1 Saint Petersburg Electrotechnical University “LETI”, Saint Petersburg, Russia:

V. B. Demidovich, Professor, Senior Researcher of Inter-branch Laboratory “Modern Electrotechnologies”, e-mail: vbdemidovich@mail.ru
V. A. Olenin, Assistant of a Chair of Robotics and Industrial System Automation

National Mineral Resources University (Mining University), Saint Petersburg, Russia:
I. I. Rastvorova, Assistant Professor of a Chair of Electronic Systems

Billets are called the long-measured, if their length is much bigger than the outside diameter of cylinders or the height or width of slabs. Peculiarity of precision heating of such billets is the necessity of creation of similar thermal conditions along length during the heating and transportation of the billets. These conditions are fulfilled, if each cross-section of the billet has the similar heating and heat losses from the beginning of heating to the beginning of plastic treatment. Various methods of electric heating of long-measured billets were discussed. Induction heating method is the most efficient and applicable. Induction heating of long-measured billets, making the reciprocal movements in several inductors, may become the alternative to the heating of the billets in one batch induction heater, where the movement of the billets along the guides is partially complicated because of the big mass or the length of the billet. The offered method shows that the billet is moving continuously, with periodical change of the movement direction on the opposite. The billet is heated in several inductors, placed along one axis. The rolls are placed between the inductors for the movement easing of the billet, which swings in the heating area of inductors with certain amplitude. Special software was developed for the joint calculation of electromagnetic and temperature fields, making possible the investigation and design of optimal constructions and control system of induction heater. The most important technological parameters (billet movement rate, current frequency, inductor power, etc) may be easy defined. There was also developed the method of assessment of technological accuracy of heating. Experimental measures have shown that maximal deflections of temperature by the billet volume are within 20 ^oС.

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