PARTICULARITIES REGARDING THE THERMAL RADIATION INSIDE THE HEATING FURNACES FOR METAL FORMING

During the thermal processes in metallurgy, it is important in many cases to know the exactly particularities of heat transfer in a complex system. In the case of steel semi-finished products heating, the most of the models refers to the heat exchange by convection and radiation or to the heat transfer by conductivity inside the material. The heat transfer by radiation has two important components: the value of the heated surface by radiation and the values of the radiation coefficient. The aim of this analysis is to establish the basic relations for a model in order to evaluate the parameters of the heat transfer and energy consumption in the case of some metallurgical heating furnaces. The article refers also to "the equivalent surface of heat transfer" (a new term proposed by the authors), connected to the modality of billets disposal in various types of heating furnaces. Starting from the considerations regarding the burning process of the fuels, there were established relations between the heat exchange coefficients, energy and metallic material saving. We are considering that it is an important difference between various types of continuous operating furnaces: while in the pusher-type furnace the billets may be disposed only one near the other, without free spaces between them, the walking-beam furnace or the rotary hearth furnace allows the disposal of the billets at the required distances. Modifying this distance, it is the possibility of acting upon: the billets stationary time in the furnace, the temperature distribution in the section of the billets and the oxidation and decarburization decrease. Saving energy and metal consumption due to the oxidation process means to have a cleaner environment.