Foundry enterprises in the production process, it is inevitable to encounter shrinkage holes, bubbles, segregation and other casting defects, resulting in a low yield of castings, and back to the furnace to face a large number of manpower, power consumption. How to reduce casting defects is casting people have been concerned about the problem. The following methods can help us to reduce the error rate in manufacturing wheel castings, auto part casting, auto casting machine and other castings.
Once you want to start pouring castings, first prepare, check and handle the melting process. If required, the lowest acceptable standard can be used. However, a better option is to prepare and apply a melting programme with close to zero defects. Avoiding turbulent inclusions on the free liquid surface This requires avoiding high flow rates on the front free liquid surface (crescent surface). For most metals, the maximum flow rate is 0.5 m/s. For closed pouring systems or thin-walled parts, the maximum flow rate is suitably increased. This requirement also means that the drop height of the liquid metal must not exceed the critical value of the 'static drop' height. Avoiding laminar entrainment of the surface crust in the liquid metal requires that there is no premature stoppage of the flow at the front end of any liquid metal stream during the entire mould filling process. The liquid metal meniscus in the pre-charge phase must remain mobile and unaffected by the thickening of the surface crusts which will become part of the casting. To achieve this effect, the liquid metal front can be designed to expand continuously. In practice, only the bottom injection 'uphill' can achieve a continuous upward process. (e.g. in gravity casting, the upward flow starts at the bottom of the sprue). This means: bottom-feeding pouring systems; no 'downhill' form of liquid metal falling or sliding; no large horizontal flows; and no stopping of the liquid metal front due to dumping or waterfall flows.