ASTM A387 Grade 22 Class 1: review the alloy and the acceptance record
For Grade 22 Class 1 plate, a complete record matters more than a familiar alloy shorthand. Gangsteel enquiries should identify the intended 2.25Cr-1Mo material together with its Class 1 designation and the evidence required by the purchaser. A supplier description, a laboratory result and a purchase line each serve different purposes; acceptance depends on whether they describe the same ordered material and condition.
Begin with the Grade 22 identity
The current official public listing is A387/A387M-25. Its Scope covers chromium-molybdenum plates for elevated-temperature welded boilers and pressure vessels, with Grade 22 identified at nominal 2.25% chromium and 1.00% molybdenum. Class 1 is one of this grade’s two tensile classes. The grade number is not a strength ranking across the family, and nominal alloy percentages are not a replacement for the detailed chemical requirements.
A receiving reviewer should be able to follow each plate back to the requested specification, grade, class and size. Agree the identification and documentation requirements at enquiry stage, particularly when several dimensions or project revisions are involved. If an offer uses only a commercial alloy description, obtain the full designation before treating its pricing as directly comparable with a properly defined Class 1 request.
| Record stage | Information to retain | Issue to resolve |
|---|---|---|
| Enquiry | A387 or A387M, Grade 22, Class 1, required edition | Is the complete designation on every applicable line? |
| Quotation | Dimensions, quantities, units and stated deviations | Are any alternatives clearly separated? |
| Condition agreement | Required thermal state and supporting evidence | Will testing represent the agreed delivery condition? |
| Inspection schedule | Required examinations, specimen bases and acceptance criteria | Are additional project requirements expressly agreed? |
| Receiving review | Plate/heat identification and required certificate form | Can results be linked to the ordered material? |
The checklist does not promise a particular certificate or inspection package. It gives the purchaser a way to request one clearly. Changes to test scope, delivery condition or material identity should be visible in the revised agreement, not hidden inside general commercial notes. For a repeat order, carry forward the actual approved requirements rather than assuming that an earlier alloy nickname contains them all.
Read maximums and analysis ranges differently
| Element | Heat analysis | Product analysis |
|---|---|---|
| Carbon | 0.05–0.15 | 0.04–0.15 |
| Manganese | 0.30–0.60 | 0.25–0.66 |
| Silicon, maximum | 0.50 | 0.50 |
| Chromium | 2.00–2.50 | 1.88–2.62 |
| Molybdenum | 0.90–1.10 | 0.85–1.15 |
| Phosphorus, max | 0.025 | 0.025 |
| Sulfur, max | 0.025 | 0.025 |
| Ni, V, Nb, B, N, Al, W |
These figures are labelled compilation references from independently reviewed Class 1 material, including dated September 2026 information. Official Table 1 and its footnotes were not inspected. Verify the table against the ordered edition before contractual acceptance; the phosphorus and sulfur entries are compilation maxima, not a claim about an unread official table. No unverified carbon footnote is supplied, and blank elements have no limit assigned here.
Silicon at 0.50% is a maximum in both analysis columns. It is not a requirement to aim for exactly that percentage. Manganese, by contrast, is expressed as a range: heat 0.30–0.60%, product 0.25–0.66%. Labelling the heat band as product analysis would change the meaning of the comparison. Preserve these distinctions when copying enquiry requirements into a quotation worksheet or checking a reported chemical result.
The chromium and molybdenum intervals describe the Grade 22 alloy chemistry more usefully than nominal numbers alone. A product analysis result should not be compared with an unexplained mixed column assembled from several sources. If the purchaser requests a restricted composition, identify each additional limit and its analysis basis separately. Grade chemistry does not change merely because a different tensile class is requested.
Keep the Grade 22 Class 1 yield minimum distinct
| Property | Reference value | Interpretation |
|---|---|---|
| Tensile strength | 60–85 ksi [415–585 MPa] | Class 1 tensile range |
| Yield strength, minimum | 30 ksi [205 MPa] | Independently checked Grade 22 Class 1 |
| Elongation, minimum; 8 in. [200 mm] gauge | No minimum established in the reviewed references | |
| Elongation, minimum; 2 in. [50 mm] gauge | 18% | Specific specimen gauge |
The yield reference is 30 ksi [205 MPa], not the Grade 11 Class 1 minimum. The independently reviewed mill datasheet dated 2017 and public compilations support the entries shown. They do not supply an 8 in. elongation minimum for this page, so that cell remains blank. A missing published figure is neither a zero requirement nor permission to borrow a percentage from another grade.
The official Tensile Requirements tables were not read. Establish the complete acceptance rules, including any applicable specimen adjustments, from the ordered documents. Elongation percentages refer to gauge lengths, not thickness categories. Likewise, the specification treats ksi and MPa as independent unit systems. Agree which system governs instead of recalculating a yield number to make it resemble a neighbouring grade’s requirement.
Thermal condition and service requirements need their own agreement
Official abstract calls for killed and thermally treated steel. The Class 1 compilation describes usual delivery options as annealed, normalized and tempered, or accelerated cooling plus temper. This compilation restatement is not the official heat-treatment clause, and no treatment temperature is prescribed here. State the condition required by the project and confirm it against the ordered edition before accepting a proposed supply route.
Elevated-temperature application in Scope does not give an individual plate a universal operating-temperature or pressure rating. Engineering selection, fabrication requirements and any special testing need their own criteria. Additional impact or examination requirements must be requested expressly rather than assumed. The official thickness limit is the composition’s capacity to meet specified mechanical properties; it is not a numerical size cap or a promise about rolling capability.
Related pages for Grade 11 Class 1 and Grade 12 Class 1 help distinguish adjacent purchasing topics. They are not sources for this page’s figures and do not authorize grade substitution. In particular, a matching tensile range does not erase a different chemistry or yield requirement.
Buyer questions
Is 205 MPa an error in the Class 1 yield reference?
No. The independently checked Grade 22 Class 1 reference is 30 ksi [205 MPa]. A value from another grade should not replace it simply because both grades share a tensile range. Verify the full requirements in the ordered documents.
What should a buyer do about the blank 8 in. elongation cell?
Resolve the required test basis from the ordered specification and project criteria. The references used here establish 18% at a 2 in. [50 mm] gauge but do not establish an 8 in. minimum. Do not complete the blank from a sibling grade.
Does 0.50% silicon mean a fixed target?
No. The public compilation labels it as a maximum for heat and product analysis. A result below that maximum is not automatically deficient on silicon; the complete ordered requirements still govern the overall chemistry assessment.
Can plate thickness be approved from this page alone?
No. Official Scope makes thickness composition-limited rather than setting one numerical maximum. The requested size, delivery condition and ability to meet the mechanical requirements must be reviewed together. This page makes no mill-capability commitment.
Can an A387 document be used automatically for SA-387 acceptance?
No. An ASTM certificate does not by itself establish SA-387 acceptance, and the reverse is not automatic. Identify the governing documents and Code edition for any dual requirement, then agree the supporting evidence before ordering.
Send a Grade 22 Class 1 enquiry for review
Provide the complete material designation, edition and size schedule with the governing units. Include delivery-condition requirements, inspection criteria, document form and any unresolved alternatives so Gangsteel can review each purchase line without assuming missing conditions.