Liquid penetrant testing is a method of detecting open defects on the surface of large forgings. The process of the method is generally to uniformly apply a material called a penetrating agent to the surface of the workpiece to be infiltrated into the interior of the defect, remove the excess penetrant after leaving the appropriate time, and dry the workpiece. The developer is applied to aspirate the penetrant that penetrates into the interior of the defect, and then the surface of the workpiece to be inspected is determined by appropriate observation.
Process parameters (eg, pre-cleaning, permeation time, etc.) are determined by the particular material used, the characteristics of the workpiece being inspected (eg, size, shape, surface condition, alloy material), the type of defect being predicted, and the like. The liquid penetrant test can indicate the presence or absence of defects and, to some extent, the nature and size.
The type of liquid penetration test. Method A is called fluorescence infiltration method, and is classified into A-1, A-2, and A-3 according to the characteristics of the penetrating agent; Method B is called a coloring infiltration method, and is classified into B-1 and B-2 according to the characteristics of the penetrating agent. B-3 method.
Materials for liquid penetrant testing, including fluorescent and color penetrants, emulsifiers (oil based water, fast and slow reactions), detergents and imaging agents. A suitable set of liquid penetrant testing materials consists of a manufacturer's recommended penetrant, emulsifier, detergent, and imaging agent. It is not recommended to mix the penetration test materials produced by several manufacturers, and note that the materials must not have harmful effects on the large forgings being inspected. The performance of the material is recommended for identification before use.
Fluorescence penetrant testing is a method of observing defect traces by excited fluorescence under the action of ultraviolet light using a penetrant. The sensitivity of the fluorescent penetrant depends on the ability of the penetrant to remain in various size defects during the test, as well as the penetrant oozing out to the developer coating layer and producing the brightness of the fluorescent display.
The water-washing type penetrant means that the surface of the workpiece to be inspected can be directly washed with water after a suitable penetration time. Since the penetrant is "blended" into the water-washing penetrant, it is necessary to remove excess penetrant on the surface of the workpiece and to ensure that the flushing is the key to the operation, so the training is qualified. It is very necessary.
The post-emulsification penetrant means that it is insoluble in water and cannot be washed away with water. Instead, a special emulsifier is needed, which can react with excess penetrant after a suitable emulsification time to form a mixture which can be washed away with water. . The proper emulsification time should be determined by experimentation.
The solvent-removing penetrant means that the excess penetrant can be wiped with a clean and lint-free material, so that most of the excess penetrant is removed, and the residual penetrant is rubbed with a lint-free material and rubbed with a little detergent. Excess penetrant is completely removed. This penetrant is often used for inspection in portable and local areas. To prevent excessive cleaning, excessive use of solvents should be prevented and direct washing of the surface of the workpiece with solvents should be prohibited.
The coloring penetration test is a method of testing using a visually observable penetrant under visible light. Most of the penetrants used were red, which showed significant traces in contrast to white-colored imaging agents. This method does not require black light, but must be observed under sufficient white light.
The emulsifier is a liquid used to emulsify excess oil penetrant on the surface of the workpiece, and after it is emulsified, it can be washed off with water. There are two types of emulsifiers: oil based and water based (containing detergent). Depending on the surface condition, viscosity, concentration and chemical composition of the workpiece, both can be emulsified in a matter of seconds to minutes.
Oil-based emulsifiers are usually available for purchase. The speed of the emulsification reaction depends on its own viscosity and chemical composition, and the high viscosity generally has a slower effect than the low viscosity. Its function is to diffuse (dissolve) into the excess penetrant on the surface of large forgings and emulsifie it. The speed of diffusion determines the time of emulsification.
Water-based emulsifiers (including detergent type), generally supplied with water diluted, used in the form of impregnation or leaching. Its function is to remove excess permeable membrane on the surface of the workpiece by washing. When the penetrant film is removed with a detergent, the water spray force or the air in the open dipping tank agitates and the emulsification time is determined by the concentration of the detergent in the water.
The role of the cleaning agent is to dissolve the surface energy by dissolving the penetrant without leaving excess penetrant.
The function of the developer is to cause the penetrant which penetrates into the defect to be sucked out by the adsorption of the applied developer and exhibited on the surface of the workpiece, thereby showing signs of the penetrant and also enhancing the sharpness of the sign.
The wet water suspension type developer is usually supplied in a state in which the dry powder is suspended in water or dissolved in water depending on the type thereof.
The water suspension type developer is a suspension in which the developer particles are suspended in water. The concentration, method of use and storage should be carried out in accordance with the manufacturer's instructions for use.
The water-soluble imaging agent is prepared by dissolving a soluble powder in water and used in the concentration recommended by the manufacturer's instructions.
The non-aqueous suspension type developer is prepared by suspending the developer particles in a carrier of a non-aqueous solvent, and is convenient to use, that is, the developer is used after removing the excess penetrant on the workpiece and drying the workpiece. Or electrostatic spray guns are sprayed onto the workpiece or sprayed with a pressure tank. After drying, the developer forms a white coating on the surface of the workpiece to counteract the penetrant.
A film-type developer, such a developer is a solution or a resin-polymerized float. Such imaging agents form a transparent or translucent coating on the surface of the workpiece, and certain types of coatings can be removed from the workpiece for storage.