ASME SA709/SA709M Grade 50
ASME SA709/SA709M Grade 50: Carbon & Low-Alloy High-Strength Steel Coil for Bridges
Full material characterization of ASME SA709/SA709M Grade 50 hot-rolled coil, with chemical, mechanical, thermal and international equivalency data strictly per official standards.
Typical processing: hot rolling, controlled rolling, normalizing, or thermomechanical control process (TMCP). Quenching and tempering generally not required for Grade 50.
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ASME SA709/SA709M Grade 50 Introduction
ASME SA709/SA709M Grade 50 is a carbon and low-alloy high-strength structural steel primarily intended for use in bridge construction. It is identical to ASTM A709 Grade 50 and is covered by the ASME Boiler and Pressure Vessel Code, Section II, Part A. The steel offers a minimum yield strength of 50 ksi (345 MPa) and excellent weldability and formability in the as-rolled, normalized or thermomechanically processed condition. It is typically supplied as hot-rolled coil, plate or structural shapes.
- Guaranteed tensile and yield strength plus high ductility
- Can be specified with optional notch toughness (Charpy V-notch) requirements for fracture-critical applications
- Used in primary and secondary bridge members, building frames, and heavy machinery
ASME SA709/SA709M Grade 50 Chemical Composition
Chemical requirements per ASME SA709/SA709M Table 1 for Grade 50. Values apply to all thicknesses up to 4 in. (100 mm) unless otherwise noted.
- Manganese content varies with product thickness to optimize strength and weldability
- Copper minimum is applicable only when atmospheric corrosion resistance is specified (optional supplement)
- Silicon is limited to ensure good surface quality
| Element | Standard Value (max unless range indicated) | Remarks |
|---|---|---|
| Carbon (C) | 0.23% | Heat analysis, t ≤ 4 in. |
| Manganese (Mn) | 1.35% (t ≤ 1.5 in.) | Thickness 1.5–4 in.: 1.50% max |
| Phosphorus (P) | 0.04% | Maximum limit |
| Sulfur (S) | 0.05% | Maximum limit |
| Silicon (Si) | 0.40% | For non-killed or killed steel; 0.15–0.40% for semi-killed products by agreement |
| Copper (Cu) | 0.20% min (when specified) | Optional for improved atmospheric corrosion resistance; if not specified, residual Cu is unrestricted but typically ≤0.40% |
ASME SA709/SA709M Grade 50 Physical and Thermal Properties
Typical physical constants for carbon steel suitable for Grade 50. These are not mandatory in the standard but are representative for design calculations.
- Properties vary slightly with exact composition and processing.
- Values are applicable at room temperature unless a temperature range is indicated.
- Thermal conductivity, specific heat and electrical resistivity are for general comparison.
| Property | Typical Value | Unit | Condition / Remarks |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | Ambient temperature |
| Modulus of Elasticity (E) | 200 | GPa | Tension, room temperature |
| Shear Modulus (G) | 80 | GPa | Calculated from E and ν |
| Poisson's Ratio (ν) | 0.30 | – | In elastic range |
| Thermal Expansion Coefficient (α) | 11.7 | 10⁻⁶/K | 0–100°C average |
| Thermal Expansion Coefficient (α) | 12.5 | 10⁻⁶/K | 0–300°C average |
| Thermal Conductivity (λ) | 50 | W/m·K | At 20°C; decreases with temperature |
| Specific Heat Capacity | 450 | J/kg·K | Approximate, 20–100°C |
| Electrical Resistivity (ρ_e) | 0.15 | μΩ·m | At 20°C |
ASME SA709/SA709M Grade 50 Mechanical Properties
Mechanical test values required by ASME SA709/SA709M for Grade 50 plate and coil (t ≤ 4 in. [100 mm]).
- Elongation measured on 2 in. (50 mm) gauge length for plate and 8 in. (200 mm) for sheet/coil; given values are for 2 in. gauge.
- Charpy V-notch impact requirements are supplemental and must be specified on the order (e.g., 15 ft·lbf at 0°F or other temperature/energy levels).
