1. Casting structure

When casting, the factors affecting the liquid and solid shrinkage of the casting, such as the structure, shape, large size, wall thickness and its transition, should be fully considered, and appropriate process parameters should be selected to prevent casting defects such as shrinkage cavity and porosity. The design of the pouring and riser system of the casting shall be reasonable. If the cold iron and other process measures are to be adopted, the location shall be reasonable, which shall not only ensure the compactness of the internal structure of the casting, but also avoid the stress concentration as far as possible.

2. Smelting

In the smelting process, try to reduce the content of harmful elements such as P and s, and reduce the content of gases and inclusions such as N, h and o. Good results can be achieved by using low phosphorus steel master alloy.

3. Heat preservation

By appropriately extending the holding time of castings in the sand mold, the main purpose is to control the unpacking temperature below 70 ℃, so as to ensure that the castings can fully complete the liquid and solid shrinkage in the sand mold and avoid the stress concentration caused by external forces.

4. Sand falling

In the process of sand falling cleaning of castings, it is strictly prohibited to water the sand mold and castings during box beating, and it is strictly prohibited to drop sand by strong external force impact such as box collision, so as to avoid cracks caused by the interaction between external force and internal stress of castings.

5. Cutting riser

According to the casting conditions, select appropriate hot cutting pouring riser process to ensure that the starting temperature of hot cutting is not lower than 300 ℃. During operation, the gas cutting gun and oxygen blowing pipe adopt vibration cutting. After gas cutting of important parts, cover the partition with asbestos cloth in time or enter the furnace for heat treatment. For castings with complex structure and special process measures such as upper crown and axial flow blade, secondary hot cutting shall be adopted.