source of bronze

i have been advised not to make my own bronze but to obtain scrap for casting, a recommended source was marine water pumps but i cant find any and im wary of getting any scrap bronze as i dont know what type it might be or what it contains. can anyone advise on a source of unleaded castable bronze?

Geoff

I can't help much but I have much the same problem. The only option for known quality bronze that I have been able to find is to buy new bronze bar of the required alloy composition - a rather expensive option. However purchasing pure metals separately to create an alloy of known composition may be just as expensive - or even more so.

I would also be interested in the reasons for not making your own bronze - dangerous fumes perhaps or difficulties in getting the metals to combine to form the alloy or some other reason. I know that manganese bronze is not recommended - I think because of the high melting point of manganese and also with difficulties in casting this alloy but I would have thought the lower melting point alloys would be feasible.

I have the raw metals ( and alloyed bronze ) and an induction furnace but have not proceeded further pending further investigation and the creation of a master and molds for the castings.

Best of luck and let us know how you get on..

Pero

Bronze is almost a thing of the past in this post-industrial era. Even seawater pumps etc tend to be made from cast iron and fitted with plastic liners and impellers these days.

Maybe contact one of the remaining commercial foundries and see if they can help?

I may be able to help with this. The problem with the common bronzes is getting the Tin to go into solution especially if you buy it in granulated form. You need to add a reductant, I came up with the following mix:

10% agricultural lime (garden shop)

35% clean quartz (kiddies play sand, but as white as possible)

10% coal dust

45% bone meal (garden shop)

If you want to melt the manganese bronzes (or brass) this works well as a capping, to prevent fumes. It also works for melting (Cu alloy) fines. The easiest bronze to pour is the alumina bronzes, and they’re more forgiving with draw making riser design easier. To improve machinability you need to add Si with the cast iron inoculant FeSi a good source. All depends on what you planning to cast and its applications.

Most of my bronzes are made using discarded copper from motors or copper plumbing piping with the alloys from various sources. The mixes and sources for the various alloys were described in different articles in ME (Backyard foundry techniques and Fantastic materials and where to find them).

I’d rather not write an essay on a forum .

Hope this helps,

Luker.

I wonder how our ancestors got on in the broze age,they had no books or forums,but they found out how to mix and melt tin and copper.

I would hazzard a guess that the copper ore they obtained had a certain amoint of tin in it so the smelting process produced the alloy as a matter of course.

regards Martin

Having the neighbouring tribe constantly trying to poke you with very sharp copper-tipped sticks would be a great incentive to try new and better ways of making pointed sticks.

i don't think you are right, Martin, although it might have been possible in one or two places. Copper and Tin ores can be mined fairly close together (eg Cornwall) but not combined in one ore. It is certain that some early bronze was made from a mixture of ores (rather than a mix of metals), and it required a lot of suck-it-and-see, as well as magic, to get anything workable or strong.

The advice 'Don't make your own, but use scrap' seems less than logical, as it is difficult to know what a lump from scrap is before you add another lump which may be quite different. Mixing your own at least offers the option of taking advice if it doesn't work.

Funny stuff advice . A bit like scrap bronze, I suppose, you never quite know ...

Cheers, Tim

In today’s News : **LINK**

https://www.bbc.co.uk/news/business-56330378

MichaelG.

Ho that's rich! And a turnaround for the books, fake goods being shipped INTO China. And not just fake copper, but fake security seals and even fake insurance documents.

.

“Thought for the day” , Tim ... Thanks !!

MichaelG.

From that fount of all knowledge (and then some), Goggle:

One theory suggests that bronze may have been discovered when copper and tin-rich rocks were used to build campfire rings. As the stones became heated by the fire, the metals contained in the rocks were melted and mixed. ... It is thought that Bronze properly appeared in the region around 3000 BC

As I said it would have been more remarkable if they had been able to produde even a relatively pure copper. Most progress relys strongly on happy accident, repurposing and copying from nature even today. Smelting could well have been stumbled on after observing the residues from fire pits surrounded by certain rocks. I would surmise that certain areas would produce different varieties of alloy long before any serious metallergy was understood or even possible. Even until recent times the quality of metals produced including iron and steel was closely ties to the ore mix and the local processes.

regards Martin

PS Fair comment from Tim Stevens regarding ores. My main point was that alloys are easy to produce, pure metal much harder. Start from the ore and see what you get. Very early efforts would have been from surface rocks which could quite easily have been mixed. Mining logically comes one an established requirement has occurred. We are after all talking about the 'first' bronzes. As I say I'm no expert just trying to think it through.

regards Martin

Edited By Martin Kyte on 10/03/2021 10:37:34

This is probably as near to ‘authoritative’ as we will find: **LINK**

https://www.copper.org/education/history/60centuries/raw_material/thebeginnings.html

MichaelG.

