What is P355QL1 material ?
P355QL1 (EN 1.8868) is a high-quality, weldable, fine-grain structural steel designed for low-temperature applications, often used for pressure vessels, tanks, and pipes due to its excellent formability and resistance to brittle cracking, supplied in a quenched and tempered (QL1) condition for enhanced mechanical properties like good yield strength.
P355QL1 is a high-performance, fine-grained alloy steel specifically engineered for the fabrication of pressure-bearing equipment. It is governed by the European standard EN 10028-6, which focuses on flat products made of steels for pressure purposes that are delivered in the quenched and tempered condition. This material is designed to handle extreme internal pressures while maintaining structural integrity in low-temperature environments, making it a critical asset for safety-regulated industries. Its material number is 1.8867.
Key Characteristics
High-End Heat Treatment: The material undergoes quenching (rapid cooling) followed by tempering (reheating) to achieve a sophisticated balance of hardness and ductility.
Fine-Grain Structure: Metallurgically treated to ensure a very small grain size, which prevents the rapid propagation of cracks.
Pressure Validation: Every plate must undergo rigorous non-destructive testing, such as ultrasonic examination, to ensure it meets the strict safety codes for boilers and vessels.
Weldability: Despite its high strength, the carbon equivalent is kept low enough to ensure it can be joined effectively using modern welding techniques.
Decoding the Name
P: Stands for "Pressure," indicating its use in pressure-bearing environments.
355: Represents the minimum yield strength of $355 \text{ MPa}$ for thicknesses $\le 50\text{mm}$.
Q: Signifies the "Quenched and Tempered" delivery condition.
L1: Indicates a specific low-temperature quality, where the material is tested for impact toughness at -40
Comparison
Vs. P355Q: While both are quenched and tempered, the standard P355Q is typically tested at $-20^\circ\text{C}$. The "L1" suffix marks a higher tier of low-temperature safety.
Vs. S355NL: S355NL is a structural steel for buildings. P355QL1 is specifically for pressure vessels and undergoes much more intensive internal defect testing.
Common Application
Industrial Boilers: Large-scale steam generation units in power plants.
Gas Storage: Stationary tanks for pressurized gases in temperate or cold climates.
Petrochemical Vessels: Scrubbers and separators used in refinery processes.
What is P355QL1 material equivalent to ?
P355QL1 is a European alloy steel (EN 1.8868) for pressure vessels, requiring specific impact toughness at low temperatures, with equivalents often falling under similar quenched & tempered, low-alloy grades like ASTM A572 Grade 50 or other P355 variations (P355NL1, P355GH), though exact matches depend on the specific application's required properties, focusing on its strength (P355 = 355 MPa yield) and "QL1" (low temp impact).
What is the difference between P355QL1 and P355Q ?
P355QL1 and P355Q are both quenched and tempered (Q) fine-grain steels for pressure vessels (P355), but P355QL1 (EN 1.8868) offers superior toughness, especially at lower temperatures (L1), due to specific fine-grain processing (normalizing rolled/thermo-mechanically rolled), whereas P355Q (EN 1.8866), while also Q&T, might have different minimum impact energy requirements or processing, with P355QL1 generally being the more refined, higher-toughness variant for demanding low-temp applications.
What is P355QL1 used for ?
P355QL1 steel, specified under EN 10028-6 for weldable, fine-grain, quenched, and tempered steels, is primarily used for manufacturing pressure vessels, boilers, storage tanks, and heat exchangers, especially in oil, gas, and high-temperature industrial applications requiring good low-temperature toughness (down to -40°C) and excellent weldability.
Chemical composition % of steel P355QL1 (1.8868): EN 10028-6-2009
| C | Si | Mn | Ni | P | S | Cr | Mo | V | N | Nb | Ti | Cu | Zr | B |
| max 0.16 | max 0.4 | max 1.5 | max 0.5 | max 0.02 | max 0.008 | max 0.3 | max 0.25 | max 0.06 | max 0.015 | max 0.05 | max 0.03 | max 0.3 | max 0.05 | max 0.005 |
Mechanical properties of steel P355QL1 (1.8868)
| Nominal thickness (mm): | to 100 | 100 - 150 |
| Rm - Tensile strength (MPa) (+QT) | 490-630 | 450-590 |
| Nominal thickness (mm): | to 50 | 50 - 100 | 100 - 150 |
| ReH - Minimum yield strength (MPa) (+QT) | 355 | 335 | 315 |
| KV - Impact energy (J) transverse, (+QT) | -40° 27 |
-20° 40 |
0° 60 |
| A - Min. elongation at fracture (%) (+QT) | 22 |
1What are the main chemical components of P355QL1 material ?
P355QL1 (EN 1.8868) is a weldable fine-grain structural steel with main components: Iron (Fe) (balance, ~96-99%), with maximum limits for Carbon (C) (around 0.16%), Manganese (Mn) (around 1.6%), Silicon (Si) (around 0.4%), Copper (Cu) (around 0.3%), Chromium (Cr) (around 0.3%), Nickel (Ni) (around 0.5%), Molybdenum (Mo) (around 0.25%), and smaller amounts of Vanadium (V), Niobium (Nb), and Titanium (Ti) for grainrefinement.
2What influence the P355QL1 mechanical properties ?
P355QL1's mechanical properties, like strength and toughness, are primarily influenced by its chemical composition (carbon, manganese, etc.), specific heat treatment (quenching & tempering) for its 'QL' grade, and manufacturing processes, determining its microstructure for applications requiring high strength and weldability, often in pressure vessels or piping.
3Is P355QL1 weldable ?
Yes, P355QL1 is a weldable fine-grain structural steel specifically designed for pressure vessels and high-temperature equipment, known for its good weldability and suitability for welding processes in current use, often used in quenched and tempered condition. It's classified as a low-temperature tough steel, meaning it retains good properties at temperatures down to -40°C and is assigned to Welding Group 1.2 in DIN CEN ISO/TR 15608.
4Can P355QL1 be used for boiler application ?
Yes, P355QL1 steel is specifically designed and widely used for boiler and pressure vessel applications, meeting standards like EN 10028-6, offering excellent weldability, high strength, and good low-temperature impact toughness after quenching and tempering, making it ideal for demanding industrial conditions.
5What is the Chinese equivalent of P355QL1 ?
The Chinese equivalent for the European standard P355QL1 (a normalized, low-temperature steel for pressure vessels, offering 355 MPa yield strength at -40°C) is typically a grade within the Q345 or Q355 series under Chinese GB standards, specifically one offering equivalent low-temperature impact toughness, such as Q345L1 or Q355L1, though direct one-to-one matches require checking specific GB standards for chemical composition and mechanical properties like the GB 713/GB/T 713 standard for pressure vessel steels.
6Which industrial standard governs P355QL1?
P355QL1 is governed by the European standard EN 10028-6. This standard specifically covers flat products (plates) made of weldable fine-grained steels that are delivered in the quenched and tempered (Q+T) condition for pressure-bearing applications.
7What is the delivery condition of P355QL1?
The steel is always delivered in the Quenched and Tempered (+QT) state. This involves heating the steel to a high temperature, rapidly cooling it (quenching) in water or oil, and then reheating it to a lower temperature (tempering) to achieve a precise balance of strength and ductility.
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