1、涂料的透气性差或者负压不足，充填砂的透气性差，不能及时排出型腔内的气体及残留物，在充型压力下形成气孔。

1, poor permeability or negative pressure of the coating, poor permeability of the filling sand, can not timely discharge gas and residue in the cavity, forming pore under the mold filling pressure.

2、浇注速度太慢，未能充满浇口杯，暴露直浇道，卷入空气，吸入渣质，形成携裹气孔和渣孔。

2, pouring speed is too slow, not filled with gate cup, exposed straight sprue, involved in the air, inhaled slag, forming a stoma and slag hole.

3、泡沫模型气化分解生成大量的气体及残留物不能及时排出铸型，泡沫、涂料层填充干砂的干燥不良，在液态合金的高温包围下，裂解出大量的氢气和氧气侵入铸件是形成气孔的主要原因。

3, the bubble model gasification decomposition to generate large amounts of gas and residue can be discharged in time to cast, foam, paint layer filling sand dry bad, surrounded by high temperature liquid alloy, a large number of hydrogen cracking and oxygen into the casting is the main reason for the formation of pores.

4、由于浇注系统设计不合理，金属液的充型速度大于泡沫气化退让及气体排出速度，造成充型前沿将气化残留物包夹在金属液体中再次气化形成内壁烟黑色的分解气孔。

4, due to the unreasonable design of the gating system, the filling speed of metal liquid is greater than that of the foam gasification and gas discharge, resulting in the gasification of the gasification residue in the metal liquid at the filling front, and then re forming the decomposition pores of the black smoke on the inner wall.

5、浇口杯与直浇道以及浇注系统之间的连接处密封不好，尤其是直浇道与浇口杯的连接密封不好，在负压的作用下很容易形成夹砂及气孔，这种现象可以用伯努利方程计算和解释。

5. The sealing between the sprue cup and the sprue and pouring system is not good, especially the connection between the sprue and the sprue cup is not good. The sand and air holes are easily formed under the action of negative pressure. This phenomenon can be calculated and explained by the Bernoulli equation.

6、型砂的粒度太细，粉尘含量高，透气性差，负压管道内部堵塞造成负压度失真，使型腔周围的负压值远远低于指示负压，气化物不能及时排出涂层而形成气孔或皱皮。

6, sand grain size is too fine, dust content is high, poor permeability, negative pressure pipeline internal blockage caused by negative pressure distortion, so that the cavity around the negative pressure value is far below the indicator negative pressure, gasification material can not timely discharge coating and form pores or wrinkled skin.

7、浇注温度低，充型前沿金属液不能使泡沫充分气化，未分解的残余物质来不及浮集到冒口而凝固在铸件中形成气孔。

7, the pouring temperature is low, the filling front metal liquid can not make the foam fully gasification, the decomposition of residual material is less than floating to the riser and solidification in castings, forming porosity.