钻杆加厚过渡带漏磁检测方法研究

Magnetic flux leakage testing method study for upset transition zone of drill pipe

通过磁折射理论及相应的有限元模型分析了加厚过渡区的磁场分布特性,主要包括由于内外径变化产生的空间磁场和由于壁厚变化产生的磁感应强度的非均匀性;找到并确认了变径产生的空间磁场是造成漏磁检测信号基线漂移的主要原因,并通过差分法进行了消除;同时,也发现了变壁厚区磁化的非均匀性会导致同当量缺陷的漏磁场信号不一致,通过分析壁厚及磁化强度对漏磁场的影响,提出深度饱和磁化方法.结果表明:该方法能有效消除钻杆过渡带区域的背景磁场干扰并保证信号一致性,使漏磁法能适用于钻杆加厚过渡带的检测.

The magnetic field refraction theory and the corresponding finite element model was carried out to analyze the magnetic field distribution of the upset transition zone. The background magnetic field caused by radius changing and the non-uniformity of magnetization caused by wall thickness changing are the main features of the upset transition zone. Then, the background field caused by ra- dius changing was confirmed to be the reason for baseline shifting, and this effect was eliminated by the differentiation method. At the same time, the non-uniformity of magnetization caused by wall thickness changing was found to be the reason which makes the magnitudes of leakage field different for the defects with same dimension. After analyzing the influence of wall thickness and magnetization on magnetic leakage field, a deep magnetic saturation method was proposed. The results show that this method Can effectively eliminate the background field in the upset transition zone and guarantee the consistency of detection signal, thus makes the magnetic flux leakage testing method suitable for the inspection of upset transition zone of drill pipe.