Ordering Q345R vessel plate: UT, heat treatment, mill certs
Vessel plate is the most tightly governed family of plate: heat-treated before delivery, ultrasonically tested, heat numbers traceable on every certificate. Q345R is its workhorse — boiler drums, petrochemical vessels, exchanger shells. This piece sorts out the three clauses that cause the most trouble: UT class, delivery condition and performance guarantee.
First: what R means, and why it is not Q345
The R in Q345R stands for the Chinese word for vessel; the grade follows GB/T713. Its chemistry sits near structural Q345/Q355, but the demands are much stricter: tighter gas and inclusion control, guaranteed properties plate by plate, performance heat treatment (normalizing) before delivery, and UT per GB/T2970. Substituting structural steel into a pressure boundary is a red line no designer or inspector will forgive.
Clause one: delivery condition
Q345R is normally supplied normalized; heavier thicknesses and elevated-temperature designs take normalized + tempered. The condition changes high-temperature yield and creep behaviour, so the contract must state the same condition the design curves assume. On arrival, check the "delivery condition" field on the certificate against the stencil — the two must agree.
Clause two: UT class and extent
UT follows GB/T2970, commonly written as plate-by-plate testing to Class II, with Class I for critical equipment. Each class step raises price and lead time — and none of it is the place to save. For plate above 60 mm destined for Class III vessels, we recommend Class I with the report enclosed.
Clause three: performance guarantee and re-inspection
A standard certificate covers chemistry, tensile, 0°C impact (per GB/T713 for Q345R) and bend. Designs above 200°C should request elevated-temperature tensile data; sour service means an R-HIC order with HIC/SSC testing on a dedicated heat. Third-party re-inspection is straightforward: samples from the plate end, matched to the certificate's heat.
Sizes and lead times at a glance
| Item | Common range | Notes |
|---|---|---|
| Thickness | 6–250 mm | above 60 mm, prefer forward booking |
| Width | 1500–4020 mm | oversize per mill capability |
| Length | 3000–15000 mm | cut lengths priced separately |
| Condition | N / N+T | state it in the contract |
| Lead time | stock 3–7 days; booking 3–5 weeks | seasonal drift |
Acceptance checklist
- Certificate vs stencil, plate by plate: grade, size, heat number all match
- Delivery condition matches the contract (N / N+T)
- UT report reaches the contracted class, heat numbers correspond
- Surface free of out-of-spec dents, pits or lamination signs
- If re-inspecting, keep the original certificate with the file