ASTM A387 Grade 5 Class 2 plate: define the analysis and acceptance basis
Gangsteel welcomes enquiries for ASTM A387 Grade 5 Class 2 pressure-vessel steel plate. A well-defined request goes beyond “5Cr plate”: it identifies the tensile class, specification edition, material condition and the documents needed for the project. For this grade, careful reading of chemical maxima is particularly important. A number without an analysis heading or a maximum designation can give a misleading impression of what is being requested.
A387/A387M-25 is the current official public edition identified here. Official Scope describes chromium-molybdenum plates intended primarily for welded boilers and pressure vessels designed for elevated-temperature service. Grade 5 is listed at nominal 5.00% chromium and 0.50% molybdenum. This nominal 5Cr-0.5Mo identity distinguishes the alloy, but does not replace the detailed composition requirements or establish a vessel’s operating rating.
Start the chemistry review with maxima, not targets
| Element | Heat analysis | Product analysis |
|---|---|---|
| Carbon, maximum | 0.15 | 0.15 |
| Manganese | 0.30–0.60 | 0.25–0.66 |
| Silicon, maximum | 0.55 | |
| Chromium | 4.00–6.00 | 3.90–6.10 |
| Molybdenum | 0.45–0.65 | 0.40–0.70 |
| Phosphorus, max | 0.025 | 0.025 |
| Sulfur, max | 0.025 | 0.025 |
| Ni, V, Nb, B, N, Al, W |
Carbon is expressed as a maximum in both analysis columns. It is not an instruction to aim for exactly 0.15%. The product silicon maximum of 0.55% is also agreed by the reviewed compilations. The heat silicon cell is deliberately blank because the sources disagree: one prints 0.50% maximum, while the other prints 0.55% maximum. Resolve that difference in the ordered edition rather than silently choosing one or combining the columns.
These are labelled public compilation figures, checked on Grade 5 references including a dated September 2026 compilation and an older stockist table. Official Table 1 was not inspected. Its limits and footnotes remain to be confirmed in the ordered specification, including phosphorus, sulfur and the unresolved heat-analysis silicon maximum. Blank element cells do not imply zero content or provide a waiver of an applicable requirement.
Heat and product analysis serve different comparison purposes. The chromium band in the product column is 3.90–6.10%, while the heat band is 4.00–6.00%; molybdenum likewise has separate intervals. If an enquiry attachment contains only one chemical row, identify its analysis type before treating it as a requirement. A mixed row assembled from convenient numbers is not a clear purchasing basis, even if each number appears somewhere in a supplier reference.
Keep the Grade 5 Class 2 specimen basis visible
| Property | Reference value | Meaning for review |
|---|---|---|
| Tensile strength | 75–100 ksi [515–690 MPa] | Class 2 tensile range |
| Yield strength, minimum | 45 ksi [310 MPa] | Class 2 minimum |
| Elongation, minimum; 8 in. [200 mm] gauge | Minimum not established by the reviewed references | |
| Elongation, minimum; 2 in. [50 mm] gauge | 18% | Specified specimen gauge |
The tensile, yield and 2 in. elongation entries were independently confirmed in two Grade 5 compilations. They are not reproduced from an inspected official Tensile Requirements table; the paid full text was not read. The references used here do not establish an 8 in. elongation minimum. That cell stays blank, rather than taking a percentage from a different A387 grade with a superficially similar strength row.
Elongation uses specimen gauge lengths, not thickness bands. A report showing only “18%” is incomplete for comparison unless its specimen basis can be established. The specification also treats ksi and MPa as independent unit systems, not exact conversions. State the governing system on the purchase documents and assess results consistently within it. Do not generate a newly rounded limit by conversion and substitute it for the selected requirement.
Make the purchase line complete before asking for a firm comparison
| Enquiry item | Purchaser information | Point to settle |
|---|---|---|
| Designation | A387 or A387M, Grade 5, Class 2, ordered edition | Retain the complete material identity |
| Dimensions | Thickness, width, length, quantity and units | List each requested size clearly |
| Delivery condition | Required thermal condition and relevant project notes | Agree the state represented by testing |
| Testing | Required tests, specimen bases and acceptance criteria | Separate additional requirements from assumptions |
| Documentation | Required certificate form and plate/heat identification | Establish the receiving-review evidence |
Class 2 must remain explicit because Grade 5 has two tensile classes under official Scope. “Higher tensile class” is a classification within the grade, not permission to replace another material selected by engineering. When a quotation proposes an alternative condition, class or grade, keep that proposal separate from the base requirement. Commercial acceptance should not conceal an unresolved technical deviation in a shortened material description.
For multiple sizes, attach the same designation and edition to every relevant line or use an unambiguous schedule reference. Include the controlling revision of any project specification. If a chemistry restriction or inspection requirement differs between lines, identify it there rather than in an unattached email note. This gives Gangsteel a clearer basis for reviewing the requested material without guessing which exception belongs to which plate.
Confirm thermal condition without turning a compilation into a treatment clause
Official abstract calls for killed and thermally treated steel. The independently reviewed Class 2 compilation describes usual delivery as normalized and tempered, or accelerated cooling followed by tempering, and states that Class 2 tensile requirements are not applicable to annealed plate. This is a compilation restatement, not the official heat-treatment clause. Confirm the exact route in the ordered edition; no treatment temperatures are prescribed here.
Official Scope limits maximum thickness by the composition’s capacity to meet specified mechanical properties. It does not supply a universal numerical thickness cap or establish a mill’s rolling capability. Dimensions and acceptance conditions therefore need review together. Welding procedures, impact tests, additional examinations and certificate forms are not default promises attached to this grade description; request the project’s requirements expressly.
The related Grade 9 Class 2 and Grade 2 Class 2 pages provide family navigation only. They are not sources for these figures or substitution approvals. Matching selected mechanical values cannot erase a different alloy chemistry, analysis basis or specimen requirement.
Buyer questions
What does the nominal 5Cr-0.5Mo description leave unresolved?
It does not specify the class, edition, analysis limits, dimensions, delivery condition or inspection package. Use the full A387 or A387M Grade 5 Class 2 designation and the project requirements when requesting a comparable offer.
Why is heat-analysis silicon blank while product silicon is shown?
The reviewed compilations agree on product silicon at 0.55% maximum but differ on the heat maximum: 0.50% versus 0.55%. The blank prevents that disagreement from being hidden. Confirm the heat requirement in the ordered edition before acceptance.
Can a buyer apply an 8 in. elongation figure from another grade?
No. These Grade 5 references establish 18% at a 2 in. [50 mm] gauge but do not establish an 8 in. minimum. Determine the complete test criteria from the ordered documents rather than filling the cell from a family comparison.
Is carbon required to equal 0.15%?
No. It is the labelled compilation maximum for both heat and product analysis, not a target value. Review it alongside all applicable chemistry requirements; a single acceptable element result does not establish complete material compliance.
Does an ASTM certificate automatically cover SA-387 acceptance?
An ASTM certificate alone is not SA-387 acceptance, and the reverse is not automatic. If both are required, identify the governing specifications and Code edition and agree the evidence for each. No current Code year or automatic dual certification is assumed here.
Request a Grade 5 Class 2 quotation review
Send the complete designation and edition, size schedule, quantity and governing units. Include the required delivery condition, test criteria, certificate form and any chemistry restrictions, highlighting the silicon requirement for resolution against the ordered documents.