Silken bronze fastener?

Silicon bronze - a marine hardware store will have silicon bronze or Everdur fasteners. McMaster, too.

Low-silicon bronze. The guy had a bad accent. d8-)

Electrical properties (I'll let you figure this one out): Electrical conductivity, volumetric, 12% IACS at 20 deg. C (68 F). Electrical resistivity, 144 n-ohms-meter at 20 deg. C.

For comparison, here's the grade of copper used for high quality wire: Electrical conductivity, volumetric, annealed, 101% IACS at 20 deg. C (68 F). Electrical resistivity, 17.1 n-ohms-meter at 20 deg. C.

What this means is that the electrical conductivity of silicon bronze sucks. It has about 1/5 of the conductivity of pure aluminum.

-- Ed Huntress

Ah, okay, now it makes more sense; thanks Ned.

Jon

"Ed Huntress" wrote:>

Okay, thanks Ed. He did say the local utility used them alot, although I don't know if it was for electrical connections or not.

BTW, is that data you posted from an accessible website by any channce? I'd like to look up brass for a comparison.

Jon

It probably is available online. There are several metals information sites; I haven't used them for a few years so I can't help there. But other people here probably know what they are.

I pulled it from a big volume from the American Society for Metals that I keep at my desk, _Properties and Selection: Nonferrous Alloys and Pure Metals_, 9th Edition. I only have this thing because I was once Materials editor for _American Machinist_. It's very expensive. You'll find it in many engineering-school libraries. It's Volume 2 of the ASM set, which includes ferrous metals and other stuff.

Silicon bronze is basically a multi-purpose corrosion-resistant bronze. It's sometimes called "naval bronze," but that's a misnomer. Other bronzes are more traditionally called naval bronze and they're better in marine environments. But silicon bronze isn't bad in that regard. Its big virtues are that it's relatively cheap and it's easy to cast, and fairly easy to machine. It's widely used for screws in the building of wooden boats. I've used a lot of it for various jobs.

-- Ed Huntress

"Silicon Bronze"

For wrought alloys a typical one would be Copper Alloy C65500. Silicon content is about 2.8-3.8%, with Manganese of about 0.5-1.3. There are some other elements permitted as impurities, but the sum of the Copper content plus the Manganese and Silicon must be 99%. This is to insure a minimum copper for conductivity.

For cast alloys C87300 is commonly used, with similar chemistry to the above.

This alloy has a nice color to it. Where copper is very reddish and many brasses are reddish, this will have more of a dark golden appearance.

It has good strength.

Mark

Right - but they're using Silicon Bronze bolts for the other properties than conductivity - environmental effects corrosion resistance, dissimilar metal galvanic corrosion resistance, and the thermal expansion rate of the bolts will be in the same ballpark as the copper parts they are bolting together.

The current should be flowing directly between the top face of the pure copper busbar and the bottom face of the copper lug you have bolted on top. The bronze bolt is just clamping the two surfaces together, and shouldn't be carrying that much of the current itself.

-->--

Aha. Well, that should be no problem then.

-- Ed Huntress

On Wed, 17 Oct 2007 14:28:12 -0700, with neither quill nor qualm, "Jon Danniken" quickly quoth:

No, no, no. Silken bronze is synthetic, primarily made up of Polyester Lead, with minor alloys of coppernumium and brass.

-- Death is more universal than life; everyone dies but not everyone lives. -- A. Sachs

'Been smoking those old Firesign Theater albums? d8-)

-- Ed Huntress

Brass exhibits about 28% the conductivity of copper.

This doesn't necessarily make it a "bad conductor. You just need more cross-sectional area to get a given resistance. Bolts are much shorter than wires, and are usually larger diameter as well. And, as Bruce noted, a bolt often clamps conductors in contact together so the conductivity of the bolt really doesn't matter all that much.

>

But note that low silicon bronze (the material in question) has 12% of the conductivity of copper. High silicon bronze (2.8 - 3.8% Si) is only 7%.

Red brass is 37%. "High conductivity bronze," also known as "penny bronze," is 41%.

Conductivity of copper alloys ranges all over the map. You really have to check the conductivity of the particular alloy to know what it is.

-- Ed Huntress

Silicon Bronze is used in electrical connectors to maintain strength at high temperatures. Not, as George points out, because of it's stellar conductivity.