MICROSTRUCTURAL AND KINETIC STUDIES OF REVERSE TRANSFORMATION IN A LOW-CARBON LOW ALLOY STEEL.

Abstract

The process of the formation of austenite in the early stage of reverse transformation was studied in a low carbon (0. 12%C) 3. 5Ni-0. 35Mo steel with acicular structures such as martensite, bainite, and tempered martensite. Based on metallographic investigations of specimens differently heated and cooled, the mechanisms of formation of globular and acicular austenite, respectively, are analyzed. It is concluded that the rate controlling step of the formation of globular austenite is the diffusion of carbon in austenite, and that acicular austenite is formed by the martensitic reverse transformation.