Magnitogorsk State Technical University named after G. I. Nosov (Magnitogorsk, Russia):

Koptseva N. V., Dr. Eng., Prof., Chair of Casting Production and Material Science, e-mail: koptsev2002@mail.ru
Chukin D. M., Post-Graduate, Chair of Casting Production and Material Science
Efimova Yu. Yu., Cand. Eng., Associate Prof., Chair of Machine-Building and Metallurgical Technologies
Nikitenko O. A., Cand. Eng., Assistant, Chair of Machine-Building and Metallurgical Technologies
Ishimov A. S., Post-Graduate, Chair of Machine-Building and Metallurgical Technologies

Dilatometrical testings of 80P steel, microalloyed with boron, have been conducted using GLEEBLE 3500 research complex. Temperature and time conditions of the experimental procedures during dilatometrical testings provided 4 different techniques with permanent heating rate (30 ºC/s), different holding time (1–3 s) and different cooling rate (1–100 ºC/s). Qualitative and quantitative features of forming its microstructure during continuous cooling with diff erent cooling rate (1.5–80 ºC/s) are established, including HV and HRC hardness distribution. These features take into account technical requirements for wire rod using afterwards for manufacture of reinforced bars. Critical points of forming different types of microstructure (ferrite, pearlite, bainite and martensite) have been determined using dilatometrical curves obtained during continuous cooling. The results of investigations allowed to formulate that it is not possible to prevent forming of excessive ferrite and pseudo-eutectoid sorbite-type structure with interlamellar distance 0.1–0.2 μm at actual cooling rate of 10 mm diameter wire rod after heating before rolling. Therefore, 10 mm diameter wire rod can’t be used for direct drawing in manufacture or wire billet for production of high-strength reinforced bars. It is recommended to use patented billet for reaching the high level of mechanical properties of reinforced bars.

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