Mechanical Properties of Ausformed Pearlitic and Bainitic Steel

Abstract

A study has been performed to clarify the effect of ausforming temperature, ausforming ratio, and subsequent isothermal heating time on the mechanical properties of ausformed pearlitic and bainitic steels. The material used in this study is a high C and Cr tool steel, which has high quench-hardenability. The results obtained are as follows:
(1) With increases of the working ratio of ausforming and of the holding time at the subsequent transformation temperature, both the hardness and the strength of ausformed pearlitic steel decrease, while the toughness of the steel increases. When the mechanical properties of ausformed pearlitic steel worked at 500°C is compared with that worked at 700°C, the former shows lower values in the hardness and strength and a higher value in the toughness than the latter.
(2) The ausformed bainitic steel worked with a comparatively heavy ratio shows a fairly good combination of the strength and toughness. On the other hand, the ausformed bainitic steel worked at 320°C is more advantageous in the strength and toughness than that worked at 500°C.
(3) With an increase of the working ratio of ausforming, both the toughness and strength of the ausformed pearlitic steel worked during the isothermal transformation from austenite to pearlite increase, while the strength of the steel worked above a certain working ratio slightly decreases.
(4) When the mechanical properties of the ausformed bainitic steel worked during the transformation from austenite to bainite is compared with that worked before transformation, the former shows a higher value in the strength and a lower value in the toughness than the latter.