Development of a High Strength Cast Iron Cylinder Block Assuring High Productivity

摘要

To improve the product competitiveness (functional improvement and weight reduction) of cast iron cylinder blocks, it is necessary to increase the material strength. To do this, it is necessary to increase the strength of casting before machining, but it will, with the existing technology, worsen the machinability to lower the productivity. To establish a new technology which satisfies both the material strength and the machinability, we have analyzed both materials and machining. As a result, it has been found that the material strength can be increased by graphite grain refinement and that the machinability by the mechanism consisting of (1) graphite chipping action by graphite grain refinement and (2) lubrication and protection by composite oxides on the tool surface. We have also succeeded in developing a manufacturing technology for controlling graphite refinement and composite oxides with molten metal treatment in casting process.