Penetration testing method for spring stainless steel materials

The basic principle of penetration testing for spring stainless steel materials is to immerse the stainless steel spring material to be tested in a highly permeable solution (penetrant), allowing it to penetrate into the surface opening defects, then remove excess penetrant, and apply a layer of developer on the surface. At this time, the remaining penetrant in the defects is extracted and observed under ultraviolet light (fluorescence method) or directly to detect the defects. The penetration testing method is not only applicable to the detection of ferromagnetic material springs, but also to the detection of non ferromagnetic materials such as copper alloys and austenitic stainless steel springs.
1、 Penetration testing method for spring stainless steel materials
(1) Springs with steel wire diameter greater than 8mm can be immersed in oil. Soak the cleaned spring in kerosene or a mixture of 50% (mass fraction) kerosene and 50% (mass fraction) l-an32 for about 20 minutes (increasing the oil temperature appropriately can shorten the soaking time, but the oil temperature is limited to 80~C). After soaking, oil will penetrate into cracks and other defects. Sandblasting the soaked spring, removing all oil stains, inspecting the surface of the spring, and identifying springs with cracks.
(2) Fluorescence detection is suitable for both large stainless steel springs and small springs. This method is similar to oil immersion detection, only changing the oil to a penetrant containing fluorescent powder. Fluorescent materials have bright color marks under near ultraviolet irradiation, making it easy to detect cracks or other open defects. Due to the toxicity of the penetrant benzene, it should be protected.
 
(3) Composed of cleaning solution, penetrant, and display solution. When using, first clean the tested surface with a cleaning solution, then spray the penetrant onto the detection area of the spring. Wait for a moment for the penetrant to penetrate the defect, then clean the surface with the cleaning solution and spray the display agent onto the surface of the spring to display the defect and make it visible. Generally, the penetrant is red.
 
(4) The penetration test of stainless steel springs can detect defects with a width of 0.01mm, making it easy to operate and use. But the disadvantage is low efficiency, the solution cannot be recycled, the cost is high, and only surface opening defects can be detected.