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铝活塞在浇注冷却过程中,有大量气体需从型腔内向外排出,这些气体一部份是由于型腔空间本身存留空气,一部份由合金从浇包注入型腔时带入的气体,还有熔融合金液与潮湿的外模、内芯及涂料作用面产生的气体等等,这许多气体都需在合金凝固前的一瞬间,通过冒口和外模及内芯的通气槽、通气孔排出,否则将被阻留在型腔内,在铸件凝固过程中,铸件表皮下形成倒梨形的皮下气孔〈见图一〉,这种气孔的位置一般有固定的区域。铸件外表面生成单个集中大气孔,这种气孔的位置一般是不固定的;
Aluminum Pistons in the casting cooling process, there is a large amount of gas to be discharged from the cavity inside out, some of these gases is due to the cavity space itself retains air, part of the alloy from the ladle into the cavity into the gas, There are molten alloy liquid and moist outer mold, the inner core and the paint produced by the role of the surface gas, etc., many of these gases are required in the alloy solidification before the moment, through the riser and the outer mold and the core of the ventilation slot, through Stomata discharge, otherwise it will be retained in the cavity, the casting solidification process, the formation of inverted pear-shaped subcutaneous pores under the skin , the location of such pores generally have a fixed area. Cast a single concentrated outer surface of the air hole, the location of such pores are generally not fixed;