1. Causes caused by holes: mainly the pores and contraction mechanisms, the pores are often round, and contraction is mostly irregular. (1) Reasons for stomach: In the filling and solidification process of a metal fluid, the casting of the casting surface or inside due to the invasion of the gas invasion. B The gas invasion sent out of paint. C alloy liquid has too high gas content, and concrete precipitation. Gas with gas in the cavity, volatile gases of paint, alloy solidification, when the mold exhausts is poor, the formation of the casting air hole is finally left. (2) Reasons for contraction: During the liquid metal solidification process, due to the reduction of volume or the final solidarity site, no liquid metal material, and shrinkage. B's uneven thickness of the cast or casting is local overheating, causing a slow solidification position, and a concave place forms on the surface during volume contraction. Due to the existence of the pores and shrinkage, the hole can enter the water when the die is performed on the surface. Causes the casting surface to bubble.

2. Corrosions of harmful impurities in the crystal of zinc alloy composition: lead, cadmium, tin will gather in the crystal world to cause corrosion of the crystal, the metal matrix and coating of the crystal corrosion and crushing, and accelerate the disaster. The top causes the surface of the casting. Especially in a humid environment, corrosion can deform, crack, and even break.

3. Causes of cracks: water, cold septum, hot cracks. 1) Water, cold lines: During the charging process, metal liquid, metal liquid entered the first contact wall prematurely, and then solidified the liquid metal and metal. , Card -like defects. Water is generally shallow on the surface of the casting; the cold lines may penetrate into the inside of the casting. 2) Heat cracks: When the wall thickness of the casting is uneven, the stress generates a solidification process; B is out early, and the metal strength is insufficient; the mold temperature of the unevenness of the C -top force is high and the grains are thick; E is harmful to the existence of harmful impurities. These parameters may crack. When the die -casting is water pattern, cold septum, hot cracks, the plating fluid will penetrate into the crack, convert it into steam baking, and the top of the top of the metal is formed to form a blisters.