Author Topic: Problems soldering steel wire  (Read 2011 times)

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tbone

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Problems soldering steel wire
« on: July 07, 2014, 01:23:56 »
I'm working on a Model Slipway kit and trying to get the railings together.  Some of the supplied stock is brass and some of it is steel wire.  The steel wire is a copper colour, looks like welding wire to me.

Anyhow, I can get the solder to stick to the brass no problem but am having no luck getting it to stick to the steel wire.  I can get it hot enough to melt the solder but it doesn't stick.  I've tried cleaning the surface with scotchbrite; this takes off the copper coating and leaves a shiny silver surface but the solder still doesn't stick.  I even tried some flux but that didn't help.

Any ideas would be appreciated.

In the alternative I can just buy brass stock to replace the steel; looking for a good source for that still.

PHILNZ

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Re: Problems soldering steel wire
« Reply #1 on: July 07, 2014, 01:43:02 »
I use copper coated mig welder wire for my rails etc. Its high tensile and can be soldered .  The roll i got was 60metres and cost $30 nz about 15 pound if converted back to uk pounds. As for soldering steel wire i dont know what flux should be used for that.

des

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Re: Problems soldering steel wire
« Reply #2 on: July 07, 2014, 02:23:45 »
Hi Tbone

My understanding is that you cannot solder steel wire using a "normal" lead-tin (or lead substitute) soft solder.  (I hesitate to say you can't do it - if I say that, then someone will immediately jump in tell us both that it can be done.)  You can braze it, but this requires brazing rod, brazing flux, and a much higher temperature flame to directly heat the material to be joined.  You can get everything you need on-line from RS Components in the UK.  However the technique is very different to using soft solder.

You can also silver solder the copper cladding, one piece to another.  The technique is similar to brazing, but uses a lower temperature flame.  I don't know if it will be successful on the steel core though.

I have just recently started working on handrails for my AZIZ kit, using copper-clad steel wire, as you are.  So far I have been able to solder the rails to the brass stanchions, but rail-to-rail connections are so weak as to be unviable.  I suspect I'll end up either brazing or silver-soldering the rails together.

Des.

tbone

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Re: Problems soldering steel wire
« Reply #3 on: July 07, 2014, 11:55:23 »
Haven't tried silver soldering yet, I guess that will be next.
Brass is so much easier to solder, if I can find a good source of thin brass I'll buy that instead

olscuzbut

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Re: Problems soldering steel wire
« Reply #4 on: July 07, 2014, 18:24:00 »
tbone,  found great hobbies an excellent supplier of all that stuff.

tbone

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Re: Problems soldering steel wire
« Reply #5 on: July 07, 2014, 20:31:40 »
Thanks, I'll check them out. Going to check a few local places too, save some shipping $ that way

Terence

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Re: Problems soldering steel wire
« Reply #6 on: July 14, 2014, 01:59:30 »
tbone
I've done a couple of experiments on soldering steel wire with excellent results.
The first requirement is a soldering iron of sufficient power - small stuff around 30 Watts will do.  Then keep the tip clean on a piece of damp rag or sponge and dipping in flux occasionall.  To transfer heat from the iron to the job you'll need at least a small blob of solder on the iron tip.  Now, to make sure there's not an oxide layer preventing good thermal contact between the solder blob, the job must be clean, and I always smear a thin bit of paste flux on the job.  The flux I use is Templers Tellux which is for copper and brass and general plumbing work.  Not sure of availability out side of the UK but the same formulation will be somewhere.  But it also works perfectly on clean steel and copper plated welding wire.  After soldering, residue can be washed off with hot soapy water, or paraffin etc.  If you need to solder stainless steel, orthophosphoric acid is a perfect flux, but usual safety precautions should be observed because it's strongly corrosive.  (But I understand that a trace is in the CocaCola formula, and it's used in alloy wheel cleaners.) One other tip:  when soldering very small parts, solder paint is very good, which you brush lightly onto both parts to be assembled, then assemble the parts and heat with an iron, or often it's better to used a mini-blowlamp.  The paint is a grey mixture of solder powder and chloride flux.  When it's heated, it quickly melts and you get a very neat joint.  It's also very good for pre-tinning parts - the layer is only a few microns thick, but greatly eases subsequent the soldering of assemblies.  The paint I use is Fryolux Paint, Sn (tin) 40%, Pb (lead) 60%, and again, it will be available outside the UK by other manufacturers.
Hope this helps and I haven't taught you to suck too many eggs ...

Cheers
Terence