Introduction to JIS G3458 Alloy Steel Boiler Tube Standard Specifications
The JIS G3458 standard outlines the requirements for heat-resistant alloy steel pipes used in high-temperature environments, particularly for applications such as heater and boiler tubes. These materials are designed to withstand extreme thermal conditions while maintaining structural integrity and performance over time.
Production Method:
| Grade | Heat Treatment |
|---|---|
| STPA 12 | Low temperature annealing, isothermal annealing, full annealing, normalizing, or normalizing followed by tempering |
| STPA 20 | |
| STPA 22 | |
| STPA 23 | Low temperature annealing, isothermal annealing, full annealing, or tempering |
| STPA 24 | |
| STPA 25 | |
| STPA 26 | Isothermal annealing, full annealing, or normalizing followed by tempering |
Chemical Composition:
| Grade | Chemical Composition (%) | ||||||
|---|---|---|---|---|---|---|---|
| C | Si | Mn | P | S | Cr | Mo | |
| STPA 12 | 0.10–0.20 | 0.10–0.50 | 0.30–0.80 | 0.035 max. | 0.035 max. | - | 0.45–0.65 |
| STPA 20 | 0.10–0.20 | 0.10–0.50 | 0.30–0.60 | 0.035 max. | 0.035 max. | 0.50–0.80 | 0.45–0.65 |
| STPA 22 | 0.15 max. | 0.50 max. | 0.30–0.60 | 0.035 max. | 0.035 max. | 0.80–1.25 | 0.45–0.65 |
| STPA 23 | 0.15 max. | 0.50–1.00 | 0.30–0.60 | 0.030 max. | 0.030 max. | 1.00–1.50 | 0.45–0.65 |
| STPA 24 | 0.15 max. | 0.50 max. | 0.30–0.60 | 0.030 max. | 0.030 max. | 1.90–2.60 | 0.87–1.13 |
| STPA 25 | 0.15 max. | 0.50 max. | 0.30–0.60 | 0.030 max. | 0.030 max. | 4.00–6.00 | 0.45–0.65 |
| STPA 26 | 0.15 max. | 0.25–1.00 | 0.30–0.60 | 0.030 max. | 0.030 max. | 8.00–10.00 | 0.90–1.10 |
Mechanical Properties:
| Grade | Mechanical Properties | |||||
|---|---|---|---|---|---|---|
| Tensile Strength | Yield Point or Proof Stress | Elongation % | ||||
| kgf/mm² {N/mm²} | kgf/mm² {N/mm²} | No. 11 or No. 12 Test Piece | No. 5 Test Piece | No. 4 Test Piece | ||
| Longitudinal | Transverse | Longitudinal | Transverse | |||
| STPA 12 | 39 {382} min. | 21 {206} min. | 30 min. | 25 min. | 24 min. | 19 min. |
| STPA 20 | 42 {412} min. | 21 {206} min. | 30 min. | 25 min. | 24 min. | 19 min. |
| STPA 22 | 42 {412} min. | 21 {206} min. | 30 min. | 25 min. | 24 min. | 19 min. |
| STPA 23 | 42 {412} min. | 21 {206} min. | 30 min. | 25 min. | 24 min. | 19 min. |
| STPA 24 | 42 {412} min. | 21 {206} min. | 30 min. | 25 min. | 24 min. | 19 min. |
| STPA 25 | 42 {412} min. | 21 {206} min. | 30 min. | 25 min. | 24 min. | 19 min. |
| STPA 26 | 42 {412} min. | 21 {206} min. | 30 min. | 25 min. | 24 min. | 19 min. |
The JIS G3458 standard ensures that these alloy steel boiler tubes meet strict quality and performance criteria. They are widely used in power plants, industrial furnaces, and other high-temperature systems where durability and resistance to thermal stress are essential. The standard also provides clear guidelines on chemical composition, mechanical properties, and heat treatment processes to guarantee consistent performance across different applications.
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