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View Full Version : Is there a test for Silicon Bronze ?



PeterSibley
12-23-2007, 05:23 AM
I've just bought a box of 50 3" x 14 g wood screws over Ebay .They have arrived and look like silicon bronze ,as advertised .I've compared the colour of the metal to other silicon bronze screws I have and they look fine ....but just to be sure ( as I intend to buy another 500 from this seller ) is there a definitive test I can use to determine the alloy ?

They did come in an old box marked Nettlefolds Silicon Bronze 14g x3"(an old Australian brand ).I may sound excessively cautious ,but these are my hood end fastenings .It would be good if they were as advertised .

P.I. Stazzer-Newt
12-23-2007, 06:29 AM
Other than employing a proper metallurgist.....

If you take a piece of brass and leave it in vinegar overnight - it usually goes red as the (weak) acid leaches out the zinc - bronze doesn't.

Canoez
12-23-2007, 09:00 AM
Don't you always figure out the screw is brass right after you twist the head off?:rolleyes::D

One guy I know used to have a spring loaded centerpunch that had a two-step tip. He'd use it on the face of a screw - bronze a one dot impression, brass a dot with another ring. Not really scientific, but it worked for him.

Todd D
12-23-2007, 09:33 AM
If you have a university nearby contact them and look for either an electron microscope with an energy dispersive analyzey or an electron microprobe. Either instrument can generate a qualitative chemical analysis in less than 60 seconds. All you need to know is if there is silicon present. Deal with the technician who actually runs the instrument, not a professor. You can probably get a quick analysis for $25 or so. I used to do this sort of thing for people all the time. It is very simple.

Thorne
12-23-2007, 10:55 AM
PI Stazzer -

I think the test works the other way. A few years ago I had heard that vinegar was the way to clean up SB fittings, and soaked some pieces for a day or so. They turned quite red, and folks on this forum said I'd done the wrong thing -- the acid leaches out the brass, leaving the red copper. Now I use a wire wheel on SB.

As far as just confirming they are some flavour of SB (there are several alloys), cutting one in half should do the trick -- just buy a brass screw of roughly the same size, cut it in half and compare the shavings and cut face -- the brass will be much more yellow.

http://www.key-to-metals.com/Article98.htm

The acid test (no pun intended) is the twist-off or breaking test. Pop several of the screws with their threads in a vice and use a brace and bit to see how hard it is to break the screw by turning it. Compare against other SB screws of the same size from different sources if possible. This process is recommended in our kind Host's book on fasteners.

Ron Williamson
12-23-2007, 12:29 PM
I have an in.-lb torque wrench that might be the ticket for Thornes' twist test.
A cordless drill with an adjustable torque setting would prolly work too.
R

ssor
12-23-2007, 01:18 PM
There are a couple of chemical tests for identifying silicon bronze or maganese bronze from scrap. The manganese bronze test uses silver nitrate solution which turns dark grey instantly on manganese bronze. The silicon bronze test uses nitric acid which forms a precipitate when some of the metal is dissolved in it. maganese bronze is also slightly magnetic.

Both these metals are found at scrap yards and produce hardly any dross when melted (compaired to other copper alloys) and they can be melted over and over and mixed together. 90% of my copper alloy castings use either one of these metals obtained from a scrap yard about 1/4th the cost of a commercial ingot supplier. They can be mixed to produce whatever color you desire. You can use the same crucible for both. I'll probably get in trouble here by saying this but I've been doing it for years.

I have never made bronze by adding tin to copper. I would have tried it but finding pure tin in a good quantity is next to impossible. It is also more expensive than commerical bronze alloy so it is pointless to try to make.

http://www.artmetal.com/brambush/forum/bramyak1/messages/814.html


major caution: avoid the brown fumes when you combine copper and nitric acid.

PeterSibley
12-23-2007, 04:17 PM
Both these metals are found at scrap yards and produce hardly any dross when melted (compaired to other copper alloys) and they can be melted over and over and mixed together.


.

Thanks for the tip re identifying manganese bronze ...however I wouldn't continually reuse it without replacing the zinc.It tends to get very weak .I've used a lot of mang bronze ,very good material ,but it must be within specs .

PeterSibley
12-23-2007, 04:19 PM
Other than employing a proper metallurgist.....

If you take a piece of brass and leave it in vinegar overnight - it usually goes red as the (weak) acid leaches out the zinc - bronze doesn't.

Thanks ,I'll try it (with the addition of a know silicon bronze sample ).

carioca1232001
12-23-2007, 04:36 PM
.......major caution: avoid the brown fumes when you combine copper and nitric acid.

