Instutute of Ferrous Metallurgy named after Z. I. Nekrasov, Dnepropetrovsk, Ukraine:

Lutsenko V. A., senior research fellow of the machine-building metal heat treatment dept., Cand. Eng., lutsenko@optima.com.ua

Golubenko T. N., research fellow of the machine-building metal heat treatment dept.

Byelorussian Steel Worls — Management Company of “Byelorussian Metallurgical Company” Holding
Bobkov P. A., head of the section rolling shop
Gordienko V. V., vice-head of section rolling shop
Gritsaenko V. I., head of the dept. of scientific and technical information

It was established that continuous cooling of chromium-molybdenum steel in the rate interval 0.03–0.16 ^oC/s, forming of ferritepearlite structure is prevalent, while in the rate interval 0.4–2.3 ^oC/s it is bainite structure and for the rates more than 8 ^oC/s it is martensite structure. In order to decrease the temperature of consequent softening annealing, the rolled product should have bainite structure. Therefore, cooling of rolled sections made of 42Cr4Mo2 electric steel  during thermomechanical treatment is expedient to conduct with ave rage mass rate 1.0–2.3 ^oC/s. Investigations of the temperature and time parameters of heat treatment of chromium-molybdenum steel have shown that period of isothermal holding during heat treatment at 550 ^oC has not substantial effect on structural changes and steel hardness. After heat treatment at the temperature higher than 600 ^oC, cementite structure with grain morphology is forming in metal and provides decrease of hardness. It was established experimentally that shortening of isothermal holding down to 3–4 hours (instead of 6.5 hours) during annealing in the temperature interval 650-680 ^oC provides decrease of hardness in chromium-molybdenum steel by 20–26% (owing to forming of up to 30% of pearlite with grain structure) and can be considered as power-saving technology.

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