Eddy current flaw detection method for seamless tube

According to the characteristics of industrial non-destructive testing, in order to realize the automatic control of the testing system, most of the eddy current testing of seamless tubes below 180mm in steel pipe enterprises adopts the traditional passing-through coil testing method. For seamless steel tubes over 180mm, if the traditional passing-through eddy current method is used for testing, there will be many problems, which are not allowed by national standards. The penetrating coil detects a circumferential surface of the surface of the steel pipe. In the eddy current flaw detection using the penetrating coil, the larger the diameter of the steel pipe to be detected, the larger the circumferential area detected by the coil, and the lower the signal-to-noise ratio. It is for this reason that the eddy current inspection standard for steel pipes stipulates that the outer diameter of the eddy current inspection using the through-type coil shall not be greater than 180mm. In addition, there are certain difficulties in the magnetization and demagnetization of the steel pipe in the through-type flaw detection of large-diameter steel pipes. Therefore, whether it is domestic or foreign, for the flaw detection of large-diameter steel pipes, point probe type eddy current flaw detection equipment is generally used.

Eddy current flaw detection method for multi-caliber seamless steel tubes:

The detection sensitivity of point eddy current testing is very high, and it has a high detection rate for cracks and fold defects distributed along the axis of the steel pipe; in addition, point eddy current testing also suppresses ambient temperature and workpiece transmission vibration. effect of influence. More importantly, the form of point eddy current probe can adapt to the flaw detection requirements of steel pipes of different diameters.

(1) First, according to the actual situation of the production line, the flaw detection method of the steel pipe spirally rotating along the production line and the probe being fixed is determined. While making the steel pipe rotate forward, let the point probe close to the surface of the steel pipe to complete the scanning of the entire outer surface.

(2) Determine the structure of the flaw detection system. First, put the six-channel eddy current probe into a probe trolley, adjust the probe trolley to meet the requirements of the diameter steel pipe to be tested by adjusting the screw, and then use the cylinder pushing and fine-tuning method to make the detection probe always press tightly against the workpiece. The surface of the workpiece is inspected, and a pair of universal wheels are installed at both ends of the probe trolley to keep a certain distance between it and the inspected workpiece.

(3) Determine the number of probes. The point probe flaw detection method needs to use multiple detection probes to increase the scanning pitch and improve the detection speed. Eddy current point probes are generally small in size and have high detection sensitivity, but at the expense of the detection speed. Increasing the coverage of the detection area of the probe can improve the detection speed, but the detection sensitivity will decrease.