ASTM A387 Grade 12 Class 2: retain the grade-specific strength level
Class 2 is a tensile classification within an A387 grade, not one universal strength level across the entire family. For Grade 12, the independently checked Class 2 reference is 65–85 ksi [450–585 MPa] tensile and 40 ksi [275 MPa] minimum yield. A Gangsteel enquiry should preserve that specific grade-and-class combination rather than replace its numbers with a neighbouring alloy’s Class 2 row.
Official A387/A387M-25 Scope identifies Grade 12 as nominal 1.00% chromium and 0.50% molybdenum. The specification covers chromium-molybdenum plates intended primarily for welded boilers and pressure vessels designed for elevated-temperature service. Its public listing establishes the nominal grade identity and availability in two tensile classes, but does not print the detailed chemistry or Tensile Requirements tables. The following numerical references are therefore labelled separately.
A lower family strength row can still be the correct Class 2 row
| Requirement | Class 2 reference | Basis to retain |
|---|---|---|
| Tensile strength | 65–85 ksi [450–585 MPa] | Grade 12 Class 2 range |
| Yield strength, minimum | 40 ksi [275 MPa] | Grade 12 Class 2 minimum |
| Elongation, minimum; 8 in. [200 mm] gauge | 19% | Specimen gauge length |
| Elongation, minimum; 2 in. [50 mm] gauge | 22% | Specimen gauge length |
These values were independently checked against the Grade 12 mill page and its 2017 datasheet, plus dated and independent public compilations. They are not a transcription of the paid official tensile table, which was not inspected. The figures are the Grade 12 Class 2 set, not a Class 1 mistake. For contrast only, the compiled Grade 12 Class 1 strength set is 55–80 ksi [380–550 MPa] tensile and 33 ksi [230 MPa] minimum yield.
That distinction is useful when two offers describe themselves only as “A387 Class 2.” Without the grade, the purchaser cannot tell whether the proposed mechanical row corresponds to the material schedule. An apparently higher strength number is not a reason to silently amend the specified grade. Keep alternatives as separately identified deviations for engineering review instead of making the quotation look compliant by changing its material designation.
Elongation is similarly specific: 19% in 8 in. [200 mm] and 22% in 2 in. [50 mm] are gauge-length minima, not thickness bands. A report comparison should retain the specimen basis and applicable adjustment requirements. The mill reference points elongation adjustments to general specification requirements; this page does not supply an unverified adjustment formula or remove the need for the complete ordered documents.
Read Grade 12 chemistry on its own analysis basis
| Element | Heat analysis | Product analysis |
|---|---|---|
| Carbon | 0.05–0.17 | 0.04–0.17 |
| Manganese | 0.40–0.65 | 0.35–0.73 |
| Silicon | 0.15–0.40 | 0.13–0.45 |
| Chromium | 0.80–1.15 | 0.74–1.21 |
| Molybdenum | 0.45–0.60 | 0.40–0.65 |
| Phosphorus, max | 0.025 | 0.025 |
| Sulfur, max | 0.025 | 0.025 |
| Ni, V, Nb, B, N, Al, W |
The chemical splits were checked in an independent stockist reference and a dated September 2026 compilation. This is a public-reference table, not official A387/A387M-25 Table 1. The phosphorus and sulfur values are compilation maxima that must be confirmed in the ordered edition. No limits are invented for the blank element row; those cells are not zero-content requirements or a licence to treat an unreviewed additional element as specified.
Grade 12 silicon is heat 0.15–0.40% and product 0.13–0.45% in these references. Chromium and molybdenum likewise need their separate heat and product ranges. A product-only line may contain valid product figures yet still be insufficient for checking a heat report. Ask which analysis the document represents and retain the correct headings rather than combining the two columns into a broad, unlabelled acceptance envelope.
