Metallographic Sample Preparation Grinding And Polishing .
Metallographic Sample Preparation Grinding and Polishing of MetalsRelated termsGrinding, Polishing, Metallographic sample preparation, DuctilityMethodMetallography is the art of preparing metallic samplesby grinding, polishing and eventual etching for subsequent microscopic examination. Grinding and polishing is to prepare the specimen surface so as toenable the microstructure to be revealed by a suitable etching procedure.EquipmentGrinding and polishing machine,50-600rpmGrinding platen, aluminium, dia. 200 mmPolishing platen, PVC, dia. 200 mmSplash guardLidMagnetic foil, dia. 200 mmMetal disk, dia. 200 mmPolishing cloths METAPO-P, dia. 200 mm,for 10-6 µm diamond , pkg. of 10Polishing cloths METAPO-B, dia. 200 mm,for 3-1 µm diamond, pkg. of 10Polishing cloths METAPO-V, dia. 200 mm,for 1-0.1 µm diamond and oxide, 10Final polishing cloths, MD-Nap,200 mm, 5SiC paper disks, d. 200 mm,grit 240, 100Diamond suspension, 6 µm, 250 gDiamond suspension, 3 µm, 250 gDiamond suspension, 1 µm, 250 g70000.93 1112570002.03 170003.03 170004.03 170005.02 170011.70 170040.25 170041.25 170042.25 1LEA5.1.01Diamond suspension, 0.25 µm, 250 g70043.25Diamond stick P, 6 µm, 24 g70050.04Aluminium oxide suspension,70055.700.05 µm, 1 lLubricant, water base, 1 l70060.70Lubricant RED, 1 l70061.70Coarse grinding disk, MD-Piano 22070020.01Coarse grinding disk, MD-Primo 22070021.01Fine grinding disk, MD-Piano 120070022.01Fine grinding disk, MD-Largo, 200 mm70023.01Fine grinding disk, MD-Allegro, 200 mm 70024.01Set of eight raw samples70001.01consisting of:brass (CuZn40Pb2F44), copper (E-CuF25),aluminium (Al99zh), Al alloy (AlMgSiPbF28),steel (9s20k), alloyed steel (x12CrMoS17)steel, 750 C heat treated, brass, 600 C heat treatedSpray bottle, 500 ml47446.00Cleaning and polishing tissues,46417.00pkg. of 50Gloves, disposable, pkg. of 10039175.03Wash bottle, plastic, 1000 ml33932.00Dropping bottle, plastic, 50 ml33920.00Funnel, d. 40 mm36888.00Brush, universal46421.07Labels, blank, 37x74 mm, 10 pcs.37677.03Marking pencils, set, waterproof38710.21Magnifier, 10x, dia. 25 mm87004.10Recommended accessories:Metallurgical microscope,trinocular, magnification up to 400xUltrasonic cleaning bath, RK100HCleansing solution, concentrated, 1 kg11111111123111177611162244.88 146423.93 138820.70 1Fig. 1: Equipment for metallographic sample preparationwww.phywe.comP5510100PHYWE Systeme GmbH & Co. KG All rights reserved1
LEA5.1.01Metallographic Sample Preparation Grinding and Polishing of MetalsTask1. Check the six metal specimens by means of themagnifier for any coarse defects.2. Grind and polish the samples according to thegeneral rules and the detailed instructions givenbelow, considering the hardness and ductility datagiven in Table 1 and the basic processing guidelines specified in Table 2.3. Evaluate the influence of the individual processparameters on the surface quality obtained in theintermediate steps and after the final polishing.4. Try to optimize the grinding and polishing procedures.Material/CodeHardness(Vickers) DuctilityBrassCuZn40Pb2F44 90mediumCopperE-CuF25 70highAluminiumAl99zh 25highAluminium alloyAlMgSiPbF28 60mediumSteel9s20k 160mediumSteel, alloyedx12CrMoS17 240mediumFig. 2: Recommended movement scheme of thesample on the grinding or polishing disk Table 1: Sample materials (not heat treated), properties influencing the grinding and polishing behaviourExperimental Procedure and ResultsAs shown in Fig.1, put the grinding and polishing machine on a clean laboratory table close to a sink andwater tap. Take care that the environment is as dustfree as possible. Place the consumables and accessories beside the machine. If not used for some time,keep all auxiliary materials in closed boxes or bags toprotect them against contamination by flying abrasiveparticles or dust.The following general rules should be obeyed: Only utmost cleanness will lead to a satisfactoryfinal polish. Carefully wash your hands and clean the machine, disk and sample after each grinding andpolishing step. It is recommended to wear disposable gloves in the polishing stages. An ultrasonic cleaner is a useful accessory foran efficient cleaning of the samples. Always use a polishing cloth only for one specific diamond grain size. In particular, avoid con-2tamination of a polishing cloth used for final polishing, i.e. for 3 µm or 1 µm grain size, with 6 µmdiamond grains. If this has happened, the clothcan then only be used for 6 µm polishing.When not in