JIS G3106 SM520B Steel
JIS G3106 SM520B Steel - High-Strength Weldable Structural Plate for SSAW Pipe
Comprehensive data sheet for SM520B steel according to JIS G3106. Covers chemical composition, mechanical and physical properties, equivalent grades, and application in spiral submerged-arc welded pipes.
Hot rolling, normalizing, welding, forming, cutting, machining
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JIS G3106 SM520B Steel Introduction
JIS G3106 SM520B is a weldable structural steel with a minimum specified yield strength of 355–275 MPa depending on thickness and a tensile strength range of 520–640 MPa. It offers good weldability, excellent toughness at 0°C, and reliable formability. This grade is commonly used for welded structures such as bridges, buildings, and offshore platforms, and is a preferred material for manufacturing spiral submerged-arc welded (SSAW) pipes used in oil and gas transmission. SM520B is typically supplied in hot-rolled condition and can be normalised if required. Its balanced mechanical properties make it suitable for heavy-duty load-bearing applications.
JIS G3106 SM520B Steel Chemical Composition
The chemical composition of SM520B is designed to provide a balance of strength and weldability. Carbon equivalent values are controlled to ensure good low-temperature toughness. Maximum contents are specified for phosphorus and sulfur to enhance cleanliness and ductility. Additional alloying elements such as Nb, V, or Ti may be added for grain refinement according to the manufacturer's practice.
| Element | Value (max, unless range) | Remarks |
|---|---|---|
| C | ≤ 0.20% | Carbon affects strength and weldability |
| Si | ≤ 0.55% | Silicon for deoxidation |
| Mn | ≤ 1.60% | Manganese improves hardenability and strength |
| P | ≤ 0.035% | Phosphorus control for ductility |
| S | ≤ 0.035% | Sulfur control for weldability and toughness |
JIS G3106 SM520B Steel Thermal and Electrical Physical Properties
These physical properties are typical for low-alloy structural steels and are not part of the JIS G3106 mandatory requirements. They provide useful data for design calculations involving thermal loads, heat transfer, and structural analysis. Values are approximate for room temperature unless otherwise noted.
| Property | Typical Value | Unit | Test Condition |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | at 20°C |
| Elastic modulus (E) | 205 | GPa | at 20°C |
| Shear modulus (G) | 79 | GPa | at 20°C |
| Poisson's ratio (ν) | 0.30 | - | at 20°C |
| Thermal expansion coefficient (α) | 12.0 | x10⁻⁶/K | 20–100°C |
| Thermal expansion coefficient (α) | 12.5 | x10⁻⁶/K | 20–200°C |
| Thermal conductivity (λ) | 53 | W/(m·K) | at 20°C |
| Thermal conductivity (λ) | 51 | W/(m·K) | at 100°C |
| Specific heat capacity | 460 | J/(kg·K) | at 20°C |
| Electrical resistivity (ρ_e) | 0.15 – 0.25 | µΩ·m | at 20°C |
JIS G3106 SM520B Steel Mechanical Properties
Mechanical properties are highly dependent on plate thickness. The yield strength decreases with increasing thickness, while tensile strength remains within the specified range. Elongation is measured on different test piece types according to JIS Z2241. Impact energy is guaranteed at 0°C for grade B with a minimum value of 27 J (V-notch, 2 mm striker). Bend test requires no cracks on the outer surface.