A popular Chemisty 'A' Level question in my time was to elucidate (from memory !) some 3 or 4 similar - but slightly different - chemical reactions that ocurred as a function of the {i]concentration of the nitric acid[/i].

The teacher had no clue as to why the concentration of nitric acid influenced the end results of the reaction.

We needed to cram it. That was that !

DaveWhitla
12-23-2007, 08:39 PM
I agree with Todd. I know you're a bit out of the way but Bond Uni should have an electron microscope. When I was at UNSW we used to use ours to authenticate medals fairly regularly for the war museum. The results will be absolutely conclusive and it only takes a few minutes including setup time. If Bond doesn't have one you could send a screw to me in Brisbane - I can get it tested at UQ.

donald branscom
12-24-2007, 02:01 AM
I've just bought a box of 50 3" x 14 g wood screws over Ebay .They have arrived and look like silicon bronze ,as advertised .I've compared the colour of the metal to other silicon bronze screws I have and they look fine ....but just to be sure ( as I intend to buy another 500 from this seller ) is there a definitive test I can use to determine the alloy ?

They did come in an old box marked Nettlefolds Silicon Bronze 14g x3"(an old Australian brand ).I may sound excessively cautious ,but these are my hood end fastenings .It would be good if they were as advertised .

Don't worry. Almost all aluminum and bronze screws have silicon in them because silicon is what makes the metal harder. Otherwise the screw would be too soft.
pistons of engines have about 22% silicon to make them hard and to cut down on expansion.

PeterSibley
12-24-2007, 03:44 AM
Thanks ,I'll try it (with the addition of a know silicon bronze sample ).

OK .........12 hours so far an no reaction visible in vinegar on either the new screws or the known sample .

The Bigfella
12-24-2007, 04:04 AM
Betya don't recycle the vinegar in the Christmas mayonaisse.

P.I. Stazzer-Newt
12-24-2007, 04:21 AM
OK .........12 hours so far an no reaction visible in vinegar on either the new screws or the known sample .

If you've got an expendable brass one, lob that in an leave it a while.

Actually any piece of (un-lacquered) brass would be a good control.

donald branscom
12-25-2007, 04:12 PM
I think you have too much time on your hands, or this is Virgo type stuff.

Like someone has time to hunt down screws and put them in a box just to trick you.
C'mom !

If it says silicon bronze screws ,they probably are.

Whats that little spot on your face?,,,,, better go see the surgeon in the hospital right away. But he might trick you though. Better get three opinions.

I think this is a classic case of cabin fever.

Jay Greer
12-26-2007, 03:10 PM
You are posing a question that has never been of much concern to me as I usually purchase fastenings from a trusted supplier. I might note that, if you are familiar with the various alloys of bronze, color and hardness are the most easy methods of identification. That is unless you are interested in more scientific means. Brass has a distinctive yellow color and is rather brittle when compared to the bronzes. Just doing a bit of filing is usually a dead give away as the dust comes off easily with either a saw or file and is rather sharp to the touch. Silicone bronze is definatly redder in color, often a ruddy shade of burnt sienna. The filings here produce a softer grain and the file passes more smoothly over the surface of the metal. Then there is Navy Bronze that looks a lot like brass but is softer in texture, machining smoothly, especialy if a bit of lead is in the alloy. Phosphor bronze is redish in color but is very hard, often being used as spring stock. Phosphor will easily fracture if an attempt is made to bend it without an ample radius. Heat treating will allow bending but will also, perminently soften the material. Manganese bronze is often used for castings where great strength is needed such as propellers and struts, is slightly magnetically attractive. A small, pencil, magnet suspended on a string will swing and hold to manganese bronze when held near it. Aluminum bronze, is a very hard material and will let itself be known as soon as one attempts to machine it. Special speeds and tool angles are required to machine it smoothly.
Jay

DaveWhitla
12-26-2007, 08:28 PM
I think you have too much time on your hands, or this is Virgo type stuff.

Like someone has time to hunt down screws and put them in a box just to trick you.
C'mom !

If it says silicon bronze screws ,they probably are.

Whats that little spot on your face?,,,,, better go see the surgeon in the hospital right away. But he might trick you though. Better get three opinions.

I think this is a classic case of cabin fever.

Yeah - I've never heard of anyone putting loose screws into any old container that happens to be handy. And containers always correctly label their contents.

PeterSibley
12-26-2007, 08:47 PM
Thanks Dave ....I'm going to ignore Mr Branscom's contribution .

Also ..............Jay , pretty much what would have thought , it seemed worthwhile to gain some input from the assembled contributors .:)