长输管道直流消磁法及其ANSYS数值模拟

焊接具有磁性的管道焊口时,焊口剩磁产生的磁场和焊接电弧产生的磁场组成复合磁场,若复合磁场的洛伦兹力大于电磁场的收缩力,焊接电弧带电粒子的运动角度将发生偏转,在宏观上表现为电弧偏吹,即磁偏吹。若电弧的偏转角度大于45°,在焊接过程中将出现严重的磁偏吹现象;反之,磁偏吹现象不明显。利用有限元软件ANSYS对管道、消磁线圈以及外部空气进行实体建模,通过对模型简化和求解,得到消磁磁场的分布情况：磁场以通电螺线管的轴线为对称轴呈对称分布,且线圈中心的磁场强度最弱,距离线圈无限远处的磁场强度为0;沿径向两端管壁的磁场强度最大,无限远处的磁场强度为0,中间区域分布较均匀。最后,对长输管道直流消磁方法进行优化,并介绍了直流消磁方法的两种基本形式。

DC degaussing method of steel pipeline and ANSYS numerical simulation of degaussed H-field

Two types of DC degaussing methods for beam of steel pipe are described in the paper. When steel pipe with magnetism is welded, the magnetic field produced by residual magnetism around beam and that by welding arc consist of a composite magnetic field, if the Lorentz force of the composite magnetic field is greater than the contractility of the magnetic field, the movement angle of the charged particles of welding arc will deviate from normal angle, which reflects by arc-blow in macroscopic view. If the arc’s deflection angle is greater than 45o, serious arc-blow will occur in welding process, or otherwise, the arc-blow will not be obvious. The authors establish solid model referring to pipeline, degaussing coils and external air with ANSYS software, and obtain the distribution curves of degaussed H-field. The simulation results by simplifying and resolving the model show that the distribution of H-field appears in symmetric axis of charged solenoid, and the strength of H-field is the weakest in the center of coil, and that of H-field at infinite far location from the coil is zero; and that of H-field of pipe wall at two ends is the biggest along the radial direction, and is zero at infinite far location, the H-field distribution in the middle area is relatively even. DC degaussing method is optimized by the authors.