Scope of JIS G3454
JIS G3454 specifies carbon steel pipes for pressure service, used for steam, water, oil, gas and air lines where strength and pressure integrity are required but corrosion resistance is not the governing factor. The standard covers the grade symbols, chemical composition, mechanical properties, dimensions, tolerances, test methods and marking.
The three grades are STPG370, STPG410 and STPG480. In the Japanese designation the letter group STPG identifies carbon steel pipe for pressure service, and the number that follows is the minimum tensile strength in newtons per square millimetre, that is, in megapascals. A grade called STPG410 therefore has a minimum tensile strength of 410 N/mm2.
Grades and Minimum Tensile Strength
| Grade | Minimum tensile strength | Typical service | Broadly comparable grade |
|---|---|---|---|
| STPG370 | 370 N/mm2 | Lower-pressure piping, bending and formed parts, general utility lines | ASTM A106 Grade A, ASTM A53 Grade A |
| STPG410 | 410 N/mm2 | General pressure piping for steam, water and oil, the most widely ordered grade | ASTM A106 Grade B, EN 10216-1 P235GH |
| STPG480 | 480 N/mm2 | Higher-strength pressure service where design stress governs | ASTM A106 Grade C |
Chemical composition, minimum yield strength and minimum elongation are specified grade by grade in the standard, and all three properties rise in step from STPG370 through STPG480. The comparison column above indicates broadly equivalent roles, not identical specifications, because each standard sets its own composition limits and tolerances.
Designation Note: STPG, STPT and STS
Japanese pipe standards are often confused because the grade symbols are similar. Carbon steel pipes for pressure service under JIS G3454 carry the STPG symbols. Carbon steel pipes for high temperature service under JIS G3456 carry the STPT symbols, such as STPT370, STPT410, STPT480 and STPT510, while carbon steel pipes for high pressure service under JIS G3455 carry the STS symbols. When a specification asks for a high-temperature pipe, the correct reference is JIS G3456 with an STPT grade, not JIS G3454.
Size Range, Dimensions and Delivery Condition
Nominal sizes: from small bore through the standard range of pipe sizes, with larger diameters available by agreement.
Wall thickness: specified in the dimensional tables of the standard or ordered as a nominal wall thickness, with tolerances applied as stated.
Manufacturing route: seamless and welded pipe according to the grade and size, with the manufacturing method stated on the order and the marking.
End finish: plain end, bevelled end for welding, or threaded end with coupling; groove-end and special end preparations are also possible.
Surface condition: bare with protective varnish, or hot-dip galvanized and painted where atmospheric corrosion protection is required.
Testing and Ordering Information
JIS G3454 requires tensile testing and hydrostatic testing or an agreed non-destructive examination, together with chemical analysis and dimensional inspection. Flattening or bending tests apply to certain sizes, and the mill issues a test certificate identifying the heat, grade and test results.
A complete order description includes the standard number and grade, the nominal size and wall thickness, the length, the manufacturing method where relevant, the end finish, the surface treatment or coating, and any additional test requirements such as impact testing or ultrasonic examination. Specifying the intended service and the applicable design code at the enquiry stage avoids grade substitution later.
International Comparison
For carbon steel pressure pipe, the closest international counterparts to JIS G3454 grades are ASTM A106 Grades A, B and C for seamless pipe, EN 10216-1 P235GH in Europe, and GB/T 8163 or GB 3087 in China, where the common carbon grade is 20 steel with a nominal carbon content of about 0.20 %. Equivalent strength grades do not automatically mean interchangeable materials, because differences in chemistry, tolerances, testing and permissible design stress can affect the qualified welding procedure and the pressure design.
FAQ
Q: What grades are covered by JIS G3454?
Three grades: STPG370, STPG410 and STPG480, where the number is the minimum tensile strength in N/mm2, that is in MPa.
Q: What does the number in STPG410 mean?
It means the pipe has a minimum tensile strength of 410 N/mm2. The grade symbol STPG identifies carbon steel pipe for pressure service.
Q: Is STPT a grade of JIS G3454?
No. The STPT symbols belong to JIS G3456 for carbon steel pipes for high temperature service. JIS G3454 uses STPG grades, and JIS G3455 uses STS grades for high pressure service.
Q: Which JIS G3454 grade is equivalent to ASTM A106 Grade B?
STPG410 is broadly comparable to ASTM A106 Grade B, since their minimum tensile strengths are 410 MPa and 415 MPa respectively, but the two specifications differ in composition limits and tolerances.
Q: What is the Chinese equivalent of ASTM A106 pipe?
GB/T 8163 covers seamless steel pipe for fluid transport, while GB 3087 and GB 5310 cover boiler and high-pressure service. The common carbon grade is 20 steel, with a nominal carbon content of about 0.20 %.
Q: What do NPS and schedule mean on a pipe order?
NPS is the nominal pipe size, a dimensionless diameter designation, while the schedule, such as Sch 40 or Sch 80, defines the wall thickness for that size. The grade defines the material and the schedule defines the dimensions.
