Carbon & alloy steel
AISI 4320
Manufacturer or standards-body identification; product values do not apply to every form or condition.
Identity / state reference
What distinguishes this material
Metallus grade-specific chemistry: C 0.17–0.22%, Ni 1.65–2.00%, Cr 0.40–0.60%, Mo 0.20–0.30%; specify core and case separately after carburizing.
- Designation in this reference
- SAE 4320
- Forms covered by the sources
- Nucor lists this grade in its hot-rolled SBQ bar programme.
- States to distinguish or confirm
- The chemistry designation does not establish a heat-treatment condition.
- Hot-rolled product route; confirm subsequent heat treatment on the order.
- 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.
Metallus Practical Data for Metallurgists, 19th edition (2024) ↗
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?
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.
Metallus Practical Data for Metallurgists, 19th edition (2024)
Grade chemistry tables, printed pp. 4–7, visually checked; supports chemistry identity, not a universal mechanical-property or delivery-condition table.
Metallus Practical Data for Metallurgists, 19th edition (2024) ↗Nucor hot-rolled bar product programme
Exact listed SBQ grades and available hot-rolled product route; not heat-treated mechanical guarantees.
Nucor hot-rolled bar product programme ↗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
- Replace unqualified international equivalents with certificate-based comparisons; the reviewed chemistry source does not certify interchangeability.
- Withdraw the legacy generic hardness (180–217 HB) and tensile-strength (1,100 MPa (160 ksi) case) 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 Carbon & alloy steel
Related references, not equivalent substitutes.