Study On Evaluation And Processing Technologies Of Micro-pits Distribution Of YAG Laser Texturing Rolls

Steel plate is the most widely used steel products. Texturing sheet, a kind of steelplate, is an important raw material in industries of the automobile, household appliances,etc. It has excellent stamping performance and coating properties due to its specialsurface morphology. It is copied by texturing roll. Roll texturing technology is atechnology which can make burnished roll textured, so the surface of the roll can havespecial surface morphology. This technology is an absolutely necessary technology toproduce texturing sheet. Presently, electrical discharge texturing(EDT) and lasertexturing(LT) are the two kinds of advanced roll texturing technologies which have beenlarge-scale applied in industry.LT steel plate has more excellent stamping performance and coating propertiesthan EDT, because the micro-pits have special surface morphology of isolating eachother by LT. However, because micro-pits are distributed under1D controllable andregular in traditional LT, the isotropic properties of LT steel plate in elongation andappearance quality are worse than EDT, thus lower the comprehensive performance ofLT texturing sheets. The perfect distributed form of micro-pits on texturing rolls isapproximate isotropic and irregular distribution.The study objective of the thesis is to overcome the disadvantages of the existingLT by studying the processing technologies of YAG texturing sheet which micro-pitsare approximate isotropic and irregular distribution. Thus the comprehensiveperformance of YAG texturing sheets can be improved.To study the uniformity of the distribution of surface roughness, the thesis comesup with an evaluation method on the distribution of surface roughness first. The thesisdefines3D height amplitudes of the surface include SRa(area-directional surfacearithmetic mean deviation), SRq(area-directional surface root mean square deviation),SRsk(area-directional surface skewness) and SRku(area-directional surface kurtosis).The thesis also establishes relative assessed area indexes, assessed direction indexes andassessed total indexes. These indexes provide a foundation for studying the quantitativerelation among surface roughness, assessed area and assessed direction. These indexesalso provide a standard for assessing the distribution of the height amplitudes based onarea, direction and total respectively. The minimum of area CV(coefficient of variation)can be used as evaluation criteria of the area-uniformity of the distribution situation onheight amplitudes in a single assessed direction. The minimum of directional CV can beused as evaluation criteria of the direction-uniformity of the distribution situation onheight amplitudes in a single assessed area. The minimum of total CV can be used asevaluation criteria of the uniformity of the total distribution situation on heightamplitudes in all assessed directions of all assessed areae.According to evaluation criteria of the direction-uniformity of the distributionsituation on height amplitudes in a single assessed area, the thesis studies the image design methods of micro-pits with approximate direction-uniformity disordereddistribution. The thesis comes up with some methods: area scrambling micro-pits imagedesign methods based on regular graphics arrangement(include square area scramblingmicro-pits image design methods based on square-aligned-array arrangement andsquare-staggered-array arrangement, and area scrambling micro-pits image designmethod based on equilateral hexagon-array arrangement), minimum interval micro-pitsimage design method, and minimum interval area scrambling micro-pits image designmethod, and acquires relative micro-pits images which provide raw data for processingvarious micro-pits with approximate direction-uniformity disordered distribution onrolls.The thesis studies processing methods for micro-pits with2D controllabledisordered distribution. The thesis comes up with some processing methods formicro-pits with2D controllable disordered distribution including local displacementmethods(including disordered delay method and disordered deflection method) andimage methods(including switch method, displacement method, switch-displacementmethod and switch-delay method). These methods provide proper technical means forprocessing more efficiently various micro-pits with approximate direction-uniformitydisordered distribution on rolls.Finally, the thesis develops a processing system of YAG laser texturing rolls basedon processing methods for micro-pits with2D controllable disordered distribution, andstudies the application of YAG laser texturing technology. The images of micro-pitswith approximate direction-uniformity disordered distribution are processedsuccessfully on the surface of rolls, thus expected goal are reached. YAG laser texturingtechnology is successfully applied on laser engraving of ceramic anilox rolls, thus thedomestic blank is filled. YAG laser texturing technology is also successfully applied onlaser micro-machining of the cylinder sleeve in an internal combustion engine.Compared with mechanical grinding, laser etching has remarkable effect on reducingcoefficient of friction and reducing the amount of wear.Height amplitudes of surface roughness based on area-direction character and theirassessed indexes proposed by the thesis are universal. They can be used to study thedistribution on general surface roughness.The main goal of laser texturing of cold steel sheet, the national key scientific andtechnological project, is to develop laser texturing sheet used on automobile outercladding parts. Its important problem is to improve isotropic character of laser texturingsheet. One of the key is to improve the isotropic character of the distribution ofmicro-pits on laser texturing sheet. The application of the subject will save a largeamount of foreign exchange for the country, and create good economic benefits forenterprises.