2. Ferritic steels

2.1 Composition

Ferritic steels are characterized by a basic composition of carbon and chromium, adjusted to maintain a ferritic structure at high temperatures. Specifically, the average chemical composition consists of 0.008% carbon (C), 16 to 18% chromium (Cr) and a limit of 0.50% nickel (Ni).

Due to this composition, these steels are almost exclusively ferritic over a wide temperature range. Consequently, they are susceptible to grain enlargement during heat treatment, welding or forming, with often cumulative effects.

What's more, they contain very little austenite at high temperatures. If cooled slowly, this austenite will transform into ferrite. If cooled rapidly, it becomes hard, brittle martensite.