Index Home About Blog
From: (Don Wilkins)
Newsgroups: rec.crafts.metalworking
Subject: Re: Brass vs. Bronze
Date: Tue, 29 Jun 1999 14:11:13 GMT

On 29 Jun 1999 01:53:45 GMT, (PumaRacing) wrote:

>There's an awful lot of hot air flying around in this thread. Using just
>copper/tin as a definition of bronze is fairly pointless and not generally
>recognised as being either useful or correct for many years now.
>Current definitions are that copper/zinc based materials are still called brass
>and other copper based alloys are called bronze regardless of tin content.

From the Handbook of Chemistry and Physics (but not a current edition)

90% Cu 10% Zn  known as commercial bronze (also as red brass)

89% Cu 9% Zn 2% Pb hardware bronze

>Both nickel and cobalt are common constituents of copper based alloys and both
>elements are ferro-magnetic. Not surprisingly, alloys containing these can have
>magnetic properties.

Actually all materials have magnetic properties.

>In fact the Ross materials handbook lists copper based alloys designed "FOR USE
>e.g. "Permet"  - 21% Ni, 29% Co, Cu remainder
>"Magnetoflex" - 20% Ni, Cu remainder - strip for magnets.

>I could go on.
>So many copper based alloys will just be attracted to a magnet and others will
>even have magnetic properties of their own.
>There is also a wide range of sintered materials having a coppery appearance
>and used for such things as bushings, engine valve seats etc. For many years I
>was convinced from the appearance that a particular engine I regularly saw had
>bronze exhaust valve seat inserts. It is only recently and by accident that I
>noticed shavings sticking to a magnetic screwdriver and now suspect that the
>material is an iron based sintered material with high copper content.
>However it is only with significant additions of either iron, nickel or cobalt
>that a copper based alloy can be either magnetic or attracted to a magnet. In
>such case a "true" bronze - i.e. primarily copper/tin will not have those

The addition of iron, nickel, or cobalt is common but is not necessary to
get a copper based magnet.

61% Cu 26% Mn 13% Al is an interesting magnet in that it does not
contain either iron, nickel or cobalt.

>Where you draw the line on what is and is not bronze is more a matter of
>semantics than engineering.

Yes many of the alloys were named by the original fabricators and do
not necessarily follow specific rules of nomenclature.

Index Home About Blog