住黑色金属、水玻璃——石英砂熔模精铸件生产中,经常出现一种靠表皮气孔”,严重时占废品的70％左右。它对不加工或加工余量小、质量要求较高的精密铸件危害十分严重。它的外貌特征是:无规律地分布在模组组合较密集、型壳制成后连成一片、厚实的铸件和铸件比较肥厚的部位上。每平方厘米气孔 Live in black metal, water glass - quartz sand casting mold casting production, often by a skin stomata ", accounting for about 70% of serious cases.It is not processing or processing margin of small, high quality requirements Precision castings endanger very serious.Its appearance is characterized by: irregular distribution in the module combination is more dense, after the shell is made into a piece, thick castings and castings more hypertrophic parts.Cells per square centimeter