Introduction to the JIS G3458 Standard for Alloy Steel Boiler Tubes
The JIS G3458 standard is specifically designed for heat-resistant alloy steel pipes that are used in high-temperature applications such as heater systems and boiler tubes. These materials are essential in industrial environments where durability and performance under extreme conditions are critical.
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 | ≤0.035 | - | 0.45–0.65 |
| STPA 20 | 0.10–0.20 | 0.10–0.50 | 0.30–0.60 | ≤0.035 | ≤0.035 | 0.50–0.80 | 0.45–0.65 |
| STPA 22 | ≤0.15 | ≤0.50 | 0.30–0.60 | ≤0.035 | ≤0.035 | 0.80–1.25 | 0.45–0.65 |
| STPA 23 | ≤0.15 | 0.50–1.00 | 0.30–0.60 | ≤0.030 | ≤0.030 | 1.00–1.50 | 0.45–0.65 |
| STPA 24 | ≤0.15 | ≤0.50 | 0.30–0.60 | ≤0.030 | ≤0.030 | 1.90–2.60 | 0.87–1.13 |
| STPA 25 | ≤0.15 | ≤0.50 | 0.30–0.60 | ≤0.030 | ≤0.030 | 4.00–6.00 | 0.45–0.65 |
| STPA 26 | ≤0.15 | 0.25–1.00 | 0.30–0.60 | ≤0.030 | ≤0.030 | 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 tubes meet the required mechanical and chemical properties for use in high-temperature environments. Each grade of the material is tailored to specific applications, offering a balance between strength, ductility, and resistance to thermal degradation. Proper selection of the appropriate grade based on the operating conditions is crucial for long-term performance and safety in industrial systems.
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