Machinability of gray cast iron for engine block

Developed countries carried out the research on the machinability of gray cast iron as early as the 1940s. After long-term experimental research, statistical analysis of factory data and mathematical derivation, someone from Aachen University of technology concluded that its maturity can be deduced from the composition of gray cast iron. With the help of maturity, we can not only judge the advantages and disadvantages of production state, but also determine its degree. Supplemented by metallographic observation, it provides direction and methods for casting producers to find problems and improve production conditions and processes. At the same time, it also changes the traditional concept that the strength of gray cast iron must be high and its hardness must be high. Therefore, it also lays a stable foundation and opens up ideas for discussing the machinability of cast iron. Collini et al. Found that quantitative metallographic analysis is a practical tool to study the machinability of gray cast iron. Excellent microstructure and machinability can be obtained by strictly controlling the casting method and process.

In recent years, through a large number of domestic research, the machinability of domestic gray cast iron cylinder block materials has also been improved. According to the anatomical analysis of imported and domestic Cummins cylinder block by Dongfeng Motor Corporation casting branch, the eutectic grain boundary of imported cylinder block is relatively easy to corrode, the grain boundary is also relatively clear, and the grain boundary of domestic cylinder block is relatively wide and fuzzy. Feng Wei and Zeng Daben solved the high strength of gray cast iron by adding alloy elements and modifying treatment, and improved the cutting performance of gray cast iron. There are many factors that affect the cutting performance, but at present, it is found that the main problem is the casting material. Therefore, this part of the research only focuses on the influence of various factors on tool wear, quantifies the cutting performance of gray cast iron from the size of tool wear and cutting force, and provides guidance for material design, inoculant selection and process design.

At present, the development trend of high-strength gray cast iron at home and abroad is mainly as follows: while obtaining high strength and stiffness, it has good casting and processing properties, that is, strength, hardness and graphitization are connected to achieve the unity of mechanical properties, casting properties and processing properties.