Liquid Nitrogen and Hardened Steel
What is the effect of liquid nitrogen
with hardened mild steel? Are there any adverse
effect that will lead to failure of that material in
future? Why are some musical instruments treated
You refer in your question to "hardened mild steel". In fact, mild steel
cannot be hardened. It has insufficient carbon content to allow
hardening. So, in short, there is no such thing as hardened mild steel.
But to try to answer your basic question, simply immersing any type of
steel (whether mild steel, or heat-treated and hardened carbon steel)
in liquid nitrogen has no lasting effect once the steel has warmed up to
Mild steel becomes somewhat more brittle at the temperature of liquid
nitrogen (or any of the common liquefied gases), but that is only a cold
temperature effect, and its normal toughness returns when the steel
returns to normal temperature.
There are some rather exotic steel alloys that need ultra-rapid cooling
from red heat, to achieve specific properties, and immersing the red
hot alloy in liquid nitrogen (rather than the usual quenching in water)
achieves a faster cooling rate. But this is simply a means of achieving
faster cooling, not any result of liquid nitrogen itself.
As for "treating" musical instruments with liquid nitrogen, I am unable
to find any references to this, nor to what might be achieved by doing
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Update: June 2012