Brazing/welding mixed metals. Copper, Brass, Steel.

I saw Nelson's entry on Copper and Stainless cutting and welding, but I'm looking for different information. May I say that I've copied that entire thread and put it into a file for future reference. Fantastic information guys! =)

Basic facts:
I'm working small scale, sheet metal below about 16ga and rod less than 1/4" diameter in copper, brass and mild steel.
Oxy-propane or Mapp gass torch.

Okay, I'm getting into torch welding again after about 15 years and I've forgotten most of what I ever knew. The only torch welding I've ever done was strictly on mild steel and I'm wanting to work in mixed metals so I need some help. I picked up a small Oxy-Mapp rig with the intent of using Oxy-Propane once the first cylinder of Mapp runs out. I'm completely at sea on what kinds of rod to use for what material. I know that there will be a different material wanted if I'm joining steel to brass vs. just brazing or soldering copper but I have no idea what to use.

Can someone give me some guidelines on rod to material?

I am planning on doing just straight brass to brass, brass/copper to steel and brass to copper. Having not worked with some of these materials in combination with one another, I'm not sure how to proceed when it comes to welding vs. soldering them. Soldering for the most part is simple for me, but I really don't know at what point I need to change over to welding instead of soldering.

So, a couple of things defining my ignorance of the subject.

Thanks,

Marshal


Ries's picture

I have found that for

I have found that for putting together dissimilar metals, not much beats tig brazing with a silicon bronze rod.
Because the tig process uses an inert gas sheild, it will work with all kinds of metals that would otherwise be very tough to deal with.

I have used silicon bronze tig brazing to put together virtually any copper based alloy, even some with high lead or zinc contents, with steel, stainless, and cast iron. It can be used to repair most cast irons, it will work on most exotic nickel and other high tech alloys, and it works well with alloys where the melting points are vastly dissimilar- say, brass to stainless.

Yes, a tig machine is expensive- although, if you are not going to weld aluminum, you can get by with just a DC machine, which is significantly cheaper- but its such a versatile, clean and neat way of making sculpture, I couldnt live without it. In fact, I have two.


warren's picture

Propane?

I am from the old school of using a torch for my metal work and been doing it since 1972. But I use the oxygen/acetylene. I have tried the propane in the past and never liked it. My reasons are that I do some very intricate welding with the torch. The propane tips do not get the heat pinpointed, especially on gas welding sheet metal.
But as far as the rods to use............just regular low fuming bronze brazing rod will do most of the welding you are desiring. I buy the bare rod and add the flux on the rod as I go along. The flux depends on what the local welding store sells. Yes you can buy flux coated rods but they have about three times (just guessing) the flux you need. Also you have to make sure all of the flux is removed or you will get what I call "salty" welds, a white powder that forms around the bead a few years down the road.
If you go copper to copper you can also do this two more different ways. The simplest is buy some Harris O rod. This is a phos copper rod and leaves a copper color.
Or you can use a de-ox copper rod and use a flux. But I am not sure how good the propane or mapp gas will work.
I think the torch is the most valuble tool in the shop. I have five different size tips for my torch plus the rose bud and the cutting tip. Maybe $600 invested with the tanks. Also if you compare on a welding chart what it costs per hour to weld you will find that an O/A weld is the cheapest. No electrical needs.

warren
http://www.metalrecipes.com


visitor's picture

Can you suggest torch tip size

I want to weld 1/8" sheet brass edge to edge. Can you suggest torch tip size and rod size to do this. The brass is CDA 260 ASTM B36.


visitor's picture

stainless steel to copper soldering????

I read your post, above, about how to weld stainless steel to copper. I am repairing a refrigerator, by installing a new capillary tube and filter drier. The filter drier is copper and the condenser coil is stainless steel. I tired to solder the two with silver, but the silver solder would not adhere to the stainless steel tubing, oh by the way both materials are tubing. I would like to know if the same process as you described above would be applicable to my situation.

Cordially,

Rudie M. McGough


Rich Waugh's picture

Rudy, I'd solder the

Rudy,

I'd solder the capillary, rather than trying to do any sort of fusion weld. Either low-temperature silver-bearing solder such as Stay-Brite or a true hard silver solder like Handy and Harmon's "Extra Easy Silver Solder."

The trick to successful solder to stainless steel is primarily, cleanliness - the metal must be chemically clean and free of oxides. Sand the surface with 400 grit wet/dry paper and then wipe clean with acetone. Do the same for the copper. Secondly, you must have the correct flux. For the low-temp solder I prefer Johnson's Stainless steel soldering flux. For the hard solder I like Battern's Self-Pickling flux. Both are liquid fluxes.

