BS ISO 6621-3:2021 pdf download – Internal combustion engines — Piston rings Part 3: Material specifications
This document classifies materials intended for the manufacture of piston rings, based on their mechanical properties and the stresses the materials are capable of withstanding.
This document is applicable to piston rings for reciprocating internal combustion engines up to and including those of 200 mm in diameter. It is also applicable to piston rings of compressors working under similar conditions.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 6507‑1, Metallic materials — Vickers hardness test — Part 1: Test method
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at
— ISO Online browsing platform: available at
4 Mechanical properties
The choice of material made in accordance with the mechanical strength criteria given in Table 1 shall also take into account the final coating of rings, engine characteristics (rating, liner surface, etc.) and microstructural features such as graphite, cementite and ferrite. ISO 6507‑1 shall be used when measuring hardness of the piston ring base material.BS ISO 6621-3 pdf download.