Phosphor Bronze vs Bearing Bronze

[Kim]

I've got another material question to pose to the collective wisdom of the forum.

What's the difference between Phosphor Bronze and Bearing Bronze?  Or any other type of Bronze for that matter.

Clearly, Bearing Bronze (C932) is intended for bearings, but really, how different is it from the other bronzes?  At Online Metals, the Phosphor Bronze is double the price of the Bearing Bronze.

For my current project, (the steam tractor) they just specified "Bronze" for the cylinders.  So I purchased bearing bronze since it was the cheapest bronze.  The project I'm gearing up for (Kozo's A3 Pensy Switcher) clearly specifies Phosphor Bronze for the cylinders (and many other parts).  But wow!  That stuff is expensive. What am I getting for that money (we're talking ~$200 for a 12" piece of 2" round bronze!)

I haven't found a lot of clarity by reading their product descriptions. Though for Bearing Bronze it does say "Welding, soldering and brazing are possible but not recommended. C932 is not heat treatable."   But I silver soldered the C932 quite handily and didn't seem to have a problem.

And if I decided that I have to step up to Phosphor Bronze, then I'll have to decide which one to get.  There's C510 and C544, both listed as Phosphor Bronze, and I can't see a difference between them but price (C544 is more expensive).

Then there's Nickel Aluminum Bronze (C630), Silicon Aluminum Bronze(C642), Silicon Bronze (C655), and Manganese Bronze (two kinds C673 and C863).  I'm finding the world of Bronze quite confusing.

What is the value of using the more expensive Phosphor Bronze instead of the less expensive (but STILL expensive!) Bearing  Bronze?
And do you have any general pointers on how one might decide on the best bronze to use?

I thank you for any insight and rules of thumb that you can share with me.
Kim

[Vixen]

Bump, Don't want this topic to disappear off the bottom of the list.

I have nothing to contribute but would like to know the answers to this rather important question.

Mike

[crueby]

Bump

I have nothing to contribute but would like to know the answers to this rather important question.

Mike

Me too! Kozo always seems to specify the phosphor bronze for everything (even bearings, for some reason), but I like the bearing bronze for both cost and ease of machining for bearings and such. Curious about suitability in boilers as well as durability in bearings between the two.

[Florian Eberhard]

Hi Kim

I have just made a little research to find out european equivalent materials.
What you call "bearing bronze" seems to be something like gunmetal.

Phosphor bronze is pretty tough material to machine, it can be used for bearings that are under really heavy load like impacts or/and high speeds.
Usually it is used agains hardened steel to have minimal wear.
Gunmetal on the other side is softer and can be used together with unhardened steel like construction grade steel.
It is recommended though to use hardened materials when you have higher loads on the bearing.

That is the theory but what is important is that phosphor bronze is tougher than gunmetal. What makes phosphor bronze so expensive is that the ingredients are quite pure and the process is also designed to keep it that way. So the effort for making it is higher and therefore explains the higher costs.
I don't know that it costs, but something like C91700 would be a bit tougher (and durable) than gunmetal but still better machineable compared to phosphor bronze.

Cheers Florian

[kvom]

Gun metal is 10% tin, while 660 Bronze is about 7%.

I doubt it makes much difference at all in model making.  I've been quite happy using 660.

[Florian Eberhard]

Gun metal is 10% tin, while 660 Bronze is about 7%.

I doubt it makes much difference at all in model making.  I've been quite happy using 660.

Well - yeah, i have looked it up, the translation seems to be quite inacurate 
However, 7% tin bronze is the one I was referring to, so this should be right.

Cheers Florian

[b.lindsey]

Wikipedia adds a little info on the reasons for using phosphorous in the alloy:
https://en.m.wikipedia.org/wiki/Phosphor_bronze

Bill

[toolznthings]

Stick with the 660 bronze. Easy to work with. Definitely don't want to use any of the aluminum bronzes.
Like Ampco 18 or such. Difficult to work with unless you need it.
Work with the 660 frequently. 

[crueby]

A key part of the question is whether the bearing bronze is okay for the boiler parts?

[Kim]

Thanks for the input Florian, KVOM, and Bill,
And thanks for the support Chris and Mike!

I don't know. At this point, I'm leaning toward just sticking with the C932 Bearing Bronze for everything (even though, as Chris says, Kozo specifies Phosphor Bronze).  As KVOM says, for our models, it probably makes little difference.

I guess my main concern would be if Steam would be damaging to C932 Bronze, and Phosphor Bronze (C510, C544) is immune to that issue or something. Then I'd probably change my mind.

