| A bell-type annealing furnace used for coldly rolling steel coil is an important equipment during producing strip steel in iron and steel company, and annealing technology has a great influence on performance and surface quality of strip steel. The furnace type of a bell-type annealing furnace is developing fast from a traditional one to HPH one. Moreover, the radial heat-transfer model is critical for improving heat-transfer efficiency, decreasing annealing time, increasing productivity and reforming mechanical properties. In addition, steel coil oxidizing will improve rejection rate and repair rate annually during annealing, which is a dominant factor of reducing yield.The working process of HPH bell-type annealing furnace is analyzed in this paper. Based on former control model and working principle, and considering production conditions, the annealing technology of steel coil in HPH bell-type annealing furnace is discussed. The main content and results presented in this paper are as follows:(1)The physical characteristics of a HPH bell-type annealing furnace during annealing is analyzed, the control model and heat-transfer mathematical model are built offline, and results are obtained according to numerical calculation technology. What is more, the software for simulating the annealing process of bell-type annealing furnace is designed. The functions of this software are as follows:the numerical simulation calculation of annealing process can be carried out by inputting data such as physical dimensions of different furnace s and dimensions of different steel coil; The temperature curves and annealing time can be got in accordance with different parameters; The results of numerical simulation calculation can be seen in a video.(2)The program for simulating the annealing process of this furnace is written by MATLAB software, by which the analysis of annealing process is simple and easy. According to the data of HPH bell-type annealing furnace, the curve of simulation calculation is compared with thermocouple temperature curve measured in practical scene to verify mathematical model.(3)The annealing technology is discussed in terms of the thickness and width of steel coil and the temperature of protective gas, then some measuress for improving the annealing technology are presented.(4)The reasons why steel coil oxidizes during annealing are analyzed, and the direct reason of steel coil oxidizing is that external oxidizing gases enter into inner cover. Two factors create this phenomenon, one is that the zone of negative pressure forms during inner gas cooling, and the other one is that the seal rings become invalid. For investigating the second factor, the flow field of kiln gas is simulated by FLUENT. Then the finite element analysis on seal rings in coil base is carried out and some improvements are proposed. At last some measures for improving the equipment are raised according to research conclusions.(5)According to experiments, it is verified that calculation model and simulation results are right. Because these results are applied to production, the time for heat treatment of steel coil is reduced,5 hours are saved averagely per furnace, the efficiency are improved by 10%, economic benefit is 25,500,000 Yuan annually, the number of steel coil oxidizing is decreased, rejection rate is less than 0.05%per month, and repair volume is less than 800t/month. |
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