Volgograd State Technical University, Volgograd, Russia

O. B. Kryuchkov, Cand. Eng., Associate Prof., Dept. of Materials Technology, e-mail: bardb@mail.ru

Tula State University, Tula, Russia
P. I. Malenko, Cand. Eng., Associate Prof., Dept. of Mechanical Engineering and Materials Science, e-mail: pawel.malenko@yandex.ru

Heating of cold ingots for forging involves a gradual increase in temperature in the metal volume at the initial stage in order to eliminate the occurrence of unacceptably high values of temperature stresses that contribute to the occurrence of cracks. In the future, heating takes place at maximum furnace power, which leads to a significant temperature drop between the surface and the center of the ingots, which increases the heterogeneity of the fibrous structure of the deformed metal in cross section and the anisotropy of its mechanical properties. The soaking zone of the furnace is designed to reduce these negative aspects by reducing the temperature drop along the cross section of the ingots at the end of heating no more than 50 °C. At the same time, the calculation of temperature changes along the length of the soaking zone is associated with difficulties. Based on the conducted laboratory experimental heating of a cylindrical billet with a diameter of 0.081 m, a length of 0.25 m and a weight of 9.8 kg made of 45 steel in an electric chamber furnace, a proposed method was proposed for calculating the temperature change of the furnace along the length of the soaking zone, based on the equality of specific heat fluxes: entering the surface of the heated ingot, and passing deep into the heated billet, the calculation results for which showed their complete coincidence with the experimental values. Based on the data obtained using computer modeling, ingots weighing 2; 10; 15 and 100 t from three steel grades 35; 40KhN and SKh15 were studied with the determination of their heating time, furnace temperature in the methodical, welding and soaking zones, as well as the temperature field along the cross section of the ingots before forging. The proposed method for calculating the temperature pressure in the melting zone allows us to regulate the temperature field along the section of the heated workpiece at the end of heating, which helps to reduce the banding of the deformed metal structure and the anisotropy of its mechanical properties.

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