Q345E SHS/RHS Pipe to GB/T 3094
Q345E SHS/RHS Pipe to GB/T 3094: Low-Temperature Toughness Structural Hollow Sections
Data sheet for Q345E square and rectangular hollow sections under GB/T 3094, featuring minimum yield strength of 345 MPa and superior low-temperature impact toughness at -40°C.
Cold drawing, welding, machining, hot-dip galvanizing
- Phone : +8618037372205
- Email : [email protected]
- WhatsApp: Contact via Whtsapp
- WeChat: +8618037372205
Q345E SHS/RHS Pipe to GB/T 3094 Introduction
Q345E SHS/RHS pipe manufactured according to GB/T 3094 is a cold-drawn special-shaped steel pipe made from low-alloy high-strength structural steel Q345E. Q345E is a quality grade in the Q345 series, distinguished by its guaranteed impact energy absorption of not less than 34J at a testing temperature of -40°C, making it suitable for critical applications in severe cold regions. The cold-drawing process provides high dimensional accuracy, smooth surface finish, and enhanced mechanical properties. This hollow section offers an excellent combination of high strength, good weldability, and superior low-temperature toughness, making it ideal for structural frameworks, heavy machinery, and infrastructure projects operating in frigid environments.
Q345E SHS/RHS Pipe to GB/T 3094 Chemical Composition
The chemical composition of Q345E is strictly controlled to enhance low-temperature impact toughness and weldability. The steel is fully killed with a fine-grained structure. Maximum carbon equivalent (CEV) is often limited to 0.45% to ensure good field weldability. Tight controls on phosphorus and sulfur significantly improve ductility and toughness.
| Element | Standard Value (max %) | Remarks |
|---|---|---|
| Carbon (C) | ≤ 0.18 | For sections ≤ 16 mm |
| Silicon (Si) | ≤ 0.50 | Deoxidation element |
| Manganese (Mn) | ≤ 1.70 | Strength and toughness enhancer |
| Phosphorus (P) | ≤ 0.025 | Strictly controlled for low-temperature service |
| Sulfur (S) | ≤ 0.020 | Strictly controlled for ductility |
| Niobium (Nb) | ≤ 0.07 | Grain refiner |
| Vanadium (V) | ≤ 0.15 | Grain refiner and precipitation hardener |
| Titanium (Ti) | ≤ 0.20 | Grain refiner |
| Chromium (Cr) | ≤ 0.30 | Residual element |
| Nickel (Ni) | ≤ 0.50 | Residual element; advantageous for toughness |
| Copper (Cu) | ≤ 0.30 | Residual element |
| Nitrogen (N) | ≤ 0.012 | Must be bound by Al, V, Nb, Ti |
| Aluminum (Al) | ≥ 0.015 (acid-soluble) | Required for fine-grain practice |
Q345E SHS/RHS Pipe to GB/T 3094 Thermal and Electrical Physical Properties
These physical properties are typical for Q345 low-alloy steel at room temperature, unless otherwise specified. They are essential for design calculations involving thermal loading, welding heat input, and structural stiffness. Actual values may vary slightly depending on the specific manufacturing process and microstructure. Electrical resistivity is provided for applications where conductivity matters, such as in electrical enclosures or earthing studies.
| Property | Standard Required Value | Unit | Test Condition |
|---|---|---|---|
| Density (ρ) | ~7.85 | g/cm³ | At 20°C |
| Modulus of Elasticity (E) | ~206 | GPa | At 20°C |
| Shear Modulus (G) | ~79.4 | GPa | At 20°C |
| Poisson's Ratio (ν) | ~0.3 | — | At 20°C |
| Linear Thermal Expansion Coefficient (α) | ~12.0 | 10⁻⁶/K | Between 20°C and 100°C |
| Linear Thermal Expansion Coefficient (α) | ~13.5 | 10⁻⁶/K | Between 20°C and 300°C |
| Thermal Conductivity (λ) | ~52.0 | W/(m·K) | At 20°C |
| Thermal Conductivity (λ) | ~47.5 | W/(m·K) | At 200°C |
| Specific Heat Capacity (c) | ~480 | J/(kg·K) | At 20°C |
| Electrical Resistivity (ρ_e) | ~0.22 | Ω·mm²/m | At 20°C |
Q345E SHS/RHS Pipe to GB/T 3094 Mechanical Properties
These properties represent the minimum requirements for the base material Q345E before cold-drawing, applicable to the finished pipe wall thickness. The cold-drawing process increases tensile and yield strength but may reduce elongation. Values are based on the base steel standard GB/T 1591 and processing standard GB/T 3094. Where multiple wall thickness ranges exist, corresponding values are shown.
