How Is P355Q Pressure Vessel and Boiler Steel Plate Made?
Every P355Q plate starts with a promise written into the standard: minimum yield 355 MPa up to 50 mm thickness, and at least 27 J Charpy energy at −20 °C. No inspection department can test that into a plate after the fact. For a quenched and tempered pressure-vessel grade, those numbers are the product of a deliberately controlled manufacturing route - and the mill test certificate (MTC) is simply the paperwork that proves each step was done.
Processing Flow Chart
| Stage | What happens |
|---|---|
| Steelmaking & refining | Converter or electric-arc-furnace melt, ladle-furnace trimming, vacuum degassing |
| Continuous casting | Molten steel cast into slabs; surfaces conditioned (scarfing/grinding) |
| Hot rolling | Slabs reheated and rolled to ordered thickness/width |
| Austenitizing | Plate heated to roughly 880–950 °C |
| Water quenching | Rapid cooling from austenitizing temperature |
| Tempering | Reheating to roughly 580–680 °C and holding |
P355Q Steel Plate Cutting
Steel plate cutting (oxy-fuel cutting) is the process of preheating the metal to its ignition temperature using an oxy-natural gas flame, followed by the release of a high-pressure oxygen stream. This induces rapid oxidation of the metal and expels the resulting slag to form a clean kerf.
Common cutting methods for steel plates include oxy-fuel cutting, laser cutting, wire EDM, mechanical shearing, plasma cutting, and ultra-high-pressure waterjet cutting.
Oxy-fuel cutting equipment involves low capital costs and remains the most economical and effective solution for heavy plate cutting, though it presents limitations when applied to thin sheet gauge materials. Consequently, heavy plates are typically processed using oxy-fuel cutting methods.
P355Q Pressure Vessel Steel Plate Chemical property
| C% | SI% | Mn% | P% | S% | N% | B% | Cr% | Mo% | Cu% | Nb% | Ni% | Ti% | V% | Zr% |
| 0.16 | 0.4 | 1.5 | 0.025 | 0.010 | 0.015 | 0.005 | 0.3 | 0.25 | 0.3 | 0.05 | 0.5 | 0.03 | 0.06 | 0.05 |
P355Q Boiler Steel Plate mechanical property
| Yield Strength, for product in mm, Mpa | Tensile Strength, Mpa | Elongation, %, min | ||||||||||||
| t≤50 | 50 | 100 | t≤100 | 100 | 22 | |||||||||
| 355 | 335 | 315 | 490-630 | 450-590 | ||||||||||
P355Q Pressure Vessel and Boiler Steel Plate Specification
| Item | Detail |
|---|---|
| Thickness | 8–200 mm (full EN 10028-6:2017 guarantee range) |
| Width × length | 1000–4200 mm × 5000–18000 mm |
| Certificate | EN 10204 3.1 standard; 3.2 and third-party inspection (SGS / TÜV / BV) on request |
P355Q Steel Plate Scope of Applications
P355Q is primarily specified in the fabrication of pressure equipment, including large spherical storage tanks (spheres), single-layer roll-welded vessels, multilayer shrink-fitted roll-welded vessels, and multilayer wrapped vessels categorized under Class II and Class III pressure vessels, as well as low-temperature pressure vessels. In oil and gas engineering projects, it is also extensively utilized for pressure vessels, boilers, storage tanks, and heat exchangers.
Comparison of Related Grades under EN 10028-6
The EN 10028-6 standard also specifies other quenched and tempered (Q&T) steel grades, including:
- P355QH: Features elevated phosphorus control/tailored chemistry optimized for higher-temperature service conditions.
- P355QL1 / P355QL2: Engineered for superior low-temperature impact toughness (P355QL1 guarantees minimum impact energy of 40 J at -50°C; P355QL2 guarantees minimum impact energy of 27 J at -60°C).
- P460Q / P500Q / P690Q: Higher yield strength grades designed for ultra-high-pressure applications.
Why Choose us?
- Our exclusive export standard packaging includes: waterproof film + moisture-proof paper + solid wood pallet + corner protectors.
- Multi-warehouse layout and long-term cooperative logistics fleets ensure convenient shipping from inland areas and direct export to ports. We provide one-stop foreign trade services including customs declaration, booking, and clearance, with full logistics tracking.
- Our self-built professional quality inspection team conducts full-process inspection from raw materials, rolling, leveling to finished product delivery, strictly controlling dimensional tolerances and surface quality to eliminate defects such as cracks, slag inclusions, and rust.
- We maintain a stock of thousands of tons of steel, with same-day shipping for standard specifications. Small trial orders and samples are supported; minimum order quantities are not mandatory.
Learn more about GNEE Steel qualifications
FAQ
Why does QT plate cost more than normalized plate?
Two reasons: the extra heat-treatment steps (austenitize, quench, temper) and the cleaner, more alloyed steel needed to quench reliably. You pay for the higher yield in thick sections and the guaranteed −20 °C toughness.
Is EN 10204 3.2 always required?
Not always. 3.1 (mill-issued) is the standard for most orders. 3.2 (third-party witnessed) is specified by the project or the purchaser when independent assurance is required - typically for critical vessels or end-client mandates. State it at enquiry so it is priced and scheduled correctly.
Is ultrasonic testing mandatory for P355Q?
Not by the base standard for every plate. UT is specified when the project or the design requires it (for example heavy-wall or critical-service vessels), usually to EN 10160 or ASTM A578 levels. Confirm the acceptance level at enquiry.
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