As early as the 1940s, developed countries have studied the machinability of gray cast iron. Nowadays, the cutting performance of gray cast iron has been deeply studied in developed countries. After a large number of long-term experimental research and factory data statistics, the maturity of gray cast iron can be derived from the composition of gray cast iron by mathematical method. The maturity shows that the influence of metallurgical factors on the material of gray cast iron can not be ignored. Through maturity, we can not only judge the quality of production conditions, but also know the degree of production conditions. Combined with metallographic observation, it can provide casting producers with methods to find problems and directions to improve production conditions and processes.
At the same time, the traditional concept of high strength and high hardness of gray cast iron has been changed. According to the maturity, the foundation for discussing the machinability of cast iron can be stably laid, and this idea can be developed at the same time. Collini et al. Found that the very practical tool for studying the machinability of gray cast iron is the quantitative analysis of metallography. Strictly controlling the casting process of gray cast iron can obtain good microstructure and excellent machinability.
The cutting performance of domestic gray cast iron cylinder block materials has been improved after a lot of research and test. However, with the international standard requirements of Chinese gray cast iron production, the problem of poor machining performance is becoming more and more prominent in production and application. With the wide application of precision and high-speed cutting machine tools, it is urgent to improve the cutting performance of gray cast iron. Casting technicians found in production research that sometimes even if the hardness, chemical composition and metallographic structure of domestic gray iron castings are similar to those of imported gray iron castings, the cutting performance of domestic gray iron castings still lags behind that of foreign countries. For example, the gray cast iron engine cylinder block produced by FAW casting is processed on the advanced processing line introduced from Germany, including a full set of cutting tools. The production efficiency reaches 800 pieces per shift, more than twice that of similar domestic processing lines.
Even so, the machinability of cylinder castings has become a thorny problem in the early stage of production. Compared with the cylinder block produced in Germany, the engine cylinder block produced by FAW casting has a significant gap in cutting performance. In terms of fine boring process, the cylinder block produced in Germany can process more than 1000 pieces with new tools every time, while the cylinder block produced by FAW casting can only process 100 pieces with new tools every time, and the wear difference of tools is more than 10 times. This not only increases the cost of tool consumption, but also reduces the production efficiency due to frequent tool change. It is more urgent to effectively improve the machinability of gray cast iron.