For the low-temp solder you can use a propane torch but for the hard solder you'll need an air/acetylene torch or oxy/acetylene. You need to be able to heat the stainless quickly and also to overcome the conductive losses in the copper. Taking too long to get it hot will cause it to oxidize and interfere with the soldering.

Rich


Brazing1972's picture

Oxy-acetylene brazing

I am simular in technique but only been brazing for 9 months. I just taught myself how to braze mild steel to 304 stainless. I used bare bronze with liberal amounts of Harris Stay silv brazing flux. The fluoride salt in it is the only thing that cleans the nickel and chromium oxides off the heated stainless to allow complete wetting of the joint by the filler. Generally, I use flux coated bronze rods and I shave about 2/3 of the flux off with a box knife if the metal is clean.

www.jtbmetaldesigns.com


visitor's picture

tig brazing copper to stainless steel

Could you please describe your technique for tig brazing copper to ss? I'm trying to weld .032 inch copper to 1/8 inch ss using silcon bronze rods. I'm having trouble melting the rod and also burning through the copper.


oldbazooka2's picture

Tig brazing copper to stainless steel

Could you describe your technique for tig brazing copper to ss? I'm trying to tig weld .032 in copper sheet to 1/8 inch ss square rod using silicon bronze filler rod. I'm having trouble get the rod to melt without burning through the copper sheet.


Rich Waugh's picture

You'll never have much luck

You'll never have much luck with that, I'm afraid. I'd stick with silver soldering.

Rich


Garage-Bound's picture

dissimilar metals

I have to second TIG welding. I have found that in DC mode, I have no problems blending (Bonding) mild steel filler rod right into copper. I have not tried it yet, but am pretty sure I could also bond brass to copper, brass to mild steel and so on. I believe (if not structural) bonding materials (if enough material is available to do so) is a great way to sidestep brazing. From my experience, on thinner materials, TIG welding has much less distortion of materials because the heat is pinpointed in a more precise area. Small (suitcase) DC TIG welders can be found used on Craigslist often in most areas for 5 to 7 hundred dollars. Some even run off 110v.


visitor's picture

Great comments

Thanks for the input guys, good info.

I'm having to run with what I've got for now and I'll look into a variety of other tools later on, as I can afford them. At least your comments will let me get my hands dirty and get back into the work.

Thanks again,

Marshal


crquack's picture

I just want to join the

I just want to join the ranks of those who recommend silver soldering.

I have soldered successfully several stainless steel pieces either to more stainless or to copper, brass or mild steel.

I use Easy Flow silver solder and a fluoride-based flux which is about 16 years old and dries out periodically. I slosh in some water and mix it into a paste and use the part of the paste with the consistency I like best.

I have never used anything else but a Bernzomatic torch with MAPP gas and later Propylene.

The biggest piece was my barbeque grill that came apart.

I agree that cleanliness is essential.

The biggest issue is cleaning the pieces afterwards (there is a recent thread on it here somewhere).

crquack


visitor's picture

copper and stainless braising

Warning! From what I have read on other sites, never use Map gas on copper it is a potentialy explosive mix!


Rich Waugh's picture

There is no problem at all

There is no problem at all using MAPP gas to solder or braze copper. The issue with copper and certain fuel gases has to do with the formation of acetylides , potentially explosive oxides of acetylene.

The primary source of problems was people piping pure acetylene through copper pipe in manifold delivery systems. In those cases acetylides formed on the *inside* of the copper pipe as the acetylene was in constant contact with it.

When soldering or brazing with MAPP gas, the copper is realy only exposed to the heat from the flame - the acetylene in the mix has been burned by then. Even if you flooded raw, unburned MAPP gas onto copper in open air you probably couldn't develop any acetylides in a short period of time. It would take days or weeks, not hours or minutes.

Whenever you read one of these dramatic statements you should do further research to determine the veracity of the claim and the exact circumstances required to duplicate the issue. Blindly accepting such "the sky is falling" statements is no less valid that blindly accepting that something or some action has no consequences. Dig for the facts!

Rich


visitor's picture

mapp gas vs copper

There is absolutely no problems with brazing copper to copper with mapp gas- I have been using nothing but mapp gas for years in the referigeration/ air con field and never have had any situations where I or my site occupants were at risk!The only safety procedure i have had to follow is having a fire extinguisher near by incase there was excessive dust/spiders webs creating an issue... or fat from cooking in a commercial kitchen not having been cleaned behind the fridge for some time and the accumulated fat smoking from the heat


visitor's picture

welding copper to SS

made beautifull tig welds on copper with the correct rod and a pulsed hi freq tig arc . now i am going to try brass or copper welded to the Stainless.. any help out there?