ISO 6621-5:2020 pdf free.Internal combustion engines一Piston rings一Quality requirements.
4 Visible defects
4.1 General
Visible defects are divided into two principle classes as described in 4.2 to 4.5.
The first class covers those defects frequently found in castings and includes such defects as porosity, sand inclusions, cavities, etc.
The second class of defect covers mechanical abrasions which may occur during forming, machining or handling of the rings, and includes scratches, dents, chipping, burrs and cracks.
Inspection of piston rings for such defects is generally carried out visually, without magnification, by inspectors having normal eyesight, corrected if necessary.
It is not intended that every ring be rigorously inspected for size and distribution of defects, but rather that the values given in the tables and text be used as a general guide. However, in case of doubt, the values given should be used as the means of judging the quality of the rings.
4.2 Pores, cavities and sand inclusions
Such defects are permissible on uncoated surfaces and edges provided that the values given in Table 1 for size, number and spacing are not exceeded.
4.3 Scratches, indentations, depressions and cracks
4.3.1 Scratches Isolated scratches are permissible provided that:
一no burrs are produced exceeding the permissible values given in 4.4.1.1;
一on turned peripheral surfaces, they are not deeper than the tool marks;
一on non-turned peripheral surfaces, they are not deeper than 0,004 mm;
一on the side faces, they are not deeper than 0,01 mm; and
一on other surfaces, they are not deeper than 0,06 mm.
4.3.2 Indentations, depressions
Indentations and depressions are permissible provided that:
— the values given in Table 1 for number and spacing of defects are met;
— no burrs are produced exceeding the permissible values given in 4.4.1.1 and
— they do not exceed the values for size and depth given in Table 2.
Rings of a plated/coated/nitrided type shall not have indentations or depressions on the periphery.
NOTE Indentations arising from hardness measurements on the side faces are acceptable provided that they do not exceed the limits given in Tables 2 and ii.
4.3.3 Cracks
No cracks are permissible in the base material.
See also 4.5.4 for chromium-plated peripheral surfaces and 4.5.6 for nitrided surfaces.
4.4 Edges
4.4.1 Edge configuration
All edges of the piston ring shall be sharp; ideally, they should be free from burrs and from ragged edges, whether arising from crumbling of material or from deburring. Such conditions are almost impossible to achieve regularly in volume production and hence both burrs and removal of edge material is permitted up to the maximum sizes given in 4.4.1.1 and 4.4.1.2.
4.4.1.1 Burrs
Burrs are permitted up to the maximum values given in Table 3. The orientation and direction of burrs shall relate to the functional surfaces of the piston ring; any burr present should point in the direction of sliding motion of the ring and not normal to the direction of sliding.
Any burrs remaining on the edges of rings should be firmly attached, forming an integral part of the edge.
4.4.2.3 Defects that do not intersect with the peripheral edges circumferentially or axially The limitations for chipping and similar defects on the chamfers at the peripheral edge and at the
peripheral edge of the gap are as follows. This type of defect is illustrated in Figure 2 and is more likely to occur on chromium plated chamfers (machined or un-machined), on machined chamfers on sprayed rings [fully coated), on PVD coated rings, and on machined chamfers on grey iron rings. The maximum values of the defects allowable are given in Table 9 and are the same for all rings with chamfers on peripheral edge and peripheral edge of the gap.ISO 6621-5 pdf download.