Cast steel components (cast steel joints, cast steel bearings, etc.) are cast as a whole in the factory, with large design freedom. The transition between each branch pipe is through chamfering to avoid or reduce stress concentration. Cast steel joints have been gradually used at the joints with large stress and complex connection in construction engineering. The application of cast steel joints has achieved good technical and economic benefits in the long-term service of engineering structures. Compared with traditional cast iron materials, cast steel materials overcome the shortcomings of easy brittle fracture and poor welding performance. It has the characteristics of high strength, good toughness, good weldability and excellent corrosion resistance, and can meet the mechanical property requirements of the structure. Based on the above advantages, cast steel members are increasingly used in offshore platforms, long-span spatial structures, bridge structures and other engineering structures.
However, due to the influence of the production process of cast steel components, the initial casting defects such as shrinkage cavity, shrinkage porosity, inclusion and crack are inevitably distributed in the steel castings. These casting defects bring potential safety hazards to the application of steel castings, so nondestructive testing will be carried out before the steel castings are produced and leave the factory, so as to ensure the quality of steel castings. At present, the traditional nondestructive testing methods include ultrasonic testing, acoustic emission testing, magnetic particle testing and radiographic testing. The common NDT methods for steel castings are magnetic particle flaw detection and ultrasonic flaw detection. Although steel castings have to undergo strict quality inspection when leaving the factory, the accuracy of nondestructive testing methods such as ultrasonic testing and magnetic particle testing in engineering is limited, and it is not possible to comprehensively test the macro and micro defects in castings. Therefore, the research on the generation and distribution of casting defects will help to deeply and comprehensively understand the internal defects of castings, further optimize the structure and process design of castings, and improve the mechanical properties of castings.
Taking 24 cast steel joints produced by a steel casting plant as samples, the macro casting defects of joints are detected by means of nondestructive testing, and the random characteristics and distribution law of casting defects among groups are studied. The relevant data and analysis conclusions provide reference for engineering design, production and application.