Q345E Low-Temperature Seamless Steel Pipe per GB/T 8163
Q345E Low-Temperature Seamless Steel Pipe per GB/T 8163 - Complete Data & Applications
Detailed properties, chemical composition, mechanical and thermal data, international equivalents, and application guidance for Q345E low-temperature seamless steel pipe according to GB/T 8163-2018.
Hot rolling, cold drawing, normalizing, quenching and tempering (as per order requirements)
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Q345E Low-Temperature Seamless Steel Pipe per GB/T 8163 Introduction
Q345E is a Chinese standard low-alloy high-strength structural steel grade specifically designed for low-temperature fluid transport seamless pipes under GB/T 8163-2018. It offers excellent strength, good toughness at temperatures down to -40°C, and reliable weldability, making it suitable for critical petroleum, natural gas, and chemical pipelines operating in cold environments.
Key features:
- Minimum yield strength of 345 MPa (for wall thickness ≤16 mm)
- Guaranteed Charpy V-notch impact energy ≥40 J at -40°C
- Low phosphorus and sulfur content for enhanced low-temperature toughness and cleanliness
- Can be supplied in hot-rolled or cold-drawn conditions with normalizing or other heat treatments
- Available in various diameters and wall thicknesses as seamless round tubes
This material combines economy with reliable low-temperature performance, and is widely adopted in China's infrastructure and industrial pipeline systems.
Q345E Low-Temperature Seamless Steel Pipe per GB/T 8163 Chemical Composition
Chemical composition of Q345E for seamless pipe according to GB/T 8163-2018 and GB/T 1591 (basis for Q355E). The phosphorus and sulfur limits are tightened for low-temperature service: P ≤ 0.020%, S ≤ 0.010%. Grain-refining elements such as Al, Nb, V, Ti are specified to ensure fine grain size and toughness.
| Element | Standard Value (max unless range) | Remarks |
|---|---|---|
| C (Carbon) | 0.18 | Heat analysis |
| Si (Silicon) | 0.50 | Heat analysis |
| Mn (Manganese) | 1.70 | Heat analysis |
| P (Phosphorus) | 0.020 | Per GB/T 8163 low-temperature requirement |
| S (Sulfur) | 0.010 | Per GB/T 8163 low-temperature requirement |
| Nb (Niobium) | 0.07 | Can be partly replaced by V and/or Ti |
| V (Vanadium) | 0.15 | Combined with Nb and Ti |
| Ti (Titanium) | 0.20 | Single or combinated |
| Cr (Chromium) | 0.30 | Residual content; intentional addition not typical |
| Ni (Nickel) | 0.50 | Residual content |
| Cu (Copper) | 0.30 | Residual content |
| Mo (Molybdenum) | 0.10 | Residual content |
| N (Nitrogen) | 0.015 | Heat analysis; higher N may be specified if sufficient grain-refining elements present |
| Al (Aluminium, acid-soluble) | ≥0.015 | Minimum required for grain refinement |
Q345E Low-Temperature Seamless Steel Pipe per GB/T 8163 Thermal and Electrical Physical Properties
These physical properties are typical for low-alloy structural steels similar to Q345E and are provided for design reference. Actual values may slightly vary depending on exact composition and heat treatment. Data are taken from general material handbooks; they are not part of the GB/T 8163 specification.
| Property | Typical Value | Unit | Test Conditions / Remarks |
|---|---|---|---|
| Density, ρ | 7.85 | g/cm³ | At 20°C |
| Modulus of elasticity, E | 210 | GPa | At room temperature |
| Shear modulus, G | 80 | GPa | At room temperature |
| Poisson's ratio, ν | 0.3 | – | At room temperature |
| Thermal expansion coefficient, α | 10.8 | 10−⁰/K | 20–100°C |
| Thermal expansion coefficient, α | 11.3 | 10−⁰/K | 20–200°C |
| Thermal expansion coefficient, α | 12.0 | 10−⁰/K | 20–300°C |
| Thermal conductivity, λ | 53 | W/(m·K) | At 20°C |
| Thermal conductivity, λ | 50 | W/(m·K) | At 100°C |
| Thermal conductivity, λ | 47 | W/(m·K) | At 200°C |
| Specific heat capacity, c | 461 | J/(kg·K) | At 20°C |
| Electrical resistivity, ρe | 0.17 | μΩ·m | At 20°C |
Q345E Low-Temperature Seamless Steel Pipe per GB/T 8163 Mechanical Properties
Mechanical properties required by GB/T 8163-2018 for Q345E seamless pipes. Tensile testing is performed at room temperature on longitudinal test pieces. Impact test temperature is -40°C. Values for yield strength depend on wall thickness. Elongation is measured on a gauge length of 5.65√S0. Bend test uses 180° bending around a former with diameter 3a (a = wall thickness). All values are minimum unless a range is given.
