Of all the shop peening standards the most ubiquitous are those from the SAE. This organization was inaugurated as the Society of Automotive Engineers with the intent of establishing and raising standards in the US automotive manufacturing sector. Since those early days the society has progressed to represent industry standards in all mobility sectors; land, sea and air. Also, an affiliate of the SAE, The Performance Review Institute (PRI), manages the Nadcap special process quality audit programme on behalf of aerospace prime contractors.

The SAE issues a comprehensive range of standards and today it is very rare to find a shot peening facility that does not use some of the many SAE specifications. For shot peening, these can be broadly considered in two categories:

• SAE "AMS" specifications for aerospace industry (AMS = Aerospace Material Specification)

• SAE "J" specifications for ground vehicles and general application. However "J" specifications are often invoked for aerospace applications and are not needlessly duplicated by AMS specifications.

The following is a summary of the most frequently encountered specifications:

To control new shot:

AMS 2431 Peening Media, General Requirements; rev B, May 2006. This comprises seven sub-specifications:

• AMS 2431/1 regular hardness cast steel
  shot (ASR)
• AMS 2431/2 high hardness cast steel
  shot (ASH)
• AMS 2431/3 Cut wire shot (AWCR)
• AMS 2431/4 Stainless steel cut wire shot
  (AWS)
• AMS 2431/5 Steel peening balls
• AMS 2431/6 Glass shot
• AMS 2431/7 Ceramic shot

These specifications include requirements for chemical composition, micro-structure, size, shape and hardness; they are individually revision controlled.

There are a number of "J" specifications that are not as comprehensive as AMS 2431 but specify requirements for single types of peening media:

• J441 Cut Wire Shot; published June 1993
• J444 Cast Shot and Grit Size Specifications
  for Peening and Cleaning; July 05
• J827 High Carbon Cast Steel Shot; July 05
• J1173 Size Classification And Characteristics
  Of Glass Beads For Peening; Sept 88
• J1830 Size Classification And Characteristics
  Of Ceramic Shot For Peening; May 87
• Specifications for Low Carbon Cast Steel
  Shot; June 91

For process control:

AMS 2430 P Shot Peening, Automatic, March 09: This specification includes requirements for the set-up, operation and verification of the process. Quality requirements for "in-process" media are detailed in this specification.

AMS 2432 B Shot Peening, Computer Monitored: This specification is normally invoked for critical parts where there is a requirement to continuously monitor the peening parameters and shut-down the process if tolerance limits are exceeded.

J2441, Shot Peening, Aug 2000: A peening specification for use in general industry.
 
For the determination & verification of intensity & coverage:

• J442 Test Strip, Holder And Gauge For
  Shot Peening; Nov 08.
• J443 Procedures For Using Standard Shot
  Peening Test Strips; Jan 03 
• J2277 Shot Peening Coverage; Jan 03

Intensity and coverage are the key measurables for all shot peening applications and hence there are no separate AMS specifications for verifying these items. These SAE specifications are essentials in any shot peening facility.

New Proposals to Categorize SAE standards:

To clarify the status of SAE specifications and optimize the on-going review procedure, new categories are proposed. The new categories will be:

• Active – the latest version of a standard available to the public. A five-year review applies to all "active" documents. This has three sub-categories:

• New (first time a standard is published)
• Revised (amended after review)
• Reaffirmed (reviewed without amendment)

• Stabilized – the latest version of a standard available, but the version has been frozen. It may be more than five years since the last time it was revised or even reviewed

• No further review required

• Ten-year review for ANS (American National Standard) documents

• Cancelled – the standard is no longer active. Use for any reason other than historical reference is not recommended.

• This category will only be used for standards that should no longer be used

The rollout of the new categories is expected towards the end of 2009 when final details will be given.

Readers are encouraged to visit www.sae.org for more information on specifications and SAE membership.

The author Paul Huyton is a member of the SAE Aerospace Materials Engineering Committee, Surface Enhancement sub-committee. Also, he is a PRI Lead Auditor for Surface Enhancement.

For questions contact paul@mfn.li

Standards Forum
by Paul Huyton,
MFN Course Director World Wide
more information at www.mfn.li/trainers