Cast iron
Gray Iron Class 20
Manufacturer or standards-body identification; product values do not apply to every form or condition.
Identity / state reference
What distinguishes this material
ASTM A48 Class 20 is a tensile-test class associated with a separately cast test bar; the casting wall and the agreed test-bar suffix remain essential.
- Designation in this reference
- ASTM A48 Class 20
- Forms covered by the sources
- Gray-iron castings; test coupon is not the casting’s full-section property map.
- States to distinguish or confirm
- Record as-cast or heat-treated delivery condition and the agreed matrix/hardness specification.
- Temperature and exposure
- No universal service-temperature limit or room-temperature property set is assigned. Use the cited product document and the purchase certificate.
Property evidence for a stated condition
No condition-specific numerical table is reproduced here
The linked sources establish the identity and the stated product/state scope. Obtain the row for your actual form, section, treatment and test conditions before adopting strength, hardness or a thermal limit.
Resolve these conditions next
- What product standard, edition and complete grade are on the material certificate?
- What product form, section size and delivery/heat-treatment condition will be machined?
- Which A/B/C/S test bar and controlling casting wall were agreed?
For machining, take the exact grade, supplied condition and measured hardness where applicable into the tool maker’s application data. A generic material-family speed is not a substitute for an operation and tool-specific recommendation.
Sources and what they establish
Reviewed 23 October 2026. A source’s publication date and the review date are different. The scope below identifies the fields checked.
ASTM A48/A48M-22 scope
General engineering gray castings; classification based on separately cast test-bar tensile tests, not every casting location.
ASTM A48/A48M-22 scope ↗Dandong Foundry gray-iron class and test-bar guide
Foundry lists A48 Classes 20/30/40/50 and test-bar suffixes; used for class identity only, not current normative acceptance values or overseas equivalents.
Dandong Foundry gray-iron class and test-bar guide ↗Source identity, a named product example and a supplied-batch certificate are different evidence. Cross-standard similarity does not approve substitution.
Corrections from the previous article
- Remove the assumed EN/JIS grade equivalence and any fixed matrix/hardness guarantee.
- Withdraw the legacy generic hardness (170 HB) and tensile-strength (152 MPa (22 ksi)) pair: the old page does not establish a matching product, heat treatment, section and test source.
- Remove the unsupported cutting-speed table and machinability percentage; select tooling only after the actual material condition is known.
Other references in Cast iron
Related references, not equivalent substitutes.