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Casting Process of Grey Iron Belt Pulley

Grey iron belt pulley is a kind of iron casting with very high technical requirements. We talked about its casting process by an example of material ASTM A48 CLASS 35, weight 1500 kg and outside diameter 1100mm.

Normally, the belt pulley requires machining to all surfaces, and no defects on the surfaces of grooves and axle hole. The hardness of casting body should be within HB 170 to HB 210.

By normal casting process, you will find there are many iron casting defects such as large sand holes and air holes on the surfaces, and serious shrinkage at the gate positions. Therefore, we used the improved casting process to solve these problems.

1. Resin sand casting process

Resin sand casting process could keep the good surface quality and reduce the sand residuals, and meet the high dimensional tolerance. As for the large belt pulley, this process will be the best foundry process.

2. Use the reinforced sand boxes

Since there are large shrinkage during cooling period, the sand boxes must be very strong to reduce the swelling amount during pouring.

3. Large casting heads

Casting heads must be very large to meet the demand of feeding. Although large casting heads will increase the production costs, but this is very necessary to reduce the shrinkage defects.

4. Use cold iron (chilling block)

Putting the cold irons at the proper positions could effectively reduce the shrinkage. Using cold irons will increase the production costs too, and cause more difficulties to production. However, as for the large belt pulley, chilling block is necessary.

5. Use air venting bars

Dandong Foundry used 8 air venting bars on the top surfaces of belt pulley. This process could efficiently vent the air, so to reduce the air holes.

6. Melting process

In order to meet the mechanical properties and density of ASTM A48 NO.35, we added alloy Cu and Cr. The final hardness of casting bodies could reach HB 170 to 190. The melting temperature should be controlled within 1290 to 1310 Celsius.

The improved casting process could make the belt pulley castings with better surface quality and less casting defects. After machining, there is no defects on the machining surfaces. The mechanical properties could meet the technical requirement of clients.

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