Thread: Copper to copper

Hi Ronen
I have done quite a bit if silver solder /brazing
A few obvious things.
Heat:
Copper is a great conductor and you need lots of heat to raise the temperature of the section you are trying to join....to a bright red
So, Oxy/Acetelene give lots of heat.
A plumber mate of mine often uses only LP gas ...BUT he uses a Turbo-Torch with the biggest jet/ nozzle ( diameter of burner tube /nozzle is about 25mm) Turbo Torch also swirls the flame and concentrates the heat. Even then it is sometimes only just hot enough.
The bigger the job the more heat required.

My daughter is a part time jeweller/silversmith and LP gas is OK to heat small jobs and flow thin silver solder.
Even then they often use an Oxy/ LPgas setup to increase heat.

Silver solder:
Plumbers mostly use about 2% silver ( yellow tip rod) for domestic work. Rods are about 1.5?? mm diameter.
It is NOT about melting the solder with a flame. You need the Copper hot enough to melt the solder when it is touched on the work..then it flows ..giving a correct join.

In that case ( ie with enough job heat) the diameter of the solder rod is less important.

Sorry I dont have a real solution...except apply more heat

Cheers
Bob

Hey Bob,

Thanks for the reply.

The soldering rod I am using has a label that says "15% 2.4mm Consolidated Alloy". I know it is has 15% silver, which should make the job easier, and the diameter is 2.4mm and that's why I think it might be too thick.

If you'll check the video links I have attached to my initial post, you will see they use a simple propane torch which produces far less heat than the mapp torch I use. The only difference I can see is the soldering alloy they use, it is softer and more flexible. If it works for them so why not for me? What type of soldering alloy do they use exactly? That's what I want to know.

As an experiment I tried soldering two pieces of copper (with the same size) using an electronic solder wire. Too easy! It melted like nothing and was surprisingly strong. I am very curious to know what is the difference between plumbing soldering alloy and electronic soldering alloy.

Thanks.

Ronen

Hi Ronen
I will have a look at the videos but before I do.......

When you talk about Electronic solder you are referring to what is commonly known as Soft solder.
The melting point is very low and hence you can use an electric soldering iron as the heat source. I am out of my depth regarding the alloy composition, but it is closely related to Lead solder.
There used to be plumbing fittings known as Yorkshire fittings which had a ring of soft ( lead) solder embedded at each flange. ...so it was a dry fitup and mild flame ( LPG)heat applied = voila!

Soft solder is not as strong and may?? crack with vibration/expansion /contraction etc.... although my father's house was plumbed with yorkshire fittings and copper over 40 years ago and still fine.

Hard solders ie.. silver brazing alloys, require more heat to melt the alloys and cause the "solder" to Flow.

Maybe 15% silver requires( marginally) more heat than say 2% ???( 15% is generally stronger)

Why not nick down to the plumbing supply and buy a stick of Yellow tip (2%) and see if that does the job.

I noticed that Bunnies were selling 2% rods which were std length but smaller diameter. Then I realised that they were about the same price as the previous thicker ones. Retailing at its best!!!

Clean the copper where you intend to join it. you can get away with anything from abrasive paper to a stainless kitchen scourer.
Flux is available... but my plumber mate rarely uses it with 2% silver.

If it is a plumbing type join you are after, try 2% .. If you require a higher silver content...then I still reckon it is more heat.
Yes, MAPP gas is better than LPG/butane but you can sit just below the flowpoint temperature and it will never seem to work.

Perhaps try your setup on some scrap 1/2''/15mm copper pipe. If that works then the 20mm you are using is just too much of a heat-sink...ie needs more heat.

Cheers Bob

PS: I have looked at the videos. Both are using Soft /lead solder...low temperature melt.
The first video looks like he is using an oxy/aceyelene torch ...that is the type of tip and narrow flame they have.
Second video is obviously LPG torch
Both easy with soft solder.
I don't know whether soft solder is legal anymore for plumbing? You would need to ask.
Plumbers certainly don't use it.
Soft solder.. like the videos.. is available ... bunnies??? and certainly radio parts/electronics suppliers/ Jaycar etc

Bob

The 2% (yellow tip) rods don't need flux on copper to copper joins. Just clean the copper with a bit of sandpaper first.

I use just the standard LP gas bottle and a primus torch; it's not the temperature of the torch that counts (BBQ propane gas burns in air at about 1,900C, which is well above the melting point of silver solder which is about 600C ), but what sort of volume of heat your torch puts out.

My torch nozzle is about 20mm across; it has no problem getting 3/4 inch copper pipe and fittings to a dull red heat for hard soldering.

Try cranking the valve fully open on your MAPP torch and give it a minute or two to really warm the assembly up - if that doesn't work, then you need a larger torch nozzle.