The defect detection method of the nodular cast iron into the cylinder

(1) The surface quality and defects of the air inlet cylinder are mainly inspected by visual inspection (VT), magnetic particle inspection (MT) and liquid penetrant inspection (PT).

Visual inspection (VT) is a nondestructive method for the first stage inspection of the quality of the cylinder castings directly with the naked eye. The defects exposed on the outer surface of the castings can be observed, and the casting section can also be inspected.

Magnetic particle inspection (MT) is one of the most important methods for nondestructive testing of the surface and near surface defects of cylinder castings. The main working principle of MT is to magnetize the castings first. If there is a defect in the detected position, the magnetic particle will accumulate in the defect position and form the magnetic mark display.

Liquid penetrant inspection (PT) is a nondestructive testing method for the surface and near surface cracks, holes and other open defects of the cylinder casting. Its main working principle is the capillary action principle of penetrant. After the penetration of the penetrant for a certain time, after removal, drying and imaging, and under the capillary action, the colorant shows the defect morphology at the defect.

(2) The internal quality and defects of the intake cylinder are mainly detected by UT. UT is the most important nondestructive testing method for defects such as the inner structure of castings, slag inclusion and shrinkage. Its main working principle is to send discontinuous ultrasonic waves with discontinuous frequency to the cylinder castings by the probe of the testing instrument. The defects are judged and detected according to the acoustic characteristics and the attenuation characteristics of bottom waves.

(3) The physical and chemical properties and microstructure of the cylinder castings are mainly tested by portable field microscope, microcomputer controlled universal testing machine, metallographic microscope and other testing equipment. Besides, the defect morphology and composition analysis are tested by scanning electron microscope and energy spectrum analysis equipment. The composition of the smelting process is detected by on-line thermal analyzer and direct reading spectrometer.