Complete SAE Shot Peening
Standards Database

AMS 2430 covers automatic shot peening with periodic intensity verification (saturation curves run at qualification, with production verification strips). AMS 2432 adds requirements for computer-monitored peening — the machine must continuously acquire and record process parameters (nozzle pressure, wheel speed, part rotation, exposure time) for every production run. AMS 2432 is increasingly required by aerospace primes for critical rotating and structural parts where process traceability is mandatory. Both reference SAE J442 and J443 for Almen strip procedures.

Saturation curves must be rerun whenever any of the following process parameters change: shot media type or size, nozzle/wheel size, air pressure (beyond ±5 psi of qualified value), nozzle standoff distance (beyond ±0.5 in), nozzle angle (beyond ±5°), part speed/rotation, or after major equipment maintenance. Additionally, AMS 2430 §7.4 requires requalification if the machine has been relocated, significantly modified, or if a periodic requalification interval (typically annual) has elapsed without change.

SAE J443 defines saturation as the point on the arc height vs. exposure time curve where doubling the peening time produces no more than a 10% increase in Almen arc height. Mathematically: if H(T) is the arc height at time T, saturation is confirmed when H(2T) ≤ 1.10 × H(T). The peening intensity is reported as the arc height at the saturation point. This definition ensures the process is operating in a stable region of the saturation curve where small variations in exposure time do not produce large changes in arc height.

Strip type selection depends on the peening intensity range required. Type N (0.051 in thick) is used for light intensities (0.006–0.016 in A equivalent), typically for fine shot media on thin sections or precision springs. Type A (0.093 in, the most common) covers general aerospace and automotive applications in the 0.008–0.024 in range. Type C (0.187 in) is used for heavy peening with large media at intensities above 0.020 in A equivalent. When the required intensity falls near the boundary between strip types, it is good practice to verify using both adjacent strip types for cross-correlation.

AMS 2430 §6.3 requires that peening media be free of contaminants that could be harmful to the part being processed. For steel components, only steel or carbon steel shot is typically acceptable. For titanium alloys, stainless steel, or aluminum, glass bead (AMS 2437) or ceramic bead (AMS 2438) is usually required to prevent galvanic contamination from ferrous media embedment. The specification also requires media to be maintained in a working mix per AMS 2431, with periodic sieve analysis and removal of broken or undersized media. Magnetic separation or classification equipment is often required to remove fractured media from the working mix.

Nadcap AC7117 requires the following documentation to be maintained and available at audit: (1) Equipment Qualification Records (EQR) for all active machines, (2) current saturation curves for each qualified process setup, (3) media certifications (C of C) per applicable AMS specification for each active media lot, (4) calibration records for all Almen gages and associated measurement equipment with NIST traceability, (5) production shop travelers with test strip arc heights, strip type, operator ID, and date for each production lot, (6) written procedures for peening, coverage inspection, media management, and equipment maintenance, (7) operator training records including initial qualification and refresher training, and (8) corrective action records for any non-conformances.