The steels can now be grouped into three very specific groups, which are:
  • Martensitic Steels: It is this group that will readily form the product of martensite with the assistance of carbide-forming elements. The martensitic steels have a high hardenability capability and require tempering after austenitizing and quenching – sometimes twice or three times depending on the other supporting alloying elements. For example, high nickel-content steels will tend to have a capacity for retained austenite that can be decomposed by multiple tempering. Martensitic stainless will form martensite because of the austenitizing temperature, the cooling rate and particularly the carbon content in relation to the chromium content. The martensitic stainless steels have a high hardenability capability.
  • Austenitic Steels: This group (excluding the austenitic stainless steels) tends to have a low carbon content (generally below 0.30% carbon).
  • Cementite Steels: This group will tend to have a carbon content greater than what is shown at the Eutectoid line on the Iron-Carbon Equilibrium diagram. They will very often form carbides with chromium, molybdenum, tungsten and vanadium.
The next presentation will discuss the effects of the alloy elements on hardenability and other mechanical properties.