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Why is heat hardening not working?


#1

Hello everybody I know this is a well trodden path but after
consulting the archives and trying out a few things I get the
impression either I dont understand or I misunderstand the
procedures This is what I do .The object I am trying to harden is a
bracelet made from sheet 925% silver the bracelet is 1.5mm thick,
turned into an oval shape to fit around the wrist

FIRST TRY

1.I heat an oven to 1200f and place the item in for 15 minutes
2.quench
3.I leave it in water until the oven cools down to 600f
4 I place it in the oven at 600f for 1 hour
5.Bench cool

When it was cold it was still soft and it hadnt hardened at all

SECOND TRY

1.Heat the oven to 600f
2.Place the item in for 2 hours (I wait until the oven is at 600f before 
I place the article in )
3 Turn the oven off and open the door and leave the item in the oven 
with the door open for 2 hours
4 Remove and quench

This didnt work

Maybe some body can see where I am going wrong ?

I also read to"flux metal" but I dont understand what this means

Does annealing mean to bring the silver up to a high teperature ??

Thanking you in advance for any help or ideas

Anthony


#2

What kind of oven do you have that can reach 1200 F ? Do you have
bezels or and applied pieces soldered on to this bracelet? If it is
basically a wire or plain cuff, it would be simplest to put it back
on the bracelet mandrel and strike it with overlapping blows using a
leather mallet. This would work harden it without the danger of
melting it or producing fire scale on it.

Flux can protect the metal from oxidation and is also a signal. If
you are annealing metal, you have reached annealing temperature when
it turns clear.

Marilyn Smith


#3

Hi Anthony, In Tim McCreights “The Complete Metalsmith” he says the
following about Heat Hardening:

“In conventional work-hardening, metal is made rigid by upsetting
the orderly arrangement of grains. A similar rigidness can be
achieved by reducing the number of dislocations and vacancies; i.e.
by creating extreme regularity. This is achieved by warming the
metal sufficiently to begin recrystalization and holding at this
temperature long enough to allow gradual ordered crystal growth. For
sterling: After all soldering is done, heat to 280C (536degrees
Fahrenheit) and hold for 2-1/2 hours. Quench in pickle and finish as
usual”

I have used this method for hardening my hand made pin stems, it
works, give it another go.

Marta


#4

This is from :

http://www.handyharmancanada.com/hbpm/silver/silver.htm

"Precipitation hardening involves the following proceduRe:

1.  Heating the alloy to 1375-1400 degrees F (745-760 degrees C.)
2.  Holding at temperature for 15 minutes.
3.  Quenching rapidly in cold water.

The alloy is now in a softened condition, and can be re-hardened by
heating to 600 degrees F (316 degrees C.) for 30-50 minutes and then
air cooling. The resulting hardness is equivalent to the hardness
obtained by cold working to a 50% reduction."

Jesse