But on this site http://www.farmerscopper.com/leaded-tin-bronze-rod.html?_vsrefdom=www.google.com it says:

Known as bearing bronze, C93200 has excellent machining properties, good hardness, as well as strength and wear resistance with excellent antifriction qualities. SAE 660 bronze has a long life span, making it an ideal alloy for bushing and bearing applications. C932 brings a machinability rating of 70, giving it a vast number of potential applications. Copper Alloy 932 is not subject to dezincification.

And isn't "dezincificaiton" the thing that people worry about with Boilers & steam?

Thanks,
Kim

[Kim]

Stick with the 660 bronze. Easy to work with. Definitely don't want to use any of the aluminum bronzes.
Like Ampco 18 or such. Difficult to work with unless you need it.
Work with the 660 frequently. 

Thanks Toolznthings, this is the kind of simple answer I need!

And I believe that 660 is the same thing as the C932 (one is SAE and one is some other standard).

Thanks,
Kim

[Kim]

A key part of the question is whether the bearing bronze is okay for the boiler parts?

Yes!  Exactly Chris!   You typed this at the same time I was writing my previous response.

I'm looking for confirmation that the Bearing Bronze isn't dangerous to use in with boilers & pressure/steam situations.

Thanks,
Kim

[Stuart]

Ali bronze wil not silver solder and is very very tough to machine

Tip if you do need to SS in put a bit of table salt into the flux then it’s ok

[Jo]

Hi Kim,

Yes Bronzes can be confusing. The cheats in us would have a peek at a model engineering supplier site and check what materials they are selling for boiler making and look to buy that stuff locally.

That bearing bronze is what you want not Phosphor bronze which is a pinkie coloured material and a real  to machine. I have both that and Ali bronze but rarely use them. I did use some Ali bronze for a valve seat cylinder head on one of the four strokes when I found a flaw in the casting 


There are lots of variations on the constituents of cast bronze as well but it is best to assume the foundry has chosen a suitable one 

Jo

[Florian Eberhard]

And isn't "dezincificaiton" the thing that people worry about with Boilers & steam?

Yes, but you need a certain amount of zinc content to get into trouble and your bearing bronze does not have enough of it.

Florian

[Ramon Wilson]

Hello Kim, bit late in replying but you might find this useful http://www.modelenginemaker.com/index.php/topic,6744.msg138122.html#msg138122

It is a reply I gave some time back and then repeated - guess it might be worth doing it again.

As a basic guide I would plump for 'yellow' cast bronze for any bearings with unhardened steel shafts, 'gunmetal' for major components. The pink coloured drawn PB is lovely stuff to machine save for one op - drilling/reaming. It work hardens easily and will grip a drill tight beyond all expectation. A way round this is to grind the drill off centre to enlarge the hole. If reaming bore the hole to minimal reaming size and use lots of coolant - it gets hot extremely quickly. It's good for bushes in boilers and bearings too but usually with hardened shafts though I do use it on the untreated EN24T big ends in my IC engines. On soft shafts it can, though not necessarily will, pick up. If it does then it becomes near impossible to remove without damage.

The one thing to bear in mind on all bronzes is the tools need to be razor sharp at all times - anything less then the material tends to get 'pushed' with resultant poor surface finish.

Hope that helps some - sorry I cant find the original post - it is there somewhere

Regards  - Ramon

Edit - grinding the drill off centre on drawn PB only works if the hole is drilled in one. Step drilling is usually the only alternative until a boring bar can be used but every drill needs to be freshly sharpened for best performance with less 'stressful' results.

[Stuart]

Bronze in it forms is copper tin mix and brass is copper zinc  hence the problem with boilers.

the real rub is all the fittings you but are all brass  but your bushes must be bronze ha they would be a pain to replace bu

Boiler fittings can be , but are better in bronze esp. for loco use you don't want a fitting to let go while driving think of the proximity of certain body parts for us gents , sorry YL's

Edit for me being dyslexic

[Kim]

Stuart, Jo, Florian, Ramon,
Thank you all for your responses here.  I really appreciate it!

Based on this, it seems that the C932 "Bearing Bronze" should be an OK choice for me to make as a suitable material for use as boiler bushes and cylinders.  If I've misinterpreted any of your excellent advice, please do let me know!

Thank you very much!
Kim

[jadge]

Yes, but you need a certain amount of zinc content to get into trouble and your bearing bronze does not have enough of it.

Correct, generally more than 15% zinc can be troublesome. Dezincification occurs in the presence of oxygen and moisture so, in theory, steam should be fine. In practise, because of the low zinc content, steam and water should be fine in contact with what we in the UK call gunmetal.

Andrew