copper based solder?

[crueby]

I came across a type of solder that I had not seen before, a copper solder sold for jewelry making. It is mostly copper, with 7 percent (as I recall) phosphorus. The melting point was in a simaler range as silver solder.
Has anyone got any experience with this stuff? Is it suitable for engine/boilers?
The attractive part is that the cost is quite a bit lower than silver solder since it has no silver, but is it good for engine/boiler work from the physical property side?

 

[rythmnbls]

I worked in an electric motor rewind shop for a few years, phos-copper as we called it was used to hard solder/braze connections in the motor windings, the phosphorous acts as a flux.

Its very easy to use, but I don't know if its suitable for boiler making.

Regards,

Steve

 

[kf2qd]

Similar to the brazing rod used in airconditioning coils. They also had verities with 1, 2 & 5% silver. Used for building copper boilers.

 

[RonGinger]

The other nice thing is since its copper it doesn't show up on the surface of the boiler. However, I was warned not to use it on boilers because the electrolytic action of the water can leach out the phosphorous. I cannot offer a reliable source for this, but the old guy that warned me was thought of as a great modeler.

Id also note you never see it on model plans or sites, so there might be a reason.

The reason might simply be 'that's not how we do it'

 

[crueby]

The reason might simply be 'that's not how we do it'

That was one of the things I was wondering - is there a real reason, or just inertia?

 

[GWRdriver]

In the USA this type of solders are known as "phos-coppers" the most popular of which is brand named "Sil-fos." These were used, as mentioned, primarily in the heating and cooling industry. About 50 or so years ago a few live steamers in the USA decided that Sil-fos would be an excellent solder for copper boilers because it was less expensive than silver solder (cheaper) and when used with cuprous alloys needed no flux (easier.) Word spread and beginning in the mid-1960s, on the basis of "cheap and easy", large numbers of model boilers were built using phos-copper. The preponderous majority of these were coal fired and after a time leakage problems began to appear. It was eventually determined by the manufacturers that phos-coppers would degrade and become brittle when exposed to a sulphorous atmosphere (ie, coal smoke) where they were never intended to be used anyway.
Cut to the chase.
In the USA one can still use whatever they please to glue their non-regulated (exempted) model boiler together but only the die-hard cheapskates still use it. The majority of US builders do not use phos-coppers for reasons of safety and boiler life span. In every other country where model boilers are regulated, for its inappropriateness for copper boiler work, phos-coppers are not allowed as an acceptable soldering medium. You can say these regulations are in place due to "inertia" but there is considerable experience behind it.

 

[crueby]

GWRdriver - thanks for the info!

 

[GWRdriver]

Hello crueby,
Glad to oblige with my understanding of it. I'm sure there will be anecdotal exceptions, those who have used phos-copper without problems, but the eventual evidence pointed to it being the source of problems from embrittlement. My first boiler, built back when it seemed to be the best of all worlds and we didn't suspect problems, was done with Sil-fos and it never was "right." I don't blame the solder for all of that, I wasn't the boiler builder then I am today, but it did develop leakage problems. I also can't agree that it's because "We've always done it that way", because we haven't always done it that way. In the early days of model engineering riveted and soft soldered construction was the norm, it's still mentioned in early editions of KN Harris's book, followed by a period of brass brazing. I have a boiler (now rendered harmless) which came off an otherwise beautifully built Maid of Kent which was brazed and is a nightmare! In that case I suspect the boiler and the rest of the loco were done by different people.We experiment, learn, and move on. TIG welding is now the new frontier. We won't know how that works out for a while.

 

[goldstar31]

Interesting but silver solder and tin based solders will also go crystalline. Again, I read and read more and more about silver soldering, welding and brazing and note that no one has mentioned something called porosity. As a very small boy brought up in the blacksmiths shop to hear the old men talking out , raising the dottle. It was local language for dottle being the remain left in the bowl of a pipe of tobacco. In boiler smithing, it was the way that the torch was used to dig into the weld pool and bring out the inclusions.
Or am I writing about another world?

Again no one seems to mention that silver solder once applied, changes its melting point.

Maybe, someone else might agree-----or disagree


Norman

 

[GWRdriver]

Norman,
I would agree (about changing melting temperature) but the question wasn't raised. That metalurgical peculiarity has come in very handy over time. For years I've made do with one silver solder on account of that, and also by carefully planning of heats and wielding of torch. That dodge doesn't always work, but it works often enough (99%) to not feel compelled to keep a second flavor of solder on hand. And yes porosity was one of the problems with phos-coppers, attributable to the hot sulphurous gasses I suppose. It also boiled easily from lingering too long with the torch.

 

[Loose nut]

There are silver-phos brazing alloys also and they definitely shouldn't be used on boilers.