ISO 6621-5-2020 pdf downlaod.Internal combustion engines一 Piston rings一 Part 5: Quality requirements. 4.5.1 Discolouring or staining of surface Discolouring or staining spread evenly or unevenly over the ring surfaces is permissible. This does not include rust. 4.5.2 Casting skin and deposits on inside surface The following defects are permitted: — unmachined (i.e. not cleaned up) areas within 50 of the gap ends; — firmly adherent deposits arising from processing of the ring. 4.5.3 Chipping on uncoated surfaces This is permissible provided the chip sizes do not exceed the maximum values established in Table 1 for pores, cavities and sand inclusions. 4.5.4 Chromium plated peripheral surface The chromium plating shall be fully coherent, in other words there shall be no visible macrocracks, pores, blisters, chromium beads (undercut bulge in the surface) or pin holes. Exceptions regarding pinholes may be agreed upon between manufacturer and customer. Chromium coatings contain a normal microscopic crack pattern which is permissible. Characteristics of the micro cracking may be determined by agreement between supplier and customer. It is not reasonable to expect no micro cracks. The customer and supplier may set a lower and upper limit to the micro cracks. 4.5.5 Spray coatings Spray coatings are not homogeneous. The acceptance conditions may be agreed between the manufacturer and customer, otherwise the manufacturer’s specifications apply. 4.5.6 Nltrided surfaces The nitrided surface shall be fully coherent, in other words there shall be no visible macro cracks or loose material. When a nitrided side face Is specified, the depth of the hard layer may fall below the specification to a minimum depth of 0,005 mm in small areas, provided the area is no more than 0,8 mm radially and 8 mm circumferentially. In addition, the total area of this defect on the side face of the ring shall not exceed 10 % of the total side face area and there shall be at least 20 mm between areas with such a defect.ISO 6621-5 pdf download.
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