Characteristics of structures of incomplete recrystallization and their effect on the properties of steels

Abstract

1. The formation of very hard martensite during cooling from temperatures slightly exceeding Ac1 substantially reduces the plasticity and impact toughness ("brittle recrystallization"). For alloy steels "brittle recrystallization" is observed not only in quenching but also in slow cooling from temperatures in the critical range. 2. The properties of structures of incomplete recrystallization are unusual and depend on the character and distribution of the austenite decomposition products and also the condition of the unrecrystallized ferrite. 3. Ferrite, not recrystallizing in the critical temperature range, is softened because of recrystallization and causes a general reduction of the properties of the steel undergoing incomplete recrystallization. The degree of weakening of ferrite depends on the original level of the properties and the heating rate, which determines the intensity of the development of recrystallization processes. 4. In steel heated in the critical temperature range there are two sections with unfavorable properties — sections with low plasticity near Ac1 and sections with low strength between Ac1 and Ac3. This must be taken into account in calculating the service life of machine parts.