The CCT diagram of the austenite transformations of the 45 steel during isothermal cooling. Dilatometric and microscopic analysis

The CCT diagram of the austenite transformations of the 45 steel during isochronal cooling makes possible to develop equations that enables prediction of structure and properties after conventional heat treatment. Dilatometric method was applied in order to work out such diagram for 45 steel austenitized at 1050 oC. Structures appeared during applied cooling rates were presented. Shapes of dilatometric diagrams described austenite transformations and microstructures are mutually related. During austenite to ferrite transformations separation for equiaxial and coniferous ferrite was possible. The border cooling rate at which coniferous ferrite starts to precipitate was determined as well as Ms and Mf temperatures. Shape of CCT diagram developed with use of isochronal cooling is different from conventional one. Obtained results were discussed on the literature basis. (author)