Are there any ways to repair cracks on the surface of castings?
Release time:
2025-02-28
When casting, it is necessary to comprehensively consider factors affecting
1. Casting Structure
When casting, fully consider factors such as the structure, shape, size, wall thickness, and transitions of the casting that affect the liquid and solid shrinkage of the casting. Select appropriate process parameters to prevent casting defects such as shrinkage cavities and porosity. The gating system design of the casting should be reasonable. If cold iron or other process measures are to be used, their placement should be reasonable, ensuring the compactness of the internal structure of the casting while avoiding stress concentration as much as possible.
2. Smelting
During smelting, minimize the content of harmful elements such as P and S, and reduce the content of gases and inclusions such as N, H, and O. Using low-phosphorus steel intermediate alloys can achieve good results.
3. Heat Preservation
By appropriately extending the heat preservation time of the casting in the sand mold, mainly controlling the opening temperature below 70℃, ensure that the casting completes liquid and solid shrinkage in the sand mold, and avoid stress concentration caused by external forces.
4. Sand Removal
During the casting sand removal and cleaning process, strictly prohibit pouring water into the sand mold and casting when knocking out the mold, and strictly prohibit using strong external force impact methods such as knocking out the mold to remove sand, to avoid cracks caused by the interaction of external forces and internal stresses in the casting.
5. Cutting the Sprue
Select an appropriate hot-cutting sprue process according to the casting conditions, ensuring that the hot-cutting starting temperature is not lower than 300℃. During operation, the gas cutting torch and oxygen blowing pipe use vibration cutting. For important parts, cover the cut sprue with asbestos cloth immediately after gas cutting or heat treat it in a furnace. For castings with complex structures such as crowns and axial flow blades that adopt special measures in the process, secondary hot cutting is used.
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