Development direction of nodular iron piston ring casting technology

According to the comparison table of various casting methods, it can be seen that each process has its advantages and disadvantages. However, according to the comprehensive analysis and comparison of factors such as the investment of production equipment, the complexity of process, the level of production efficiency and the difficulty of machining, the double piece elliptical casting method is a casting method with good economy and high quality, It should be the preferred process method.

(1) Double piece ductile iron ring casting is the main method of mass production. Because the double piece ring can be molded by 2145 or automatic or semi-automatic high-pressure molding machine, it can be arranged in line or not in line. It is poured in stacked boxes. The adaptability of large and small rings is very strong, the production efficiency is high, and it is suitable for mass production, It can reduce the blank production cost “With the design of elliptical ring die, the machining allowance of inner and outer circles is small, which can be used for profiling machining of inner and outer circles, the distribution of pressure curve is more reasonable, and the slicing processing of blank is relatively simple. It can be sliced in a single piece or clamped into a series of slices. When slicing, the shrinkage and looseness of the center is cut off, and the shrinkage and looseness defect of the center is not found in a single piece ring, so the blank quality is more reliable. Therefore, double piece casting is the main method for mass production of nodular iron rings 。

(2) On the basis of double piece ring casting, the four piece elliptical blank casting method is developed. According to the design principle of double piece ring mold, the ring mold is designed into four piece elliptical form, which is shaped by three station automatic or semi-automatic high-pressure molding machine. The draft angle of the ring mold is 0.5 ° – 1 °, and stacked box pouring. At present, Gertz company in Germany has mass produced four pieces of ductile iron ring blanks. This modeling method can greatly reduce the workload of modeling and cleaning, increase the casting productivity, further reduce the casting cost of blanks, and the 2145 top box shock compression molding machine is no longer applicable, The only station high-pressure molding machine designed and manufactured by Chongqing No. design and Research Institute of domestic machinery industry and Zhejiang Linhai casting machinery factory provides suitable molding equipment for the production of four blank rings. The blank cleaning also includes st6-m shot blasting machine of Disha (Changzhou) Machinery Co., Ltd. and deburring machine of Chongqing No. 3 Institute, but it is also necessary to design a special high-efficiency slicing machine for four blank rings.

(3) Single piece nodular iron ring is suitable for small cylinder diameter motorcycle ring and micro car ring. It has high modeling productivity, can be directly ground without slicing, and has short production cycle. However, the quantity of returned materials reaches more than 80%, which requires conditional production on the premise of using most of the returned materials in the production of alloy cast iron rings.

(4) In addition to the production of automatic molding line, cylinder casting is generally normal cylinder. The process of elliptical cylinder is complex and it is difficult to popularize and apply. Manual sand mold cylinder has low productivity, poor adaptability to varieties and high scrap rate of casting sand holes. This process will be eliminated first. Japan’s Guangyang or Desa automatic molding production line has too much investment and poor adaptability to varieties. This process method is difficult to be popularized and applied in the future. Centrifugal casting cylinder has high productivity, no need for sand treatment system, less investment, simple process and convenient operation. However, the machining allowance of inner and outer circles of centrifugal cylinder is too large, part of both ends of blank is not used, the slicing efficiency is low, and there are shrinkage defects. This process method will not be popularized and applied. For the lost foam casting method, its core shrinkage and looseness cannot be removed, which is its fatal defect. Although the nodular iron ring has high strength after quenching and tempering, and the ring with slight core shrinkage and looseness can be used as long as there is no slag hole defect, it is only applicable to the accessory ring of motorcycle mini car and cannot be used as the main engine ring, Nor can it be used as nodular iron ring of vehicle diesel engine with large power and load. This 7 technology method is difficult to be popularized and applied in the future.