Golubenko T. Improvement of the modes of heat treatment of rental from chrome-molybdenum steel for responsible motor-car details

The rental of metal of uninterruptedly-casted vacuum-treated steel. Improvement of modes of the heat treatment providing receiving the demanded a structural condition and hardness for decrease of energy consumption at production of rental out of 42Cr4Mo2 steel for the critical motor vehicle parts. Metallographic, electronic-microscopical, dilatometric, quantitative microanalysis, hardness assessment. The kinetics of transformations of overcooled austenite decay is studied under continuous cooling of the constructional steel (0,39 % of carbon), alloyed steel 1,08% of chrome and 0,25% of molybdenum. It is shown that increase of the content of a molybdenum from 0,16% to 0,25% and chromium from 0,99% to 1,08% narrows the temperature interval of the diffusive transformation, and when cooling with average speeds 0,07°C/sec and 1,0°C/sec in the interval of temperatures of 610-430°C and 595-560°C respectively there is an area of high stability of the overcooled austenite. It is established that cooling rate increase with 0,4-0,5°C/sec to 0,6-0,8°C/sec after hot deformation of chromium-molybdenium steel leads to the decrease of a share of a perlite from 15-20% to 5-10% and to increase in a share bainite from 65% to 75% which after the subsequent heating and endurance at subcritical temperatures have lower values of a microhardness, than a spheroidized perlite that causes common decrease in hardness of steel. The results are used at OJSC "Byelorussian Metallurgical Works – Managing Company of the Holding "Byelorussian Metallurgical Company" by development of heat treatment modes of the rolled metal out of medium-carbon alloyed steel with saving of energy resources. Metallurgy. Applied in industry.