Introduction to JIS G3458 Alloy Steel Boiler Tube Standard Specifications
The JIS G3458 standard is specifically designed for heat-resistant alloy steel pipes used in high-temperature environments, such as fluid conveying systems in heaters and boiler tubes. These materials are essential in industrial applications where durability and performance under extreme conditions are critical.
Production Methods:
| 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. |
These specifications ensure that the alloy steel pipes meet the necessary standards for strength, ductility, and resistance to high temperatures, making them suitable for use in power generation, chemical processing, and other demanding industrial applications. Proper selection of the appropriate grade based on operating conditions is crucial to ensuring long-term performance and safety.
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