you're trying to solder thick rods, you might have your work cut out for you.  This was with a good electric solder station. 

I use CA now and I'm good with it.  But for my models I use mainly brass, the aluminum as a sheet application only.

 

[Pete J.]

Just a bit more info for you.  When connecting metal parts there are really only three ways to do it.  Welding is most common and as Bill said, it involves melting two pieces together to form a single homologous piece at the joint.

  The second is what I like to call the peanut butter method AKA gluing.  Like a peanut butter sandwich, you take two pieces of metal and put some goo between them that grips both pieces and holds them with the strength of the goo.

  The third is a mechanical method such as a nut and bolt or rivet. 

  Each of these has advantages and disadvantages.  Welding is generally the strongest but melting points of metal vary significantly from metal to metal and in some cases, the alloys of the same metal will have wildly different melting points.  Case in point is 7057(aircraft grade) aluminum and 6061(general structural) have a melting point that is around 100 degrees Fahrenheit different.  When attempting to weld aluminum this can be a huge difference.  So, there is no easy way to generally weld two dissimilar metals with out a lot of knowledge and experience.

  The peanut butter method(or gluing) is much easier in that you slather some adhesive(super glue, epoxy, solder or what have you) on the two pieces and let it set.  The problem is that adhesives may or may not bond well to the surfaces that you are trying to join.  Add to that that different metals expand and contract at different rates, depending on the metal and thus pull the adhesive apart along the shear plane.  Some adhesives have the flexibility to handle this others do not.  This is why super glues on plastic parts often fail if you put them in a freezer.  Dissimilar metals are even worse. 

  The mechanical method is of threading or screwing or riveting is also very strong but the size of item that we use can make doing this a challenge.  Very small screws are hard to come by and can be very expensive. 

  My recommendation is a combination of the second and third method.  Modelers for years have been "pinning " pieces together.  The combination of adhesives and a mechanical pin can make for a very strong bond.  Simply drill a small hole through both of the parts to be jointed(or multiple holes is stronger) and apply your adhesive.  The pin reduces stress along the shear plane and improves the joint significantly in most cases.  You can also often just glue the pin in place and it will hold very well

[LDO]

As a plumber, I solder copper and brass all the time. If you're using round tube, you'll need to use a round file that's the same diameter as the rod to make a "fishmouth" on the end of each piece that will get soldered. It needs as much contact area as possible.

You need to get the brass very clean; remove all the oxidation. Solder will not stick otherwise. Use a good flux. I use "No Korrode" from plumbing supply stores, but I also never solder anything smaller than 1/2" inside diameter. Whatever brand or type of flux you get, it IS absolutely necessary. It is a barrier that keeps oxygen away from the metal, preventing oxidation. Some fluxes are more of a pain to clean up afterward. Don't let that bother you. Worst case scenario, you clean up with a solvent and toothbrush when the chassis is complete.

I have not soldered model car chassis, but I have soldered tank gun barrels and muzzle brakes that I machined from brass. A lot of aftermarket parts like that are aluminum, but I prefer brass. It is supposed to be cut dry (no cutting fluid/coolant. Ideal for tabletop machine tools), and IMHO, solder is much better than superglue for holding metal together.

I made this gun barrel and brake, plus a few others, for my friend Karl Leidy. At the the time, this Russian 122mm barrel was not available from the aftermarket.

 

Edited December 21, 2015 by LDO

[Art Anderson]

When I built up the chassis, front axle and springs for my 1904 Knox Waterless, I used Stay-Brite Silver Solder (available at electronics stores, and some hobby shops) for one simple reason:  Unlike lead/tin solder, silver solder joints don't melt as easily once solidified as will lead alloy solders--a lesson I learned in reading British scratchbuilder Gerald Wingrove's books (he used silver solders exclusively on his models which were built mainly from brass), as silver solder joints require a good bit more heat to melt than does the original solder, for whatever reason.  Rather than a torch (which I used on the Knox) I now use an ordinary soldering pencil, as torches, even the micro-sized ones, put out way too much heat, making controlling the solder all that much more difficult, where an iron or pencil allows for much finer control, with a bit of practice, just a bit of solder goes a long way, flows completely into the joint with very little in the way of excess needing to be cleaned off. BTW, a package of StayBrite silver solder comes with a bottle of flux which is more than enough to outlast the use of the solder itself--and not all that expensive, either.

