Bronze - Unsolderable

What on earth have they sold me. A year or so back, I bought some CZ 121 bronze bar as stock. Today I made a couple of 1/4 BSP bushes and went to solder them onto a brass plate with COMSOL. The solder flowed on the brass plate, but the bushes just turned black and would not 'wet' to the solder.

I thought it a bit strange, so on a piece of scrap brass, turned up another scrap of the CZ 121 - same problem and the solder would not adhere to it.

Moving on, I tried a bit of silver solder - same problem.

What have I got hold of ? Not CZ121 for sure. It looks like bronze - turns like bronze

Bob

CZ 121 is a brass not a bronze so who knows what you have

On the plus side you got a bargain if it is bronze

I think it's a flux problem and that it may be a leaded bronze , in which case suggest you talk with CuP Alloys regarding a suitable flux . I've always found them most helpful . No connection other than a satisfied customer .

Trevor.

Sounds like "Aluminium Bronze" ??

That can be very difficult to solder, dont ask how I know.

Phil

I had a similar problem with a bar stamped "Holfos" a while back. I think I just avoided the problem in the end.

Martin

If , as Phil suggests it is aluminium bronze , then you may find adding 20% - 25% household salt to your existing flux will help inhibit the aluminium oxides from forming .

Trevor.

Tried mixing a bit of salt with the silver solder flux, no joy there.

Abandoned the solder idea, chucked the bushes in the bin, removed the marking off the remains of the bar, then used a different piece of stock material.

Job done and the COMSOL flowed lovely with BAKERS fluid as flux.

Ps: this isn't boiler related !

Just wondering if it was sintered (porous) bronze loaded up with oil ? Usually this would make a lot of smoke when cooked and you didn't mention this so probably not.

Gerry

Obviously we don't know what your bar stock is/was, but could you just clarify what you mean by "silver solder"?

Comsol has some silver content.

As others have said, CZ121 is a brass. What you have may be aluminium bronze. Or even a monkey metal, I have come across a brass with more zinc than is good, but its cheap. Sounds a bit odd. Noel.

Hi Bill, I started with COMSOL ( higher temp lead solder from Cup Alloys). No Go!

Then with some scrap bits, tried a joint between brass sheet and a disc of the mystery metal. Used Cup Alloys 455 silver solder rods(55% silver) with their EF flux. The mystery metal turned black and wouldn't "wet" . By comparison, the scrap sheet of brass "wetted" nicely and the silver solder flowed nicely. Adequate heat, joint prep was from fresh turned material and no coolant.

I do stress that I do not lay the problem at Cup Alloy material or even my soldering and silver soldering skills. I think my mystery metal must be some sort of bearing bronze (not sintered). It came from a metal supplier to the marine industry. Unfortunately that was some time ago and I don't have the invoice any longer.

Tried again with a mix of table salt and EF flux - No Go.

The material turned nicely, but was tough to drill and very tough to put a 1/4" BSP tap through the bush. I just thought my ancient tap was blunt, but by comparison, when I re-made the bushes in some stock brass, they passed through quite easily.

The material turned nicely, but was tough to drill and very tough to put a 1/4" BSP tap through the bush. I just thought my ancient tap was blunt, but by comparison, when I re-made the bushes in some stock brass, they passed through quite easily.

That smacks as a description of typical aluminium bronze. I have a project with a large(ish) chunk on the lathe. Turns nicely, but is b****r to tap.

Try a magnet, if it's slightly magnetic, it's alumininium bronze.

Regards Ian.

NDY and CirClip, thanks Ian, you are on the money. just tested it with a magnet, as you say, slightly magnetic.

Now what do I use 2 feet of 5/8" Al Bronze for ?

Bob

Edited By Speedy Builder5 on 25/02/2023 11:03:44

Another way to check is to measure length and diameter to get volume, then weigh it and calculate density - Al bronzes are less dense than brass

Now what do I use 2 feet of 5/8" Al Bronze for ?

A couple of hefty yellow metal drifts?

I can go back to bed now ! Objective achieved, I;ve learn something new today ! Ali bronze is slightly magnetic. Thank you circlip. Noel.

Corrosion resistant, high strength, used a lot in marine environment. I've seen ali bronze nuts on stainless bolts, no galling.