Key Technologies Research Of Wall Thickness Online Automatic Measurement And Grinding Of Zr-4Zirconium Alloy Tube Billet

Because Zr-4alloy has excellent resistance to thermal neutron radiationembrittlement performance, moderate mechanical properties and good machiningperformance, it has been universally used as fuel rod cladding material of the nuclearpower pressurized water reactor. However, our country does not yet have reached thelevel of manufacturing nuclear grade zirconium sponge, the Zr-4fuel rod claddingmaterials (tube billets) used in Chinese operating and under construction PWR are allprovided by foreign suppliers, it is detrimental to establish an independent nuclearindustry system. To establish self-contained Zr-4alloy tube billet production line, thefirst needs to be fixed is blooming of the tube and the design&manufacturingtechnology of its accessory equipments. In which, tube billet automatic abrasive beltrepair grinding technology is one of the major technical barriers needs to be tackled.The paper first carried out the belt grinding mechanism basic research on Zr-4alloy material, various thickness measurement methods were compared, presented anew belt grinding process method which can finish the thickness of the Zr-4alloy tubebillet, developed a new type belt grinding automation equipment which can realizethickness automatical online measurement and repair grinding functions.Main research contents and conclusions are as follows:1. Clarified the critical infrastructure issues which involves in the Zr-4alloy tubebillet belt grinding processes; utilizing the test platform for the basis research of the beltgrinding process, explored the interactive generating mechanism between abrasive andworkpiece, obtained the main factors impact on material removal rate and surfaceroughness; using advanced testing equipments, observed the micro worn surface andworkpiece surface topography, deeply analyzed the main processing defects and causes,provided theoretical and applied research to the optimization control parameters for therealization of grinding process in industrial field.2. Evaluated the five common thickness measurement methods used under normaltemperature, the one using ultrasonic wave was chosen; studied the ultrasonic couplingsystem, including the couplants, coupling modes, coupling parameters and probeselection, and so forth; put forward the “local overflow water immersion” ultrasonicpulse-echo thickness measurement method and “tube billet rotates around its axis, probedevice moves in a straight line intermittently” testing method. 3. Successfully developed a new type of abrasive belt grinding automaticprocessing equipment, by means of modern digital design software designed the maincomponents of the machine and measuring device matched the machine, such asmachine bed, grinding head components and measuring head components etc;established the numerical control system; finished the design work of electriccontrolling circuit of the machine tool and selection work of key electric components.4. Finished the accuracy and stability of the thickness measure system testexperiment and thickness measuring process experiment of the Zr-4alloy tube billet,then some main factors that impact on the precision of the measure system wereanalyzed; carried out experiment research and verification work about the thicknessabrasive belt regrinding process performance of the Zr-4alloy tube billet, analyzed theeffects of belt linear velocity, grinding pressure, belt envelope angle, workpiece rotatingspeed and grinding head feed speed on regrinding capacity, presented the recommendedapplication scope of the related parameters.