6. What are metal carbides and what is their significance?

The strength of all alloy and carbon steels is derived from the metal carbides formed during the mill processing. The carbon in steels combines with iron, vanadium and with chromium, as well as many other metal alloy additions to form compounds, which are a very hard phase within the iron matrix. Tool steels generally have high carbon content (above .8%) and can be made very hard – but brittle.

7. What exactly is chromium?

Chromium is a metal and is typically used for plating because it is shiny. It is also used as an alloy addition to iron to form a stainless steel. A stainless steel must contain at least 12% chromium, but these lean chromium steels can still show some rust on the surface. Using 18% chromium will make a more rust resisting stainless. Exposing any stainless to oxygen at temperatures above 1200˚F will cause the chromium to join the oxygen and therefore leave the surface depleted in chromium if it falls below 12% the surface will show rust.