Introduction to JIS G3458 alloy steel boiler tube standard specifications
The JIS G3458 standard is formulated for heat-resistant alloy steel pipes used as high-temperature fluid conveying pipes for heaters and boiler tubes.
Production Method:
| Grade |
Heat treatment |
| STPA 12 |
Low temperature annealing isothermal annealing, full annealing, normalizing full annealing, normalizing or normalizing followed by tempering |
| STPA 20 |
| STPA 22 |
| Low temperature nnealing, isothermal annealing, full annealing or followed tempering |
| STPA 23 |
| STPA 24 |
| Isothermal annealing, full annealing or normalizing followed by tempering |
| STPA 25 |
| STPA 26 |
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 |
0.15max. |
0.50 max. |
0.30~0.60 |
0.035 max. |
0.035 max. |
0.80~1.25 |
0.45~0.65 |
| STPA 23 |
0.15max. |
0.50~1.00 |
0.30~0.60 |
0.030 max. |
0.030 max. |
1.00~1.50 |
0.45~0.65 |
| STPA 24 |
0.15max. |
0.50 max. |
0.30~0.60 |
0.030 max. |
0.030 max. |
1.90~2.60 |
0.87~1.13 |
| STPA 25 |
0.15max. |
0.50 max. |
0.30~0.60 |
0.030 max. |
0.030 max. |
4.00~6.00 |
0.45~0.65 |
| STPA 26 |
0.15max. |
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. |
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