EN10025-6 S550QL Structural Steel Plate

EN10025-6 S550QL Structural Steel Plate

EN10025-6 S550QL Quenched & Tempered High-Strength Structural Steel Plate

Comprehensive technical data for S550QL steel plate according to EN 10025-6:2019. Includes chemical composition, mechanical properties, physical properties, equivalent grades, and application guide.

Quenching and tempering (Q+T); can be cut, welded, and cold formed with appropriate precautions.

EN10025-6 S550QL Structural Steel Plate Introduction

S550QL is a quenched and tempered, high-yield-strength structural steel according to EN 10025-6:2019. It belongs to the carbon and low-alloy steel category with a minimum yield strength of 550 MPa in thicknesses up to 50 mm. The designation S stands for structural steel, 550 for the minimum yield strength in MPa, Q for quenching and tempering delivery condition, and L for impact toughness guaranteed at -50 °C. This grade offers excellent combination of high strength, good toughness at low temperatures, and weldability, making it suitable for demanding structural applications such as bridges, offshore structures, heavy machinery, and cranes. It is typically supplied in the as-quenched and tempered condition.

EN10025-6 S550QL Structural Steel Plate Chemical Composition

The chemical composition of S550QL steel is controlled according to EN 10025-6:2019. Maximum limits are defined for most elements to ensure consistent strength, toughness, and weldability. The steel shall contain grain-refining elements; if aluminium is used, the minimum Al content is 0.015%. Other elements may be added as agreed.

ElementValue (max, unless range)Notes
Carbon (C)≤ 0.20
Silicon (Si)≤ 0.80
Manganese (Mn)≤ 1.70
Phosphorus (P)≤ 0.020
Sulfur (S)≤ 0.010
Nitrogen (N)≤ 0.015
Boron (B)≤ 0.005
Chromium (Cr)≤ 1.50
Copper (Cu)≤ 0.50
Molybdenum (Mo)≤ 0.70
Niobium (Nb)≤ 0.06
Nickel (Ni)≤ 2.0
Titanium (Ti)≤ 0.05
Vanadium (V)≤ 0.12
Zirconium (Zr)≤ 0.15
Aluminium (Al)≥ 0.015Minimum when used as grain refiner; otherwise adequate N-binding elements shall be present.

EN10025-6 S550QL Structural Steel Plate Thermal and Electrical Physical Properties

The following physical properties are typical values for quenched and tempered high-strength low-alloy steels. They are not mandatory requirements of EN 10025-6 but provide useful data for engineering calculations. Values may vary slightly with heat treatment and composition.

PropertyTypical ValueUnitTest Condition / Temperature
Density (ρ)7.85g/cm³20 °C
Modulus of elasticity (E)210GPa20 °C
Shear modulus (G)≈ 81GPa20 °C
Poisson's ratio (ν)0.3–20 °C
Thermal expansion coefficient (α)11.5 × 10⁻⁶/K20 – 100 °C
Thermal expansion coefficient (α)12.5 × 10⁻⁶/K20 – 200 °C
Thermal expansion coefficient (α)13.5 × 10⁻⁶/K20 – 300 °C
Thermal conductivity (λ)≈ 40W/(m·K)20 °C
Specific heat capacity (c)≈ 460J/(kg·K)20 °C
Electrical resistivity (ρₑ)≈ 0.23 × 10⁻⁶Ω·m20 °C

EN10025-6 S550QL Structural Steel Plate Mechanical Properties

The mechanical properties are guaranteed for the quenched and tempered condition. Values depend on product thickness. Impact energy is measured on Charpy V-notch transverse test pieces at -50 °C. Bend test requirements apply for cold formability verification.

