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