方管表麵缺陷的檢測方（fāng）法，主要有以下五種：一電渦流檢測.電（diàn）渦（wō）流檢測有多種形式，常用的有常規渦流檢測、遠場渦流檢測、多頻（pín）渦流檢測和脈衝渦流檢測等，利用電渦流傳感器對金屬（shǔ）進行感應，方管表（biǎo）麵不同缺（quē）陷類型和形狀將產生不同類型的（de）信號。其優點是檢測精度高、探測靈敏度高，檢測速度快，能檢測待檢測管（guǎn）材的表麵及亞表麵，且不受待檢測方管表麵油汙等（děng）雜質（zhì）的影（yǐng）響。缺點是易將非缺陷（xiàn）結構（gòu）判定為（wéi）缺陷，誤檢率較高，檢測分辨率不容易調整。
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. 二超聲波檢測
Two-Ultrasound Detection
利用（yòng）超聲波進入物體遇到缺陷時，一部分聲波會產生反射，發射和接（jiē）收器可（kě）對反射波（bō）進行分析，就能異常精確（què）地（dì）測出缺陷來。超聲波檢測常用於鍛件檢測，檢測探傷靈（líng）敏度（dù）高，但是（shì）不易檢查形狀複雜的管材，要求被（bèi）檢查的方管表麵有一定光潔度，並需有耦合劑充填滿探頭和被檢查表（biǎo）麵之間的空隙。
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（fěn）法檢測
Detection by three magnetic powder method
磁粉法檢測（cè）的原理是在方管材料中實現磁場（chǎng），根據缺陷處的漏磁場與（yǔ）磁粉的相互作用，當表麵和近表麵有不連續或缺陷時，則在不（bú）連（lián）續處或（huò）缺陷處磁力線發生局部畸變產生磁極。其優點是設備投資（zī）少，可靠性高，具有直觀性。缺點是操作成本高，不能對缺陷準確分類，檢測速度較低。
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.
四紅外線檢測
Four Infrared Detection
通過高頻感應線圈，在方管表麵產生感應電流，感應電流（liú）會導致缺陷區（qū）域消耗更多電能，引起（qǐ）局部溫度升高，通過紅外線檢測局部溫度，從而確定缺陷深度。紅外線檢測一般用於平直（zhí）表麵的缺陷檢測，不適合檢測表（biǎo）麵不平整金屬。
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.
五漏磁檢測
Five magnetic flux leakage detection
方管的漏磁檢測方（fāng）法和磁粉檢測方法非常相似，適用範圍、靈（líng）敏度和可靠性較磁粉檢測方法更強。
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.
