ISO 12686 pdf download.Metallic and other inorganic coatings — Automated controlled shot-peening of metallic articles prior to nickel, autocatalytic nickel or chromium plating, or as a final finish
1 Scope
This International Standard describes the requirements for automated, controlled shot-peening of metallic articles prior to electrolytic or autocatalytic deposition of nickel or chromium, or as a final finish, using shot made of cast steel, conditioned cut wire, ceramic shot or glass beads. The process is applicable to those materials on which test work has shown it to be beneficial within given intensity ranges. It is usually not suitable for brittle materials. Hand- peening and rotary flap-peening are specifically excluded. Shot-peening induces residual compressive stresses in the surface and near surface layers of metallic articles, and changes the surface microstructure (including phase transformation), thereby controlling or limiting the reduction in fatigue properties that occurs from nickel or chromium plating of the article, or increasing the fatigue properties of unplated articles.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of this International Standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards.ISO 565:1 990, Test sieves — Metal wire cloth, perforated metal plate and electroformed sheet — Nominal sizes of openings. ISO 21 94:1 991 , Industrial screens — Woven wire cloth, perforated plate and electroformed sheet — Designation and nominal sizes of openings. ISO 331 0-1 :1 990, Test sieves — Technical requirements and testing — Part 1 : Test sieves of metal wire cloth. ISO 3453:1 984, Non-destructive testing — Liquid penetrant inspection — Means of verification. ISO 6933:1 986, Railway rolling stock material — Magnetic particle acceptance testing.
3 Terms and definitions
For the purposes of this International Standard, the following terms and definitions apply. 3.1 Almen strip UNS G1 0700 carbon steel specimens that are used to calibrate the energy of a shot-peening stream (see Figure 1 ) 3.2 Almen strip holding fixture fixture for holding Almen strips in suitable locations that represent the position and angular orientation of the surfaces of a part where intensity is to be determined and verified (see Figure 2) 3.3 arc height flat Almen strips which, when subjected to a stream of shot moving at an adequate velocity, will bend in an arc corresponding to the amount of energy transmitted by the shot stream NOTE The height of the curved arc measured in millimetres is the arc height, measured by an Almen gauge (see Figure 3). 3.4 automatic equipment shot-peening equipment in which parts, fixtures, nozzles and peening parameters are preset by hand or by locating fixtures and verified by inspection personnel NOTE Peening time is monitored automatically and air pressure or wheel speed is set manually. 3.5 residual compressive stresses layer in compression below the surface created by cold-working or stretching the surface beyond the elastic limit by shot-peening NOTE The depth of compressive stresses is measured from the crown of the dimple to the depth. 3.6 coverage extent of obliteration of the original surface by dimples produced by impact from individual shot particles, expressed as a percentage NOTE 1 00 % coverage is defined as that leaving 2 % or less of the original surface unpeened because the estimation of coverage of the impressions is difficult when this is about 98 % of the total surface. “1 00 % coverage” is a theoretical limiting value. Hence, the term “complete coverage” is preferred. Usually, complete coverage requires increasing the base time, i.e. the time of peening to reach 98 % coverage, by 1 5 % to 20 %. Values of 200 % to 300 %, etc. are obtained by multiplying this run time by 2, 3, etc.