The machinability of gray cast iron is affected by different melting methods. From a large number of research and tests, it is concluded that the hardness of molten iron melted in cupola is higher than that melted in electric furnace, which is not conducive to the improvement of machinability. The higher tapping temperature can not only ensure the gray cast iron with clear contour and no cold lap, but also homogenize the molten iron structure, and improve the mechanical properties and processability of gray cast iron.
So far, the tapping temperature of gray iron castings is generally required to be above 1480 ℃ to produce high-quality products. It is generally believed that increasing the tapping temperature can improve the machinability of gray iron castings; Moreover, high tapping temperature can fully dissolve the coarse graphite in pig iron and homogenize the metallographic structure of cast iron.
In the process of casting, chilling occurs at the edge of the casting, and more carbides will be generated in the metallographic structure, and even white mouth will be generated there, which will seriously deteriorate the machinability of the casting. When designing the, the casting fillet radius should be increased as much as possible, so as to alleviate the chilling of the casting edges and improve the cutting performance of the casting.