方管表面（miàn）缺陷的检测方法，主要有以下五种：一电涡流检测.电（diàn）涡流检测有多种形式，常用的有常规涡（wō）流检测、远场涡流（liú）检测、多频涡流检测和脉冲涡流检测等，利用电涡（wō）流传（chuán）感（gǎn）器对金属进（jìn）行感应，方管表（biǎo）面不同缺陷类型和形状将产生不同类型的（de）信号。其优点（diǎn）是检测精度（dù）高、探（tàn）测灵敏度高，检（jiǎn）测速度（dù）快，能检测待检测管材的表面（miàn）及亚表面，且不受（shòu）待检测方管表面油污等杂质的影响。缺点是易将非缺陷（xiàn）结构判（pàn）定（dìng）为缺陷，误检率较（jiào）高，检测分（fèn）辨率不容易调整。
There
are five main methods to detect the surface defects of square tubes: one is eddy
current testing. Eddy current testing has many forms, such as conventional eddy
current testing, far-field eddy current testing, multi-frequency eddy current
testing and pulse eddy current testing. Using eddy current sensors to induce
metal, different types and shapes of defects on square tubes surface will
produce different types of signals. It has the advantages of high detection
accuracy, high detection sensitivity, fast detection speed, can detect the
surface and sub-surface of the pipe to be tested, and is not affected by the
impurities such as oil contamination on the surface of the square pipe to be
tested. The disadvantage is that it is easy to judge the non-defective structure
as a defect, the false detection rate is high, and the detection resolution is
not easy to adjust. 二超声波检测
Two-Ultrasound Detection
利用超声波进入物体遇到缺陷时，一部（bù）分声波（bō）会产生反射，发射和接收器可（kě）对反射波进行分析，就能异常精确地（dì）测出缺陷来。超声波检测常用于锻件检测，检测探伤灵敏度高，但是不（bú）易检查形状复杂的（de）管材，要求被检查的方管表面有一定光洁（jié）度，并需有耦合剂充填满探头和被检查表面之间的空隙。
When
ultrasound enters an object and encounters a defect, a part of the acoustic wave
will produce reflection. The transmitter and receiver can analyze the reflected
wave, and the defect can be detected abnormally and accurately. Ultrasound
detection is often used for forging detection, which has high detection
sensitivity, but it is not easy to inspect the pipe with complex shape. It
requires that the surface of the inspected square pipe should have a certain
degree of smoothness, and the coupling agent should be used to fill the gap
between the probe and the inspected surface.
三磁粉法检测
Detection by three magnetic powder method
磁粉法检测的原理是在方管材料中（zhōng）实现磁场，根（gēn）据缺陷处的漏（lòu）磁（cí）场与磁粉的相互作（zuò）用，当表面（miàn）和近表面有不连续或缺陷时，则在不连续处或缺陷处磁力线发生局部畸变产生磁极。其优点是设（shè）备（bèi）投资少，可靠性高，具有直观性。缺点是操作成本高，不能对缺陷准确（què）分类，检测速度较低。
The
principle of magnetic particle method is to realize magnetic field in square
tube material. According to the interaction between leakage magnetic field at
defect and magnetic particle, when there is discontinuity or defect on surface
or near surface, the magnetic line at discontinuity or defect will distort
locally to produce magnetic pole. Its advantages are less investment in
equipment, high reliability and intuition. The disadvantage is that the
operation cost is high, the defect can not be accurately classified, and the
detection speed is low.
四红外线检测
Four Infrared Detection
通过高频感应线（xiàn）圈，在方管表面（miàn）产生感应电流，感应电流会导致缺陷区（qū）域消耗更多电能，引起局部温度升高，通过红外线检测局部温度（dù），从而确定缺（quē）陷深度。红外（wài）线检测一般用于平直表面（miàn）的缺陷检测，不适合检测表面不平整金属。
Through
high frequency induction coil, induction current is generated on the surface of
square tube. Induction current will cause more electric energy to be consumed in
defect area, causing local temperature to rise. The defect depth can be
determined by infrared detection of local temperature. Infrared detection is
generally used for flattening surface defect detection, not suitable for
detecting surface irregularity metal.
五漏磁（cí）检测
Five magnetic flux leakage detection
方管的漏磁检测方法和磁粉检测方法非常相似，适用范围、灵敏度和可靠性较磁粉检（jiǎn）测方法更强（qiáng）。
The magnetic flux leakage
testing method of square tube is very similar to that of magnetic powder testing
method, and its application scope, sensitivity and reliability are stronger than
that of magnetic powder testing method.
