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S355 | High Strength Structural Steel

Structural Steel
Structural Steel

S355 | High Strength Structural Steel

S355 is a non-alloy structural steel under EN 10025 with a minimum yield strength of 355 MPa. The name “S” stands for structural steel, and “355” indicates the yield strength in MPa. It is also known by equivalent grades such as Q355B (GB) and A572 Grade 50 (USA). S355 features good weldability, high strength, and moderate toughness, making it suitable for construction, bridges, and heavy machinery.

We can supply the S355 sub-series from 6 to 300 mm according to standards EN 10025-2, 3 and 4 respectively.

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Description

What is S355?

S355 is a structural steel made of about 98% iron with small amounts of carbon, manganese, silicon, and phosphorus. It is typically supplied in solid plates, bars, or sections and processed through hot rolling. S355 features high strength, good weldability, and moderate toughness, making it ideal for construction, bridges, wind turbines, and heavy machinery. It has several subgrades based on impact energy: S355JR (27J at +20°C), S355J0 (27J at 0°C), S355J2 (27J at -20°C), and S355K2 (40J at -20°C). Its equivalents include Q355B (China) and A572 Grade 50 (USA).

Characteristics of S355 Steel

S355 steel offers excellent impact toughness and good weather resistance, making it reliable in harsh environments. It comes in multiple quality grades (JR, J0, J2, K2, N, M) to suit various temperature conditions and applications. The material provides high strength, good weldability, and flexibility for structural uses. S355 is widely used in construction, bridges, offshore structures, wind turbines, and heavy equipment. For applications needing higher strength or enhanced corrosion resistance, alternatives like S460, Corten Steel, or HSLA (ASTM A588, A572) Steel may be more suitable.

Chemical Compositions

ElementS355JR / J0S355J2S355K2S355NS355M
Carbon, C≤ 0.24%≤ 0.22%≤ 0.22%≤ 0.18%≤ 0.16%
Silicon, Si≤ 0.60%≤ 0.60%≤ 0.60%≤ 0.50%≤ 0.50%
Manganese, Mn≤ 1.60%≤ 1.60%≤ 1.60%1.00–1.70%1.10–1.70%
Phosphorus, P≤ 0.045%≤ 0.035%≤ 0.035%≤ 0.025%≤ 0.025%
Sulfur, S≤ 0.045%≤ 0.035%≤ 0.035%≤ 0.020%≤ 0.020%
Nitrogen, N≤ 0.012%≤ 0.012%≤ 0.012%≤ 0.012%≤ 0.012%
Copper, Cu≤ 0.55%≤ 0.55%≤ 0.55%≤ 0.55%≤ 0.55%
Aluminum, Al≥ 0.02%≥ 0.02%≥ 0.02%≥ 0.02%≥ 0.02%
Iron, FeBalanceBalanceBalanceBalanceBalance

Physical Properties

PropertyS355JR / J0S355J2S355K2S355NS355M
Density7.85 g/cm³ / 0.284 lb/in³7.85 g/cm³ / 0.284 lb/in³7.85 g/cm³ / 0.284 lb/in³7.85 g/cm³ / 0.284 lb/in³7.85 g/cm³ / 0.284 lb/in³
Melting Point1425–1540 °C / 2597–2800 °F1425–1540 °C / 2597–2800 °F1425–1540 °C / 2597–2800 °F1425–1540 °C / 2597–2800 °F1425–1540 °C / 2597–2800 °F
Boiling Point~3000 °C / ~5432 °F~3000 °C / ~5432 °F~3000 °C / ~5432 °F~3000 °C / ~5432 °F~3000 °C / ~5432 °F
Thermal Conductivity50 W/m·K / 289 BTU/(hr·ft·°F)49 W/m·K / 283 BTU/(hr·ft·°F)49 W/m·K / 283 BTU/(hr·ft·°F)47 W/m·K / 272 BTU/(hr·ft·°F)46 W/m·K / 265 BTU/(hr·ft·°F)
Electrical Conductivity6.99 MS/m / 6.99 MS/m6.80 MS/m / 6.80 MS/m6.80 MS/m / 6.80 MS/m6.50 MS/m / 6.50 MS/m6.40 MS/m / 6.40 MS/m
Specific Heat Capacity480 J/(kg·K) / 0.114 BTU/(lb·°F)480 J/(kg·K) / 0.114 BTU/(lb·°F)480 J/(kg·K) / 0.114 BTU/(lb·°F)490 J/(kg·K) / 0.117 BTU/(lb·°F)490 J/(kg·K) / 0.117 BTU/(lb·°F)
Thermal Expansion Coefficient12 × 10⁻⁶ /K / 6.7 × 10⁻⁶ /°F11.9 × 10⁻⁶ /K / 6.6 × 10⁻⁶ /°F11.9 × 10⁻⁶ /K / 6.6 × 10⁻⁶ /°F11.7 × 10⁻⁶ /K / 6.5 × 10⁻⁶ /°F11.5 × 10⁻⁶ /K / 6.4 × 10⁻⁶ /°F
Electrical Resistivity142 nΩ·m / 142 nΩ·m145 nΩ·m / 145 nΩ·m145 nΩ·m / 145 nΩ·m150 nΩ·m / 150 nΩ·m152 nΩ·m / 152 nΩ·m

