posted 11-09-2006 02:48 PM               

Tobin Bronze is also known as Admiralty Brass or Admiralty Metal.

There are three alloys under this name, all with the same nominal composition and differing only in their minor element content.

The nominal composition is within limits
Copper 71%
Zinc 28%
Tin 1%

Their copper alloy designations are
C44300,
C44400, and
C44500.

The maximum amounts of the minor elements are:

C44300 0.02 to 0.10% arsenic;
C44400 0.02 to 0.10% antimony; and
C44500 0.02 to 0.10% phosphorus.

Other maximum minor element amount limits for all three alloys are:

0.07% lead and
0.06% iron.

Alpha brass is a single phase alloy that contains copper and up to about 38% zinc without changing structure based on the crystalline structure of copper. In excess of this amount of zinc a second phase will appear in its microstructure, visible under a microscope when a sample of the metal is polished and etched properly.

Admiralty metal is an alpha-beta bronze, i.e. two distinct phases in its microstructure.

Chemical analysis is one way to tell what the alloy is. Sometimes old timers can tell what an alloy is by dropping it on the floor and listening to the sound.

I don't know what the splotch of red paint signifies.

Never get a metallurgist started. Some of us never know when to quit.

[This message has been edited by Gene (edited 11-09-2006).]

posted 11-11-2006 12:21 PM               

Here's the web site of the Copper Development Association:
http://www.copper.org/homepage.html

Everything you ever wanted to know about copper and its alloys.

The American Society for Testing and Materials (ASTM) and the Society of Automotive Engineers (SAE) developed a six-digit numbering system to designate alloys. The old three-digit system is retained in the new system.

Alloy 464 is now C46400. There are three other alloys with this same nominal composition within certain limits:

Cu 60%
Zn 39.2%
Sn 0.2%

The other alloys in the group are:

C46500, up to 0.10% arsenic;
C46600, up to 0.10% antimony;and
C46700, up to 0.10% phosphorus.

Trade names for these alloys are:

C46400 unihibited naval brass;
C46500 arsenical naval brass;
C46600 antinonial naval brass; and
C46700 phosphorized naval brass.

I have always wondered if uninhibited naval brass likes wild parties. (A bit of metallurgical humor to wake everyone up.)