spaco wrote:
I assume you are talking celcius, since Fahrenheit temps in that range
would yield dark straw to red. At, let's say, 475 C (887 F), you have
just about run out of temper colors. So, if you are only approximating
this temp range(450 to 500), you may be getting things a little hotter
than you used to be doing. You need to be down at about 350 C to get
blue, I think.
I also agree that the lubricant may be protecting the metal from
oxidizing.
Lastly, I forget what "nickel silver" is, but I don't think it
contains any silver anyway. If it did contain silver, then all bets are
off. Isn't it British slang for something like O1 tool steel?
Pete Stanaitis
------------------------------------
wrote:
I need some advice.
I am taking stamped metal parts (nickel silver) and heating them up to
about 450 - 500 degrees. Many of them change color from a shiney
silver to a bluish color. This is the effect I want.
Lately, many of the parts are not changing color. When stamped, we
use a light coating of kerosene for die lube. Sometimes we run fairly
dry.
IS the color change a result of the light kerosene? Is it a function
of temperature? What can I do to ensure that all the parts turn
bluish?
Thank You,
Wayne
I can help on this one.
Nickel silver is a trade name for nickel brass. with anything from 5 to
10% nickel.
the rest is zinc average 25% the rest is copper.
Its used or was for lots of decorative fancy ware and cutlery. as
stamped it becomes surprisingly springy.
Now as to colouring it.
1. you need to have it clean, have you got any 3M compressed scotchbrite
wheels? fine grade. I use them exclusively for metal cleaning.Run Dry of
course with proper dust extraction.
The you need a soft ie fully oxidised propane flame with your item
sitting on a grid of some sort , the flame is applied from undernreath
and the burner ,I use a 2in dia slow running clamped onto the stand
then as the flame licks over onto the top of your metal youll find it
will oxidise to what ever colour yoiu want as the temperature rises. you
can do this by eye.. Remove from the grid with a spatula or tongs and
place onto say a sheet of ali to cool. repeat. Ive done hundreds this
way on copper brass, nickel silver, bronze etc..
Ted Frater
Dorset
UK.