The NH25-35GR long-life alloy redefines the performance limits of reformer tubes. Its exceptional high-temperature strength not only equips equipment with the rugged endurance to withstand 1100 °C, but also revolutionizes design—by optimizing wall thickness it enables highly efficient heat transfer and fuel savings. Ultimately, on the same platform, it boosts your operating temperature by 15 °C, unlocking higher throughput and delivering a double leap in both efficiency and output.
Microstructure
The high-temperature endurance strength of the alloy was evaluated using standard stress rupture tests, with test temperatures ranging from 950℃ to 1100℃. The mechanical properties at room temperature were determined through tensile tests, including tensile strength, yield strength, and elongation. The microstructural stability was evaluated through metallographic observation and analysis of carbide precipitation behavior.
Stress-fracture curve
The stress rupture curve (Figure 1) shows that the average rupture stress and 95% confidence interval of NH25-35GR are both higher than those of NH25-35 microalloy, indicating a significant improvement in its high-temperature creep resistance. Under the same service conditions, the high-temperature strength of NH25-35GR is at least 15% higher than that of traditional materials.
Mechanical properties at room temperature
The mechanical property test results at room temperature are presented in Table 1. NH25-35GR exhibits a tensile strength of ≥480 MPa, a yield strength of ≥250 MPa, and an elongation rate of ≥10%, all of which are higher than those of the traditional NH25-35 microalloy.
Mechanical properties at room temperature
| Performance | Tensile strength (Mpa) | Yield strength (Mpa) | Elongation (%) |
| NH25-35GR | ≥480 | ≥250 | ≥10 |
| NH25-35 MIC | ≥450 | ≥250 | ≥8 |
Excellent stress fracture strength and creep resistance
Good organizational stability, oxidation resistance, and carburizing resistance
The wall thickness of the furnace tube has decreased by 18%, and the operating temperature has increased by 15℃
Improve thermal efficiency and increase production capacity
Calculate the wall thickness of furnace tubes based on API 530 standard
The design conditions are: a lifespan of 100000 hours, a pressure of 3 MPa, a temperature of 1000 ℃, and an inner diameter of 100 mm. The calculation results are shown in the table, and the minimum wall thickness of NH25-35GR is 12.4 mm, which is about 18% lower than the traditional material's 14.7 mm. The corresponding reduction in outer diameter helps to reduce equipment weight and improve thermal efficiency.
In addition, the allowable operating temperature of NH25-35GR can be increased to 1100 ℃, which is 15 ℃ higher than traditional materials. This feature not only extends the lifespan of the furnace tube, but also helps to improve production capacity and reduce energy consumption.
Parameters | Values | |
Design Life | 100000 Hour | |
Design Pressure | 3MPa | |
Design Temperature | 1000℃ | |
Reformer Tube ID | 100mm | |
Material | NH25-35GR | NH25-35 Micro-Alloy |
Allowable Stress | 13.6MPa | 11.7MPa |
Per API 530 | MSW = (P x ID) / (2 x Sr –P) | |
Calculated Minimum Wall | 12.4mm | 14.7mm |
OD ID+2MSW+1.6 outer surface roughness layer | 126.4mm | 131mm |
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