Abstract
This study focused on the ultrasonic nondestructive testing and quality evaluation method of cast-steel parts. The study reviewed and evaluated the current testing capabilities of various establishments, including the simulation tests and judgment criteria of surface and internal defects. The relationship between the actual defect size and the penetration depth was calculated according to the energy output, sound velocity and caliper data, and the mapping method (pitch-catch) was used to detect flaws of optimum size. The evaluation of quality was established based on the depth of the principal flaw, the number and nature of the other flaws, and their total area. The results showed that this evaluation method is appropriate for cast-steel parts.
Significance of This Study
The ultrasonic testing of cast-steel parts determines the integrity and quality of products and guides the improvement of product quality. Therefore, ultrasonic testing and quality evaluation are of considerable importance in the foundry industry. The findings of this study can be used in the integration of well organized testing strategies, improved signal-processing techniques, and optimized defect recognition to ensure the quality reliability of cast-steel parts.
Introduction
Cast-steel parts are widely used in the foundry industry and have very stringent quality requirements. The in-service performance of these parts is of great importance. Therefore, in order to ensure the safety of cast-steel parts, an effective quality evaluation method is required. Various techniques are available for the evaluation of these parts, including visual inspection and dimensional measurement. These techniques are not accurate enough for the detection of fine flaws or cracks, as well as for the evaluation of their sizes. Therefore, the ultrasonic nondestructive testing protocol is necessary for evaluating the integrity of cast-steel parts and for determining their quality.
Simulation Tests and Judgment Criteria
To simulate the tests on actual cast-steel parts, two methods were proposed. The traditional method was developed to simulate the real parts in an ideal environment. This was done by fabricating a target block that contains metallic and/or nonmetallic features, such as cracks and porosity. The results indicated that the traditional method can be used to assess the defect detection and sizing capabilities of various ultrasonic flaw detectors. The second method was the finite element modeling, which involved the use of a 3D computer software to simulate the actual parts. The finite element modeling was more complex, but provided a higher degree of accuracy than the traditional method. This study employed both methods to assess the testing capabilities of various establishments. The following criteria were employed to determine the testing accuracy of the establishments: the defect type, size, orientation, and shape.
Results and Analysis
After calculating the relationship between the actual defect size and the depth of the principal flaw, the mapping method (pitch-catch) was used to detect flaws of optimum size. The results showed that this method is able to detect the principal flaw at a depth of 1.5 mm or less. Further, the total area of the defects was evaluated using the ratio of the total nonradiating area to the total area of the casting. The results indicated that the ratio is inside 0.3, which is the criterion for evaluation. Therefore, the use of this method to evaluate the quality of cast-steel parts was established.
Conclusion
This study established that the ultrasonic nondestructive testing and quality evaluation method of cast-steel parts is effective in establishing the integrity and quality of these parts. The results showed that the established method is appropriate for cast-steel parts. The findings of this study will contribute to the well organized testing strategies, improved signal-processing techniques, and optimized defect recognition of cast-steel parts.
