High-efficiency precision grinding technology represented by slow-cut deep-cut grinding, high-speed ultra-high-speed grinding and high-efficiency deep-cut grinding is an important technology for the development and production of aero-engines. It requires relevant research institutes, manufacturers and other units in basic theory. Cooperation in application technology, promotion and demonstration, and emphasis on system construction, system construction and team building.
Professor Ding Wenfeng, professor and doctoral supervisor of Nanjing University of Aeronautics and Astronautics
The aero engine is known as the “Pearl of the Industrial Crownâ€, and its design, materials and manufacturing technologies play a key role in the development of the aviation industry.
The advanced aero-engine is one of the important indicators that reflect a country's scientific and technological level, military strength and comprehensive national strength. Developed countries have historically listed it as a national strategic industry and focused on development [1]. At this stage, in order to meet the needs of a new generation of aircraft with ultra-high speed, high altitude, long-haul time, and ultra-long range, and also to improve the reliability and thrust of the aero-engine, its parts (such as discs, shafts, blades, gears, casings) Etc.) Not only the high-strength and tough-to-machine materials such as titanium alloys and nickel-based superalloys are widely used, but the structure is more and more complicated, the machining allowance is very large, and the processing precision is required to be higher and higher. Therefore, the manufacturing technology is proposed to be higher. Request [2]. The traditional cutting method has been difficult to fully meet the technical requirements of high-efficiency precision machining of aero-engine parts at this stage.
Main problems in efficient and precise grinding technology for aero-engine parts
Grinding processing that achieves numerous micro-cutting by a large number of abrasive grains under the control of a binder and further removes the workpiece material from a macroscopic perspective has long been a category of precision machining. In recent years, with the advent of high-efficiency precision grinding technology represented by slow-cut deep-cut grinding, high-speed ultra-high-speed grinding, and high-efficiency deep-cut grinding, the division of the traditional "rough-cut fine grinding" of grinding and cutting The pattern has changed dramatically. The ability of the grinding process to obtain the required machining accuracy of the part can exceed the usual cutting process in many cases, and even the material processability can be easily reversed. High-efficiency precision grinding technology has shown broad application prospects in the manufacture of aero-engine parts based on high-strength and tough-to-machine materials such as titanium alloys and nickel-base superalloys.
Figure 1 shows the grinding characteristics of titanium alloy and nickel-base superalloy. High grinding temperature, high grinding force, easy adhesion of grinding wheel and difficult to control the quality of grinding surface are common phenomena at present. The resulting low grinding efficiency, short tool life and poor quality stability have become aero engine parts. Common problems faced by efficient precision grinding.
Figure 1 Characteristics of grinding of titanium alloy and superalloy
Development Status and Application of High Efficiency Precision Grinding Technology for Aeroengine Parts
In order to achieve efficient and precise grinding of aero-engine parts, many domestic and foreign units have carried out technical research and application promotion work in grinding machines, processes, tools and cooling. The following is a brief introduction to the development of high-efficiency precision grinding technology from the aspects of process, tool and cooling.
1 Research on high-efficiency precision grinding technology
The so-called high-efficiency precision grinding refers to a grinding technique that increases the material removal rate by increasing the depth of resection or the feed rate of the workpiece. Under the premise of ensuring the processing quality, it can also achieve the same material removal rate as turning and milling, and can complete the processing of large margin or complex profile by one clamping. Table 1 lists the range of parameters for the typical high-efficiency precision grinding process at this stage.
(1) Slow-feed deep-cut grinding.
Slow-moving deep-cut grinding, also known as peristaltic grinding, is the first high-efficiency precision grinding process developed. Grinding is carried out at a slow feed rate of 20 to 300 mm/min at a normal cutting speed using conventional corundum abrasive wheels at regular grinding speeds [3-4]. For titanium alloy and nickel-based superalloy parts, the processing precision of slow-cut deep-cut grinding can reach 0.001mm, the surface roughness R a can reach 0.4~0.2μm, and the material removal rate is usually 1~5mm3/(mm· s). Slow-feed deep-cut grinding technology has been widely used in the processing of various forming surfaces and grooves, such as blade grooving and gears of aero-engines. However, how to solve the sudden burn of the slow-cut deep-cut grinding process and the severe wear of the grinding wheel are the main problems.
(2) High speed super high speed grinding.
The assumptions made by Carl. J. Salmon of Germany in the 1930s regarding the relationship between cutting speed and cutting temperature indicate that the grinding process is pointing towards high-speed and ultra-high-speed development, while the diamond and CBN superabrasive grinding wheels are high-speed. The development of ultra-high speed grinding technology provides the necessary conditions [5-6]. High-speed ultra-high-speed grinding can achieve the two goals pursued by modern manufacturing technology, namely, improving production efficiency and improving product quality. Practice has proved that if the grinding wheel speed is increased from 35m/s to 80m/s, the production efficiency can be increased by 30%~60%, the durability of the grinding wheel is increased by 0.7~1 times, and the surface roughness of the workpiece is reduced by about 50%.
Table 1 Parameter range of typical grinding process at the current stage 
Europe's high-speed ultra-high-speed grinding technology started at the earliest. In the 1960s, the grinding speed of the laboratory has reached more than 200m / s. In the early 1990s, the grinding test of the highest grinding wheel speed of 350m / s was achieved. In the mid-1990s, Professor F. Klocke of the Aachen University of Technology in Germany conducted an ultra-high-speed grinding test with a grinding wheel speed of 500 m/s. China's high-speed ultra-high-speed grinding research started late, and related work is mainly concentrated in Nanjing University of Aeronautics and Astronautics, Northeastern University, Hunan University, Zhengzhou Abrasives Grinding Research Institute and other research institutes. Xu Jiuhua's research group combines single abrasive grinding with superhard grinding wheel grinding. Through experimental research and physical simulation, it reveals material removal behavior, chip formation mechanism and force-thermal coupling in high-speed ultra-high speed grinding. Etc., provide theoretical basis and basic data for high-speed ultra-high speed grinding wheel design, heat transfer enhancement, process optimization, production application, etc. [7]. At present, high-speed ultra-high-speed grinding has achieved certain results in the application verification of aero-engine parts (such as blades and turbine disks).
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