We are just now concerned only with the steels of classes one and two—the carbon steels. As explained in a previous chapter, these are alloys of iron with not more than 2 per cent of carbon.
High Carbon Tool Steel (1.25 Per Cent C) as Cast
(Magnification 70 diameters)
Low Carbon Tool Steel (.50 Per Cent C) Annealed
(Magnification 70 diameters)
Low Carbon Tool Steel (.50 Per Cent C) as Cast
(Magnification 70 diameters)
Medium Carbon Tool Steel (.86 Per Cent C) as Cast
(Magnification 400 diameters)
Carbon is the element the presence of which confers upon iron the ability to harden when cooled suddenly from a cherry-red heat, as by quenching in water or oil. If the steel contains less than four-tenths of one per cent of carbon it has little or no hardening power under this treatment; but steel with six-tenths of one per cent or more of the element, has the wonderful property of being slightly malleable when in the annealed state, but extremely hard and brittle after this sudden cooling—leads a dual life, so to speak.