| Property | Value | Unit | Condition / Thickness |
|---|---|---|---|
| Yield strength (ReH) | ≥ 365 – actual standard min 355 | MPa | Thickness ≤ 16 mm |
| Yield strength (ReH) | ≥ 355 | MPa | Thickness > 16 mm & ≤ 40 mm |
| Yield strength (ReH) | ≥ 335 | MPa | Thickness > 40 mm & ≤ 75 mm |
| Yield strength (ReH) | ≥ 325 | MPa | Thickness > 75 mm & ≤ 100 mm |
| Yield strength (ReH) | ≥ 315 | MPa | Thickness > 100 mm & ≤ 160 mm |
| Yield strength (ReH) | ≥ 295 | MPa | Thickness > 160 mm & ≤ 200 mm |
| Tensile strength (Rm) | 520 – 640 | MPa | All thicknesses |
| Elongation (A) | ≥ 14 | % | Thickness ≤ 5 mm (No.5 test piece) |
| Elongation (A) | ≥ 19 | % | Thickness > 5 mm & ≤ 16 mm (No.5 test piece) |
| Elongation (A) | ≥ 15 | % | Thickness > 16 mm & ≤ 50 mm (No.1A test piece) |
| Elongation (A) | ≥ 21 | % | Thickness > 40 mm & ≤ 100 mm (No.1A test piece) |
| Elongation (A) | ≥ 23 | % | Thickness > 100 mm (No.1A test piece) |
| Bend test (180°) | D = 1.5t (t ≤ 16 mm) | - | No cracks allowed, bend inside radius |
| Bend test (180°) | D = 2.0t (16 < t ≤ 100 mm) | - | No cracks allowed |
| Impact energy (KV₂, Charpy V) | ≥ 27 | J | 0°C, transverse specimen |
JIS G3106 SM520B Steel Exact Equivalent Material Standards and Substitute Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| Japan | JIS G3106 | SM520B | Original standard; base material |
| Korea | KS D3515 | SM520B | Identical chemical and mechanical requirements |
| Taiwan | CNS 2947 | SM520B | Same designation, equivalent properties |
JIS G3106 SM520B Steel Application Introduction
SM520B is extensively used in heavy welded structures that demand good strength and impact toughness. It is particularly suitable for manufacturing SSAW (spiral submerged-arc welded) pipes for oil, gas, and water transmission pipelines, as well as structural hollow sections. The material can be processed by welding (all common methods), hot/cold forming, and machining.
Product Applications: SSAW steel pipes (spiral welded pipes for linepipe and structural use), Welded H-beams, box columns, and heavy structural sections, Large-diameter storage tanks and pressure vessels (with additional standard requirements), Piling pipes and structural tubulars, Flanges, connectors, and welded assemblies
Processed into products: Pipeline sections for oil and gas transmission (SSAW pipe strings), Bridge girders, trusses, and stiffeners, Column base plates and anchor frames, Offshore platform legs and bracing pipes, Crane booms and heavy equipment chassis, Wind turbine tower shell plates
Application industries: Construction and infrastructure (bridges, high-rise buildings, stadiums), Oil & gas (transmission pipelines, storage tanks), Shipbuilding and marine engineering (offshore platforms, jackets), Heavy machinery and equipment manufacturing, Wind energy (tower sections, foundations)
JIS G3106 SM520B Steel Similar / Substitute Materials
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | GB/T 1591-2018 | Q355B / Q355C | Yield ~355 MPa, tensile 470-630 MPa, impact 20°C / 0°C; lower tensile strength |
| China | GB/T 1591-2018 | Q420C | Yield ≥420 MPa, tensile 520-680 MPa, impact 0°C; higher yield, similar tensile |
| EU | EN 10025-2 | S355J0 / S355J2 | Yield 355 MPa, tensile 470-630 MPa, impact 0°C / -20°C; tensile range lower |
| EU | EN 10025-3 | S420N / NL | Yield 420 MPa, tensile 520-680 MPa, impact -20°C / -50°C; normalized |
| USA | ASTM A572/A572M | Grade 50 [345] | Yield 345 MPa, tensile 450 MPa; lower strength |
| USA | ASTM A572/A572M | Grade 55 [380] | Yield 380 MPa, tensile 485 MPa; still below SM520B requirements |
| International | ISO 630-3 | S420N | Yield 420 MPa, tensile 520-680 MPa; higher yield |
Notes:
SSAW pipe applications: When SM520B steel strip is used for spiral submerged-arc welded pipe, the base material's properties are inherited, but the pipe manufacturing process (forming, welding, and expansion) may alter some characteristics. Supplementary testing such as weld seam toughness and hydrostatic testing is typically carried out to the relevant pipe standard (e.g., API 5L, ISO 3183, or JIS G3457). For low-temperature service, impact requirements can be enhanced by selecting SM520C (0°C impact) or by specifying additional requirements per agreement. The carbon equivalent (CE) and weldability should be evaluated according to the actual thickness.
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