GB/T 8163 20# Seamless Steel Pipe for Liquid Service
GB/T 8163 20# Fluid Seamless Pipe – Properties, Equivalents & Applications
Explore detailed material data for 20# carbon steel seamless pipe per GB/T 8163: chemical composition, mechanical properties, physical constants, international equivalents, and typical uses in fluid transport systems.
Hot rolling, hot expanding, cold drawing, cold rolling; subsequent normalization +/- tempering is common. Fabricable by cutting, threading, cold bending, welding (with appropriate consumables).
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GB/T 8163 20# Seamless Steel Pipe for Liquid Service Introduction
20# is a premium carbon structural steel specified in GB/T 8163 for seamless pipes used in fluid transmission. It delivers a reliable balance of strength, ductility, and weldability, making it a workhorse material for low- and medium-pressure pipelines. Typical delivery condition is hot-rolled or cold-drawn followed by normalizing, ensuring a fine-grained ferrite-pearlite microstructure. The grade is widely utilized to convey water, oil, gas, and other fluids at temperatures generally below 350 °C. Its well-controlled composition (C 0.17–0.23%, Mn 0.35–0.65%) yields tensile strength ≥410 MPa and yield strength ≥245 MPa for wall thickness ≤16 mm. The steel also exhibits good machinability and can be cold bent or formed.
GB/T 8163 20# Seamless Steel Pipe for Liquid Service Chemical Composition
Limits as per GB/T 8163-2018 for grade 20. The steel is a plain carbon steel with restricted phosphorus and sulfur to ensure ductility and weldability. Residual elements such as chromium, nickel, and copper are controlled to avoid detrimental effects on hot workability.
| Element | Standard Value (%) | Remarks |
|---|---|---|
| Carbon (C) | 0.17 – 0.23 | Key strength contributor |
| Silicon (Si) | 0.17 – 0.37 | Deoxidizer |
| Manganese (Mn) | 0.35 – 0.65 | Counters sulfur hot shortness |
| Phosphorus (P) | ≤ 0.035 | Maximum limit |
| Sulfur (S) | ≤ 0.035 | Maximum limit |
| Chromium (Cr) | ≤ 0.25 | Residual element |
| Nickel (Ni) | ≤ 0.30 | Residual element |
| Copper (Cu) | ≤ 0.25 | Residual element |
GB/T 8163 20# Seamless Steel Pipe for Liquid Service Thermal and Electrical Physical Properties
Typical ambient-temperature values for grade 20 carbon steel in normalized condition. These data are not mandatory in GB/T 8163; they are provided for design calculations. Thermal expansion is given for the temperature range 20–100 °C.
| Property | Typical Value | Unit | Test Condition / Remarks |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | At 20 °C |
| Modulus of Elasticity (E) | 207 | GPa | At 20 °C |
| Shear Modulus (G) | 80 | GPa | Calculated from E and ν |
| Poisson's Ratio (ν) | 0.30 | – | Elastic range |
| Thermal Expansion Coefficient (α) | 11.8 × 10⁻⁶ | K⁻¹ | 20–100 °C |
| Thermal Conductivity (λ) | 50.7 | W/(m·K) | At 20 °C |
| Specific Heat Capacity | 486 | J/(kg·K) | At 20 °C |
| Electrical Resistivity (ρe) | 0.20 | Ω·mm²/m | At 20 °C |
GB/T 8163 20# Seamless Steel Pipe for Liquid Service Mechanical Properties
Minimum requirements for room-temperature tensile testing according to GB/T 8163-2018. Values apply to the normalized condition. Elongation is reported for longitudinal strip specimens; transverse elongation is 20% min when required.
| Property | Standard Requirement | Unit | Test Condition |
|---|---|---|---|
| Tensile Strength (Rm) | 410 – 550 | MPa | Room temperature, longitudinal test piece |
| Yield Strength (ReH) | ≥ 245 | MPa | Wall thickness ≤ 16 mm |
| Yield Strength (ReH) | ≥ 235 | MPa | Wall thickness > 16 mm to 30 mm |
| Yield Strength (ReH) | ≥ 225 | MPa | Wall thickness > 30 mm |
| Elongation (A) | ≥ 25 | % | Longitudinal, gauge length 5.65√S₀ |
| Elongation (A) | ≥ 20 | % | Transverse, if required |
GB/T 8163 20# Seamless Steel Pipe for Liquid Service Fully Equivalent Material Standards and Substitutable Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | GB/T 8163 | 20# | Original base standard and grade |
| USA | ASTM A106 | Grade B | Seamless carbon steel pipe for high-temperature service; similar chemistry and strength |
| Japan | JIS G3456 | STPT370 | Carbon steel pipes for high temperature service |
| Europe | EN 10216-1 | P235GH | Seamless steel tubes for pressure purposes – non-alloy steel with specified elevated temperature properties |
| International | ISO 9329-1 | PH26 | Seamless steel tubes for pressure purposes – technical delivery conditions |
GB/T 8163 20# Seamless Steel Pipe for Liquid Service Application Introduction
20# seamless pipes under GB/T 8163 are engineered for low- and medium-pressure fluid conveyance in a variety of industries. They can be easily cut, threaded, bent, and welded using standard techniques. The material is not recommended for highly corrosive or cryogenic services without additional testing.
Product Applications: Water mains and distribution piping, Steam and condensate return lines, Natural gas distribution pipelines, Oil transmission pipelines (low pressure), Compressed air pipelines, Fire sprinkler mains
Processed into products: Tubular pipes and nipples, Pipe bends (hot or cold formed), Reducers, tees, and elbows (fabricated from pipe), Flanged connections (welded-on flanges), Threaded pipe couplings, Structural members in modular piping supports
Application industries: Building and construction (water supply, HVAC), Petrochemical (oil & gas gathering lines, process piping), Power generation (cooling water, steam condensate), Chemical processing (mild chemical transfer), Fire protection systems, Hydraulic and pneumatic systems
GB/T 8163 20# Seamless Steel Pipe for Liquid Service Similar/Alternative Materials Recommendation
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | GB/T 699 | 20 | Quality carbon structural steel (bar) – same chemical core but not pipe-specific |
| China | GB/T 8162 | 20# | Seamless pipe for structural purposes – similar composition, lower emphasis on pressure tightness |
| USA | ASTM A53 | Grade B | Welded and seamless pipe – slightly wider composition range; often used for general fluid transport |
| USA | API 5L | Grade B | Line pipe for oil and gas transportation – comparable strength, different quality requirements |
| Europe | EN 10210-1 | S235JRH | Hot finished structural hollow sections – similar strength, not primarily for pressure fluids |
Notes:
GB/T 8163-2018 also covers impact test requirements when agreed (KV₂ ≥ 27 J at 20 °C for 20#). Hydrostatic or non-destructive electric testing is mandatory for pressure containment verification. When the pipe is intended for welding, the carbon equivalent is typically ≤ 0.44% to ensure good weldability without preheating for thin walls. Always confirm with supplier test certificates regarding actual delivery condition and supplementary testing.
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