| 摘要 |
PURPOSE:To form finer spheroidal graphite and to improve workability such as machining and boring in the stage of casting a crankshaft stock with a spheroidal graphite cast iron by heating or cooling the respective parts of the crankshaft stock. CONSTITUTION:A molding sand layer 6 is formed on the inside of a casting cavity 2 of a metallic mold 1 for casting the crankshaft. The melt of a gray cast iron inoculated with Fe-Si is poured into the mold through a sprue 10 and is passed through runners 3 so as to react with a spheroidal graphitizing agent 4 essentially consisting of Mg to form the molten spheroidal graphite cast iron which is then cast into the casting cavity 2. Parts 2a for forming crank arms, part 2b for forming the connecting end of a flywheel and part 3c for forming the connecting end a transmission member are insulated of heat by the layer 6 and parts 2d for forming crank pins and parts 2e for forming crank journals are heated and insulated by heaters 9; therefore, the molten metal is cast with good run over the entire part of the cavity 2. The parts 2d for forming the crank pins and the parts 2e for forming the crank journals are quickly cooled by cooling water pipes 81, 82 after casting. Since the stock consists of the fine spheroidal graphite cast iron having the structure essentially consisting of the ferrite, the stock permits easy working such as machining, grinding and boring. |
