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Basic Research on Creep Feed Grinding of Titanium Alloy with Monolayer Brazed CBN Wheels

Author: YangChangYong
Tutor: XuJiuHua
School: Nanjing University of Aeronautics and Astronautics
Course: Mechanical Manufacturing and Automation
Keywords: Titanium alloy monolayer brazed CBN grinding wheels creep feed grinding grinding force specific grinding energy temperature surface integrity
CLC: TG580.1
Type: PhD thesis
Year: 2010
Downloads: 193
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Abstract


Titanium alloys are widely used in the aerospace engine, such as impeller, leaf disc and blade, because of their excellent mechanical strength and resistance to surface degradation. While titanium alloys are machined with traditional abrasive tools, the surface quality is difficult to be controlled and the tool worn quickly. Cubic boron nitride (CBN) wheels have been utilized and taken good effects in grinding titanium alloy for CBN abrasive grits have some distinguished properties, such as extremely high hardness, superior thermal stability, large chemical inertia and excellent thermal conductivity. However, the shortcomings of low holding strength for grains and limited storage space for chips are always accompanied with the traditional multiplayer sintered and monolayer electroplated CBN abrasive tools. Therefore, it is helpful to develop the innovative CBN wheel and scientifically to evaluate the performance of grinding wheel for promoting titanium alloy machining with good quality ad high productivity. The innovative monolayer brazed CBN grinding wheels are developed and evaluated in the creep feed grinding of titanium alloy, in order to enhance the machining efficiency of titanium alloy. While cutting titanium alloy blade tenon, there are some problems, so gringding is considered to replace cutting. According to the design and machining requirements of the lamina rabbet, an innovative monolayer brazed CBN profile grinding wheel is developed and used to machine the rabbet in the production field.The main contents in this paper are as follows:(1) The innovative monolayer brazed CBN grinding wheels is designed according to the requirements of brazing technique to realize the creep feed grinding of titanium alloys. Moreover, on the basis of determined the suitable brazing process, the machining process of the grinding wheel hub mainly controlling the rotary accuracy of the wheel and the equal height characteristics of grains is effectively controlled, this kind of CBN grinding wheel applied to creep feed grinding of titanium alloy is successfully developed.(2) The creep feed grinding experiments are conducted to investigate the grinding performance of the innovative monolayer brazed CBN wheel by the means of studying the grinding force, temperature an specific energy as well as the wear of the grains. The experiment results show that the grinding force and temperature can be controlled effectively while creep feed grinding titanium alloy TC4 with the monolayer brazed CBN wheel and the machining efficiency can be improved obviously. Rare earth La can improve the performance of brazed CBN wheels. On the other hand, the abrasion wear is the leading wear behavior for the brazed CBN grinding wheels. The disadvantageous phenomenon, such as the fallout of CBN grits, has never happened during the experiment, which indicates that strong joining to the grains has been realized in the brazed abrasive tools. Thus, the excellent abrasion resistance of CBN grains could be exhibited completely.(3) The effect of the maximum undeformed chip thickness on the grinding specific energy is evaluated and the critical threshold of the maxmum underformed chip thickness is discussed, which can be used as a direction in the design and manufacture of brazed CBN wheels as well as the selection of machining parameters while creep feed grinding titanium alloys.(4) According to the design and machining requirements of the lamina rabbet of some aerospace engine turbine, the innovative monolayer brazed CBN profile grinding wheels are designed and manufactured. The grinding experiments are carried out in the production site. The dimension accuracy of the tenon is assessed and the results indicate that it completely meets the requirement to blade tenon of aero-engine. Compared with cutting, the efficiency and quality stability are improved obviously. And the results indicate that the grinding performance of brazed CBN wheel is better than that of vitrified ones.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metal cutting and machine tools > Grinding and grinding machine > General issues > Grinding principle and calculation
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