Micro structural solder/braze/weld help

[V8Goose]

Hi there...

I am an aeromodeller, whose hobby is making and flying large scale radio control planes. (Like this one, no its not mine, but you get the idea)

http://www.goosesworld.com/dump/jet.jpg

I have been doing this for over 30 years. It requires a good working knowledge of woodworking, fibreglass, carbon fibre, structure and obviously, metalwork.

I am here to ask and learn how to successfully solder, braze and weld differing types of metals that I work with as my latest attempts have all but failed.

I am trying to figure out the correct materials, fluxes etc to connect music wire, brass and aluminium together and if possible, to each other.

I have had excellent results with Durafix for aluminium welding.

I should explain that I use a 'plumbers gas torch' for heat and I have been experimenting with plumbers rosin core solder, metalwork solder and a low temperature brazing rod (which i bought with me from overseas. I have one left, cant find any in Canada, and im not sure what it is, seems bronze or suchlike).

Music wire is sold in many sizes to modellers and is the most practical way to fabricate the many small parts and assemblies we need. I guess it is a case-hardened steel and for the life of me, I cannot get a good structural joint with it. (sizes range from .5mm to 6mm)

I have wrapped in in soft copper wire prior to solder, scuffed, fluxed, soldered and brazed it together but the filler material simply flows around it as if it were waterproof. Sometimes the joint looks good but has no strength.

Im not expecting to penetrate or bond the filler material with the parent material at this temperature, but expect better results.

Of course I am desperate to understand this as I am finishing a large & important project that requires these skills.

I am now wondering if i need more temperature by buying a MAPP gas kit or even oxy-acetalene in the form of a mini torch kit used by say, a jewelery maker or such like. I can get my parent materials from warm to red hot but heat doesnt seem to be the problem.

I would love to know where to buy brazing rod (Canada) and a little more about the compounds for certain applications. If i need to move into welding these materials, I will do so.

I apologise for the long-winded thread, but would rather give you the correct information first up.

Any help you can give me is greatly appreciated...

Thanks!

Goose

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[ckm]

Your piano wire might be stainless steel or chromed. At any rate, it's not likely you will be able to braze it with a propane torch, you will need a small acetylene rig.

Check out tinmantech.com for some supplies you might need. Kent White (who runs Tin Man Tech) is a master fabricator like they don't make anymore, someone for which the word master was invented....

I think he may have some silver braze that might work. Check out the Meco small torch as well, I use it for everything.

HTH,

Chris
(not a master, still lots to learn)

[jalessi]

Silver solder will work fine.

For soldering small diameter stainless control rod, propane will be more than sufficient for a heat source.

Silver solder only requires about 1100 degrees Fahrenheit.

Jeff...

[V8Goose]

Hi guys...

Thanks for your replies.

The piano wire is steel and is not chromed but does appear to be case hardened.

I am liking the Meco torch, can I run it on something other than acetalene?

Ah silver solder... I dont know where to get it, whether there is differing compounds etc... each time I ask someone for it, they look at me like Im from outer space...

Cheers!

Goose

[Geof]

Another name for 'silver solder' is Braze 450 or low temperature brazing rod.

Try going to a hobby store that caters to people who do jewellery for a hobby. You can get all manner of different silver solders with different melting points that make it possible to build up small fabrications using succesively higher melting point to avoid remelting previous joints.

Piano wire is not case hardened it is a high carbon steel and is through hardened during the manufacture which is why it is so strong and springy. If you silver solder this at a temperature that is too high you will anneal it and the strength drops dramatically. You can soft solder it okay and I think some of the very low melting point silver solders may be okay if you are very careful.

[V8Goose]

Thanks Geof!

Do you know of anywhere that sells this sort of stuff online?

I will find out if they ship to Canada. I'm all for supporting local business but Canada is unbelievable.

Cheers

Goose

[diecutter]

For various temperatures of silver solder try www.swestinc.com or www.riogrande.com. For an inexpensive Mapp gas outfit, I bought one from Lowes for about $27.00 that works great for small work; even has a soldering attachment.

[Geof]

I don't know about places to buy stuff I just know it is used by people doing jewellery work as a hobby; my father-in-law did this.

Try Googling, I just used 'hobby silver smith ottawa' and got a few thousand hits.

[Diamond_Bonder]

http://www.wattflyer.com/forums/showthread.php?t=11175 discusses soldering piano wire to piano wire.

Your problem is likely that the steel is oxidized by the time it gets to soldering temperature because it is not cleaned aggressively enough prior to soldering, and the flux you are using is not active or strong enough to prevent oxides from forming during heating and soldering. Rosin flux just isn't aggressive enough to keep the steel clean. You need acid flux, and likely acid core solder (and use safety glasses to keep the stuff from spattering in your eyes).

Sand the wire good with sandpaper where it is being soldered and make sure you don't contaminate it by touching it. A typical trick in electronics is to wet the surface of a copper wire with solder (tinning the wire) with solder before trying to solder it to another wire or part. You may have success doing the same; coat each part with solder, put the assembly together; more flux, heat, more solder. (Aluminum parts are difficult to solder under any conditions).

Silver solder will do the same thing at higher temperatures than will solder, but oxides on the surface of the metal will create the same problems. The temperatures reached in silver soldering will definitely decrease the strength of the piano wire.

If you really want to connect everything together with a minimum of problems, you can electroplate all the surfaces with nickel, which is then easy to solder. Plating aluminum with nickel is beyond the ability of a hobbyist, so check the phone book for electroplating.