Fundamental Investigation of Brazed CBN Heat Pipe Grinding Wheels
Author:Chen Jia Jia
Supervisor:fu yu can
The burn behavior of grinding is the main problem that restricts high-efficiency grinding of difficult-to-machining materials such as titanium alloys and super alloys.The existing cooling technologies mostly based on the coolant.However,because of the complexity and closeness of the grinding contact zone during high-efficiency grinding and profile grinding,the coolant is difficult to be injected into the contact zone.Besides,the use of the coolant is also contrary to the idea of green machining.In this paper,abrasive brazing technology and heat pipe technology was combined to solve the problem caused by high grinding temperature.Brazed CBN heat pipe grinding wheels were designed and investigated for specific processing object.The heat transfer mechanism and heat transfer performance of the heat pipe grinding wheels were analyzed by both two phase simulation and experiments.The influence of heat flux,filling ratio and rotational speed of the grinding wheels were also studied.The grinding wheels were finally manufactured and applied in dry grinding of Ti-6Al-4V and Inconel 718,which verified the high heat transfer performance of the heat pipe grinding wheels.The major research works are included as follows:(1)The structures of axial rotating heat pipe and radial rotating heat pipe were designed.CBN grains were brazed on the grinding wheels by furnace brazing and high frequency induction brazing respectively.(2)The thermal conductivity of the grinding surface on the heat pipe grinding wheel under different arrangement was tested and the forced convection heat transfer coefficient was analyzed,which offered datas for later researches.(3)Results suggest that natural convection tends to dominate boiling with the increase of the rotational speed in the evaporator section.Film condensation was proved to be the heat transfer mechanism in the condenser section.The heat transfer performance of the two heat pipe grinding wheels was evaluated under different heat flux,filling ratio and rotational speed.Finally,the appropriate grinding parameters were determined.(4)Brazed CBN axial rotating heat pipe grinding wheel and radial rotating heat pipe grinding wheel were manufactured.Comparative experiments were carried out by dry grinding of Ti-6Al-4V(formed surface)and Inconel 718(flat surface)with both heat pipe grinding wheels and normal grinding wheel.Grinding temperatures and the workpiece surface were studied to evaluate the heat transfer performance of the two grinding wheels.Results show that heat pipe grinding wheel has great superiority in green machining of difficult-to-machining materials.