EN 10219 S355MLH SSAW Pipe
EN 10219 S355MLH SSAW Pipe: Thermomechanical Rolled Fine Grain Structural Steel Hollow Section
Complete material data for EN 10219 S355MLH SSAW pipe including chemical composition, mechanical properties, physical performance, international equivalents, and application guidance for structural engineering.
Cold forming, welding, thermomechanical rolling, cutting, machining
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EN 10219 S355MLH SSAW Pipe Introduction
S355MLH is a thermomechanical-rolled fine-grain structural steel grade in accordance with EN 10219-1:2006, intended for cold-formed welded structural hollow sections, including spiral submerged arc welded (SSAW) pipes. This steel offers a minimum yield strength of 355 MPa for thicknesses up to 16 mm and guaranteed Charpy-V impact energy at -20°C. With excellent weldability, low-temperature toughness, and good formability, it is widely used in demanding structural applications such as bridges, offshore platforms, buildings, and pipelines. The ML designation indicates thermomechanical rolling with special requirements for chemical composition and carbon equivalent (CEV) to ensure optimal weldability and toughness.
EN 10219 S355MLH SSAW Pipe Chemical Composition
The chemical composition of S355MLH is strictly controlled to achieve fine-grained microstructure and weldability. Carbon equivalent (CEV) shall not exceed 0.39 for thermomechanical rolled products, based on EN 10219-1:2006 Table 3. Al total must be at least 0.020% for fine grain practice. Microalloying elements such as Nb, V, Ti are optionally added for grain refinement and precipitation strengthening.
| Element | Value (max, unless specified) | Remarks |
|---|---|---|
| C | 0.14 | Maximum |
| Si | 0.50 | Maximum |
| Mn | 1.60 | Maximum |
| P | 0.025 | Maximum |
| S | 0.020 | Maximum |
| Nb | 0.05 | Maximum |
| V | 0.10 | Maximum |
| Alt (total Al) | 0.020 min | Minimum for fine grain practice |
| Ti | 0.05 | Maximum |
| Ni | 0.30 | Maximum |
| Cr | 0.30 | Maximum |
| Cu | 0.25 | Maximum |
| Mo | 0.10 | Maximum |
| N | 0.015 | Maximum |
EN 10219 S355MLH SSAW Pipe Thermal and Electrical Physical Properties
Physical properties are typical for fine-grain structural steels of this strength level and are not part of the mandatory standard specification. Values may vary slightly depending on exact chemistry and temperature. Data are based on ambient (20°C) unless otherwise stated.
| Property | Value | Unit | Test condition |
|---|---|---|---|
| Density (ρ) | 7850 | kg/m³ | 20°C |
| Modulus of elasticity (E) | 210 | GPa | 20°C |
| Shear modulus (G) | 81 | GPa | 20°C |
| Poisson's ratio (ν) | 0.3 | - | 20°C |
| Thermal expansion coefficient (α) | 12 | 10⁻⁶/K | 20 - 100°C |
| Thermal conductivity (λ) | 47 | W/(m·K) | 20°C |
| Specific heat capacity (Cp) | 460 | J/(kg·K) | 20°C |
| Electrical resistivity (ρe) | 0.22 | 10⁻⁶ Ω·m | 20°C |
EN 10219 S355MLH SSAW Pipe Mechanical Properties
Mechanical properties are valid for wall thicknesses up to 65 mm at room temperature, according to EN 10219-1:2006 Table 5. Yield strength (ReH) decreases with increasing thickness. Minimum impact energy (KV) is guaranteed at -20°C for longitudinal Charpy-V specimens. The bend test radius depends on wall thickness and ensures ductility. Requirements are for the base metal of the finished hollow section.
