冷轧薄板试样电阻加热过程分析

Analysis of Resistance Heating Process for Cold-Rolled Strip Samples

为了确定薄板试样电阻加热系统的参数,掌握加热过程中电功率和电流的变化规律以及试样温度场的分布,利用电、热学理论,并结合有限元软件对薄板试样电阻加热过程进行了分析.针对特定的试样尺寸,确定加热变压器的功率为150 kW,副侧最高电压为24 V,最大输出电流为10 kA.对流和导热损失的功率可以忽略,因此,加热过程中输入的电功率主要用于试样的升温和弥补高温辐射热损失,以恒定速率加热时在低温和高温段所需的加热电流较大,中间温度段电流较小;由于水冷电极的影响,试样的温度场呈现中间高,两端低的梯形分布趋势.

To determine the parameters such as input power, heating current, samples＇ temperature distribution, and their variations the resistance heating process of cold-rolled strip samples was investigated on the electric and thermal theories in combination with FEM. For the samples with definite size, the maximum output power, voltage and current of the transformer used are determined as 150 kW, 24 V and 10kA, respectively. It was found that in the heating process, the input power mainly plays the role to increase the sample temperature and compensate for the energy loss due to thermal radiation, while the energy loss due to convection and conduction is negligible. When heating at a constant rate, the heating current required in the low and high temperature sections is higher than that in the intermediate section. The ~arnple temperature field presents a trapezoidal distribution, i. e., high at the middle but low at both ends under the conductive influence of a pair of water-cooled clampers which tightly clamp the samples.