Magnetic flux leakage detection method and application of seamless tube

Magnetic flux leakage detection method and application of seamless steel tube (smls):

Magnetic particle inspection and magnetic flux leakage inspection are collectively referred to as magnetic flux leakage inspection. Physically speaking, they belong to the same detection method. They are used for the detection of ferromagnetic materials, and they are all detected by the leakage magnetic field to find the defects in the material. One of the magnetic particle leakage detection methods in the magnetic particle inspection room is widely used in practice, and the use of detecting elements to determine the existence of magnetic leakage is another method of magnetic leakage detection. In recent years, pipes and bars in the metallurgical industry have been It is more and more used in flaw detection, and this flaw detection method is often referred to as magnetic flux leakage flaw detection.

1. Magnetic particle inspection

Magnetic particle inspection of seamless steel pipes is generally used for the inspection of the undetectable area of the pipe end that exists in the automatic inspection equipment, that is, the inspection of the pipe end. Generally, the fluorescent magnetic particle inspection method is used to perform longitudinal and axial magnetization of the pipe end within about 300mm. Generally, magnetization is used. The coil magnetizes the steel pipe longitudinally, the mandrel is energized to magnetize the steel pipe axially, and a composite magnetic field is formed to inspect the defects in all directions on the inner and outer surfaces and near the surface. Display of magnetic marks on the inner and outer surfaces. The method adopts the fluorescent magnetic particle flaw detection method, which has the advantages of high detection sensitivity, simple and convenient operation, intuitive detection results, no sterile area within the detection range, high degree of automation, and fast inspection speed. The inspection capacity can match the capacity of the previous automatic flaw detection equipment, but since the magnetic traces need to be observed by the human eye, the inspection quality and reliability depend entirely on human factors.

2. Magnetic flux leakage detection

The magnetic flux leakage detection of seamless steel tubes realizes the detection of defects by using sensors to detect the leakage magnetic fields of defects. The relative motion state of the sensor and the steel pipe to be detected is used to cut the magnetic lines of force, and the defect signals are obtained after processing by electronic instruments.

Magnetic flux leakage testing equipment is generally composed of magnetizing power supply, magnetizing coil (yoke), detection probe, probe rotating device (or steel pipe rotating device), demagnetization (transverse flux leakage needs to be demagnetized), marking and other devices. Magnetic flux leakage testing is generally divided into longitudinal magnetic flux leakage testing equipment and transverse magnetic flux leakage testing equipment. The longitudinal magnetic flux leakage testing equipment applies circumferential magnetization to the steel pipe to detect longitudinal defects on the inner and outer surfaces and near-surface of the steel pipe; Transverse magnetization is applied to detect transverse defects on the inner and outer surfaces and near surfaces of the steel pipe.

3. Magnetic flux leakage detection has the following advantages:
Easy to automate;
Has high detection reliability;
A preliminary assessment of defects can be achieved;
It has the characteristics of high efficiency and no pollution.

At the same time, the magnetic flux leakage detection also has the improvement effect of electromagnetic flaw detection, which affects the sensitivity of flaw detection. If the contact method is used for flaw detection, the wear of the probe will affect the detection sensitivity.