JIS G3429 STH12 Alloy Seamless Steel Tubes For High Pressure Gas Cylinder
JIS G3429 STH12 Alloy Seamless Steel Tubes for High Pressure Gas Cylinder
Material
STH12 is a seamless gas-cylinder tube grade under JIS G3429, widely used as the base tube for manufacturing high-pressure steel gas cylinders. It belongs to the C–Mn (manganese steel) family, balancing strength, ductility, and forming performance for cylinder body processing.
Specifications
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Standard: JIS G3429 (Seamless steel tubes for high pressure gas cylinders)
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Tube type: Seamless; hot-finished or cold-finished (marking commonly shown as -S-H / -S-C)
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Typical size range (industry supply):
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OD: 19.05–114.3 mm
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WT: 2.0–14 mm
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Length: up to 16,000 mm
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Typical tolerances (commonly used for cylinder tube supply): OD ±1%, WT +30% (project-specific agreement recommended)
Main Features
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Seamless structure (no weld seam), designed for pressure-bearing cylinder bodies.
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Controlled chemistry suitable for forming, heat treatment planning, and stable performance batch-to-batch.
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Safety-focused inspection basis: hydrostatic testing and/or NDT routes can be specified per order.
Our Advantages
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“How do you ensure the tube truly meets JIS G3429 chemistry?”
We control heat chemistry to the JIS G3429 composition window and provide traceable heat/lot identification and inspection documentation aligned with JIS delivery practice. -
“Can you guarantee pressure integrity (leak-free)?”
JIS G3429 allows hydrostatic testing; unless a higher pressure is specified by the buyer, the standard uses 5 MPa as the minimum hydrostatic pressure basis and requires no leakage. -
“Do you support ultrasonic / eddy-current NDT for internal and surface defects?”
NDT can be specified using ultrasonic or eddy-current routes, and alternative equivalent NDT can be agreed when required by the project or local regulation. -
“What about surface quality and repair policy?”
Tubes must have good internal/external surface finish with no harmful defects; surface dressing is permitted within thickness tolerance, while weld repair is not allowed—a key point for cylinder safety. -
“Will every tube be traceable and properly marked?”
Marking can include grade, manufacturing method symbol (hot/cold finish), dimensions, and manufacturer ID to support full traceability through cylinder forming and testing.
Chemical Composition
Unit: wt.% (heat analysis)
| Grade | C | Si | Mn | P (max) | S (max) | Ni | Cr | Mo |
|---|---|---|---|---|---|---|---|---|
| STH11 | ≤0.50 | 0.10–0.35 | ≤1.80 | ≤0.035 | ≤0.035 | |||
| STH12 | 0.30–0.41 | 0.10–0.35 | 1.35–1.70 | ≤0.030 | ≤0.030 | |||
| STH21 | 0.25–0.35 | 0.15–0.35 | 0.40–0.90 | ≤0.030 | ≤0.030 | ≤0.25 | 0.80–1.20 | 0.15–0.30 |
| STH22 | 0.33–0.38 | 0.15–0.35 | 0.40–0.90 | ≤0.030 | ≤0.030 | ≤0.25 | 0.80–1.20 | 0.15–0.30 |
| STH31 | 0.35–0.40 | 0.10–0.50 | 1.20–1.50 | ≤0.030 | ≤0.030 | 0.50–1.00 | 0.30–0.60 | 0.15–0.25 |
Mechanical Properties
| Grade | Yield Strength (MPa) | Tensile Strength (MPa) | Elongation (%) |
|---|---|---|---|
| STH11 | ≥245 | ≥410 | ≥20 |
| STH12 | ≥315 | ≥480 | ≥18 |
| STH21 | ≥355 | ≥550 | ≥20 |
| STH22 | ≥410 | ≥590 | ≥18 |
| STH31 | 345 | 540–640 | 16 |
Execution Standards (Common Options by System)
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JIS: JIS G3429 (material tube for cylinders); cylinders referenced by JIS B 8230 / JIS B 8241
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ASTM: ASTM A519 (seamless mechanical tubing, often used for cylinder-related tubing projects); ASTM A372 is also commonly referenced in cylinder supply chains depending on scope and jurisdiction.
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EN / ISO (widely used in Europe & international transport tube systems): EN ISO 11120 / ISO 11120 (refillable seamless steel tubes for compressed gas transport systems); EN 10216 / EN 10297 are often used for pressure-purpose / engineering seamless tubes when specified.
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GOST: GOST 8732-78 (hot-deformed seamless steel pipes) and related seamless pipe standards as specified by project documentation.
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GB: GB/T 18248-2021 (Seamless steel tubes for gas cylinder).
Application Areas
High-pressure gas containment and transport, especially where seamless integrity and traceability are mandatory.
Typical where-used examples:
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Industrial gas cylinders: oxygen, nitrogen, argon, CO₂ shielding gas for welding/cutting.
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Medical cylinders: medical oxygen cylinder bodies and related high-pressure containers.
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Energy & mobility: CNG cylinders / high-pressure storage cylinders (project-specific grade selection required).
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Chemical & specialty gases: high-purity or reactive gases requiring reliable cylinder shells.
Q: Are you trading company or manufacturer ?
A: manufacturer,also can do trading.
Q: How long is your delivery time?
A: Generally speaking,it is 10-15 days if the goods are in stock,or it is 30-40 days if the goods are not in stock, it is according to quantity.
Q: Do you provide samples? is it free or extra ?
A: Yes, we could offer the sample for free charge but need pay the cost of freight.
Q: What is your terms of payment ?
A: Payment<=2000USD, 100% in advance. Payment>=2000USD, 30% T/T in advance ,balance before shippment.
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