Study Of CNC Abrasive Belt Grinding Process For Zr-4Alloy Tube’s Wall Thickness Based On Ultrasonic Thick Measure

Alloy based on zirconium and added other element is refractory metal materialwhich widely used in nuclear reactors. Zirconium alloy has excellent mechanicalproperties, good workability and weldability. Even in the300℃to400℃hightemperature and high pressure water and steam, zirconium alloy has good corrosionresistance, small thermal neutron absorption cross section and excellent compatibilitywith nuclear fuel, it is ideal structural material for nuclear reactor core.In order to achieve the required tube wall thickness and surface famishment,zirconium alloy tube must be handled accordingly in its inner and outer surfaces beforeentering the cladding tube production plant. At present, the major technology, to polishsurface defects and finishing grinding of the zirconium alloy tubes, is introduced inabroad, which is limited to improve the geometric accuracy such as uniformity of tubewall thickness. The tube wall thickness and surface famishment of zirconium alloy tubemainly depends on the belt grinding of external surface.In China, in despite of a long history of application of the abrasive belt grindingtechnology, it’s developmental delay, and the processing technology and equipment ofzirconium alloy tube long-term dependence and subjected to foreign, there has not beenan automatic abrasive belt grinding machine at home that applicable in nuclearprecision requirements. This subject on the basis of the centering cylindrical grindingtechnology proposed a technology based on ultrasonic detection to realize automaticgrinding of the zirconium tube wall thickness.Nuclear Zr-4alloy tube as the research object, the author carried out the followingwork from theory and experiment:1) About nuclear zirconium alloy tube and it’s material properties, to carry outgrind ability and abrasive belt grinding feasibility analysis.2) The study of nuclear zirconium alloy belt grinding mechanism. For the materialZr-4alloy, which is difficult to machine, the workpiece is prone to ablation during thebelt grinding process, and the chemical reaction between the belt abrasive and theworkpiece will create zirconium pollution and flammable chips, as well as the integrityof the workpiece surface and the morphology of surface is difficult to guarantee.Contrapose the above problems, we study the affect of material removal rate, beltgrinding wear extent and grinding process parameters to the grinding characteristics. 3) The study of Zr-4alloy wall thickness law and CNC belt grinding processparameters. According to the characteristics of Extrusion and bore grinding process,carrying out the study of zirconium alloy tube wall thickness distribution law;According to Zr-4alloy pipe wall thickness distribution and processing requirements,proposing a method based on ultrasonic thickness measurement technology CNCabrasive belt grinding; Analysising the grinding strategy and grinding processparameters, then coming to a reasonable belt grinding process parameters; Verifying thereasonableness of abrasive belt grinding methods and processes by belt grinding test.4）The study of Zr-4alloy pipe belt grinding surface quality (mainly smoothtransition and surface roughness). For Zr-4alloy tube grinding "step", carrying out asmooth process of the outer surface of the pipe and the causes and effects of Zr-4alloypipe tactless factors; Having a study of different belt combination of Zr-4alloy tubeouter surface roughness.