DIN 17175 ST45-8 Seamless Boiler Tube
ST45-8 Boiler Seamless Steel Pipe – DIN 17175 Carbon Steel for High-Temperature Service
Comprehensive material data sheet for ST45-8 seamless carbon steel tube conforming to DIN 17175, used in boilers, superheaters, and pressure piping.
Hot-rolled or cold-drawn; normalizing (+N) required
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DIN 17175 ST45-8 Seamless Boiler Tube Introduction
ST45-8 is a seamless unalloyed carbon steel tube grade specified in DIN 17175, designed for elevated-temperature service in boilers, pressure vessels, and piping systems. It is supplied in the normalized (+N) condition, ensuring uniform structure and reliable mechanical properties. The steel offers good weldability, moderate strength, and adequate oxidation resistance up to approximately 480°C. Key features:
- Carbon-manganese steel with controlled silicon for heat resistance
- Minimum yield strength of 255 MPa for wall thickness ≤ 16 mm
- Suitable for power plant boiler tubes, superheater, and economizer applications
- Delivered as hot-finished or cold-drawn seamless tube, usually normalized
Although superseded by EN 10216-2 grades, ST45-8 is still widely referenced for replacement and specific engineering requirements.
DIN 17175 ST45-8 Seamless Boiler Tube Chemical Composition
Ladle analysis limits according to DIN 17175. The steel is unalloyed carbon steel with controlled silicon for improved oxidation resistance at elevated temperatures. Values are maximum unless a range is indicated.
| Element | Mass Fraction (%) | Notes |
|---|---|---|
| Carbon (C) | 0.21 max | |
| Silicon (Si) | 0.10 – 0.35 | |
| Manganese (Mn) | 0.40 – 1.20 | |
| Phosphorus (P) | 0.040 max | |
| Sulfur (S) | 0.040 max |
DIN 17175 ST45-8 Seamless Boiler Tube Thermal and Electrical Physical Properties
These are typical values for unalloyed carbon steel in the normalized condition and are applicable to ST45-8. Actual values may vary slightly depending on heat treatment and composition within the standard range.
| Property | Value | Unit | Test Condition |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | 20 °C |
| Elastic modulus (E) | 210 | GPa | 20 °C |
| Shear modulus (G) | 81 | GPa | 20 °C |
| Poisson's ratio (ν) | 0.3 | – | 20 °C |
| Thermal expansion coefficient (α) | 12.5 | 10⁻⁶/K | 20 – 100 °C |
| Thermal expansion coefficient (α) | 13.1 | 10⁻⁶/K | 20 – 200 °C |
| Thermal expansion coefficient (α) | 13.9 | 10⁻⁶/K | 20 – 400 °C |
| Thermal conductivity (λ) | 51 | W/(m·K) | 20 °C |
| Thermal conductivity (λ) | 50 | W/(m·K) | 100 °C |
| Thermal conductivity (λ) | 46 | W/(m·K) | 300 °C |
| Specific heat capacity (cp) | 460 | J/(kg·K) | 20 °C |
| Electrical resistivity (ρe) | 0.20 | µΩ·m | 20 °C |
DIN 17175 ST45-8 Seamless Boiler Tube Mechanical Properties
Room-temperature tensile properties as specified in DIN 17175 for ST45-8 tubes. The yield strength decreases with increasing wall thickness. Elongation values are minimum requirements. Bend test and impact properties are not mandatory unless separately agreed.
| Property | Value | Unit | Test Condition |
|---|---|---|---|
| Yield strength (ReH) | ≥ 255 | MPa | Wall thickness ≤ 16 mm |
| Yield strength (ReH) | ≥ 245 | MPa | 16 < wall thickness ≤ 40 mm |
| Yield strength (ReH) | ≥ 235 | MPa | 40 < wall thickness ≤ 60 mm |
| Tensile strength (Rm) | 440 – 550 | MPa | Room temperature |
| Elongation (A), longitudinal | ≥ 22 | % | Room temperature |
| Elongation (A), transverse | ≥ 20 | % | Room temperature |
DIN 17175 ST45-8 Seamless Boiler Tube Directly Equivalent Standards and Substitute Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| Germany | DIN 17175 | ST45-8 | Original specification |
| European Union | EN 10216-2 | P265GH | Current European equivalent for boiler tubes; tensile strength range 410–570 MPa, yield ≥ 265 MPa |
| USA | ASTM A106/A106M | Grade B | Seamless carbon pipe for high temperature; tensile ≥ 415 MPa, yield ≥ 240 MPa |
| Japan | JIS G3456 | STPT410 | Carbon steel pipe for high-temperature service; tensile ≥ 410 MPa, yield ≥ 245 MPa |
DIN 17175 ST45-8 Seamless Boiler Tube Application Introduction
ST45-8 is a well-established boiler tube grade used primarily for service temperatures up to 480°C. Its normalized condition provides a uniform ferritic-pearlitic microstructure that ensures reliable high-temperature strength and long-term creep resistance. The grade is widely accepted for pressure parts in thermal power stations and industrial boilers.Key considerations:
- Excellent for welded boiler structures when using appropriate filler metals (e.g., rod or wire with Mn content matching base metal)
- Not intended for sour service (H₂S) or low-temperature applications without impact test qualification
- Usually supplied in fixed lengths or coils, with surface protection against atmospheric corrosion
Product Applications: Boiler tubes and pipes, Superheater and reheater tubes, Economizer tubes, Steam and water separation pipelines, Heat exchanger tubes for non-corrosive media
Processed into products: Water wall panels (membrane walls), Superheater coil assemblies, Reheater pendants, Economizer inlet/outlet headers, Steam drum connecting pipes, Downcomer and riser tubes in natural circulation boilers
Application industries: Power Generation (fossil fuel and biomass boilers), Petrochemical and refining (heat exchangers, process piping), Industrial Boiler Manufacturing, Pressure Vessel and Piping Fabrication, Cogeneration and Combined Heat & Power Plants
DIN 17175 ST45-8 Seamless Boiler Tube Similar/Comparable Alternative Materials
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| European Union | EN 10216-2 | P235GH | Lower strength carbon steel boiler tube (Rm 360–500 MPa); may be suitable for less demanding service |
| China | GB/T 5310 | 20G | Similar carbon steel for high-pressure boiler tubes; tensile 410–550 MPa, yield ≥ 245 MPa |
| USA | ASTM A179/A179M | Grade A | Cold-drawn low-carbon steel tube for heat exchangers; lower strength, only for low-temperature use |
| Russia | GOST 1050-88 | 20 | Carbon structural steel; comparable base composition but different product form |
Notes:
DIN 17175 has been withdrawn and integrated into European standards. ST45-8 is now commonly substituted by EN 10216-2 P265GH for new construction. However, for repair and replacement of existing boiler installations designed to the original DIN standard, ST45-8 tubes may still be ordered under dual certification. Hydrostatic and non-destructive testing requirements (e.g., eddy current or ultrasonic inspection) must be agreed upon at the time of ordering.
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