use, the cloths must be kept strictlyseparated. For storage, it is best to seal the drycloths in plastic bags. Use a waterproof pen tolabel the metal backed cloth on the rear as wellas the bag or box with the respective grain size.Use separate platens for grinding and polishing,e.g. the aluminium platen for grinding and thePVC platen for polishing. It is recommended, especially in the grindingsteps, to move the samples in circles of about 6to 8 cm diameter, close to the periphery of thedisk and usually counter to its direction of rotation, about half the time on the left and on theright side (see Fig. 2). This will help to wear thedisk uniformly.For a gentler attack of the specimen surface dueto a slower relative sample/disk speed, you maychange the sample position to the central areaof the disk and/or move the sample on the stationary disk for the last few seconds. This shouldbe done with very slight or even no pressure.The pressure exerted with your hand on thesample, the speed of sample movement, the rotation speed of the disk, the kind of cloth, theabrasive and lubricant quantities, and the durations of the individual processing steps are important parameters that influence the result.All abrasion products must be removed from thegrinding disks after each use by means of abrush and clean water and from the polishingcloths from time to time with distilled water andsome household detergent.The wetted resin-bonded diamond grinding diskMD-Piano and the resin-bonded silicon carbidegrinding disk MD-Primo should be dressed oc-PHYWE Systeme GmbH & Co. KG All rights reservedP5510100
Metallographic Sample Preparation Grinding and Polishing of Metals casionally by means of the included dressingstick, if the grinding efficiency seems to have deteriorated.The silicon carbide paper disks (grit 240) aredesigned for coarse grinding of very soft materials (e.g. aluminium) as an alternative to MDPrimo. Better results, however, may be obtainedby fine grinding with MD-Piano 1200 as the firststep. SiC paper should be used with plenty ofwater. An SiC paper grinding disk is consumedin most cases after a maximum service time ofone minute.The lifetime of the grinding disks MD-Piano, MDPrimo, MD-Allegro and MD-Largo is very high, ifthey are carefully handled, and usually corresponds to the lifetime of more than 100 siliconcarbide paper disks. They can be used until thegrinding spots have been completely worn out.The aluminium oxide polishing suspension is tobe used only in combination with a METAPO-VMaterialBrass LEA5.1.01or MD-Nap cloth for final polishing, particularlyfor soft metals. With hard materials, a satisfactory final polish is frequently already obtained after 3 µm diamond polishing. Always use a separate cloth for oxide polishing.The RED lubricant contains oily componentsand therefore provides a smoother attack.For exchange, cautiously lift the metal-backeddisk from the machine platen and take care notto bend it too much. Permanently deformeddisks must be discarded.After use, always cover the machine with the lidprovided.It is advisable to use the 50 ml dropping bottlesfor economical dosage of abrasive suspensionsand lubricants and for avoidance of environmental contamination by spraying. Provide thebottles with labels for identification.Step 1MD-Primo 220Lubricant: waterTime: 2 minSpeed: 300 rpmStep 2MD-Largo/6µ DStLubricant: w.b.Time: 4 minSpeed: 150 rpmStep 3METAPO-B/3µ DSuLubricant: REDTime: 3 minSpeed: 150 rpmStep 4METAPO-V/1µ DSuLubricant: REDTime: 2 minSpeed: 150 rpmCopperMD-Primo 220Lubricant: waterTime: 1 minSpeed: 300 rpmMD-Largo/6µ DStLubricant: w.b.Time: 3 minSpeed: 150 rpmMETAPO-B/3µ DSuLubricant: REDTime: 2 minSpeed: 150 rpmMETAPO-V/1µ DSuLubricant: REDTime: 1.5 minSpeed150 rpmAluminiumMD-Piano 1200Lubricant: w.b.Time: 1 minSpeed: 150 rpmMETAPO-B/3µ DSuLubricant: REDTime: 3 minSpeed: 100 rpmMD-Nap/OSuLubricant: noneTime: 1 minSpeed: 100 rpmAluminium AlloyMD-Primo 220Lubricant: waterTime: 1 minSpeed: 150 rpmMD-Largo/6µ DStLubricant: w.b.Time: 3 minSpeed: 150 rpmMETAPO-V/3µ DSuLubricant: REDTime: 2 minSpeed: 150 rpmMETAPO-V/OSuLubricant: noneTime: 1 minSpeed: 100 rpmSteelMD-Piano 220Lubricant: waterTime: 2 minSpeed: 300 rpmMD-Allegro/6µ DStLubricant: w.b.Time: 3 minSpeed: 150 rpmMETAPO-P/6µ DSuLubricant: w.b.Time: 2 minSpeed: 150 rpmMETAPO-B/3µ DSuLubricant: REDTime: 2 minSpeed: 150 rpmSteel, alloyedMD-Piano 220Lubricant: waterTime: 3 minSpeed: 300 rpmMD-Allegro/6µ DStLubricant: w.b.Time: 3 minSpeed: 150 rpmMETAPO-P/6µ DSuLubricant: w.b.Time: 3 minSpeed: 150 rpmMETAPO-B/3µ DSuLubricant: REDTime: 2 minSpeed: 150 rpmTable 2: Grinding and polishing guidelinesDSt Diamond Stick, DSu Diamond Suspension, OSu Oxide Suspension, w.b. water basewww.phywe.comP5510100PHYWE Systeme GmbH & Co. KG All rights reserved3