Mechanical Properties

PropertyS355JR / J0S355J2S355K2S355NS355M
Tensile Strength470–630 MPa / 68,170–91,370 psi490–630 MPa / 71,100–91,370 psi490–630 MPa / 71,100–91,370 psi510–680 MPa / 73,950–98,610 psi510–680 MPa / 73,950–98,610 psi
Yield Strength355 MPa / 51,490 psi355 MPa / 51,490 psi355 MPa / 51,490 psi420 MPa / 60,900 psi420 MPa / 60,900 psi
Elastic Modulus210 GPa / 30,458 ksi210 GPa / 30,458 ksi210 GPa / 30,458 ksi210 GPa / 30,458 ksi210 GPa / 30,458 ksi
Poisson’s Ratio0.27–0.300.27–0.300.27–0.300.27–0.300.27–0.30
Brinell Hardness146–187 HB150–190 HB150–190 HB180–220 HB180–220 HB
Rockwell Hardness84 HRB (approx.)85–90 HRB (approx.)85–90 HRB (approx.)90–95 HRB (approx.)90–95 HRB (approx.)
Vickers Hardness150–190 HV160–200 HV160–200 HV200–240 HV200–240 HV
Elongation18–22%16–20%16–20%12–16%12–16%

Data After QT(Quenching and Tempering) Processing

 

PropertyS355JR / J0 (QT)S355J2 (QT)S355K2 (QT)S355N (QT)S355M (QT)
Tensile Strength750–950 MPa / 108,800–137,800 psi800–1000 MPa / 116,000–145,000 psi800–1000 MPa / 116,000–145,000 psi850–1100 MPa / 123,250–159,500 psi850–1100 MPa / 123,250–159,500 psi
Yield Strength500–650 MPa / 72,500–94,300 psi550–700 MPa / 79,800–101,500 psi550–700 MPa / 79,800–101,500 psi600–750 MPa / 87,000–108,800 psi600–750 MPa / 87,000–108,800 psi
Elastic Modulus210 GPa / 30,458 ksi210 GPa / 30,458 ksi210 GPa / 30,458 ksi210 GPa / 30,458 ksi210 GPa / 30,458 ksi
Poisson’s Ratio0.27–0.300.27–0.300.27–0.300.27–0.300.27–0.30
Brinell Hardness230–300 HB240–320 HB240–320 HB260–340 HB260–340 HB
Rockwell Hardness95–100 HRB (approx.)96–102 HRB (approx.)96–102 HRB (approx.)98–104 HRB (approx.)98–104 HRB (approx.)
Vickers Hardness240–300 HV250–320 HV250–320 HV280–340 HV280–340 HV
Elongation10–14%8–12%8–12%6–10%6–10%

Industries & Applications

IndustriesProducts
ConstructionBeams, Columns, Trusses, Frames, Railings
Bridge EngineeringBridge Girders, Decks, Supports, Bearings, Guardrails
Offshore StructuresOil Rigs, Wind Turbine Foundations, Platforms, Piping Systems, Anchors
Heavy MachineryCranes, Excavators, Bulldozers, Forklifts, Loaders
EnergyWind Towers, Solar Panel Frames, Hydropower Structures, Pipeline Supports, Transformers
AutomotiveChassis, Suspension Arms, Truck Frames, Axle Housings, Body Panels
Rail InfrastructureRails, Sleepers, Platforms, Signal Structures, Overhead Line Supports
ShipbuildingHulls, Deck Plates, Bulkheads, Masts, Containers
Mining EquipmentDrilling Rigs, Conveyor Systems, Crushers, Shovels, Dump Trucks

Machining

S355 Steel Heat Treatment

  1. Normalizing:
    • Heat to 850–900°C (1560–1650°F), hold until uniform temperature.
    • Effect: Refines grain structure, improves toughness, and prepares the steel for machining or further heat treatment.
  2. Annealing:
    • Heat to 680–750°C (1256–1382°F), then cool slowly in the furnace.
    • Effect: Reduces hardness, relieves internal stress, and enhances ductility.
  3. Quenching:
    • Heat to 860–920°C (1580–1690°F), then rapidly cool in water or oil.
    • Effect: Increases hardness and strength but reduces toughness.
  4. Tempering:
    • After quenching, reheat to 500–680°C (932–1256°F), followed by air cooling.
    • Effect: Restores toughness, reduces brittleness, and adjusts hardness.
  5. Stress Relieving:
    • Heat to 550–650°C (1022–1202°F), hold for 1–2 hours, and cool in air.
    • Effect: Minimizes residual stresses from welding or machining without significant changes in hardness or strength.

S355 Surface Finish

  1. Shot Blasting: Improves surface cleanliness and adhesion for coatings.
  2. Pickling: Removes rust, scale, and impurities, enhancing corrosion resistance.
  3. Galvanizing: Adds a zinc layer to protect against corrosion.
  4. Powder Coating: Provides a durable, decorative, and corrosion-resistant finish.
  5. Painting: Adds color, protection, and environmental resistance.
  6. Anodizing (for special alloys): Increases corrosion resistance and wear properties.
  7. Polishing: Creates a smooth, reflective surface for aesthetic or functional purposes.

Custom surface treatment requirements can be accommodated upon request.

Disclaimer
The above heat treatment instructions and surface finish processing methods for S355 steel are provided for informational purposes only. Actual results may vary based on specific conditions and equipment used. Testing is recommended, and a metallurgical expert or material supplier should be consulted to ensure the processes are suitable for your specific application. The user assumes all risks and liability for the use of this information.

 

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