Nominal 1Cr-0.5Mo is a useful grade description, but it does not mean an exact 1.00% chromium result is required on every report. The reference heat chromium range is 0.80–1.15%, while the product range is 0.74–1.21%. The contract’s applicable requirements govern the comparison. Any extra restricted-chemistry request should identify both the element and analysis basis and remain visible as a purchaser condition.
Delivery state and specification coverage are separate decisions
The official abstract describes killed steel that is thermally treated. Usual Class 2 delivery as normalized and tempered, or accelerated cooling plus temper, is a labelled compilation restatement here; it is not an inspected official heat-treatment clause. Those compilations also say that Class 2 tensile requirements do not apply to annealed plate. Resolve the exact delivery route against the ordered edition instead of assuming annealed material can be accepted on the same Class 2 basis.
No tempering or quenching temperatures are supplied, and no welding or impact performance is implied by the grade name. Describe any additional tests, condition-specific evidence or subsequent fabrication requirements in the enquiry with their acceptance criteria. A supplier page should help organize that discussion, not replace the purchaser’s engineering review with a generic claim that a treatment or test package is included.
Official Scope limits maximum thickness by the composition’s capacity to meet specified mechanical properties. This does not establish a fixed numerical cap or a manufacturing capability. Use the actual thickness, width and length schedule for quotation review. Inch-pound and SI values are independent unit systems, so select the governing system and keep dimensions and acceptance comparisons consistent rather than combining converted boundaries or rounded strength values.
Resolve quotation exceptions before comparing price
| Possible omission or change | Purchaser response | Record to retain |
|---|---|---|
| Grade or class not written | Require Grade 12 and Class 2 explicitly | Complete material designation and ordered edition |
| Different strength row supplied | Check the grade/class identity, not just whether numbers are higher | Agreed requirements or formally reviewed deviation |
| Only one chemistry heading shown | Establish whether heat or product analysis is represented | Correctly labelled analysis and heat reference |
| Delivery condition left open | Confirm the required thermally treated state | Condition linked to tests and documents |
| Document route assumed | Define required certificate form and any additional acceptance basis | Traceable order-specific agreement |
For related alloy topics, consult ASTM A387 Grade 11 Class 2 and ASTM A387 Grade 22 Class 2. These links do not serve as numerical sources or approval of interchangeability. An ASTM certificate is not automatic SA-387 acceptance; the reverse is not automatic either. Any dual-certification requirement needs explicit review, and no current ASME Code year is assigned on this ASTM page.
Buyer questions
Is 450–585 MPa tensile and 275 MPa yield a Class 1 error?
No. The independently checked Grade 12 Class 2 public reference is 65–85 ksi [450–585 MPa] tensile and 40 ksi [275 MPa] minimum yield. A different A387 grade’s Class 2 numbers should not be substituted merely to make family pages look consistent.
What does the nominal 1Cr-0.5Mo description establish?
Official A387/A387M-25 Scope lists Grade 12 at nominal 1.00% chromium and 0.50% molybdenum. That identifies the alloy grade, not an exact required percentage on a report. Review the applicable heat or product ranges under the ordered edition.
Can the Grade 12 silicon product range be used as a heat limit?
No. The labelled compilation gives product 0.13–0.45% and heat 0.15–0.40%. Preserve the analysis headings. Correct product data alone does not provide a complete basis for comparing heat results or establishing every official chemistry requirement.
How are the two elongation entries used?
They correspond to 8 in. [200 mm] and 2 in. [50 mm] specimen gauges, with public-reference minima of 19% and 22%. They are not thin-plate and thick-plate categories. Confirm the reported gauge and applicable adjustment rules during document review.
What should be resolved if an offer leaves condition or certification open?
Agree the thermal delivery state, required tests and certificate form before purchase approval. The usual Class 2 route described here is compilation guidance to confirm in the ordered edition. Neither dual certification nor acceptance under a separate SA-387 designation is automatic.
Submit a Grade 12 Class 2 enquiry
Include the full specification and edition, dimensions, quantity and governing units. Add the required delivery condition, inspection criteria and document form, identifying proposed alternatives separately from the specified material.