Effect of drying time of shell on casting quality

The burr defect generally occurs on the outer surface or a large plane of the stainless steel casting, and the irregular or intermittent irregular protrusion forms a burr flash. The reason for the formation of the burr is that the crack occurs before the casting, and after the molten steel is injected, it penetrates into the crack of the shell, and a burr defect is formed after solidification. There are two types of shell drying processes:

1. The temperature of the surface layer drying room is controlled within the range of 20-24 ° C, and the humidity is in the range of 60%-70%, without wind or breeze drying.

2. The temperature between the transition layer and the back layer drying is in the range of 22-26 ° C, and the humidity is between 50% and 55%. When blowing, it is required to blow strong wind, but do not face the mold shell, try to make the air flow in the dry room.

Within the above-mentioned drying process control range, we conduct tracking experiments for different drying times for castings such as valve bodies and quick joints which are prone to surface burrs. It was found that the casting having a surface layer dried for about 4 hours was almost free of burrs. The burrs of the castings dried after 6-8h are obviously increased, and the longer the burrs are, the more obvious the burrs are. Castings with a backing layer dried for 4 h had more burrs, while castings dried for 8 h and 12 h had almost no burrs.

In summary, the drying time of the surface layer should not be too long, otherwise the crack of the shell will be cracked, generally controlled within 4h; the drying time of the back layer should not be too short, the drying of the shell is not thorough, and it also affects the crack of the shell and the surface burr of the stainless steel casting. An important factor, so the drying time should be determined to be 8-12h or more.