| Property | Value | Unit | Test condition / wall thickness (t) |
|---|---|---|---|
| Upper yield strength (ReH) | ≥355 | MPa | t ≤ 16 mm |
| Upper yield strength (ReH) | ≥345 | MPa | 16 < t ≤ 40 mm |
| Upper yield strength (ReH) | ≥335 | MPa | 40 < t ≤ 65 mm |
| Tensile strength (Rm) | 470 - 630 | MPa | t ≤ 40 mm |
| Tensile strength (Rm) | 450 - 610 | MPa | 40 < t ≤ 65 mm |
| Elongation after fracture (A) | ≥22 | % | t ≤ 40 mm, L0 = 5.65√S0 |
| Elongation after fracture (A) | ≥21 | % | 40 < t ≤ 65 mm, L0 = 5.65√S0 |
| Charpy-V impact energy (KV, longitudinal) | ≥27 at -20°C | J | t ≤ 40 mm |
| Charpy-V impact energy (KV, longitudinal) | ≥27 at -20°C | J | 40 < t ≤ 65 mm |
| Bend test (bend angle 180°) | mandrel diameter = 2a | - | t ≤ 16 mm, a = specimen thickness |
| Bend test (bend angle 180°) | mandrel diameter = 3a | - | 16 < t ≤ 40 mm, a = specimen thickness |
EN 10219 S355MLH SSAW Pipe Completely Equivalent Material Standards and Replaceable Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| Europe | EN 10219-1 | S355MLH | Original specification for cold-formed hollow sections |
| United Kingdom | BS EN 10219-1 | S355MLH | Adopted EN standard, identical requirements |
| Germany | DIN EN 10219-1 | S355MLH | Adopted EN standard |
| France | NF EN 10219-1 | S355MLH | Adopted EN standard |
| Italy | UNI EN 10219-1 | S355MLH | Adopted EN standard |
| International (ISO) | ISO 630-2 | S355ML | Comparable mechanical and impact properties, but for flat products; not hollow sections |
EN 10219 S355MLH SSAW Pipe Application Introduction
S355MLH SSAW pipe is suited for heavy structural components operating at low ambient temperatures. Its fine-grain thermomechanical rolling provides an optimal combination of strength, weldability, and ductility. It is extensively used in:
- Structural frameworks for buildings and industrial plants
- Offshore and marine structures, including jackets and topsides
- Bridges, both as main chords and bracing
- Wind turbine towers and transition pieces
- Foundation piles and soil retaining systems
- Conveyor tubes and material handling equipment
Product Applications: Spiral welded pipes for load-bearing members, Circular, square and rectangular hollow sections, Combined wall (king pile) systems, Jacket legs and bracing for offshore platforms, Tubular trusses for long-span roofs, Transition pieces and tower sections for wind turbines
Processed into products: SSAW pipes (diameter typically > 400 mm, wall thickness up to 65 mm), Columns and beams in building frames, Piles and sheet pile connectors, Boom and arm sections for cranes, Supports and mounts for industrial machinery, Casing tubes and diaphragm walls
Application industries: Civil and structural engineering, Offshore oil & gas, Renewable energy (wind), Shipbuilding and marine construction, Bridge construction, Heavy machinery and equipment
EN 10219 S355MLH SSAW Pipe Similar/Alternative Materials with Comparable Performance
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| USA | ASTM A572/A572M | Grade 50 [345] | Similar minimum yield (345 MPa) and tensile, but impact temperature is not guaranteed unless specified; chemical composition differs |
| USA | ASTM A500/A500M | Grade C | Cold-formed welded structural tubing; yield strength 345 MPa, but impact properties not automatically guaranteed; suitable for applications where low-temperature toughness is not required |
| Japan | JIS G3466 | STKR490 | Welded structural hollow sections; minimum yield 325 MPa; can be considered with engineering assessment |
| Europe | EN 10219-1 | S355J2H | Similar strength and -20°C impact; produced by normalizing rolling instead of thermomechanical rolling; weldability and toughness comparable |
| Europe | EN 10210-1 | S355MLH | Hot-finished version; same strength and toughness; may be used when hot-finished tolerances and surface quality are acceptable |
Notes:
- The CEV (carbon equivalent) for S355MLH shall not exceed 0.39 based on ladle analysis, which is critical for weldability and crack prevention during fabrication.
- Surface condition and dimensions are in accordance with EN 10219-2 for tolerances unless otherwise agreed.
- For SSAW pipes, the usual supply length ranges from 6 to 18 meters; non-destructive testing (UT, RT) of the weld seam may be specified by the purchaser.
- If hot-dip galvanizing is required, the silicon content should be controlled to avoid excessive coating thickness; this should be agreed at the time of ordering.
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