Introduction to JIS G3458 Alloy Steel Boiler Tube Standard Specifications
The JIS G3458 standard outlines the specifications for heat-resistant alloy steel pipes used in high-temperature fluid conveying systems, particularly in heaters and boiler tubes. These pipes are designed to withstand extreme temperatures and maintain structural integrity under harsh operating conditions.
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 boiler tubes meet the necessary performance criteria for use in high-temperature environments. The chemical composition and mechanical properties are tailored to provide optimal strength, ductility, and resistance to thermal degradation. Understanding these standards is essential for engineers and manufacturers involved in power generation, industrial heating, and related applications.
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