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. The permeability of the coating is poor or the negative pressure is insufficient, the permeability of the filling sand is poor, the gas and residue in the cavity can not be discharged in time, and the pores are formed under the 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. The pouring speed is too slow to fill the gating cup, expose the straight runner, entrap into the air, inhale the slag, and form entrapped pores and slag holes.
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 foam model is decomposed into a large amount of gas and the residue can not be discharged in time. The dry sand with foam and coating layer is desiccant. Under the high temperature of the liquid alloy, a large amount of hydrogen and oxygen are poured into the casting, which 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 the metal liquid is greater than that of the foam gasification and the gas discharge rate. The filling front will cause the gasification residue to be encapsulated in the metal liquid again to form a decomposed hole in 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 connection between the runner cup and the runner and the pouring system is not well sealed, especially the connection between the runner and the runner cup is not well sealed. Under the action of negative pressure, it is easy to form sand inclusion and porosity. This phenomenon can be calculated and explained by 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. The granularity of molding sand is too fine, the content of dust is high, and the permeability is poor. The negative pressure distortion is caused by the blockage in the negative pressure pipeline, which makes the negative pressure around the mold cavity far lower than the indicated negative pressure, and the gasifier can not discharge the coating in time to form pores or wrinkles.
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, pouring temperature is low, filling front metal liquid can not make the foam fully vaporized, the undecomposed residual material is not enough to float to riser and solidified in the casting to form pores.
8、钢水脱氧不良、炉台、炉内、包内除渣不净，镇静时间过短，浇注过程中挡渣不力，浇注工艺不合理造成渣孔。
8. Poor deoxidization of molten steel, unclean slag removal in the hearth, furnace and ladle, too short sedation time, inadequate slag retaining during pouring process, and unreasonable pouring process resulting in slag hole.
9、内浇道开设位置不合理，充型时形成死角区，由于型腔内气体压力作用，使气化残留物积聚在死角处形成气孔，内浇道截面积过大，使充型速度大于泡沫气化退让速度，吞食泡沫，在合金内部分解气化，而气体无法排出形成气孔。
9. The position of the inlets is not reasonable, and the dead zone is formed when filling. Due to the gas pressure in the cavity, the gasification residue is accumulated at the dead end to form pores. The section area of the ingot runner is too large, so that the filling speed is larger than the foam gasification and withdrawal speed, and the foam is partially vaporized in the alloy, and the gas can not be discharged. Stomata.
10、浇口杯容量太小，金属液形成涡流，侵入空气生成气孔。
10, the capacity of the gate cup is too small, the molten metal forms eddy, and invades the air to form pores.