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S Mirror-finiSh tainless steel alloys, StainleSS SteelS first developed in While such standards 1912, often require are undoubtedly valua polished finish to be able, they can also used in applications such conceal considerable as cutlery, tableware and differences in what other domestic appliances, may seem to be identito name a few. cal products from difSurface finish types for ferent suppliers. The commercially supplied research described stainless steel sheet are here was prompted detailed in various stanwhen we compared dards. ASTM A480-12 and several samples of No. EN10088-2 are two; BS 8 mirror finish from 1449-2 (1983) is still availdifferent manufacturable, although no longer ers and saw that, in active. These standards optical terms, they were are very similar in that they define eight grades Micrographs of cMp Super no.8 (top) and an unnamed competi- anything but identiof surface finish for stain- tor (below), X500. these images demonstrate that significant cal. Even with only less steel. Grade 7 is ���buff differences in surface finish of seemingly identical mirror-finish the naked eye, it was polished,��� while the high- stainless can occur. however, discussions with the supplier have evident that some were est polish���the so-called left some uncertainty as to the finishing process used to produce better than others as mirror polish���is desig- cMp Super no.8. the product is manufactured in asia and is mirrors. We then used nated Grade 8. (In the case said to be finished using wet alumina slurry, which would not various instrumental of EN10088-2, it is desig- generally be considered a chemical mechanical polishing process. techniques to more (Photos courtesy of Pacific Plus Corp.) rigorously compare nated 2P.) samples from three These standards describe, different manufacturers, designated any quantifiable way other than in qualitative terms, how such a as R, O and A. specifying ���a non-directional finish mirror finish is obtained by mechanithat is reflective and has good image cal polishing using progressively Surface characterization clarity.��� The specification goes on finer grades of abrasive and, finally, Today, there���s an entire branch to say only that ���the surface will be a polishing compound. However, of science dedicated to the characessentially free from grit lines due to these standards don���t define the terization of a surface in terms of its the initial grinding stages.��� optical quality of surface finish in table 1���StainleSS Steel Mirror SaMpleS Manufacturer Measurement 3 (��m) (��m) Ra 0.023 0.029 0.026 Rz Rimex Test Results Measurement 2 (��m) Orion Measurement 1 0.380 0.660 0.680 Statistics Max Min Range 0.026 0.029 0.023 0.0060 0.573 0.680 0.380 0.3000 Average Note: 0.022 0.020 0.023 0.022 0.023 0.020 0.0030 0.140 0.130 0.160 0.143 0.160 0.130 0.0300 Ra 0.027 0.033 0.042 0.034 0.042 0.027 0.0150 Rz Aalco Ra Rz 0.300 0.440 0.650 0.463 0.650 0.300 0.3500 K7061 Settings Lt = 17.5 mm Lc = 2.5 n=5 pfonline.com 23