Ductile iron manhole covers covers Suining Neijiang, Leshan ductile iron covers cast iron covers Suining, Neijiang, Leshan cast iron covers cast iron covers ductile iron castings ductile iron manhole covers presentation has been applied in almost all major industrial sectors, these sectors require high strength, ductility, toughness, abrasion resistance, severe thermal and mechanical shock, high temperature or low temperature, corrosion resistance and dimensional stability. In order to meet the conditions of use of these changes, many of the existing grades of ductile iron, provides mechanical properties and rationality can kiss a very wide range. Ductile iron manhole covers production process (a) stringent requirements of chemical composition, carbon and silicon content of the original liquid iron requirements than gray iron, ductile lower manganese, phosphorus, sulfur content (b) the temperature of molten iron released higher than gray cast iron to compensate for the ball, bred loss treatment temperature of molten iron (III) were ball handling, which was added to the iron ball agent (four) were added inoculant inoculation (five) ductile illiquid, shrink large, and therefore requires a higher temperature and larger casting gating system size, rational application of the riser, chills, sequential solidification principles (six) heat treatment