STPG 370 is a low-carbon steel pipe grade specified in the Japanese standard JIS G 3454.
STPG 370 has a minimum tensile strength of 370 MPa and a minimum yield strength of 215 MPa.
STPG 370 can be produced as seamless steel tubes or welded steel tubes using the electric resistance welding (ERW) process. It is suitable for use in pressure piping systems with operating temperatures of up to 350°C.
Next, we will take a look at STPG 370 from manufacturing processes, chemical composition, mechanical properties, hydrostatic pressure tests, non-destructive testing, and galvanized coating.
JIS G 3454 STPG 370 can be manufactured using the seamless or ERW manufacturing process, combined with appropriate finishing methods.
| Symbol of grade | Symbol of the manufacturing process | |
| Pipe manufacturing process | Finishing method | |
| STPG370 | Seamless: S Electric resistance welded: E |
Hot-finished: H Cold-finished: C As electric resistance welded: G |
Seamless can be specifically divided into:
S-H: Hot-finished seamless steel pipe;
S-C: Cold-finished seamless steel pipe;
ERW can be specifically divided into:
E-H: Hot-finished electric resistance welded steel pipe;
E-C: Cold-finished electric resistance welded steel pipe;
E-G: Electric resistance welded steel pipe other than hot-finished and cold-finished ones.
JIS G 3454 allows the addition of chemical elements not in the table.
| Symbol of grade | C | Si | Mn | P | S |
| max | max | — | max | max | |
| JIS G 3454 STPG 370 | 0.25% | 0.35 % | 0.30-0.90% | 0.040 % | 0.040% |
STPG 370 is a low-carbon steel in terms of its chemical composition. Its chemical composition is designed to enable it to be used in environments not exceeding 350°C, with good strength, toughness, and high-temperature resistance.
| Symbol of grade |
Tensile strength | Yield point or proof stress |
Elongation min, % |
|||
| Tensile test piece | ||||||
| No.11 or No.12 | No.5 | No.4 | ||||
| N/mm² (MPA) | N/mm² (MPA) | Tensile test direction | ||||
| min | min | Parallel to the pipe axis | Perpendicular to pipe axis | Parallel to the pipe axis | Perpendicular to pipe axis | |
| STPT370 | 370 | 215 | 30 | 25 | 28 | 23 |
In addition to the tensile strength, tensile strength, and elongation mentioned above, there is also a flattening test and bendability.
Flattening Test: When the distance between the two plates reaches the specified distance H, there shall be no defects or cracks on the surface of the steel pipe.
Bendability: The pipe should be bent 90° at a radius of 6 times its outer diameter. The pipe wall must be free of defects or cracks.
Each steel pipe is subjected to a hydrostatic test or non-destructive testing to check for any defects that are not visible to the naked eye.
Hydrostatic Test
According to the scheduled grade of the wall thickness of the steel pipe, select the appropriate water pressure value, maintain it for at least 5 seconds, and check whether the steel pipe is leaking.
| Nominal wall thickness | Schedule number: Sch | |||||
| 10 | 20 | 30 | 40 | 60 | 80 | |
| Minimum hydraulic test pressure, Mpa | 2.0 | 3.5 | 5.0 | 6.0 | 9.0 | 12 |
The JIS G 3454 steel pipe weight table and Pipe schedule can be viewed by clicking the following link:
· JIS G 3454 Steel Pipe Weight Chart
· schedule 10, schedule 20, schedule 30, schedule 40, schedule 60, and schedule 80.
Non-destructive Test
If ultrasonic inspection is used, it should be based on a stricter standard than the UD class signal in JIS G 0582.
If eddy current testing is used, it should be based on a standard that is more stringent than the EY class signal in JIS G 0583.
In JIS G 3454, uncoated steel pipes are called black pipes and galvanized steel pipes are called white pipes.
White pipe: galvanized steel pipe
Black pipe: non-galvanized steel pipe
The process for white pipes is that the qualified black pipes are shot-blasted or pickled to remove impurities from the surface of the steel pipe and then galvanized with zinc that meets the JIS H 2107 standard of at least grade 1. Other matters are carried out in accordance with the JIS H 8641 standard.
The characteristics of the zinc coating are checked in accordance with the requirements of JIS H 0401, Article 6.
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