Non-destructive testing refers to a method of detecting macroscopic defects on the surface or inside of castings and materials under test conditions that do not damage them. NDT is also known as NDT. There are many methods of non-destructive testing. In actual industrial production, the commonly used non-destructive testing methods are: radiographic testing, ultrasonic testing, magnetic particle testing and penetrant testing.
Penetration testing (PT) is also a kind of non-destructive testing. Its basic principle is to use the good permeability and capillary action of colored penetrants or fluorescent penetrants to narrow gaps. After penetration, removal, and imaging treatment, the surface defects are enlarged and displayed. , in order to judge the defect type, location and size. Penetrant testing is to use visual inspection or magnifying glass to detect discontinuities in the openings on the surface of the casting. However, penetration testing cannot accurately reflect the nature, shape, size and depth of discontinuous defects.
Penetrant is the most critical material in penetrant inspection, and its quality directly affects the sensitivity of inspection. Penetrants must have excellent wetting properties to ensure penetrating properties. When the penetrant is mixed with colored dyes or fluorescent dyes, it is beneficial to the development of defects. Colored flaw detection uses colored dyes as a color display agent for penetrants, while fluorescent flaw detection uses fluorescent powder as a luminescent agent for penetrants. Shading methods can operate in indoor or outdoor environments. Fluorescent penetrant inspection uses fluorescence emitted under ultraviolet light emitted by a black light to reveal surface defects, so it must be performed in a dark room.
Castings that need penetrant inspection must be cleaned before inspection, and their surface roughness should meet the corresponding quality level requirements. The rust, scale and paint, grease, moisture, etc. on the surface of the casting must be removed. After the penetrant inspection is completed, the surface of the casting should be removed from the penetrant and developer, dried and, if necessary, protected against corrosion.
Characteristics of Penetrant Testing and Its Scope of Application:
1. The method and equipment are simple and adaptable.
2. The shape of the casting is not limited, and the surface roughness of the inspected area is related to the quality level of the casting.
3. Simple operation, high sensitivity, and not limited by material properties.
4. Only casting defects on or near the surface of the casting can be detected.