Causes of casting sand holes

What is the reason for casting sand holes? Today, Haiyao Xiaobian leads everyone to understand:

Main reason:

1: The sand in the cavity is not clean.

2: Invade the sand from the open place such as the sprue or riser before pouring.
3: The strength of the sand type is not enough, and it is caused by the external force.
4: The casting is not continuous or the pouring speed is too slow, so that the sand in the cavity cannot float smoothly to the riser and stay in the lower temperature.
5: The temperature is too high, the pouring speed is too fast, and the sprue is rolled into the sand.