LEA5.1.01Metallographic Sample Preparation Grinding and Polishing of MetalsNow attach a magnetic foil to each of the platens(aluminium and PVC). Stick a METAPO-P cloth,METAPO-B cloth and METAPO-V cloth with theirself-adhesive backs to three of the thin metal disks.The grinding disks and the MD-Nap polishing clothare already provided with metallic backs for magneticfixation. Attach the fresh water and drain hoses to themachine and connect the machine to the mains.Carefully read the Operating Instructions. Put thealuminium platen on the machine. Cautiously place acoarse grinding disk (MD-Piano or MD-Primo) on themagnetic cover of the aluminium platen, taking carenot to bend it excessively.Select a sample from the set, switch on the machineand set it at an operating speed of about 300 rpm or150 rpm, depending on the sample selected (see Table 2). Apply some water from the spray bottle or lubricant from a dropping bottle on the rotating disk surface according to the specifications in the table. Holdthe sample firmly with three fingers and push it gentlywith one of the circular faces down onto the rotatingdisk, moving it in circles of 6 to 8 cm in diameter at aspeed of one to two full circles per second. Avoid toomuch pressure, which would produce deepscratches. Frequently change the position of thesample from one to the other side of the disk (seeFig. 2), with the last circles in the central region of thedisk at minimum pressure. Lift the sample from thedisk after some time, e.g. 30 seconds, to see if thecircular grooves from the prior machine processing(turning lathe) have disappeared and have been replaced by a pattern of coarse scratches (cp. Fig. 3). Ifthis is not the case, continue grinding with repeatedinspection of the surface condition by means of themagnifier or an optional microscope. Keep the disksurface wet during the whole grinding procedure.Clean the sample in running water and proceed tothe next step. For step 2, replace the coarse grindingdisk by a fine grinding disk MD-Largo or MD-Allegro,depending on the material. These disks require theaddition of diamond abrasive. The diamond stick (6µm grain size) is used to apply a small abrasivequantity on the disk surface by one or two lightstrokes across the running disk, from the centre tothe periphery for uniform distribution. Use the recommended lubricant to keep the disk humid - not wet!- during the whole processing step. Inspect the surface repeatedly by means of the magnifier to see if allbroad scratches from the previous step have beenremoved. After this step the surface should show asystem of considerably finer scratches (cp. Fig. 4).Note the presence of three coarser scratches in Fig.4, which may be remainders from step 1. Rinse thesample carefully in running water, clean the machineenvironment, and wash your hands to remove anyresidues of 6 micron diamond grains.4Fig. 3: Surface condition of brass sample after step1, magnification: 100xFig. 4: Surface condition of brass sample after step2, magnification: 100xNow replace the aluminium platen by the PVC platenprovided with a METAPO polishing cloth according tothe information given in Table 2. Make the disk humidby putting one or two millilitres of the recommendedlubricant on the running disk. Distribute some dropsof the recommended polishing suspension from adrop bottle on the running disk, moving the bottlefrom the centre to the rim of the disk. Apply the lubricant and the diamond suspension very economicallyto keep the cloth uniformly humid, but avoid any surplus quantity to be splashed away from the cloth.Cloth polishing may require a somewhat higher pressure than that needed in the grinding steps. This polishing step will already produce a fairly good finishwith only very fine scratches (see Figs. 5 and 6).For the final step (step 4) the same strict rules ofcleaning apply as in the previous steps. The diamondsuspension is spread over the final polishing clothlike in step 3. For oxide polishing, a separate clothMETAPO-V or MD-Nap must be used, and no additional lubricant is to be applied together with the aluminium oxide suspension. Examples of possible sur-PHYWE Systeme GmbH & Co. KG All rights reservedP5510100
