中文摘要：

大直径薄壁弯头广泛应用于油气输送管道工程,采用局部感应加热并通过液压推制成形是弯管加工的主要工艺方法,由此,装备的液压推制速度和感应加热参数的准确匹配成为影响弯管质量的重要因素。针对感应加热过程中集肤效应对加热效果影响的不确定性,在感应加热理论分析的基础上,研究了基于集肤效应的关键参数,同时借助有限元模拟计算的方法,分析各工艺参数对管材感应加热过程中焦耳热分布的影响,并通过建立正交试验实现参数组优化。结果表明：感应加热装置的设计应综合考虑电流频率、电流密度、管材与感应圈距离3个参数的变化梯度对集肤效应的影响,得到最优参数组,为与之相匹配的弯管推制速度提供准确的设计参数要求,在保障弯管质量的同时,大大提高装备现场调试及生产的效率。

英文摘要：

The large-diameter thin-walled elbow is widely applied in oil and gas pipeline engineering, and it is mainly manufactured by means of local induction heating and hydraulic pushing and bending. Therefore, the accurate matching between the hydraulic pushing speed and the induction heating parameters is the important factor affecting the quality of elbows. Considering the uncertainty of skin effect on heating result in the process of induction heating, the key parameters based on skin effect were investigated after the induction heating theory was analyzed. Then, the effects of all technological parameters on Joule heat distribution in the induction heating process of pipes were analyzed by virtue of finite element simulation calculation method. And finally, parameter sets were optimized by means of orthogonal tests. It is indicated that the effects of variation gradient of three parameters（current frequency, current density and pipe-inductor distance） on the skin effect shall be analyzed comprehensively in the design of induction heating device, so that the optimal parameter set can be obtained and the accurate design parameters for its matching elbow pushing speed can be provided. And consequently, field debugging and production efficiency of equipment is improved significantly while the quality of elbow is ensured.