| Property | Standard Required Value | Unit | Test Condition / Wall Thickness (t) |
|---|---|---|---|
| Minimum Upper Yield Strength (ReH) | ≥ 345 | MPa | t ≤ 16 mm |
| Minimum Upper Yield Strength (ReH) | ≥ 335 | MPa | 16 mm < t ≤ 40 mm |
| Minimum Upper Yield Strength (ReH) | ≥ 325 | MPa | 40 mm < t ≤ 63 mm |
| Tensile Strength (Rm) | 470 - 630 | MPa | t ≤ 100 mm |
| Minimum Percentage Elongation After Fracture (A) | ≥ 21 | % | Longitudinal; t ≤ 40 mm |
| Minimum Percentage Elongation After Fracture (A) | ≥ 20 | % | Longitudinal; 40 mm < t ≤ 63 mm |
| Impact Energy (KV2) | ≥ 34 | J | Longitudinal; -40°C (Quality Grade E) |
| Bend Test (180° Cold Bending) | d = 3a (for t ≤ 16 mm) | — | Mandrel diameter (d), specimen thickness (a). No cracks. |
| Bend Test (180° Cold Bending) | d = 4a (for t > 16 mm) | — | Mandrel diameter (d), specimen thickness (a). No cracks. |
Q345E SHS/RHS Pipe to GB/T 3094 Fully Equivalent Material Standards and Substitutable Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | GB/T 1591-2018 | Q345E | Base standard for hot-rolled steel; chemical and mechanical match for -40°C service. |
| China | GB/T 8162-2018 | Q345E | Seamless steel tubes for structural purposes, equivalent to the base steel for hollow sections. |
| International | ISO 630-2:2021 | Fe510D | D-quality grade covers -20°C; E-grade equivalent from ISO 630-6 for fine-grain steels may be required for exact low-temp match. |
| Europe | EN 10025-2:2019 | S355J2+N | J2 grade tests at -20°C. For full -40°C equivalence, S355K2 or S355ML/NL to EN 10025-3/4 is recommended. |
| Europe | EN 10219-1:2006 | S355J2H | Cold-formed welded structural hollow section. J2H grade is -20°C test; check with manufacturer for -40°C options. |
| USA | ASTM A500/A500M-21 | Grade C | Standard for cold-formed structural tubing. No specific low-temperature grade; supplemental Charpy testing must be specified to match Q345E at -40°C. |
Q345E SHS/RHS Pipe to GB/T 3094 Application Introduction
Q345E SHS/RHS pipes are engineered for demanding structural applications where high load-bearing capacity, excellent weldability, and guaranteed toughness at sub-zero temperatures are critical. The square and rectangular profiles provide flat surfaces for easy joining, high torsional resistance, and modern architectural aesthetics. Their superior low-temperature toughness ensures structural integrity even under dynamic loads in frigid climates, such as those found in northern China, Russia, and Scandinavia.
Product Applications: Prefabricated steel structural frameworks for cold storage and polar research stations, Heavy-duty truck chassis and trailer frames, Telecommunication and power transmission towers, Highway guardrails, sign gantries, and lighting poles, Modular bridge structures and pedestrian overpasses, Conveyor gantries and material handling systems in mines
Processed into products: Load-bearing columns, beams, and trusses in buildings, Boom and arm sections for excavators and telescopic cranes, Spreader bars and lifting fixtures for cranes, Chassis rails, cross-members, and roll cages for off-road vehicles, Tower body segments and flanges for wind turbines, Rectangular headers and manifolds for hydraulic systems, Solar tracker torque tubes and support frames
Application industries: Heavy Infrastructure & Bridge Construction, Multi-story and Industrial Building Frames, Construction and Mining Machinery (e.g., excavator booms, crane lattice structures), Shipbuilding and Offshore Platforms (for secondary structural members), Renewable Energy (wind turbine towers, solar tracking structures), Agricultural and Forestry Equipment, Railway and Automotive Structural Components
Q345E SHS/RHS Pipe to GB/T 3094 Closely Similar or Substitute Material Recommendations
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | GB/T 3094-2012 | Q345D | SHS/RHS pipe with identical strength but a higher minimum service temperature of -20°C compared to -40°C for E-grade. A cost-effective alternative for less severe cold climates. |
| China | GB/T 1591-2018 | Q355E | Updated standard with fine-tuned chemistry (e.g., lower Mn, narrower microalloy ranges) and guaranteed -40°C toughness, fully replacing Q345E in new GB/T 1591 design. |
| Europe | EN 10219-1:2006 | S420MH | Higher minimum yield strength (420 MPa) thermomechanically rolled hollow section with good cold formability, suitable for weight-reduced designs when higher strength is needed. |
| Japan | JIS G 3466:2015 | STKR490 | General structural carbon steel square tube, approx. 490 MPa tensile strength. No low-temperature guarantee, but widely used for general structures. Needs special inquiry for low-temp Charpy data. |
| Russia | GOST 30245-2012 | C355 | Bent closed welded square and rectangular sections with minimum 355 MPa yield strength, chemically comparable to S355, suitable for structural frameworks. |
Notes:
Welding: Preheating to 50-100°C is recommended for thick-walled sections (>30mm) and in humid conditions. Standard welding consumables matching ER50-6 (GMAW) or E5015/E5016 (SMAW) are suitable. Galvanizing: Q345E can be hot-dip galvanized, but its silicon content (~0.20-0.40%) should be controlled to avoid excessive zinc-iron intermetallic growth. Ordering Note: When ordering to GB/T 3094, always specify the corner profile (e.g., R=2t or R=3t) and the necessary low-temperature Charpy test certification at -40°C to ensure full Q345E properties. Corrosion Protection: For severe environments, consider duplex coatings or weathering steel alternatives like Q355NH.
- Share
