Using computer modelling with originally developed semi empirical physical grounded models study of structure formation when austenite transformation during cooling by certain regime in eutectoid steel was carried out. The model allowed us to predict final structure. Cooling curves leading to fine pearlite (almost without bainite) and lower bainite (with a small part of fine pearlite) structures were find out. The results obtained could be useful for high carbon ordinary instrumental and constructional steels with higher manganese production and processing (rails, cord and rope wire, springs, low stressed instruments). Realization of the fine pearlite obtaining regime needs equipment that could provide cooling rates from 0.04 deg./sec. to 6.6 deg./sec. with average value of 1.1 deg./sec.. For bainitic structure obtaining the range of cooling rates provided shoud be from 0.14 deg./sec. to 14.0 deg./sec. with average value of 2.2 deg./sec. The cooling intensivity must have an ability to arbitrary and controlled changing during process.