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Heat hardening


#1

I need to heat harden a piece in brass made primarily of 3/32" rod.
Any thoughts? Thanks. ED


#2
    I need to heat harden a piece in brass made primarily of 3/32"
rod. Any thoughts?  Thanks. ED 

As before on the ArtMetal site, non ferrous metals need to be WORK
HARDENED to get them hard, the opposite of ferrous metals where you
heat then quench to harden them.

So hammer, bend, peen or what ever but work the metal to harden it.

John Dach


#3

Quenching hot brass will harden it unlike copper.

Marilyn Smith


#4
    Quenching hot brass will harden it unlike copper. >Marilyn
Smith 

Hate to disagree with you Marilyn but quenching it makes it softer
just like copper. It is possible to heat treat some types of brass
(there are literally dozens of different types) to make them harder
but it is done by precipatation hardening not quenching.

Jim
James Binnion Metal Arts
Phone (360) 756-6550


#5
    Quenching hot brass will harden it unlike copper. 

I’m afraid that I have to disagree with you. Except for a few odd
alloys, copper alloys all anneal with a quench from red hot. I work
with a lot of brass, and annealing is a way of life.

Ron Charlotte – Gainesville, FL
@Ron_Charlotte1 OR afn03234@afn.org


#6
  I'm afraid that I have to disagree with you.  Except for a few
odd alloys, copper alloys all anneal with a quench from red hot.  I
work with a lot of brass, and annealing is a way of life. 

You’re right that brasses don’t harden. But a major exception to
your statement would be silver or gold alloys containing significant
copper, such as sterling silver and most yellow and white golds.
Because copper is not completely soluble in either silver or gold,
heat treating to cause precipitation hardening (also called age
hardening), IS possible. Of course, these aren’t actually copper
alloys with copper as the major component, but worth mentioning
anyway. In the case of a few of the gold alloys, the hardness you
can get can equal or even exceed the degree of hardness you can get
with cold working, though the hardness achieved this way may tend to
be also more brittle/.less tough than a similar degree of hardness
from working the metal.

Peter


#7
...in either silver or gold, heat treating to cause precipitation
hardening (also called age hardening), IS possible 

Hi, Peter.

I know how to do this with siver (it’s in the Rio catalog)-- 650
degrees for 1/2 hour-45 minutes-- but can you give details on a
couple of gold alloys? Does this work on the relatively high karat
(softer) alloys such as 18 or 22 yellow? Thanks!

–No�l


#8
    You're right that brasses don't harden.  But a major exception
to your statement would be silver or gold alloys containing
significant copper....<snip> 

I kind of evaded those under the category of “odd alloys” because
the explanation is more complex than I was willing to go into.
There are also oddballs like phosphor bronzes.

I’ve not had a chance to try the heat hardening process on silver
yet ( I still work largely in base metals) but it is on my list of
things to master. As I understand it, it’s about the equivalent of
a 25 to 50 percent reduction work hardening.

Ron Charlotte – Gainesville, FL
@Ron_Charlotte1 OR afn03234@afn.org


#9
It is possible to heat treat some types of brass (there are
literally dozens of different types) to make them harder but it is
done by precipatation hardening not quenching. 

Jim-- what is precipatation hardening? I work a lot with brass and
need to harden it after I have finished fabricating my pieces. Work
hardening is not an option for most of these because of the
complexity of the form and the joints. Any thoughts would be
helpful. Thanks.

Erica
Duffy


#10
  I know how to do this with siver (it's in the Rio catalog)-- 650
degrees for 1/2 hour-45 minutes-- but can you give details on a
couple of gold alloys? Does this work on the relatively high karat
(softer) alloys such as 18 or 22 yellow? 

The procedure is similar in the gold alloys. Check the details in
the chart at the back of Alan Reviere’s Professional Goldsmithing
book. Nice chart. Nice book.

It works in higher karat golds IF the alloying metals are more
copper weighted instead of the common alloys which often have more
silver than copper. With 22K, you won’t get as much hardening as
with 18K, but you can get some, especially if it’s a rose gold. If
the alloy is mostly silver, you won’t get significant hardening. With
the 18K, likewise. If it’s an 18K yellow, similar to the usual
italian yellow colors, then it may not have enough copper in it to
give you all that much hardening. But those with more copper, say
at least half copper in the copper to silver ratio, then it can be
significant. And the 18K rose golds, those with much more copper
than silver, or mostly copper, are among the alloys that give the
highest levels of hardness with heat treatment. An 18K red gold, only
copper and gold, will become so hard and brittle that dropping it on
the floor can be risky. It might shatter. In this case, part of the
hardening is not just precipitation hardening, but the formation of
an ordered array structure that one normally needs to try and avoid,
to keep the metal from being so brittle as to crack too easily.

