| Chemical element zirconium has excellent nuclear properties,alloy which use zirconium as matrix and involving other elements has already been widely used as tube material of fuel cladding of nuclear power water-cooled reactor.As the first protection to prevent directly contact of nuclear fuel,the zirconium alloy cladding tube is subjected to unusually complex and harsh external environment.So in order to prevent its local corrosion damage due to processing defects and to extend its service life,in the actual production,the uniformity of the wall thickness and the processing quality of the external surface of the zirconium alloy tube are strictly required.To solve problem of uneven distributed tube wall thickness which caused by hot extrusion and grinding of inner bore and to meet the requirement of high quality external surface processing of zirconium alloy tube billet,this paper is mainly about method of ensure the uniformity of the wall thickness(the wall thickness deviation ? ?0.2mm)and the smoothness of the outer surface(surface roughness Ra?0.8?m)in the case of there is a certain degree of elliptic(about 10%D)and curvature(about 2.5/1000mm).Studied on the key technologies of ultrasonic measurement of tube wall thickness and its belt grinding process,a set of software which can automatically generate NC grinding program is developed,ensure the uniformity of the wall thickness and the smoothness of the outer surface,and the machining efficiency is improved remarkably,provides solutions for solving problems because of the strict requirements for the thickness of the cross section and the quality of the surface of the zirconium alloy tube billet.1.In order to ensure the uniformity of the wall thickness of the zirconium alloy tube billet,the following research work has been carried out in this paper:(1)First of all,the scheme of the automatic ultrasonic measurement system for the wall thickness is completed,the measurement of the wall thickness of the tube billet is realized by the ultrasonic;(2)Secondly,the wall thickness ultrasonic measurement path is planned,the data of wall thickness is processed,according to the wall thickness value,the corresponding angle value and diameter,the coordinates of the measuring points are calculated,and using triplet B spline curve to reconstruct the model of the tube billet,and the wall thickness deviation and the grinding area distribution are obtained;(3)And then wall thickness of the data processing and the tube model reconstructionis integrated by using C++ programming.Developed a wall thickness measurement and grinding software,the software can be used as a "brain",which can automatically generate the numerical control NC grinding program for the wall thickness of the tube billet;(4)Finally,completed the processing on over wall thickness tolerance zone by belt grinding.And wall thickness will be measured once again by ultrasonic and if the wall thickness deviation is still serious,the abrasive belt grinding will be carried out again.In this way,the wall thickness deviation is controlled below 0.2mm.2.Under the condition of uniform wall thickness,In order to ensure the smoothness of the outer surface of the zirconium alloy tube billet,the external surface is processed using the method of integral polishing,the following research work has been carried out:(1)At first,a surface roughness analysis model is established on the basis of the application of Central Composite Design method,which has a mapping relationship with the main parameters of grinding process parameters(belt speed,grinding pressure,belt feeding speed and tube rotation speed);(2)Secondly,the optimal combination of process parameters is obtained after investigating the interaction effect of the grinding parameters on surface roughness;(3)Finally,the zirconium alloy tube billet is processed using the method of integral polishing with the optimal combination of process parameters,In this way,the surface roughness is controlled below 0.63 mm. |
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