ASTM A302 Grade C: review the nickel-bearing material as its own grade
An ASTM A302 Grade C purchase should start with a named nickel-bearing grade, not a request for any A302 plate at a similar strength. Grade C is manganese-molybdenum-nickel pressure-vessel plate under the official public A302/A302M-17(2022) listing. Gangsteel enquiries should identify the ASTM designation, edition and required condition before chemistry and test documents are compared with the project’s material schedule.
The official public Scope gives Grade C tensile strength of 80–100 ksi [550–690 MPa]. Grade identity still matters when family members share strength figures: a tensile result alone cannot identify the required alloy. Grade C is not interchangeable with the higher-nickel Grade D. Nor does an ASME companion designation automatically establish ASTM acceptance. Treat chemistry, mechanical reporting and certification basis as separate checks that must all be resolved.
Use nickel to verify identity, not to promise service performance
The public-reference nickel band is 0.40–0.70% on heat analysis and 0.37–0.73% on product analysis. These are independently checked Grade C values from public compilations. A wider product band is not the heat acceptance range. The distinction is especially important when a quotation attaches a chemistry sheet without explaining whether it reports ladle analysis or a product check.
| Element / thickness basis | Heat analysis | Product analysis |
|---|---|---|
| Carbon, max; up to 1 in. [25 mm], inclusive | 0.20 | 0.20 |
| Carbon, max; over 1 to 2 in. [over 25 to 50 mm], inclusive | 0.23 | 0.23 |
| Carbon, max; over 2 in. [50 mm] | 0.25 | 0.25 |
| Manganese | 1.15–1.50 | 1.07–1.62 |
| Silicon | 0.15–0.40 | 0.13–0.45 |
| Molybdenum | 0.45–0.60 | 0.41–0.64 |
| Nickel | 0.40–0.70 | 0.37–0.73 |
| Phosphorus, max | 0.025 | |
| Sulfur, max | 0.025 |
Source limits: this is a labelled public-reference compilation, not the official paid chemical table. A dated Grade C trader compilation separates heat and product analysis; an undated compilation prints compressed product-style ranges. Carbon’s maxima cover both analyses under the compilation note. Separate product phosphorus and sulfur limits were not established here and remain blank. Confirm the requirements in the edition named on the purchase order.
Read carbon against the ordered thickness, and distinguish ranges from maxima when checking the report. A report can contain the expected nickel result yet still need review for manganese, molybdenum, carbon or document identity. Avoid reducing material acceptance to a nickel percentage. Likewise, specified nickel content by itself does not establish an impact-temperature rating, a corrosion-service approval or a fabrication procedure for the intended vessel.
Mechanical figures need their gauge lengths attached
| Property | Grade C figure | Status and reporting note |
|---|---|---|
| Tensile strength | 80–100 ksi [550–690 MPa] | Official A302/A302M-17(2022) public Scope |
| Yield strength, minimum | 50 ksi [345 MPa] | Independently checked Grade C public compilations |
| Elongation, minimum; 8 in. [200 mm] gauge | 17% | Public-reference minimum for the stated gauge |
| Elongation, minimum; 2 in. [50 mm] gauge | 20% | Public-reference minimum for the stated gauge |
The elongation percentages describe specimen gauge lengths, not plate-thickness bands. Retain both gauges in the enquiry review instead of presenting one general elongation value. Grade C’s two public-reference minima must not be replaced by another grade’s figures merely because its tensile range is similar. Ask for clarification where a report leaves the specimen basis unclear; an isolated percentage is not enough for a like-for-like comparison.
Inch-pound and SI values are independent systems under the specification. Choose the governing system and use it consistently for dimensions, limits and report review rather than combining a converted value with a limit from the other system. The bracketed references here are not exact conversion instructions. Acceptance against the ordered edition is different from checking whether a calculator gives an approximately similar number.
