(西北工业大学凝固技术国家重点实验室, 西安 710072
西安交通大学, 西安 710049)
摘 要: 推导了一个适用于中小尺寸板状熔体表面电磁压力的计算公式。该式给出了电磁压力系数 p与板厚a、电流频率f、以及材料的电磁参数μγ之间的准确关系。主要结果如下: (1) 当f,a,以及μγ足够大, 使得板的厚度a与电流集肤厚度δ的比a/δ>2. 2时, 电磁压力系数是一个常数( p=1), 电磁压力可由公式 pm=B2/2μ计算。 (2) 但若f,a,以及μγ比较小,使a/δ<2.2,则电磁压力必须由系数 p进行修正。也就是说,电磁压力不仅由熔体表面的磁感应强度 B 决定而且也由板的厚度a,电流频率f,以及材料的电磁参数μγ决定。
关键字: 电磁约束成形 电磁压力 磁感应强度
(State Key Laboratory of Solidification Processing, Northwestern Polytechnic University, Xi'an 710072, P. R. China
Xi'an Jiaotong University, Xi'an 710049, P. R. China)
Abstract:An equation used to calculate electromagnetic pressure for confining and shaping a platelike melt with small or medium thickness is brought forward. The equation gives a precise relationship between electromagnetic pressure factor p and current frequency f, melt thickness a and electromagnetic parameter μγ. The main results can be summarized as follows: (1) As the f , a, and μγ are large enough, causing the ratio of melt thickness to current skining depth a/δ to be larger than 2.2, the p will be a constant( p=1) and the electromagnetic pressure can be calculated with pm=B2/2μ. (2) As the f, a, and μγ are not large enough, and the ratio a/δ is less than 2.2, the factor p is no longer a constant but changes from 1 to 0 with the decrease of a/δ. In this case, the value of electromagnetic pressure is determined not only by magnetic flux density B but also by the current frequency f, melt thickness a and electromagnetic parameter μγ.
Key words: electromagnetic confinement and shaping; electromagnetic pressure; magnetic flux density