Massachusetts fire apparatus modeler, Charlie "Chariots of Fire" Rowley does the very same thing, and to see his brass work is to see sheer artistry--less excess solder than any glue you can think of.

Back in my 1960's slot car days, when building 1/32 slot car chassis from sheet aluminum, I used K&S square brass tubing for axle bearings, and epoxied those in place on the aluminum chassis--then once the epoxy was cured, put the chassis in Mom's kitchen oven at about 350-degrees, and baked it for about an hour--after which, the epoxy turned about as brown as a drop of Coca Cola, and was strong enough to handle even the worst crashes--never had one of those axle bearings break off the aluminum frame.  Gerald Wingrove also built numerous model cars needing polished aluminum bodywork--for which he used epoxies to hold the aluminum sheetmetal components together--if you've ever seen even pics of his masterpieces, they are truly works of art, BTW.

Art

[aurfalien]

Hi all and many thanks for the replies.

Art, I'll try that solder, seems cool.

[Kit Basher]

If you want some inspiration, check this out: http://www.modelcarsmag.com/forums/topic/41299-adventures-in-solderinghot-rod-wrecker-project-update-2115/

[aurfalien]

Thats totally killer KB.  I love that kind of stuff.

[Ace-Garageguy]

... I love that kind of stuff.

Then you should like this little youtube video about Gerald Wingrove's work.   https://www.youtube.com/watch?v=GbyoTU-ucxM

[Muncie]

good information already

here's a couple of soldering tips - I've used a 40 watt soldering iron for some slot car chassis - with practice it's easier than it looks and you can amaze your friends

A paste type flux may be easier to use than a liquid - it will stay where you put it. Apply the flux where you want the solder. Heat the metal that you are soldering.  Melt the solder on the metal, not the soldering iron. The metal needs to be hot for the solder to flow into the joint and stick. The solder flows toward heat and will flow onto/into the joint.

I tend to not fishmouth (trim the ends to match the next part) so there is some space for the solder.  A close fit doesn't have much strength.  Experience is the best guide for how tight the parts need to fit.  Some connections my need to be drilled and pinned for alignment during soldering.

Some fluxes come off with a bit of hot water and a stiff brush or steel wool - no drama

There are some good articles on soldering in the new Slot Cars Magazine - three issue are out there now.

The usual cautions about acid, burning acid holes in clothing (or skin), heat, hot metal, being careful not to burn flesh and that sort of thing apply.

Edited December 22, 2015 by Muncie

[aurfalien]

This stuff seems interesting;

http://www.solder-it.com/shop/item.aspx?itemid=162

Its an all in one sort of thingy; pasty flux mixed with solder in a syringe.  I like it, or at least the concept.

Edited December 23, 2015 by aurfalien

[afx]

This system intrigues me and looks very simple.

[aurfalien]

 

Wow, that stuff looks darn kEwl!

Very very interesting.

[aurfalien]

Hi Art,

I got some of that Stay Bright stuff and a new iron from JoAnnes for 50% off.  My old iron was, well, old as I use it a lot at work for circuit boards/electrical etc repairs...  prolly one of the few IT guys that still knows how to repair a circuit board and follow flow charts.

At any rate I'll ping back with how well it goes.

[Art Anderson]

Hi Art,

I got some of that Stay Bright stuff and a new iron from JoAnnes for 50% off.  My old iron was, well, old as I use it a lot at work for circuit boards/electrical etc repairs...  prolly one of the few IT guys that still knows how to repair a circuit board and follow flow charts.

At any rate I'll ping back with how well it goes.

I used it extensively in my '13 T build, for plug leads, and making my own front radius rods, cannot reccomend it enough!