Peter


#11

The 18 K gold copper alloy is age hardenable, Maximum gold - copper
hardness is achieved at about 25 % copper. Age hardening is
possible between about 15- 25% copper , a heat treatment formula
would be quench from 700C then age for several hours at 300-400C.
Gold silver alloys can age harden with a maximum hardness at
about 35% silver. The silver gold system does not harden as much as
the gold copper one. Sorry i can’t be much more help. You need the
phase diagrams for the material of choice and know how to read
them. These are not always easy to find . Jesse


#12
Gold silver alloys can  age harden   with a maximum hardness at
about 35% silver. The silver gold system does not harden as much
as the gold copper one. 

Are you sure about this Jesse? From what I’ve read, silver and gold
are completely intersoluable at all temperatures. That would suggest
to me that precipitation hardening shouldn’t occur. I’ve not tested
this, just trying to think it through here…

Peter


#13
     Gold silver alloys can  age harden   with a maximum hardness
at about 35% silver. The silver gold system does not harden as much
as the gold copper one. 
    Are you sure about this Jesse?  From what I've read, silver
and gold are completely intersoluable at all temperatures.  That
would suggest to me that precipitation hardening shouldn't occur. 
I've not tested this,  just trying to think it through here... 

Peter You are right I was thinking about the ternary gold silver
copper alloy not the silver gold binary. The gold silver alloy
is a solid solution across the whole composition range . But
there is apparently ( ?) a small alpha prime zone in the gold
silver binary at lower temperature in the range around 50% which
has a maximum hardness. Not a great harness increase.

I only have a citation in a 1991 reference for this and not the
original source which was"Composiyion of binary alloys" M Hanson,
McGraw Hill (1958) page 227. This reference will be a data
collection from other places not an original source.

This is not shown in the web collection at:
http://cyberbuzz.gatech.edu/asm_tms/phase_diagrams/#Au

This does not go below 900C

Jesse


#14

Jesse, Gold and silver form a complete range of solid solutions
therefore no precipitation of a second phase to create a
precipitation hardening effect. Is there some other hardening
mechanism you are referring to?

James Binnion Metal Arts Phone (360) 756-6550 Toll Free (877) 408 7287
Fax (360) 756-2160 http://www.mokume-gane.com jbin@mokume-gane.com
Member of the Better Business Bureau


#15

Marilyn, I should have done a little more digging before I sent that
note about brass not heat hardening. The ones metalsmiths normally
work with( Cartridge Brass, Red Brass, and Gilding metal do not)
however I had several people contact me off list asking for a type
of brass that would harden with heat treatment so I did a little
research. It turns out there is a type of brass that will get
harder by quenching it from a high temperature. It is called Muntz
metal and is 40%zinc and 60% copper. If it is held at 800 C (1472 F)
for 30 min. and rapidly cooled by quenching in water it can achieve
a considerable hardening effect. It will reach a hardness close to
heavily cold worked fine silver (95 Brinell) as compared to its
fully annealed state which is about the same as annealed sterling
silver (60 Brinell) with additional precipitation heat treating (300
C for 30 min. followed by water quench) it can get almost as hard as
heavily cold worked sterling silver (130 Brinell). So next time I
will try to look before I leap.

My apologies.

Jim James Binnion Metal Arts Phone (360) 756-6550 Toll Free (877) 408
7287 Fax (360) 756-2160 http://www.mokume-gane.com @James_Binnion
Member of the Better Business Bureau


#16

Serendipity strikes again-- I found a current available considered
reliable reference to the age hardening of gold - copper alloy
system. There is a reference to this in Brepohl’s “The theory and
practice of goldsmithing” , page 29 with a phase diagram on page
30. The composition reported is centered at 40% a little lower
than the older 50% in the other reference and higher than the 35 %
I originally mentioned. Heat soaking below 400 C (300 C)
produces the hardened state.

I don’t know where I first saw his and I wasn’t looking for it now-
it was just there.

jesse


#17

Heat-treatable 14k gold is available from Hoover & Strong. This is
desirable when you need to put rigidity or spring back into annealed
pieces, pin stems, posts, etc. They make other heat treatable alloys as well. Jan