制造高质量铸件的十大准则.doc

制造高质量铸件十大准则 1.Start with a good quality melt 从高质量的熔炼开始 Immediately prior to casting, the melt shall be prepared, checked, and treated, if necessary, to bring it into conformance with an acceptable minimum standard. However, preferably, prepareand use only near-defect-free melt. 2. Avoid turbulent entrainment of the surface film on the liquid 防止表面氧化膜的湍流卷入 This is the requirement that the liquid metal front (the meniscus) should not go too fast. Maximum meniscus velocity is approximately 0.5 ms-1 for most liquid metals. This maximum velocity may be raised in constrained running systems or thin section castings. This requirement also implies that the liquid metal must not be allowed to fall more than the critical height corresponding to the height of a sessile drop of the liquid metal. 3. Avoid laminar entrainment of the surface film on the liquid 防止层流薄膜的卷入 This is the requirement that no part of the liquid metal front should come to a stop prior to the complete filling of the mould cavity. The advancing liquid metal meniscus must be kept `alive (i.e. moving) and therefore free from thickened surface film that may be incorporated into the casting. This is achieved by the liquid front being designed to expand continuously. In practice this means progress only uphill in a continuous uninterrupted upward advance; i.e. (in the case of gravity poured casting processes, from the base of the sprue onwards). This implies _ Only bottom gating is permissible.仅允许底注 _ No falling or sliding downhill of liquid metal is allowed.不允许倾注或下坡式浇注 _ No horizontal flow of significant extent.不能有大平面流动 _ No stopping of the advance of the front due to arrest of pouring or waterfall effects etc.不能有前端中断的瀑布式浇注 4. Avoid bubble entrainment 防止气泡卷入 No bubbles of air entrained by the filling system should pass through the liquid metal in the mould cavity. This may be achieved by: _ Properly designed offset step pouring basin;恰当设计的阶梯浇口盆 fast back-fill of properly designed sprue;恰当设计的后充满直浇道 preferred us