called chrome nickel steel. This increases the hardness to a high degree
and adds strength without much decrease in ductility. Chrome steels are
used for high-speed cutting tools, armor plate, files, springs, safes,
dies, etc.

Manganese has been mentioned under _Steel_. Its alloy is much used for
high-speed cutting tools, the steel hardening when cooled in the air and
being called self-hardening.

Molybdenum is used to increase the hardness to a high degree and makes the
steel suitable for high-speed cutting and gives it self-hardening
properties.

Nickel, with which is often combined chromium, increases the strength,
springiness and toughness and helps to prevent corrosion.

Silicon has already been described. It suits the metal for use in
high-speed tools.

Silver added to steel has many of the properties of nickel.

Tungsten increases the hardness without making the steel brittle. This
makes the steel well suited for gas engine valves as it resists corrosion
and pitting. Chromium and manganese are often used in combination with
tungsten when high-speed cutting tools are made.

Vanadium as an alloy increases the elastic limit, making the steel
stronger, tougher and harder. It also makes the steel able to stand much
bending and vibration.