In the production process of Casting PRG castings, non-destructive testing is a key link to ensure product quality. Its methods are diverse and have their own characteristics, and accuracy assessment is also crucial.
First of all, one of the commonly used non-destructive testing methods is ultrasonic testing. Ultrasonic testing uses the characteristics of reflection and refraction when ultrasonic waves propagate inside the casting to detect defects. For Casting PRG castings, the ultrasonic waves emitted by the ultrasonic probe propagate relatively stably in uniform materials. When encountering defects such as pores, slag inclusions or cracks, some ultrasonic waves will be reflected back. By analyzing the time, amplitude and other parameters of the reflected wave, the location and approximate size of the defect can be determined. For example, when testing PRG castings with tiny pores inside, ultrasonic testing can clearly capture the ultrasonic signal reflected by the pore interface, thereby accurately determining the depth position of the pore. It has high accuracy. For defects greater than 1 mm, the positioning accuracy can be controlled within a few millimeters, and it can effectively detect defects at deeper locations inside. However, for castings with complex shapes and rough surfaces, the coupling effect of ultrasonic waves may be affected, resulting in a slight decrease in detection accuracy.
Secondly, radiographic testing is also an important means. It uses X-rays or gamma rays to penetrate the casting, making the film sensitive or the detector receiving signals to form an image. For Casting PRG castings, radiographic testing can intuitively present the shape, size and distribution of internal defects. For example, when testing castings with shrinkage cavities inside, the outline and relative density difference of the shrinkage cavities can be clearly seen on the radiographs. The accuracy of radiographic testing depends on factors such as the energy of the radiation source and the resolution of the film or detector. Generally speaking, for volumetric defects, such as larger shrinkage cavities, the detection accuracy can reach about 10% of the defect size, but the cost of radiographic testing is high, and there are radiation protection requirements for operators, and the detection speed is relatively slow.
Magnetic particle testing is suitable for detecting surface and near-surface defects of ferromagnetic materials. For the part of Casting PRG castings containing ferromagnetic components, the magnetic powder is evenly sprinkled on the magnetized casting surface. If there are defects, due to the distortion of the magnetic lines of force, the magnetic powder will gather at the defect to form magnetic traces. For example, when detecting surface cracks, the magnetic powder will form obvious traces along the crack distribution, which is convenient for observation and judgment. Its detection accuracy can reach about 0.1 mm for surface open defects, but it can only detect ferromagnetic materials and is powerless for deeper internal defects.
Finally, in terms of accuracy assessment, multiple factors need to be considered comprehensively. In addition to the accuracy indicators of the detection method itself, it is also related to the skill level of the operator, the calibration and maintenance status of the detection equipment, and the material, shape, and surface condition of the casting. Regularly calibrating and assessing the detection equipment and personnel using standard defect test blocks can effectively improve the reliability of detection accuracy. At the same time, the combination of multiple non-destructive testing methods can complement each other for verification, and more comprehensively and accurately evaluate the quality of Casting PRG castings, ensuring their safety and reliability in subsequent use.
