图示的铸件因呛火废品率有时竟高达90％以上。但如果在造型前把铁柄烘干加热到50～60℃,加热时间15～20分钟,再放入型腔,浇注时就不再呛火了,这是为什么呢? 如铁柄不经烘干,常温下放入型腔,铁柄的“体温”就比型腔内壁低,特别是刚用过的旧砂。型腔内的水蒸汽凝聚在相对温度较低的铁柄上,形成一层小 Pictured castings due to choke rejection sometimes as high as 90% or more. However, if the iron handle in the modeling before drying heating to 50 ~ 60 ℃, heating time of 15 to 20 minutes, and then into the cavity, casting no longer choke fire, which is why? Dry, at room temperature into the cavity, the iron handle “body temperature” lower than the cavity wall, especially the old sand just used. The water vapor in the cavity is condensed on the iron handle with relatively low temperature to form a small layer