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金属镁与氧的亲合力较强,镁合金在高温时迂到空气或水后极易燃烧。因此,在砂型铸造镁合金铸件时,必须往型砂中添加防燃的附加物,以保证在浇注过程中镁铸件不会燃烧。目前我国生产镁铸件的工厂都是往型砂中加入8～10%的氟附加物,其主要成分是NH_4F、(NH_4):SiF_6和NH_4BF_4等。这些氟化物受热分解后,在铸件表面生成Mg_3 B_2、Mg F_ 2等致密的保护膜,同时分解出NH_3、HF、SiF_4等较稳定的气体,对镁合金起防燃的保护作用。但是这些HF、SiF_4等含氟气体对生产厂房和设备的腐蚀损害较大,对生产工人的健康危害尤其严重。长期吸入较高浓度的含氟气体,将引起粘膜充血和骨骼、肝肾的病变,广大生产工人强烈要求改变这种状况。
Metallic magnesium and oxygen strong affinity, magnesium alloy at high temperatures after the air or water is extremely easy to burn. Therefore, sand casting magnesium alloy castings, the sand must be added to add anti-flammable additives to ensure that magnesium casting in the casting process will not burn. At present, China’s production of magnesium castings factory are added to the sand 8 to 10% of fluorine adduct, the main component is NH_4F, (NH_4): SiF_6 and NH_4BF_4 and so on. When these fluorides are decomposed by heat, dense protective films such as Mg 3 B 2 and Mg F 2 are formed on the surface of castings, and more stable gases such as NH 3, HF and SiF 4 are decomposed at the same time, which protects the magnesium alloy against ignition. However, these HF, SiF_4 and other fluorine-containing gases are more damaging to the corrosion of production plants and equipment, especially for the health workers. Long-term inhalation of higher concentrations of fluorine-containing gas will cause mucosal congestion and bone, liver and kidney disease, the majority of production workers are strongly urged to change this situation.