ASTM A387 Grade 5 Class 1: agree the delivery condition before ordering
A Grade 5 Class 1 plate enquiry should make the intended material condition visible, rather than leave it to be inferred from an alloy name. Gangsteel can review a clearer purchasing requirement when the selected tensile class, thermal state and acceptance criteria are supplied together. For a project that specifies Class 1, a quotation should respond to that selection without quietly changing the class or treating one delivery route as universal.
The official public edition identified for this material is A387/A387M-25. Its Scope covers chromium-molybdenum steel plates primarily intended for welded boilers and pressure vessels designed for elevated-temperature service. Grade 5 is nominally 5.00% chromium and 0.50% molybdenum. This establishes the familiar 5Cr-0.5Mo family identity, while the class identifies a tensile level within that particular grade.
Class 1 allows a condition discussion, not an assumed recipe
The official abstract states that the steel is killed and thermally treated. The detailed official heat-treatment clause was not inspected. The independently reviewed Class 1 compilation describes usual delivery as annealed, or normalized and tempered, or accelerated cooling followed by tempering. It describes annealed plate as Class 1 only. This is a compilation restatement to confirm in the ordered edition, not an assertion that any one route is mandatory for every enquiry.
Write the required delivery state on the material schedule and ask for a proposed alternative to be identified as such. An as-rolled description does not resolve the thermally treated requirement. Equally, selecting annealed material is not permission to assume that every other acceptance item has been satisfied. The agreed condition and the condition represented by the mechanical evidence need to be consistent before documents are accepted.
No thermal-processing temperature or fabrication procedure is specified here. If the purchaser needs testing to represent a further project condition, explain that requirement and its acceptance basis during enquiry review. Such instructions should not be replaced by a general statement that the plate is suitable for welding or elevated-temperature service. Those descriptions do not settle the engineering requirements of an individual vessel.
Read the Grade 5 Class 1 strength row on its own terms
| Property | Reference value | What to retain |
|---|---|---|
| Tensile strength | 60–85 ksi [415–585 MPa] | The Class 1 range |
| Yield strength, minimum | 30 ksi [205 MPa] | The Grade 5 Class 1 minimum |
| Elongation, minimum; 8 in. [200 mm] gauge | Minimum not established by the references used here | |
| Elongation, minimum; 2 in. [50 mm] gauge | 18% | The specimen gauge with the percentage |
These Class 1 entries were independently checked in an older stockist compilation and a Grade 5 compilation dated September 2026. Official Tensile Requirements tables were not read. The 205 MPa yield reference belongs to this grade and class; it should not be “corrected” merely to resemble a different A387 row. Use the ordered specification for the complete specimen provisions and any applicable adjustments.
The blank 8 in. elongation cell is deliberate. The reviewed Grade 5 Class 1 references establish the 2 in. minimum but do not establish an 8 in. minimum for this page. A blank does not mean zero elongation is acceptable, or that the purchaser can disregard a governing test requirement. It means that the applicable criterion must be resolved from the complete ordered documents rather than borrowed from another grade.
Gauge lengths are not thickness bands. Preserve the test basis beside an elongation result when preparing an inspection comparison. Ksi and MPa are also independent unit systems, not exact conversions for mixing within one acceptance calculation. The purchaser should state the governing system and retain it consistently through the order and report review instead of recalculating selected values to create new limits.
Separate known Grade 5 composition from the unresolved heat-silicon limit
| 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 |
This chemical table is not official Table 1; that paid table was not inspected. Chemistry is organized by grade, not tensile class. The figures are labelled compilation references requiring confirmation in the ordered edition, particularly phosphorus, sulfur and the heat-analysis silicon limit. No requirement is invented for an unassigned element, and blank cells do not mean that the element is absent.
The silicon heat maximum remains unresolved between the two reviewed compilations: one gives 0.50% maximum and the other 0.55% maximum. Both agree on product silicon at 0.55% maximum. The heat cell is therefore left blank rather than presenting one disputed figure as an official limit. Carbon at 0.15% is likewise a maximum in both columns, not a required target composition.
Maintain the heat/product distinction for manganese, chromium and molybdenum as well. Their separate intervals should travel with the analysis heading when requirements are copied into a quotation attachment. If a purchaser requests narrower chemistry, distinguish that additional restriction from the public reference. A chemical match alone cannot establish Class 1 mechanical compliance or prove that the proposed delivery condition is the agreed one.
Provide a purchase line that can be reviewed without guessing
| Information | Purchaser instruction | Review purpose |
|---|---|---|
| Material identity | A387 or A387M, Grade 5, Class 1 and required edition | Keep the selected class explicit |
| Size and quantity | Thickness, width, length, quantity and units per line | Connect each physical item to its material requirement |
| Thermal state | Required delivery condition and relevant project notes | Resolve the condition before comparing evidence |
| Testing and documents | Required tests, criteria and certificate form | Agree what receiving inspection must review |
| Traceability | Required plate/heat identification and schedule references | Keep evidence connected to the order |
Official Scope limits maximum thickness only by the composition’s capacity to meet the specified mechanical properties. It does not provide a numerical cap or establish available rolling capability. Submit the requested dimensions with the complete material requirement. Additional impact testing, examinations or a particular certificate form require explicit agreement; this page makes no default promise about those items.
For related purchasing topics, see Grade 9 Class 1 plate and Grade 2 Class 1 plate. These are navigation links, not technical sources or substitution approvals. A family comparison can help frame a question, but cannot authorize changing the material selected on the project schedule.
Buyer questions
Is annealed Grade 5 automatically the correct choice for every Class 1 enquiry?
No. The labelled Class 1 compilation includes annealed, normalized-and-tempered and accelerated-cooling-plus-temper delivery. Resolve the required route against the ordered edition and project instructions rather than selecting a universal default.
Why should the 205 MPa yield entry remain unchanged in a preliminary comparison?
It is the independently checked Class 1 reference paired with 30 ksi for Grade 5. Matching another grade’s preferred number is not a valid reason to replace it. The complete ordered documents govern acceptance.
What is needed if an enquiry specifies an 8 in. elongation criterion?
Provide the governing specification and test requirements for review. This page leaves that minimum blank because it was not established in the reviewed Grade 5 references. Do not fill the gap with an unrelated grade’s percentage.
Can the silicon heat maximum be assumed from the product column?
No. The product maximum is agreed at 0.55%, but the reviewed heat maxima differ between 0.50% and 0.55%. Keep that question open until the ordered edition establishes the applicable heat limit.
Does one ASTM certificate establish both ASTM and ASME acceptance?
An ASTM certificate alone is not SA-387 acceptance, and the reverse is not automatic. A dual requirement needs identified governing documents, an applicable Code edition and agreed supporting evidence. No current Code year is assigned here.
Discuss the Grade 5 Class 1 delivery requirement
Send the project designation and edition, size schedule, quantity, unit system and required thermal state. Include the test criteria and requested certificate form, with any chemistry questions listed separately for review against the ordered specification.