What are the marking and identification requirements for JIS G3463 steel tube?

JIS G3463 is the Japanese Industrial Standard that governs stainless steel tubes for boilers and heat exchangers. When you order JIS G3463 tubes for a superheater, a condenser, or a heat exchanger bundle, the markings on each tube are not decoration. They are the technical record that ties every tube back to its grade, its manufacturing method, and its heat of steel. Knowing what these marking and identification requirements actually say helps you verify that what arrives on site is exactly what was specified, and it makes inspection and traceability far simpler.

What is JIS G3463?

JIS G3463 specifies requirements for stainless steel tubes used to exchange heat between the inside and outside of the tube, such as superheater tubes of boilers, heat exchanger tubes, condenser tubes, and catalyser tubes used in chemical and petroleum industries. It generally applies to tubes with outside diameters from 15.9 mm to 139.8 mm. The standard covers austenitic, austenitic-ferritic (duplex), and ferritic stainless grades, with symbols such as SUS304TB, SUS304HTB, SUS316TB, SUS316LTB, SUS321TB, and SUS347TB. The "TB" suffix stands for tube for boiler and heat exchanger.

One point is worth clarifying early. Carbon steel boiler and heat exchanger tubes, including the STB and STBA grades, are covered by a separate standard, JIS G3461. JIS G3463 is strictly for stainless steel tubes. If your project specifies STB or STBA grades, confirm the correct standard before you order so that the markings, tests, and certificates all line up.

Why marking and identification matter

Marking is the first link in the traceability chain for any pressure-service tube. A clear, complete marking lets you confirm the grade and manufacturing method at a glance, and it lets inspectors match each tube to its mill test certificate. In boiler and heat exchanger service, where tubes operate under high temperature and pressure, a mix-up between grades can create a real safety hazard. That is why the standard treats marking as a mandatory requirement rather than an optional extra.

Core marking requirements under JIS G3463

Under the marking clause of JIS G3463, each tube must be identified with the following items:

• Symbol of grade. For example, SUS304TB, SUS316LTB, or SUS321HTB. This tells you the stainless grade and that the tube is intended for boiler and heat exchanger service.
• Symbol of manufacturing method. Seamless tubes are marked S-H (hot finished) or S-C (cold finished). Welded tubes are marked A (automatic arc welded), L (laser welded), E (electric resistance welded), G (as-welded electric resistance welded), or B (welded with the weld area processed).
• Manufacturer's name or trademark. This identifies the mill responsible for the tube.

The marking method must not impair the tube. For tubes of small outside diameter, where marking each individual tube is impractical, the standard allows the marking to be applied to the bundle or to a tag attached to the bundle instead.

Additional identification elements to check

Beyond the minimum required by the standard, a reliable supplier will normally add a few more identification details that make verification much easier:

• Standard number. The marking should reference JIS G 3463 so there is no doubt which standard applies.
• Size. Outside diameter and wall thickness, so the tube can be matched against the purchase order.
• Heat number or lot number. This is the key that links the tube to its chemical analysis and mechanical test results.
• Inspection certificate. A mill test certificate should be provided on request, and the heat numbers on the tubes should match the certificate.

How to read a typical JIS G3463 marking

A typical marking might read SUS304TB-S-C. Reading from left to right, SUS304TB is the grade symbol (304 stainless steel, boiler and heat exchanger tube), S means the tube is seamless, and C means it is cold finished. A marking such as SUS316LTB-A tells you the tube is a low-carbon 316 grade produced by automatic arc welding. Once you know the code, you can confirm at a glance whether the tube matches the specification on your order.

What to check when receiving JIS G3463 tubes

• Confirm the grade symbol matches the purchase order before the tubes are unloaded.
• Verify the manufacturing method symbol matches what was ordered, especially if seamless tubes were specified but welded tubes are supplied.
• Check that the heat number appears on the tube and matches the mill test certificate.
• Confirm the outside diameter and wall thickness are within tolerance. For JIS G3463 tubes, the outside diameter tolerance is typically plus or minus 1 percent or 0.5 mm, whichever is greater.
• For small-diameter tubes, check the bundle tag if individual tubes are not marked.
• Request the inspection certificate if it was not supplied with the shipment.

Common marking mistakes to avoid

• Confusing JIS G3463 with JIS G3461. The former is stainless steel; the latter covers carbon steel STB and STBA grades.
• Accepting tubes whose markings have been painted over, ground off, or removed during handling.
• Assuming every tube in a bundle shares the same heat number. Always verify the actual marking.
• Ignoring the manufacturing method symbol. Seamless and welded tubes have different service limits, and the difference matters in high-pressure applications.

Sourcing JIS G3463 tubes with complete documentation

Marking and identification are only as reliable as the supplier behind them. EZ Steel Industrial Co., Ltd. supplies JIS G3463 steel tube for boiler and heat exchanger applications, with more than 12 quality checkpoints across production. The company operates under ISO 9001 quality management and holds API 5L and API 5CT product certification, and it can provide hydrostatic testing, ultrasonic testing, positive material identification, and full mill test certificates with every order. Its stainless steel tube range covers seamless and welded options for pressure, pipeline, and structural service, and its heat exchanger tube program supports power generation, petrochemical, marine, and shipbuilding projects.

Conclusion

Marking and identification are the first line of verification for any JIS G3463 stainless steel tube. By knowing what to look for, the grade symbol, the manufacturing method symbol, the manufacturer's mark, the size, and the heat number, you can confirm compliance, protect traceability, and avoid costly mix-ups on site. When you need JIS G3463 steel tube with complete markings and documentation, contact EZ Steel Industrial for a quote.