The Chemical Composition, Mechanical Properties, and Applications of Common 20G Seamless High-Pressure Boiler Steel Pipes

20G seamless high-pressure boiler steel pipes are high-quality steel pipes designed specifically for high-pressure environments. Their chemical composition strictly adheres to the GB/T5310 standard, primarily containing carbon (0.17%-0.24%), silicon (0.17%-0.37%), and manganese (0.35%-0.65%). Phosphorus and sulfur contents are controlled to ≤0.030% to ensure material purity. These pipes exhibit excellent mechanical properties, including a tensile strength of 410-550 MPa, a yield strength of≥245 MPa, an elongation of≥24% longitudinally and ≥22% transversely, and excellent low-temperature toughness. Heat treatment processes such as normalizing (880-940°C) further refine the grain size and enhance performance. 20G seamless steel pipe is widely used in high-pressure boilers (such as superheaters and economizers), petrochemical equipment, nuclear power systems, and machinery manufacturing. Common specifications range from 57×3.5mm to 426×12mm, and custom processing is available. Its high surface quality and strong corrosion resistance make it an ideal material for critical industrial equipment. When selecting a pipe, parameters should be determined based on the GB/T5310 standard and actual operating conditions.

First, the chemical composition of 20G seamless high-pressure boiler steel pipes.

The chemical composition of 20G seamless high-pressure boiler steel pipes strictly complies with the GB/T5310 standard. The main components include:

Carbon: 0.17%-0.24% (slightly different references vary, ranging from 0.17% to 0.23%)

Silicon: 0.17%-0.37%

Manganese: 0.35%-0.65%

Phosphorus and Sulfur: ≤0.030% each (some references have stricter requirements, requiring P ≤0.025% and S ≤0.020%)

Chromium, Nickel, and Copper: ≤0.25% each

Molybdenum: ≤0.15% or ≤0.08%

Vanadium: ≤0.08% or ≤0.15%

Total residual elements: ≤0.70%

Second, the mechanical properties of 20G seamless high-pressure boiler steel pipes.

20G seamless steel pipes possess excellent mechanical properties, suitable for high-pressure environments:

Tensile strength: 410-550 MPa

Yield strength: ≥245 MPa

Elongation: ≥24% longitudinally, ≥22% transversely

Impact toughness: ≥40J longitudinally, ≥27J transversely

Hardness: ≤197 HB or ≤217 HBW

Low-temperature toughness: Maintains good performance even at low temperatures.

Third, the heat treatment process for 20G seamless high-pressure boiler steel pipes.

Heat treatment is a key step in improving the performance of 20G seamless steel pipes. The main processes include:

- Normalizing: Temperature range of 880-940°C, used to refine grain size, improve uniformity, and enhance mechanical properties (adjustable based on production conditions; for example, normalizing can be substituted for a final rolling temperature ≥900°C).

Other auxiliary processes:

- Tempering: 680-750°C, to eliminate quench brittleness and improve toughness (applicable to other alloy steels). - Quenching and Tempering: Tempering is required for special requirements, such as wall thicknesses ≥40mm.

Fourth, Applications of 20G Seamless High-Pressure Boiler Steel Pipes.

20G seamless steel pipes are widely used in the following equipment:

- High-Pressure Boilers: Used for heating surface pipes, economizers, superheaters, reheaters, etc., withstanding high temperatures and high pressures (≤650°C, ≥9.8MPa).

- Petrochemical Industry: Applications such as reactors, heat exchangers, and pipelines, suitable for corrosive media environments.

- Nuclear Power and Energy: Applications such as nuclear reactor cooling systems and offshore platform piping, which require radiation and corrosion resistance.

- Machinery and Automotive: Applications such as bearing sleeves and engine exhaust pipes.

Fifth, Common Specifications of 20G Seamless High-Pressure Boiler Steel Pipes.

20G seamless steel pipes come in a variety of sizes, including the following (unit: outer diameter x wall thickness, mm):

- Small diameter: 57×3.5, 76×4, 89×4.5, 108×4.5, or 6"

- Medium and large diameter: 159×6, 219×6, 273×7 or 8", 325×8 or 9", 377×10, 426×12"

- Special requirements: Outer diameter up to 760mm, wall thickness up to 140mm (using hot expansion or cold drawing).

Sixth, Other Characteristics of 20G Seamless High-Pressure Boiler Steel Pipes.

- Surface Quality: The inner and outer walls must be free of defects such as cracks and folds. A slight oxide layer is permitted.

- Processability: Deep processing (stamping, bending, etc.) and custom welding are supported, and delivery to the factory is possible.

- Corrosion Resistance: Surface treatment (such as plating) enhances corrosion resistance.

Summary: 20G seamless high-pressure boiler steel pipes have become a key material in the industrial sector due to their high strength, resistance to high temperatures and pressures, excellent processability, and wide applicability. Strict control of their chemical composition and heat treatment processes ensures stable performance. Common specifications cover a wide range of applications, from routine to specialized. Specific model selection should be considered based on actual operating conditions and confirmed with reference to the GB/T5310-2023 standard for technical specifications.