The steam erosion of the water pump is caused by the vaporization of water. The vaporization of water has a certain relationship with the temperature and pressure. Under a certain pressure, when the temperature rises to a certain value, the water begins to vaporize; if the pressure is reduced to a certain value at a certain temperature, the water will also vaporize. This pressure is called the pressure of water at this temperature. If the pressure in a local area is equal to or lower than the vaporization pressure corresponding to the water temperature, the water will vaporize there. After the vaporization occurs, many small steam bubbles with steam and gas will be formed. When the foam flows from the water flow from the low -pressure area to the high -pressure area, the steam bubbles are ruptured under the action of high pressure, and the high -pressure water flows to the space possessed by these original vapor bubbles at high speed to form a impact force. Under the influence of water shock pressure, the metal surface forms fatigue and is severely damaged. Therefore, the process of the formation, development, and rupture of steam bubbles is called the phenomenon of auto erosion.