1. Difficulty in mold filling of steel castings
According to the casting process manual, when the maximum contour size of low alloy structural steel is 1250~2000 mm, the minimum wall thickness of sand casting steel castings is 20 mm. The Laplace force caused by the surface tension of liquid metal can seriously affect the flow state of the filling liquid, and the role of viscous force is also prominent. The material of the guide rail steel casting is ZG32MnMo, and the length of the guide rail steel casting is 1596 mm, between 1250 and 2000 mm. The Laplacian force reduces the mold filling ability of the steel liquid. At the same time, due to the complex and long mold filling path of the steel casting, serious heat loss is caused. These two factors have caused difficulties in the complete mold filling of the steel casting, which is one of the difficulties in the forming and development of the guide rail steel casting.
2. Difficult to control the dimensional accuracy of steel castings
The contour length of the guide rail steel casting is up to 1596 mm, with a complex structure and a lack of relevant guidance documents for reference. If the matching of the strength of the mold material and the shrinkage rate of the metal material is not accurately grasped, it is difficult to meet the accuracy requirements of the steel casting. At the same time, the steel casting belongs to the “flat plate” type hollow structure, with ribs distributed in a crisscross manner and uneven wall thickness, which is easy to form internal stress and lead to deformation of the steel casting, and dimensional accuracy is difficult to control, Moreover, heat treatment can easily lead to deformation. Therefore, the dimensional accuracy control of steel castings is one of the difficulties of this study.
3. Internal quality of steel castings is difficult to control
The steel casting ribs of the guide rail are crisscrossed, and there are multiple places where the wall thickness transitions and abrupt changes, making it difficult to feed and prone to shrinkage cavities and porosity defects. In addition, the overall outer contour of the guide rail steel castings is large and the structure is complex, resulting in complex filling paths for liquid metal. The long flow paths for liquid metal make it difficult to control the consistency of the performance of different parts of the steel castings, requiring high requirements for heat treatment processes.