Observations on continuous cooling transformation characteristics of alloy steels

This investigation on continuous cooling transformation characteristics of 0.34% to 0.38% carbon alloy steels containing nickel, manganese, chromium and molybdenum showed that addition of chromium to nickel steel lowered the cooling rates for the formation of bainite without affecting the cooling rates for the formation of pearlite or ferrite. Similar effect was observed on adding chromium to manganese steels. Addition of molybdenum to chromium adding chromium steel led to the formation of bainite and pearlite in most of cooling rates covered by the present investigation. It was further observed that at the cooling rates leading to the precipitation of an appreciable amount of acicular or proeutectoid ferrite, the remaining austenite was enriched in carbon and was reluctant to transform and Ms temperatures of these steels were depressed. Sub-zero treatment of such steels showed that considerable amount of austenite was retained at cooling rates when ferrite and upper bainite are the first products to form. (Messrs R.K. Dubey and P.K. Gupte, Scientists, National Metallurgical Laboratory, Jamshedpur)