When we talk about steel shots and steel grits, SAE standards are often mentioned. What are these SAE standards about? What are the details in these standards?
Who is SAE?
According to the illustration on SAE website (https://www.sae.org/).
SAE International is the leader in connecting and educating mobility professionals to enable safe, clean, and accessible mobility solutions.
SAE is a global association of more than 128,000 engineers and related technical experts in the aerospace, automotive and commercial vehicle industries. Our core competencies are life-long learning and voluntary consensus standards development.
SAE International is the world’s leading authority in mobility standards development.
SAE Standards Related to Steel Shots and Steel Grits
SAE J827: High-Carbon Cast-Steel Shot
This SAE Recommended Practice describes chemical composition and physical characteristic requirements for high-carbon cast-steel shot to be used for shot peening or blast cleaning operations.
Latest version: Oct. 01, 2019
SAE J444: About Cast Shot and Grit Size Specifications for Peening and Cleaning
This SAE Recommended Practice pertains to blast cleaning and shot peening and provides for standard cast shot and grit size numbers. For shot, this number corresponds with the opening of the nominal test sieve, in ten thousandths of inches1, preceded by an S. For grit, this number corresponds with the sieve designation of the nominal test sieve with the prefix G added. These sieves are in accordance with ASTM E 11.
The accompanying shot and grit classifications and size designations were formulated by representatives of shot and grit suppliers, equipment manufacturers, and automotive users.
Latest version: September 01, 2012
SAE J2175: Specifications for Low Carbon Cast Steel Shot
This SAE Recommended Practice describes chemical analysis, hardness, microstructure, and physical characteristic requirements for low carbon cast steel shot to be used for shot peening or blast cleaning operations.
Latest version: June 01, 2015
Summary Important Content of SAE J2175
1. Chemical Composition
The chemical composition of finished low-carbon steel shots should satisfy the following requirements.
| Carbon | 0.10 to 0.15% |
| Silicon | 0.10 to 0.25% |
| Manganese | 1.20 to 1.50% |
| Aluminum | 0.05 to 0.15% |
| Phosphorus | 0.035% maximum |
| Sulfur | 0.035% maximum |
2. Objectionable Defects
2.1 Particle Shape
No more than 5% of the particles in a shot sample shall be elongated. An elongated particle is one whose length is in excess of twice the maximum particle width.
2.2 Voids
No more than 10% of the particles in a sample shall contain voids. A void is a smooth surfaced internal hole and must be greater than 10% of the particle to be considered harmful and counted as a void.
2.3 Shrinkage
No more than 10% of the particles in a sample shall contain shrinkage. A shrinkage area is an internal cavity with an irregular dendritic surface and must be greater than 40% of the particle area to be considered harmful.
2.4 Cracks
No more than 5% of the particles in a shot sample should contain cracks. A crack is a linear discontinuity whose length is greater than three (3) times its width and its length is greater than 20% of the diameter or shortest dimension of the particle and radial in orientation.
2.5 Microstructure
Carbide networks, partial decarburization, and grain boundary segregation are undesirable. No more than 15% of the particles tested shall have these defects.
2.6 Nonmagnetic Material
No more than 1% of the shot sample, by weight, shall be nonmagnetic material.
3. Density
The density of low carbon cast steel shot shall be not less than 7 g/cc.
4. Mechanical Tests
To conform with revised SAE J445.
5. Inspection Procedures
5.1 Sampling
Samples for chemical analysis, hardness, microstructure, density, objectionable defects, and mechanical testing shall be carefully obtained to be representative of each shipment of the production lot.
5.2 Sample Mounting for Testing
Shot samples used for testing for hardness, microstructure, and objectionable defects shall be mounted one layer deep in bakelite or other suitable strong metallurgical sample mounting media.
The mounted sample shall be ground to the center of the particle and polished by acceptable
methods for examination using a microscope. When grinding and polishing the sample, care must be taken not to overheat the sample and affect the microstructure and/or hardness.
5.3 Hardness Testing
Hardness measurements shall be taken at the half radius on a minimum of ten (10) randomly selected particles in the mounted sample.
The hardness shall be determined by using ASTM E 384 and using a 500 gf load for sizes LCS-280 and finer and 500 or 1000 gf load for sizes LCS-330 and larger. Other microhardness test methods may be used as long as a reliable hardness conversion can be obtained by calibrating various machines against known standards. Approximate conversions to Rockwell C hardness numbers are obtained from ASTM A 370.
5.4 Microstructures
The mounted and polished sample shall be etched with 2% Nital and examined at approximately 500X magnification.
5.5 Objectionable Defects
Objectionable defects shall be measured using a microscope with a 10X magnification. All of the particles contained in the mount shall be evaluated.
5.6 Density
Density shall be determined by placing 50 ml of ethanol or methanol in a 100 ml graduate, adding 100 g of shot, and recording the increase in volume. Dividing 100 g by the volume in for more critical density measurements.
5.7 Nonmagnetic Material
A hand magnet shall be used to separate the magnetic shot from the nonmagnetic contaminants. The non-magnetic contaminants shall be weighed and the percentage of the original sample weight calculated.
5.8 Chemical Analysis
Any suitable ASTM analytical procedure for steel may be used to test chemical analysis.