Technical Analysis and Application Value of 25MnG High-Pressure Boiler Steel Tubes

First, Material Definition and Standard Origin of 25MnG High-Pressure Boiler Steel Tubes.
SA-210C (25MnG) is a seamless carbon-manganese steel tube in the ASME SA-210 standard, specifically designed for boilers and superheaters, belonging to pearlitic heat-resistant steel. In 1995, my country adopted it into the GB5310 standard, naming it 25MnG, and clearly limiting the carbon and manganese content to optimize weldability and material stability. By limiting the carbon content (≤0.30%) and increasing the manganese content, this material significantly improves strength while maintaining plasticity, becoming a core material in the field of high-pressure boiler steel tubes.

Second, Core Characteristics and Performance Advantages of 25MnG High-Pressure Boiler Steel Tubes.
1. Chemical Composition Optimization of 25MnG High-Pressure Boiler Steel Tubes.
- Carbon ≤0.30%: Reducing the carbon content decreases the risk of embrittlement in the weld heat-affected zone, improving weld quality.
- Manganese 0.29%~1.06%: Solid solution strengthening improves yield strength by approximately 20% compared to traditional 20G materials, while maintaining plasticity (elongation ≥30%) and toughness.
- Phosphorus, Sulfur ≤0.035%: Strict control of impurity content reduces the risk of brittle fracture at high temperatures.

2. Excellent Mechanical Properties of 25MnG High-Pressure Boiler Steel Tubes.
- Tensile Strength ≥485MPa, Yield Strength ≥275MPa: Meets the stringent strength requirements of high-pressure boilers.
- Hardness ≤89HRB: Balances strength and processing performance, facilitating cold bending, hot expansion, and other processes.

3. High-Temperature Stability of 25MnG High-Pressure Boiler Steel Tubes.
- Pearlitic Structure: Provides excellent creep resistance, allowing for long-term operating temperatures below 500℃ (below 450℃ in some applications), suitable for components such as water-cooled walls, economizers, and low-temperature superheaters.
- Anti-oxidation and corrosion performance: Compositional design reduces high-temperature oxide layer peeling, extending the service life of the steel pipe.

Third, Application Scenarios and Economic Benefits of 25MnG High-Pressure Boiler Steel Tubes.
1. Typical Application Components of 25MnG High-Pressure Boiler Steel Tubes
- Thermal power boilers: Water-cooled wall systems, economizer components, and low-temperature superheater piping for 300MW and 600MW units.
- Chemical equipment: High-temperature and high-pressure reactors, heat exchangers, and other applications requiring corrosion resistance and thermal fatigue resistance.

2. Cost Optimization Benefits of 25MnG High-Pressure Boiler Steel Tubes.
- Wall thickness reduction: Compared to 20G material, SA-210C can reduce the pipe wall thickness by approximately 15%~30%, saving up to 100 tons of steel per 300MW boiler.
- Improved heat transfer efficiency: Thinner steel pipe walls reduce thermal resistance, improving overall boiler thermal efficiency and reducing fuel consumption.
- Reduced processing costs: Excellent cold and hot processing performance reduces manufacturing steps and shortens the production cycle.

Fourth, Production Process and Quality Control of 25MnG High-Pressure Boiler Steel Tubes.
Manufacturing Process of 25MnG High-Pressure Boiler Steel Tubes
- Hot Rolling as the Main Process: Precise dimensional control and excellent surface quality are achieved through high-temperature rolling.
- Cold Drawing/Continuous Rolling as an Auxiliary Process: Meets the requirements for small-diameter, high-precision pipes and adapts to complex structural processing.
- Heat Treatment Delivery: Eliminates internal stress, stabilizes microstructure and properties, and ensures long-term material stability.

Strict Testing Standards for 25MnG High-Pressure Boiler Steel Tubes
- Hydrostatic Test: Each pipe is individually tested for sealing to prevent leakage risks.
- Flaring/Flattening Test: Verifies the material's plastic deformation capacity and processing safety.
- Microstructure and Grain Size Control: Optimizes high-temperature performance and avoids strength reduction caused by microstructure coarsening.

Fifth, Selection Recommendations and Precautions for 25MnG High-Pressure Boiler Steel Tubes.
- Temperature Limitation: Long-term operating temperature must be strictly controlled below 500℃ to avoid strength reduction caused by pearlite spheroidization.
- Welding Process: Low-hydrogen welding electrodes are preferred; interpass temperature should be controlled to prevent cold cracking.
- Regular Maintenance: Inspect the pipe surface for oxide layers, corrosion pits, and cracks; replace aging components promptly.
- Alternative Comparison: For higher strength or corrosion resistance, SA-213 T22 (Cr-Mo steel) or TP347H (austenitic stainless steel) can be considered, but costs will increase significantly.

Summary: Value Positioning of 25MnG High-Pressure Boiler Steel Tubes: 25MnG high-pressure boiler steel tubes, with their strength-plasticity balance, high-temperature stability, and cost optimization potential, have become the benchmark material in the field of medium and low-pressure boiler steel tubes. Their application not only improves boiler operating efficiency and safety but also promotes cost reduction and efficiency improvement in the industry through material thinning and process simplification. For power and chemical projects that prioritize economy and reliability, SA-210C (25MnG) is the preferred option for high-pressure boiler steel tube selection.