Thread: Mystery Silver Brazing Rod? Stamped "5P"

Hi there

I have been cleaning up and sorting brazing stuff.

I found an interesting smallish section of what appears to be Silver Brazing rod, 0.118 inch dia and stamped "5P".

When scraped with a knife, it looks very slightly more yellowish than CIG SBA245, but much less than say Tobin Bronze, melts slightly higher than SBA245, and a little less to "wick" than SBA245, and has no tip colour.

As it came from an old workshop, it may be up to 70 years old.

I am just curious.
I know that this is incredibly difficult, but does anyone recognise it please?

Thanks

I have no idea personally, but did find this when searching online

https://www.mkt.ee/en/silver-brazing...en-cp-104.html

Steve

Thanks Steve.

Probably a lower silver content type rod for plumbing etc.

I see that CIG now stock only a flux coated 45% rod, and even that is possibly "obsolete", and, ... that a search on CIG website for SBA245 returns no product.

Lucky for me that 45% rod is still widely available in other brands and outlets.

Originally Posted by mike48

Thanks Steve.

Probably a lower silver content type rod for plumbing etc.

I see that CIG now stock only a flux coated 45% rod, and even that is possibly "obsolete", and, ... that a search on CIG website for SBA245 returns no product.

Lucky for me that 45% rod is still widely available in other brands and outlets.

SBA245 contains cadmium - that is probably why it is no longer listed.

I don't know what 5P is but 5% Ag and containing P (Phosphorus) is a possibility.

I'm not sure if it is still used but alloys containing phosphorus were used for brazing (not braze welding) copper/brass tight fitting socket type joints in plumbing etc.

Jack

My money is on a 5% silver content rod.
Let's face it, if you are buying engineering supplies that are up to 70 years old, you probably wont be using it on anything of importance where you'd need to be assured of the metallurgical properties of the rod and weld deposit.

If you were feeling scientific, a 45% silver rod has a solid to liquid state between 640-680 celsius. Compare that to a 5% rod which has a range between 654-810.
A rudimentary testing method might be:
Provide heat to a heatsink of some capacity (metal block), measure temp at top surface as heat is applied from below. If a small sample of your mystery rod melts at a higher temp, chances are its a lower silver content that a 45% rod you are familiar with. Compare similar diameters of course.
...Or just use the rod and leave it as one of life's little mysteries.