Thickness and thermal condition belong on the same enquiry
The official Scope makes maximum thickness dependent on the composition’s ability to achieve the specified mechanical properties. It does not establish a fixed numerical cap in the public information used here. Therefore, a requested size must be reviewed with its material condition and required results. A thickness appearing in a trader’s supply range is not a specification-wide upper limit and is not a Gangsteel capacity statement.
For ordinary delivery, a dated public Grade C compilation restates normally as-rolled at 2 in. [50 mm] and under, with normalizing, stress relieving or both possible when ordered; above 2 in. [50 mm], normalized. Treat this as a compilation restatement, to be checked in the ordered edition, not as a verified paid official heat-treatment clause. The agreed purchase line should remove ambiguity about condition without inventing temperatures or a default quench-and-temper route.
The official family abstract requires killed steel conforming to fine-grain requirements. This is not a benefit unique to Grade C. Detailed general requirements, test conditions and any additional examinations must be reviewed against the project documents. Do not derive a guaranteed impact result or a welding parameter from the grade name. Where a fabrication cycle affects the required evidence, raise that issue before the material order is finalized.
Keep the ASTM acceptance route explicit
| Check | Information required | Question to resolve |
|---|---|---|
| Specification identity | A302 or A302M, Grade C, ordered edition | Does the offer name the required ASTM material? |
| Unit system and size schedule | Thickness, width, length and quantity in the chosen system | Are all purchase lines unambiguous? |
| Chemistry evidence | Heat identity, analysis type and applicable limits | Are product-style ranges being mislabelled as heat limits? |
| Condition and tests | Delivery state, required examinations and acceptance criteria | Do the reports represent the agreed condition? |
| Documentation | Certificate form, plate identification and result linkage | Can the purchaser reconcile the plate with its evidence? |
If the project is considering the Code companion, use the related ASME SA302 Grade C page for that separate acceptance topic. For a lower-strength Mn-Mo family topic, see ASTM A302 Grade A plate. These are related-topic links, not numerical sources or substitution approvals. An ASTM certificate is not automatic SA-302 acceptance, and an SA-302 certificate is not automatic ASTM acceptance.
A practical receiving review follows the purchase schedule line by line: match identification, verify the required designation and condition, then compare the reported chemistry and mechanical results on their stated basis. Record missing information as an open question rather than silently treating another grade, unit system or certificate heading as equivalent. This keeps commercial descriptions from replacing the material requirement.
Buyer questions
Why specify Grade C when another A302 grade has the same tensile range?
Strength does not define the full material identity. Grade C is the nickel-bearing Mn-Mo-Ni grade with its own public-reference chemistry and elongation. The drawing’s specified grade remains controlling; neither another family member nor a higher-nickel grade is an automatic substitute.
What nickel figures should be used for preliminary Grade C review?
The labelled public reference is 0.40–0.70% heat and 0.37–0.73% product. Keep the analysis types separate and confirm the ordered-edition limits. Do not judge a heat-analysis result against the wider product range or treat a generic alloy description as a chemistry report.
How should Grade C elongation be reported?
The public references give 17% minimum in an 8 in. [200 mm] gauge and 20% in a 2 in. [50 mm] gauge. These are not thickness categories. Preserve the gauge-length information when comparing the required values with reported test results.
Does Grade C automatically arrive normalized?
Not as a blanket website promise. The ordinary-delivery compilation distinguishes 2 in. [50 mm] and under from thicker plate, and also allows ordered conditions for thinner material. Confirm the applicable edition and put the required condition on each relevant purchase line.
Can a companion ASME certificate settle an ASTM Grade C order?
Not by its name alone. The required ASTM designation, edition and supporting conformity evidence must be reviewed. Dual certification is an explicit contractual matter, not an assumed property of Grade C. Agree the document form and any additional tests before acceptance.
Prepare a Grade C material enquiry
Send the ASTM grade and edition, dimensions, quantity, required delivery condition and testing schedule. Include document requirements and any unresolved service or fabrication constraints so quotation review can address the actual purchase basis without assuming equivalence.