Metallographic Sample Preparation Grinding and Polishing of MetalsLEA5.1.01face appearances after final polishing are shown inFigs. 7 and 8. If the polish is not yet fully acceptableafter step 4 diamond polishing, a fifth step using asmaller grain size with MD-Nap may follow.Fig. 5: Surface condition of aluminium alloy afterstep 3, magnification 200xFig. 6: Surface condition of brass sample after step3, magnification 200xFig. 7: Surface condition of aluminium alloy afterstep 4, magnification 200xFig. 8: Surface condition of brass sample after step4, magnification 200xThe aluminium sample requires a special treatmentbecause of the extremely low hardness of the metal.Fine grinding on an MD-Largo disk would lead to theimpression of many of the partially loose (rolling)diamond grains into the surface of the sample, leaving a condition as shown in Fig. 9. It is therefore recommended to apply a combined plane and fine grinding as a first step with a fine-grained MD-Piano 1200with fixed diamond grains embedded in a resin matrix. The final processing is carried out on a very„soft“ cloth, having a high elasticity of the fibres,thereby largely preventing the diamond grains frombeing impressed into the soft aluminium surface (seeFig. 10).Since the final results are highly dependent on thepressure forces applied to the specimen during grinding and polishing as well as on the relative sample/disk speed, the process would be fairly reproducible only if a repeatable, adjustable pressurecould be applied. Therefore, in manual grinding andpolishing, achieving a desired surface quality is amatter of „feeling“ and experience. Ideally, at the endof the final polishing step, any visible deformation(scratches and other surface defects) from the preceding steps should have been removed, and thesample should exhibit a mirror-like, virtually scratchfree surface.Basic TheoryThe behaviour of metals in mechanical surfacetreatment strongly depends on their macroscopicproperties, i.e. hardness and ductility, which, in turn,are determined by their microstructures.A solid metal is normally produced by solidificationfrom a melt. In the course of the solidifying process,micro-crystals are formed around incidentally produced nuclei, wherein the atoms arrange in an ordered three-dimensional system, called a crystal lat-www.phywe.comP5510100PHYWE Systeme GmbH & Co. KG All rights reserved5
LEA5.1.01Metallographic Sample Preparation Grinding and Polishing of Metalstice. The crystals grow in all directions until theytouch their neighbours and form boundaries. Their final sizes, shapes and crystallographic orientationsare random. Thus a macroscopic piece of metal hasa microstructure consisting of many interlocking crystallites, also called „grains“. The microstructure determines the mechanical properties of the metal. Itcan be distorted by mechanical stress, e.g. processing by rolling or drawing, or by thermal treatmentssuch as annealing, tempering and quenching. Theseprocesses alter the size, shape and/or orientation ofthe grains and thereby also modify the macroscopicproperties, causing stress production or relief, ductility increase, hardening, etc. While in a pure metal theindividual crystallites (grains) are normally equal incomposition and structure (apart from elements forming polymorphic modifications), and differ only bysize, shape and orientation, the microstructures of alloys are in most cases characterized by „phases“ ofdifferent composition (dual-phase or multi-phasestructures).The formation of phases depends on theability of the constituent metals to produce mixedcrystals (complete or partial solid solutions) or intermetallic compounds. Complete solid-solution formers,e.g. gold and silver, form single-phase alloys. Thecomposition of the phases, displayed in a „phasediagram“, is temperature and concentration dependent. The phase structure may have a very great influence on the physical and chemical properties of thealloy, e.g. melting range or melting point, corrosionresistance, electrical conductivity and thermal conductivity, expansion coefficient, tensile strength,abrasion resistance, hardness and ductility. Thismeans that the microstructure of pure metals as wellas the phase structure of alloys will also determinetheir behaviour in grinding and polishing processes.The physical processes prevailing in grinding andpolishing are determined not only by the mechanicalproperties of the material but also, apart from the operational parameters of the grinding and polishingprocedures, by the inherent properties of the grindingdisks, polishing