Testing of a CNC control abrasive belt grinding machine based on ultrasonic thick measure for nuclear zirconium alloy

摘要

A highly efficient precision grinding method was proposed for the development of Zr-4 alloy used in nuclear industry. The key techniques to develop this new grinding machine are presented in detail, including soft grinding wheel head, ultrasonic thickness measurement system. An automatic polishing and grinding system was built, which is based on ultrasonic thickness measurement technology. According to a lot of grinding experiments, reasonable, accurate and efficient Zr-4 Alloy grinding parameters was determined. The experiments show that when the line speed of belt is about 18 m/s; the workpiece feed rate is 1000mm/min; grinding head cylinder pressure is 0.12Mpa, the silicon carbide abrasive belt of P80 particle size can get 0.02mm grinding amount and achieve excellent grinding effect. The alloy of Zirconium-based added other element has excellent mechanical properties, good workability and weld ability. In the 300 ~ 400 °C high temperature and high pressure water and steam, it has good corrosion resistance. Thermal neutron absorption cross section is small and nuclear fuel compatibility is good. Therefore, zirconium alloy is ideal for nuclear reactor core structural material [1-3]. Before entering the cladding tube manufacturing plant, the inner and outer surfaces of the Zr-4 alloy pipe must be processed in order to achieve the required pipe wall thickness and surface roughness. At present, China mainly import diamond deep hole honing technology from the Swedish SUNNEN to grinding the defect of Zr-4 alloy tube's inner surface and finish geometric dimensions. And the inner surface roughness of tube can reach Ra0.32μm. However, this method is limited ability to increase the pipe wall thickness uniformity. The wall thickness of tube mainly depends on mechanical grinding to the outer surface.