Interesting Michael.

regards Martin

Seems odd to suggest making your own as I would think it far more difficult to get plain tin though copper scrap is plentiful.
I thought I'd posted before. If you check some scrap yards you may find one that does more than just deal in cars. I found one a few years ago, although some miles away, that specialised in getting the better metals out of the much bigger car yard next door. The manager turned out to be a home machinist so was ME friendly and had a barrel for the bronze, another for brass, though the concentrated on aluminium.

I made my own bronze for my Crampton castings, the only problem was porosity. However I read in an old ME that the solution is to add phosphorus. This is easy, all you need is the solder they use for refrigeration which is cheap, I got a kilo on ebay for £14. You don't need much, it de-oxidises it. I used scrap copper, 5% tin which was from a reel of lead free solder and 5% lead. You dissolve the tin first then the lead and the phosphorus solder just before pouring. I think you would get the porosity even with ingot bronze. The ancients were wonderful at casting bronze, you should see the 2000 odd year old lost wax bronze horns in the museum in Dublin.

Gentlemen, If the reason for needing bronze is to avoid the issue of dezincification in models then the use of a bronze of unknown alloy but having been made to avoid this problem, having served it's time and shown NO sign of dezincification and now being scrap is better than starting with possibly less than pure ingredients and making an unproven alloy. In the context of marine waterpumps, most notably made by Jabsco I expect the alloy could be accertained if really needed. When for example making the bushes for a boiler, Bronze is specified, then the boiler inspector is going to expect a proper Cu/Sn alloy (gun metal) not some homemade alloy of unverifyable metal. It would be good grounds to refuse to test or pass the pressure vessel. If bronze is required for it's wearing properties, then how many 100s of thousnds of milles for the bearings ?

If you are unable to find bronze in the UK then you are looking in the wrong places. I would guess that with current metal prices you will be lucky to find scrap bronze for less than £5 a Kilo. There are several metal suppliers who will be happy to supply in ingot, but often with a minimum charge

Copper has an affinity for Oxygen and when molten will absorb it, only to give it up on solidifying - porosity. There are 2 ways to deal with this A) remove it before pouring or B) stop it being there in the first place. The use of crushed charcoal on top of the melt will keep it away in the first place. For A use deoxidising cartidges - which contain phosphorous. Silphos solder as it;s name implies contains silver.

As for pure metals, cornish tin ore was contaminated with arsenic, another metal ! And copper is often contaminated with small amounts of arsenic. Old lead, as in church roofs is purified as it contains silver, in amounts worth recovering.

At the level we are talking about here, the main thing is that the metal we use is of the right type for the job, not wether it's perfect !

For those who wish to cast copper or it's alloys I have a quantity of deoxidising cartridges PM me. Noel

Hi Noel, nice to hear from a fellow foundry man on this topic. In my nick of the woods getting anything is tricky, even buying from a scrap merchant is a nightmare. If they do want to sell you scrap they sell it at LME prices, but typically they just refuse. The coal/coke etc. trick to cover the melt works really well but if you mixing and melting alloys and fines you need a little more to strip the oxides off the surface.

I have cast numerous boiler components and have never had any issues, mostly from mixed alloys to get the specific grade I was looking for. If you interested here’s a little video a good friend of mine put together some time back. That little loco is still giving me loads of fun on our track, had a good days steaming this past weekend.

Hi Luke, I wondered if you would stay silent or join the fun ! Knowing of the issues in your neck of the woods was my reason for stating "in the UK"! The preoccupation with precise alloys and industrial standards is hardly relavent in our scales, so long as it is safe and works does it matter ? If it has 2%Zn, 0.3%Ni, 3% Pb, 8% Sn If any of the whole numbers vary by 1 or2 % does it make any significant difference ? If you make your own alloys you only know what you started with not what you have in the end, most notebly a loss of Zn. For bronzes, which is where this started, it can be bought in ingot form, 7Kg and £9 per Kg =£56 +vat and carriage! Tin £30/Kg

Or buy off cuts and smelt. Best wishes Noel.