cloths, abrasive media, and lubricants.In principle, grinding and polishing are chip formingprocesses. Due to their hardness, their sharp edges,and the load forces acting on them, the diamondgrains penetrate more or less deeply into the metalsurface. Since the metal surface and the diamondgrains move counter to each other, long scratchesare produced on the metal surface. The abrasivemechanism is somewhat similar to the action of aturning tool. In the grinding procedures, abrasion iseffected by diamond or silicon carbide grains quitefirmly fixed in a bonding material, e.g. a resin, as isthe case in the MD-Piano and MD-Primo disks. Assoon as an abrasive grain is worn, it will be torn outof its resin bond and carried away together with the6metal debris through the free spaces between thegrinding spots. The grinding steps differ by grain sizeand therefore produce different scratch widths andscratch depths. The scratch depths are assumed tobe less than one fifth of the scratch widths. In the finegrinding disks MD-Allegro and MD-Largo the diamond grains must be added and become partly fixedin the embedding material of the grinding hexagonsand partly are free to roll. An abrasion process thatuses rolling grains is called „lapping“. Thus the effective mechanisms of such disks are partial grindingand lapping. However, as those diamond particleswhich will not instantly become fixed in one of theresin hexagons are quickly carried away through theintermediate spaces, the process is considered to bepredominantly grinding rather than lapping. The different scratch widths and depths are not only due todifferent grains sizes but also to the different hardness of the bonding media of the grinding disks. Thepolishing cloths are composed of fabrics of variousfibre materials and textures. The dense texture of apre-polishin
Grinding, Polishing, Metallographic sample prepara-tion, Ductility Method Metallography is the art of preparing metallic samples by grinding, polishing and eventual etching for sub-sequent microscopic examination. Grinding and pol-ishing is to prepare the specimen surface so as to enable the microstructure to be revealed by a suit-
2. Metallographic sampling of archaeological artifacts 3. Mounting and preparation of metallographic specimens 4. Etching metallographic specimens 5. Common etchants for copper, copper alloys, iron, steel, and silver 6. Principles of the metallurgical microscope 7. Format for notes on the examination of metal objects 8.
Grinding wheel selection, Qw, Vw Wheel dressing parameters Limitations of on-board inspection Grinding Wheel 101 Grinding wheel definitions and descriptions Dressable and Non-dressable grinding wheels Tool wear Hands on Lab or Gear Grinding Simul
different operations like turning, threading, tapper grinding, end drilling etc. The plant has the capacity to do most of operation except taper grinding. Presently the plant has to outsource the shaft to outside plant for the taper grinding. presently the plant have a grinding machine of G 17-22U, which means it is a universal grinding machine that can machine a job up to 220mm diameter shaft .
29. Grinding Machines Grinding Machines are also regarded as machine tools. A distinguishing feature of grinding machines is the rotating abrasive tool. Grinding machine is employed to obtain high accuracy along with very high class of surface finish on the workpiece. However, advent of new generation of grinding wheels and grinding machines,
difficult to grind than conventional structural steel. In order to achieve successful results when grinding tool steel, it is necessary to choose the grinding wheel with care. In turn, choosing the right grinding wheel and grinding data requires an understanding of how a grinding wheel works
Introduction of Metallographic Specimen Preparation Objective: 1. Metallographic Sample Preparation. 2. To study the importance of the various steps in sample preparation. 3. To understand the need of mounting, polishing and etching. Introduction: Metallography is the study of the microstructure of metals and alloys by means of microscopy.
Metallographic preparation of stainless steel Thorough diamond polishing and final . colour etching (Beraha II), showing deformation Surface of stainless steel after 3µm polish, DIC 25x showing deformation from grinding chemical, medical and food industries, in professional kitchens, architecture and even jewelry. Metallography of stainless .
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