| Property | Standard Requirement | Unit | Test Conditions |
|---|---|---|---|
| Tensile strength, Rm | 490 – 630 | MPa | Room temperature, longitudinal |
| Yield strength, ReH | ≥345 | MPa | Wall thickness ≤16 mm, room temp., longitudinal |
| Yield strength, ReH | ≥325 | MPa | Wall thickness 16 mm < t ≤ 30 mm |
| Yield strength, ReH | ≥295 | MPa | Wall thickness >30 mm |
| Elongation after fracture, A | ≥20 (longitudinal) | % | Gauge length 5.65√S0, room temp. |
| Elongation after fracture, A | ≥18 (transverse, if specified) | % | Gauge length 5.65√S0, room temp. |
| Charpy V-notch impact energy, KV2 | ≥40 (full-size specimen) | J | At -40°C, 10×10×55 mm specimen |
| Bend test (180°) | No cracks or defects | – | Form diameter = 3a (a = wall thickness), room temp. |
Q345E Low-Temperature Seamless Steel Pipe per GB/T 8163 Full Equivalent Material Standards and Replaceable Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| Europe | EN 10216-3 | P355NL1 (1.0566) | Seamless steel tubes for pressure purposes – low temperature; matching yield strength and -40°C impact test requirement. |
| Europe | EN 10297-1 | E355NL (1.0580) | Seamless circular steel tubes for mechanical and general engineering purposes – low temperature; comparable mechanical and toughness properties. |
| International | ISO 3183 | L360NE | Petroleum and natural gas industries – steel pipe for pipeline transportation systems; if impact testing at -40°C is agreed, it can replace Q345E. |
Q345E Low-Temperature Seamless Steel Pipe per GB/T 8163 Application Introduction
Q345E seamless pipe is designed for low-temperature fluid transportation, offering a reliable combination of strength, toughness, and weldability. Typical applications and products include:
Product Applications: Low-temperature fluid pipelines (oil, gas, chemicals), Heat exchangers and condenser tubes for low-temp service, U-bend tubes for cryogenic applications, Pressure vessels and storage tanks for liquefied gases, Refrigerant piping in industrial refrigeration systems, Process pipework in LNG regasification terminals
Processed into products: Seamless pipe spools and line pipes, Elbows, tees, reducers, and flanges (when fabricated from pipe), Tube sheets and headers (machined from pipe sections), Compressor and pump connections for cold fluids, Instrumentation tubing and impulse lines
Application industries: Oil and gas extraction and transmission, Petrochemical and chemical processing, Liquefied Natural Gas (LNG) and Liquefied Petroleum Gas (LPG) facilities, Refrigeration and cryogenic engineering, Offshore and marine structures (low temperature service), Power generation (cooling water, auxiliary piping in cold areas)
Q345E Low-Temperature Seamless Steel Pipe per GB/T 8163 Similar / Alternative Material Recommendations
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | GB/T 6479-2013 | Q345E | Seamless steel tubes for high-pressure chemical fertilizer equipment; similar chemical and mechanical properties, also low-temperature toughness guaranteed. |
| Europe | EN 10025-3 | S355NL | Hot rolled structural steel; when formed into pipes, can provide similar strength and low-temperature toughness, but certification for pipe form required. |
| USA | ASTM A572/A572M | Grade 50 (with -40°C impact supplement) | High-strength low-alloy structural steel; impact test at low temperature must be agreed separately; provides equivalent yield and tensile strength. |
| Japan | JIS G3455 | STS410 (low-temp. version by agreement) | Carbon steel tubes for high pressure service; not directly equivalent but can be modified to low-temp. requirements, similar strength level. |
Notes:
- Q345E seamless pipes are supplied according to GB/T 8163-2018; surface quality, dimensions, and hydrostatic testing comply with the standard.
- For low-temperature service, Charpy impact tests are mandatory; individual impact value shall not be less than 70% of specified average (i.e., min 28 J).
- Ultrasonic or other non-destructive testing can be ordered as a supplementary requirement.
- Welding of Q345E requires appropriate low-hydrogen procedures and may need preheat/interpass temperature control depending on thickness.
- The material is not intended for high-temperature or sour service unless specifically qualified by additional standards.
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