- Bend test: 180° bend around a pin with diameter depending on thickness and specimen orientation; no cracks on outside of bent portion.
| Property | Standard Requirement | Unit | Test Condition / Remarks |
|---|---|---|---|
| Yield Strength (ReH) | ≥ 50 | ksi | t ≤ 4 in. (100 mm) |
| Yield Strength (ReH) | ≥ 345 | MPa | t ≤ 4 in. (100 mm) |
| Tensile Strength (Rm) | ≥ 65 | ksi | t ≤ 4 in. (100 mm) |
| Tensile Strength (Rm) | ≥ 450 | MPa | t ≤ 4 in. (100 mm) |
| Elongation (A) | ≥ 21 | % | 2 in. gauge; t ≤ 2 in. (50 mm) |
| Elongation (A) | ≥ 18 | % | 2 in. gauge; 2 in. < t ≤ 4 in. |
| Bend Test | 180° bend, no cracks | – | Pin diameter follows ASTM A6/A6M; e.g., 2.0t for longitudinal, 2.5t for transverse for t≤1 in. |
ASME SA709/SA709M Grade 50 Identical/Equivalent Material Standards and Designations
The table lists ASME SA709/SA709M Grade 50 together with identical and directly comparable international standards. These materials are considered chemically and mechanically interchangeable for most structural applications.
| Country/Region | Standard | Grade / Designation | Remarks |
|---|---|---|---|
| USA | ASTM A709/A709M | Grade 50 | Identical to ASME SA709 Grade 50 |
| USA | ASTM A572/A572M | Grade 50 | Similar strength, but without mandatory notch toughness; can be substituted with impact test supplement |
| Europe | EN 10025-2 | S355JR / S355J2 / S355K2 | Equivalent strength (355 MPa yield); J2/K2 provide guaranteed impact energy |
| China | GB/T 1591 | Q355B / Q355C / Q355D | Equivalent to Grade 50; B/C/D denote different impact temperatures |
| Japan | JIS G3106 | SM490A / SM490B / SM490C | 490 MPa tensile class; SM490B/C with Charpy requirements |
| India | IS 2062 | E350 | Grade E350 matches 345–355 MPa yield range |
ASME SA709/SA709M Grade 50 Application Introduction
ASME SA709/SA709M Grade 50 is specifically designed for welded, bolted or riveted construction, especially in bridges but also in buildings and other structures. Its guaranteed minimum toughness (when ordered with supplemental requirements) makes it suitable for dynamically loaded and low-temperature environments.
- Can be shaped into various structural components using conventional cold forming and machining.
- Excellent weldability with low-carbon equivalent, allowing all common welding processes (SMAW, SAW, GMAW, FCAW).
- Pre-heat and interpass temperature control generally not required for thicknesses below 2 in. (50 mm) under normal conditions.
Product Applications: Rolled coil for further processing into cut-to-length plate, Fabricated bridge girders, stringers and floor beams, Tubular structures and hollow sections (when converted via ERW or other methods), Bolted or welded built-up sections, Transmission towers and poles (structural shapes)
Processed into products: Bridge bearing plates and connection plates, Web and flange plates for plate girders, Cross frames and diaphragms, Stiffeners and bracing members, Heavy equipment frames and crane rails, Pile caps and sheet piling accessories
Application industries: Bridge and highway infrastructure, Building and civil engineering, Railway and transit structures, Offshore and marine (secondary structures), Heavy machinery and equipment manufacturing
ASME SA709/SA709M Grade 50 Similar Substitute Materials and Their Characteristics
The following grades offer comparable strength and may be used as alternatives when full compliance with ASME SA709 is not mandatory. Slight differences in chemistry, toughness or delivery condition should be considered during design.
| Country/Region | Standard | Grade / Designation | Remarks |
|---|---|---|---|
| USA | ASTM A992/A992M | Grade 50 | Wide-flange shapes; equivalent strength but limited to structural profiles; commonly used in building frames |
| USA | ASTM A588/A588M | Grade 50 | Weathering steel with improved atmospheric corrosion resistance (>4× carbon steel); similar strength level |
| Europe | EN 10025-3 | S355N / S355NL | Normalized fine-grain steel; superior toughness at low temperatures |
| China | GB/T 1591 | Q345C / R (old designation) | Older Chinese standard still in use; essentially the same as Q355C |
| International | ISO 630-2 | S355D | Structural steel with minimum yield 355 MPa and ductility similar to SA709 Grade 50 |
Notes:
All data are based on ASME SA709/SA709M-2019 (identical to ASTM A709/A709M-18).
- Optional supplementary requirements such as Charpy V-notch toughness (S5), through-thickness tensile testing (S10), or ultrasonic examination should be specified at the time of order when needed.
- For improved atmospheric corrosion resistance, consider the similar strength weathering grades A709 Grade 50W or HPS 50W.
- Coil products may have slightly different tolerances and mechanical properties from plates; refer to the relevant ASTM A6/A6M and ASTM A709 appendices.
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