Is there any remedy for the surface crack of the casting

1. Casting structure

 

When casting, the structure, shape, size, wall thickness and transition of the casting should be fully considered, which affect the liquid and solid shrinkage of the casting, and the appropriate process parameters should be selected to prevent casting defects such as shrinkage and porosity. The design of the casting gate system should be reasonable, if the process measures such as cold iron should be used, the location should be reasonable, not only to ensure the density of the internal organization of the casting, but also to avoid the occurrence of stress concentration.

 

2. Smelting

 

In the smelting process, the content of harmful elements such as P and S is reduced as far as possible, and the content of gases and inclusions such as N, H and O is reduced. Through the use of low phosphorus steel intermediate alloy, can play a very good effect.

 

3. Heat preservation

 

By appropriately extending the holding time of the castings in the sand mold, it is mainly to control the unpacking temperature below 70 ° C to ensure that the liquid and solid shrinkage of the castings is fully completed in the sand mold to avoid the occurrence of stress concentration caused by external factors.

 

4. Drop sand

 

In the process of casting shakeout cleaning, it is strictly prohibited to water the sand mold and castings when hitting the box, and it is strictly prohibited to use strong external impact such as box knocking to avoid cracks caused by the interaction between external forces and the internal stress of the casting.

 

5. Cutting riser

 

According to the casting conditions, the appropriate hot cutting pouring and rising process is selected to ensure that the starting temperature of hot cutting is not less than 300℃. During operation, the gas cutting gun and oxygen blowing tube are cut by vibration. After gas cutting, cover the partition with asbestos cloth or enter the furnace for heat treatment. For the castings with complex structure and special measures taken in the process, the secondary hot cutting is used.