Engineering Procedure for Calculating Furnace Heating and Thermostatic Control Conditions of a Hot-Charged Slab
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ENGINEERING PROCEDURE FOR CALCULATING FURNACE HEATING AND THERMOSTATIC CONTROL CONDITIONS OF A HOT-CHARGED SLAB S. V. Lukin,1 A. A. Zbrodov,2 and K. Yu. Levashev3
UDC 669.04
The paper discusses an engineering procedure, which enables the automation of the process of calculating furnace heating and thermostatic control parameters of hot-charged steel slab blanks under the rational heat treatment conditions. During hot charging, the blanks coming out of a continuous casting machine at an average temperature of about 1,000 °С are placed inside the heating furnaces in the hot condition, which results in a considerable decrease of their heating time, incremental reduction of specific fuel consumption, and lowering of the metal oxidation level. The procedure allows calculating the required duration of heating of the slabs loaded into the furnace in the hot condition with a sufficient degree of simplicity and accuracy and without the use of nomograms. It also allows determining the required duration of thermostatic exposure (i.e., soaking of heated slabs under adiabatic conditions) to equalize the temperature profile over the slab cross-section. The provided relationships can be used to determine the heating duration for slabs with different thicknesses depending on the temperature at which they were charged into the furnace. Keywords: blank, slab, heating furnace, heating, thermostatic soaking, hot charging.
Steel blanks coming out of the continuous casting machines (CCM) have high bulk temperature (about 1,000 °C and above) and contain a significant amount of physical heat. The most rational method of utilizing this heat is a so-called “hot charging,” when hot blanks are charged into the heating furnaces to be heated before rolling. In addition, instead of heating the blanks coming out of CCMs in the furnace at a sufficiently high temperature, it is possible to soak them in a so-called “thermos” under adiabatic conditions to equalize the temperature over the cross-section of the blanks immediately before rolling [1, 2]. If the temperature of the blanks after soaking inside the thermos is not sufficient for rolling, additional furnace heating is required, but even then the specific fuel consumption will be a lot less compared to heating blanks from the cold state. In the Russian Federation, steel blanks are heated in the rolling mill furnaces mainly from the cold state, and the heat of the blanks coming out of CCMs is practically not used [3–5]. When placing slabs in the thermos after a CCM, small heat losses occur through its walls [1]. The surface temperature of the slab becomes slightly lower than in the center. While performing engineering calculations, this fact can be neglected, and the temperature at which slabs are charged into the heating furnace after thermossoaking is almost the same over the entire cross-section. The calculations of the heating time performed according to the developed engineering procedure have confirmed the above assumption. The authors of study [6] have suggested and justified a rational
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