PropertyValueUnitTest Condition / Thickness (t, mm)
Yield strength (ReH)≥ 550MPat ≤ 50
Yield strength (ReH)≥ 530MPa50 < t ≤ 100
Yield strength (ReH)≥ 510MPa100 < t ≤ 150
Yield strength (ReH)≥ 490MPa150 < t ≤ 200
Tensile strength (Rm)640 – 820MPat ≤ 50
Tensile strength (Rm)640 – 820MPa50 < t ≤ 100
Tensile strength (Rm)620 – 800MPa100 < t ≤ 150
Tensile strength (Rm)590 – 770MPa150 < t ≤ 200
Elongation after fracture (A)≥ 16%All thicknesses (L₀ = 5.65√S₀, longitudinal)
Impact energy (KV) at -50°C≥ 27Jt ≤ 150 (transverse, average of 3)
Impact energy (KV) at -50°C≥ 27J150 < t ≤ 200 (transverse, average of 3)
Bend test (180°) – mandrel diameter2t–t ≤ 16
Bend test (180°) – mandrel diameter3t–16 < t ≤ 40
Bend test (180°) – mandrel diameter4t–40 < t ≤ 63
Bend test (180°) – mandrel diameter5t–63 < t ≤ 100
Bend test (180°) – mandrel diameter6t–100 < t ≤ 150
Bend test (180°) – mandrel diameter7t–150 < t ≤ 200

EN10025-6 S550QL Structural Steel Plate Fully Equivalent Material Standards and Replaceable Grade Designations

Country / RegionStandardGradeRemarks
EuropeEN 10025-6:2019S550QLOriginal specification
InternationalISO 630-6:2023S550QLDirect equivalent in ISO standard
GermanyDIN EN 10025-6S550QLGerman adoption of EN standard
United KingdomBS EN 10025-6S550QLBritish adoption of EN standard
FranceNF EN 10025-6S550QLFrench adoption of EN standard
ItalyUNI EN 10025-6S550QLItalian adoption of EN standard
International (withdrawn)ISO 4950-3:1995E550DDFunctional equivalent; same strength and low‑temperature toughness class

EN10025-6 S550QL Structural Steel Plate Application Introduction

S550QL combines high strength, excellent low‑temperature impact toughness, and good weldability. It is ideal for fabricating heavily loaded, welded structures that must perform at temperatures down to -50 °C. Care must be taken during welding (preheat, interpass temperature control) to maintain toughness in the heat‑affected zone. Typical carbon equivalent value (CEV) is ≤0.54 for plate thickness ≤50 mm, ensuring good weldability with appropriate procedures.

Product Applications: Welded plate girders and box columns, Offshore platform structural members, Mobile crane booms and lattice masts, Heavy‑duty truck frames and excavator arms, Bridge main girders and arch ribs, Large‑scale industrial containers and silos

Processed into products: Structural beams, columns, and nodes, Boom segments and telescopic arms, Load‑bearing plates and reinforcement ribs, Welded T‑joints and cruciform connections, Penstock and pipe shell sections, Base frames for heavy machinery

Application industries: Construction and civil engineering (bridges, high‑rise buildings), Offshore and marine structures (platforms, decks, jack‑up rigs), Heavy machinery and equipment manufacturing, Mining and earthmoving equipment, Crane and lifting technology, Pressure vessel and penstock fabrication (where applicable)

EN10025-6 S550QL Structural Steel Plate Similar / Comparable Material Grades

Country / RegionStandardGradeRemarks
EuropeEN 10025-6S500QLLower yield strength (≥500 MPa), same toughness class; may be an economical alternative where 550 MPa is not required.
EuropeEN 10025-6S620QLHigher yield strength (≥620 MPa), same toughness class; suitable for weight reduction when higher strength is acceptable.
EuropeEN 10025-6S550QSame strength level, impact test at 0 °C instead of -50 °C; for less severe low‑temperature service.
JapanJIS G 3128SHY550High yield strength steel for welded structures, similar strength level but different chemical approach and testing conditions.
USAASTM A514 / A517Grade –Quenched and tempered alloy steels with minimum yield ≥ 690 MPa; significantly higher strength; not a direct substitute but may be used in over‑matched designs.

Notes:

Welding considerations: Preheat temperature typically 100–200 °C depending on plate thickness and hydrogen control. Heat input should be limited to avoid excessive grain coarsening in the HAZ. Post‑weld heat treatment is generally not required. Carbon equivalent (CEV) values conforming to EN 10025-6: t≤50 mm ≤0.54, 50Surface condition: Plates are normally supplied with an as‑rolled and quenched surface; descaling or blast cleaning may be performed upon request. Tolerances: Thickness, flatness, and dimensional tolerances according to EN 10029 or as agreed. Certification: 3.1 inspection certificate per EN 10204 is standard.

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