EN10025-6 S550Q Quenched & Tempered High Yield Steel
EN10025-6 S550Q Quenched & Tempered High Yield Steel - Comprehensive Properties & Equivalents
Detailed material data for S550Q carbon and low-alloy high-strength steel coil under EN 10025-6, including chemical composition, mechanical and physical properties, international equivalents, and applications.
Hot rolling, quenching and tempering, welding, forming, cutting
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EN10025-6 S550Q Quenched & Tempered High Yield Steel Introduction
S550Q is a quenched and tempered fine-grain structural steel defined in EN 10025-6, with a minimum yield strength of 550 MPa. It combines high strength with good weldability and impact toughness, making it suitable for heavy structural engineering under demanding conditions.
- Fine-grain microstructure achieved through microalloying (Nb, V, Ti)
- Controlled chemical composition restricts harmful elements
- Supplied in the quenched and tempered (Q+T) condition
- Available in three toughness grades: S550Q (0°C), S550QL (-20°C), S550QL1 (-40°C)
EN10025-6 S550Q Quenched & Tempered High Yield Steel Chemical Composition
Chemical composition in accordance with EN 10025-6 for S550Q. Values are maximum limits unless a range is specified. The steel is microalloyed to promote fine grain structure and achieve the required mechanical properties.
| Element | Standard Value (max) | Remarks |
|---|---|---|
| Carbon (C) | 0.20 | Controls hardenability and strength |
| Silicon (Si) | 0.80 | Deoxidizer, contributes to strength |
| Manganese (Mn) | 1.70 | Improves hardenability and toughness |
| Phosphorus (P) | 0.020 | Restricted to maintain ductility and toughness |
| Sulfur (S) | 0.010 | Low sulfur for cleanliness and impact properties |
| Nitrogen (N) | 0.015 | Controlled to avoid strain ageing |
| Boron (B) | 0.005 | Enhances hardenability in low levels |
| Chromium (Cr) | 1.50 | Increases hardenability and corrosion resistance |
| Copper (Cu) | 0.50 | May be present from scrap; slight corrosion resistance |
| Molybdenum (Mo) | 0.70 | Improves hardenability and high-temperature strength |
| Niobium (Nb) | 0.06 | Grain refiner, precipitation strengthener |
| Nickel (Ni) | 2.00 | Enhances toughness and hardenability |
| Titanium (Ti) | 0.05 | Grain refiner, forms stable carbides/nitrides |
| Vanadium (V) | 0.12 | Precipitation strengthener, grain refiner |
| Zirconium (Zr) | 0.15 | Optional; may be used for sulfide shape control |
EN10025-6 S550Q Quenched & Tempered High Yield Steel Thermal and Electrical Physical Properties
These physical properties are typical for quenched and tempered structural steels and are not specified in EN 10025-6. They are provided for design guidance. Values may vary slightly with exact composition and heat treatment condition.
| Property | Typical Value | Unit | Test Condition / Remark |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | Room temperature |
| Modulus of elasticity (E) | 210 | GPa | Room temperature, tensile |
| Shear modulus (G) | 81 | GPa | Calculated from E and ν |
| Poisson's ratio (ν) | 0.3 | – | Elastic range |
| Thermal expansion coefficient (α) | 12 × 10⁻⁶ | /°C | 20°C – 100°C |
| Thermal conductivity (λ) | ~50 | W/(m·K) | Room temperature |
| Specific heat capacity (cₚ) | ~460 | J/(kg·K) | Room temperature |
| Electrical resistivity (ρₑ) | ~0.20 | µΩ·m | Room temperature |
EN10025-6 S550Q Quenched & Tempered High Yield Steel Mechanical Properties
Minimum mechanical properties for S550Q in the quenched and tempered condition. Values depend on product thickness. Impact toughness is evaluated by Charpy V-notch test. The base grade S550Q specifies 0°C impact temperature; higher grades QL and QL1 require lower temperatures (not shown).
| Property | Standard Requirement | Unit | Test Condition |
|---|---|---|---|
| Yield strength (ReH) | 550 | MPa | Thickness ≤ 50 mm |
| Yield strength (ReH) | 530 | MPa | 50 mm < Thickness ≤ 100 mm |
| Yield strength (ReH) | 510 | MPa | 100 mm < Thickness ≤ 150 mm |
| Tensile strength (Rm) | 640 – 820 | MPa | Thickness ≤ 150 mm |
| Elongation after fracture (A5) | ≥ 16 | % | Thickness ≤ 50 mm; gauge length 5.65√S0 |
| Elongation after fracture (A5) | ≥ 16 | % | 50 mm < Thickness ≤ 100 mm |
| Elongation after fracture (A5) | ≥ 16 | % | 100 mm < Thickness ≤ 150 mm |
| Impact energy (KV2) | ≥ 27 @ 0°C | J | Longitudinal Charpy V-notch; base S550Q grade |
EN10025-6 S550Q Quenched & Tempered High Yield Steel Completely Equivalent Material Standards and Substitutable Grade Recommendations
| Country / Region | Standard | Grade | Remarks |
|---|---|---|---|
| International (ISO) | ISO 630-6 | S550Q | Direct equivalent; same quenched & tempered fine-grain structural steel |
| China | GB/T 16270 | Q550 (Q550D, Q550E) | Equivalent grade with comparable strength and toughness; Q550D for -20°C, Q550E for -40°C |
| European Union | EN 10025-6 | S550QL / S550QL1 | Higher toughness variants of the same standard; identical base chemistry and strength |
EN10025-6 S550Q Quenched & Tempered High Yield Steel Application Introduction
S550Q steel is designed for heavy-duty welded structures where high strength, good toughness, and adequate weldability are required. Its balanced alloy design allows reliable fabrication using common welding techniques while maintaining excellent mechanical properties.
Product Applications: Crane booms, jibs, and chassis, Bridge structural members, Offshore platform decks and legs, Excavator buckets and booms, Pressure vessel shells, Heavy-duty welded beams and columns
Processed into products: Welded box sections and rolled beams, Cut and formed plates for machine frames, Welded pipe nodes for truss structures, Reinforced structural nodes, Lifting lugs and shackle plates, Chassis side members and crossmembers
Application industries: Construction and civil engineering, Heavy machinery and equipment, Offshore and marine engineering, Transport and lifting equipment, Mining and earthmoving, Pressure vessels and storage tanks
EN10025-6 S550Q Quenched & Tempered High Yield Steel Similar or Substitute Material Recommendations
| Country / Region | Standard | Grade | Remarks |
|---|---|---|---|
| USA | ASTM A656/A656M | Grade 80 | Hot-rolled, controlled-rolled high-strength low-alloy plate with min. yield 550 MPa; not quenched & tempered but comparable strength |
| USA | ASTM A514/A514M | Grade Q (e.g., Type Q) | Quenched & tempered alloy steel plate with higher yield strength (690 MPa); higher strength alternative |
| Japan | JIS G 3128 | SHY590 | High yield strength steel for welded structures (quenched & tempered); approximately 590 N/mm² yield, suitable for heavy welding |
| Germany | DIN EN 10025-6 | S690Q | Higher strength quenched & tempered grade from same standard (690 MPa); may be a viable upgrade when weight saving is required |
Notes:
S550Q should be welded with low-hydrogen processes and preheat as required by thickness and carbon equivalent. Post-weld heat treatment is generally not required but may be applied for stress relief. For severe forming, hot forming or stress relieving after cold forming is recommended. Always refer to the latest EN 10025-6 standard for complete technical delivery conditions and permissible tolerances.
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