Method for liquid penetrant inspection of large forgings

Release time:

09 Mar,2023

Liquid penetrant testing is a method for detecting open defects on the surface of large forgings. The process of this method can be summarized as: evenly coat the surface of the inspected workpiece with a material called penetrant, make it penetrate into the defect, remove the excess penetrant after an appropriate time, dry the workpiece, and then use the developer to suck out the penetrant that penetrated into the defect, and then determine whether there are traces on the surface of the inspected workpiece through appropriate observation.

The process parameters (e. g., pre-clean, breakthrough time, etc.) are determined by the particular material used, the characteristics of the workpiece being inspected (e. g., size, shape, surface condition, alloy material), and the type of defect expected. Liquid penetrant inspection methods can indicate the presence of defects and their location, and to a certain extent their nature and size.

Materials used for liquid penetrant testing, including fluorescent and dye penetrants, emulsifiers (oil-based plus water-based, fast-response and slow-response), detergents and developers. A suitable group of liquid penetrant inspection materials consists of penetrants, emulsifiers, detergents and developers recommend by the manufacturer. It is recommended not to mix penetrant inspection materials from more than one manufacturer, taking care that these materials do not have a deleterious effect on the large forgings being inspected. It is recommended that you use the reference block to determine the properties of the material before use.

Fluorescence penetration detection is a method to observe defect traces by fluorescence excited by penetrant under the action of ultraviolet light. The sensitivity of the fluorescent penetrant depends on the ability of the penetrant to retain defects of various sizes during the detection process, and the brightness of the penetrant to penetrate into the developer coating and produce a fluorescent display.

Water-washing penetrant means that after an appropriate penetration time, the surface of the workpiece to be inspected can be directly cleaned with water. Since this penetrant "mixes" the emulsifier into the water-washable penetrant, it is key to remove excess penetrant from the surface of the workpiece and ensure that it is not excessively cleaned. Therefore, it is necessary to train qualified operators.