SYMPOSIA PAPER Published: 01 January 1975

Discussion of ASTM Method for Rating Inclusions


Since nonmetallic inclusions are always present in steel, it is important to identify and classify the size and type of inclusion. ASTM has set up basic guidelines obtaining samples and rating the inclusion. Under microscopic examination, the size, distribution, number, and type of inclusions are examined and compared to various standard ASTM charts.

The examination and rating of six samples taken in a systematic way as outlined by an ASTM procedure generates the nonmetallic inclusion rating for that heat. There are four ASTM bearing specifications that cover different grades of steel used in the bearing industry: ASTM Specification for High-Carbon-Chromium Ball and Roller-Bearing Steel (A 295-70); ASTM Specification for High Hardenability Bearing Steels (A 485-63); ASTM Specification for Carburizing Steels for Anti-Friction Bearings (A 534-65); and, ASTM Specification for Special Quality Ball and Roller Bearing Steel (A 535-65).

The ASTM method of evaluating bearing steels is commercially oriented to enable the steel producer to consistently evaluate numerous heats of steel.

Author Information

Donze, JJ
The Timken Company, Canton, Ohio
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Developed by Committee: A01
Pages: 3–9
DOI: 10.1520/STP32282S
ISBN-EB: 978-0-8031-4656-3
ISBN-13: 978-0-8031-0289-7