JIS G3429


JIS G3429 Steel Pipe

JIS G3429 seamless steel tubes are the epitome of precision and quality. These tubes are specifically designed for the manufacture of seamless steel gas cylinders, a crucial component in industries requiring gas solutions. The Japanese standard JIS G3429 ensures that these tubes are perfect for high-pressure environments, making them indispensable in the manufacture of gas cylinders as specified in JIS B8320 and JIS B8241. Our manufacturing process, whether it’s the seamless process, electric resistance welding, or butt welding, ensures the highest quality product. With UNIACERO, you’re not just getting a product; you’re investing in reliability, durability, and excellence.

JIS G3429 Specification

Our JIS G3429 tubes are manufactured with precision, ensuring they meet the stringent requirements of the standard. The tubes undergo rigorous quality checks, including ultrasonic joint inspection and magnetic flux leakage testing, ensuring they are free from defects. They can be delivered in hot-rolled, cold-rolled, normalizing, or annealing states, depending on your requirements. Our tubes are also available in various surface coatings, end types, and joint methods, ensuring they fit seamlessly into your operations.

Production StandardASTM A500
Manufacturing ProcessesSMLS (Hot Finished Seamless)
SMLS (Cold Drawn Seamless)
Outside Diameter21.3mm – 114.3mm (3/4″ – 4″)
Wall Thickness2 – 40 mm
Pipe Length5 – 16 meters
Steel GradeJIS G 3429 STH11JIS G 3429 STH21
JIS G 3429 STH12JIS G 3429 STH22
Corrosion PreventionLacquer, Varnish, Oiling, Galvanizing
End ProcessesSquare Cut, Bevelling, Threading, Grooving
Further ProcessingWelding, Bending, Hole Drilling, Punching, Swaging, Tapering, Flaring, Expanding

JIS G3429 Dimension Table


The dimensions of our JIS G3429 tubes are meticulously crafted to ensure they fit seamlessly into your operations. With an outer dimension ranging from 19.05mm to 114.3mm, a wall thickness between 2.0mm to 14mm, and a maximum length of 16000mm, our tubes are versatile and adaptable to various applications.

Dimensions shall be conform to the agreement between the purchaser and the manufacturer.

Chemical Requirements of JIS G3429

Our JIS G3429 tubes are manufactured with a specific chemical composition to ensure their durability and strength. The chemical compositions vary depending on the grade, ensuring that the tubes are perfectly suited for their intended application. From the carbon content to the presence of elements like Silicon, Manganese, Nickel, Chromium, and Molybdenum, every aspect is calibrated for optimal performance.

Symbol of GradeCSiMnPSNiCrMo
STH110.5 max.0.10 to 0.350.18 max.0.035 max.0.035 max.a)a)a)
STH120.30 to 0.410.10 to 0.351.35 to 1.700.030 max.0.030 max.a)a)a)
STH210.25 to 0.350.15 to 0.350.40 to 0.900.030 max.0.030 max.0.25 max.0.80 to 1.200.15 to 0.30
STH220.33 to 0.380.15 to 0.350.40 to 0.900.030 max.0.030 max.0.25 max.0.80 to 1.200.15 to 0.30
STH310.35 to 0.400.10 to 0.501.20 to 1.500.030 max.0.030 max.0.50 to 1.000.30 to 0.600.15 to 0.25
  • Alloy elements other than those in this table may be added as required.
  • Note a) Ni,Cr or Mo, when added as necessary,shall not be added to such a degree that the specified values of another grade are satisfied,marking the grade no longer discernible.

Mechanical Requirements of JIS G3429

Mechanical strength is paramount when it comes to seamless steel tubes. Our tubes are designed to withstand high pressures, making them ideal for high-pressure gas cylinder manufacturing. Their high strength at elevated temperatures and excellent creep strength make them the preferred choice for challenging environments.

Mechanical Properties
Hydraulic test characteristics:
Tubes shall withstand the applied hydraulic pressure of 5 MPa without leakage.
The purchaser may designate the pressure of over 5 MPa.
Nondestructive examination characteristic
Tubes shall be examined by either of ultrasonic flaw detection or eddy current flaw detection,and there shall be no signal at least equal to that from the artificial defects of the reference test piece of working sensitivity division UD of JIS G 0582 or working sensitivity division EY of JIS G 0583. Other nondestructive examinations in place of the ultrasonic flaw detection or eddy current flaw detection may be applied upon the agreement between the purchaser and the manufacturer.

Steel Grades in JIS G3429

UNIACERO offers a diverse range of steel grades under the JIS G3429 standard. These include STH11, STH12, STH21, STH22, and STH31. Each grade has been crafted to cater to specific application needs, ensuring optimal performance. For instance, C-Mn steel grades (STH11, STH12) are ideal for general applications, while Cr-Mo steel grades (STH21, STH22) are perfect for high-load environments. The Ni-Cr-Mo steel grade, STH31, offers enhanced performance attributes, making it suitable for specialized applications.

Production Tolerance of JIS G3429

Precision in production is vital for the safety and performance of the steel tubes. Our JIS G3429 tubes are manufactured with strict tolerances to ensure their reliability. The outside diameter has a tolerance of 1%, ensuring a perfect fit. The wall thickness comes with a +30% tolerance, guaranteeing the tube’s strength. Furthermore, the disparity in wall thickness is maintained within 20% of the nominal wall thickness, ensuring uniformity. Lastly, the length tolerance is >+30mm, ensuring consistency across all tubes.

Tolerance on outside diameterTolerance on wall thicknessTolerance on wall thickness disparityTolerance on length
1%+30%Within 20% of the nominal wall thickness>+30mm -0

Our Advantages

  1. Over 25 years of experience in pipeline production and installation.
  2. Comprehensive inspection equipment.
  3. Independent product serial numbers for traceability.
  4. Advanced production equipment – Seamer high-frequency welding machine from the United States.
  5. Complete qualifications – API 5L/API 5CT/FM/UL fire pipe certification, etc.
  6. Wide range of products – independently developed solar torque tubes, highly favored in the European market.
  7. Customers spread across the globe.
  8. Excellent after-sales service and sense of responsibility.

Application Scenarios

Our steel pipes are engineered to withstand high temperatures, corrosive environments, and varying pressures, ensuring reliability and safety in the complex petrochemical processes. 

Whether it’s transferring crude oil, natural gas, or chemical intermediates, the robustness and versatility of steel pipes make them indispensable components of the plant’s infrastructure, contributing to efficient production and maintenance of stringent safety standards.

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