Properties of low-alloy steel with a martensitic-ferritic structure

Abstract

1. After quenching from the (α+γ) region, the structure of steel 12KhM consists of ferrite and martensite with a different relationship between the structural components. An increase in the quenching temperature from the two-phase region leads to an increase in the martensite content in the structure and to variation in its morphology from lamellar to stacked. 2. Variation in the strength of the steel, which has a martensitic-ferritic structure, is determined primarily by the size of the ferrite grain and the percentage of martensite by volume. For a constant ferrite-grain size, the ultimate strength and yield point increase linearly with increasing martensite content in the structure. Like the properties of the ferrite and martensite themselves, these factors have a significant effect on strength. 3. A stereological parameter — the size of the ferrite-ferrite contact, which takes into account as a whole the size of the ferrite grain and martensite content in the structure — is introduced as a characteristic of the two-phase martensitic-ferritic structure. The linear dependence of ultimate strength and yield point on the size of the ferrite-ferrite contact is established.