JIS G 3461 specifies carbon steel tubes used for heat transfer between the inside and outside of the tube.
Typical applications defined by the standard include boiler water tubes, smoke tubes, superheater tubes and air preheater tubes, as well as heat exchanger, condenser and catalyser tubes used in chemical and petroleum industries.
Specified Standard Edition: JIS G 3461:2023
Standard Title: Carbon Steel Tubes for Boiler and Heat Exchanger
JIS G 3461 permits both seamless and electric resistance welded manufacturing routes. This FYN product page covers seamless JIS G 3461 tubes.
The standard does not apply to steel tubes for fired heaters or steel heat exchanger tubes for low-temperature service.
JIS G 3461 specifies three carbon steel grades:
The numerical designation reflects the minimum specified tensile-strength level of each grade.
Grade selection should follow the boiler or heat exchanger design, operating conditions and approved project material specification.
| Parameter | General Standard Scope |
|---|---|
| Outside Diameter | 15.9–139.8 mm |
Other dimensional requirements, wall thicknesses and tolerances should be specified according to JIS G 3461 and the purchase requirements.
FYN manufacturing capability is stated separately below and should not be interpreted as the dimensional scope of the JIS standard.
| Element | STB340 | STB410 | STB510 |
|---|---|---|---|
| Carbon (C) | ≤0.18% | ≤0.32% | ≤0.25% |
| Silicon (Si) | ≤0.35% | ≤0.35% | ≤0.35% |
| Manganese (Mn) | 0.30–0.60% | 0.30–0.80% | 1.00–1.50% |
| Phosphorus (P) | ≤0.035% | ≤0.035% | ≤0.035% |
| Sulfur (S) | ≤0.035% | ≤0.035% | ≤0.035% |
| Property | STB340 | STB410 | STB510 |
|---|---|---|---|
| Minimum Tensile Strength | 340 MPa | 410 MPa | 510 MPa |
| Minimum Yield Point / Proof Stress | 175 MPa | 255 MPa | 295 MPa |
Elongation requirements depend on tube outside diameter, test-piece type and orientation.
For the applicable standard test conditions, minimum elongation requirements include:
| Grade | Minimum Elongation Values Under Applicable Test Conditions |
|---|---|
| STB340 | 35% / 30% / 27% |
| STB410 | 25% / 20% / 17% |
| STB510 | 25% / 20% / 17% |
The applicable value should be determined according to the tube dimensions and tensile-test specimen requirements of JIS G 3461.
Heat-treatment requirements depend on grade and manufacturing method.
For cold-finished seamless tubes, the applicable heat-treatment conditions are:
| Grade | Heat Treatment |
|---|---|
| STB340 | Low-temperature annealing, normalizing or full annealing |
| STB410 | Low-temperature annealing, normalizing or full annealing |
| STB510 | Normalizing |
The required delivery condition should be confirmed according to the grade, manufacturing method and project specification.
Inspection and testing are carried out according to JIS G 3461 and the purchase specification.
Applicable requirements include:
Reverse flattening requirements apply to the relevant electric resistance welded tube route and are therefore not part of FYN’s seamless-tube product scope.
Supplementary quality requirements can be specified by the purchaser where applicable.
JIS G 3461 provides for the selection of hydraulic test characteristics or nondestructive test characteristics.
The required test method should be stated in the purchase specification where project-specific requirements apply.
FYN can review the following testing methods according to the ordered tube specification and applicable acceptance requirements:
JIS G 3461 includes requirements for U-bent tubes used in heat exchanger applications.
For U-bent tube enquiries, please provide:
| Required Information | Details |
|---|---|
| Grade | STB340 / STB410 / STB510 |
| Tube Dimensions | Outside diameter × wall thickness |
| Straight Length | Required straight length |
| Bend Radius | Required bend radius |
| Leg Length | Required leg length |
| Heat Treatment After Bending | Where required |
| Inspection | Required inspection and testing |
| Quantity | Required order quantity |
| Drawing | U-bend drawing, where available |
U-bend manufacturability is subject to dimensional and technical review.
| Parameter | Capability |
|---|---|
| Grades | STB340 / STB410 / STB510 |
| Manufacturing | Seamless — Cold Drawn / Cold Rolled |
| Outside Diameter | 6–114 mm |
| Wall Thickness | 0.8–25 mm |
| Length | Up to 40 m |
| Heat Treatment | According to Grade & Manufacturing Method |
| Inspection | Hydrostatic / UT / ET as specified |
| U-Bent Tubes | Subject to technical review |
| Documentation | MTC / Inspection Documentation / TPI as required |
| Third-Party Inspection | Available upon request |
| Custom Sizes | Subject to grade and technical review |
| MOQ | According to grade, size and production requirements |
JIS G 3461 standard requirements and FYN manufacturing capability are stated separately.
Grade and size availability are confirmed according to the exact grade, outside diameter, wall thickness, length, heat treatment and inspection requirements.
JIS G 3461 seamless carbon steel tubes are used for heat-transfer equipment where the applicable STB grade is specified.
For heat-transfer surfaces carrying water or steam in industrial and power boiler systems.
For boiler smoke-tube and superheater applications where JIS G 3461 carbon steel tubing is specified.
For tubular air preheaters transferring heat between boiler flue gas and combustion air.
For heat-transfer equipment in chemical, petrochemical and other process applications.
For applicable chemical and petroleum processing equipment covered by the JIS G 3461 scope.
For replacement projects where the applicable JIS G 3461 grade is specified.
JIS G 3461 should not be specified for fired-heater tubes or low-temperature heat exchanger tubes.
Final grade selection should follow the applicable equipment design, operating conditions and project material specification.
Available documentation can include:
Required documentation should be specified during the RFQ stage.
Typical export packing includes:
Long-length or U-bent tubes may require special packing and transportation arrangements.
Production lead time depends on grade, dimensions, quantity, heat treatment and inspection requirements.
For quotation, please specify:
JIS G 3461 + Grade + OD × Wall Thickness × Length + Quantity
The required grade should be clearly identified as STB340, STB410 or STB510.
| Required Information | Details |
|---|---|
| Standard | JIS G 3461 |
| Grade | STB340 / STB410 / STB510 |
| Outside Diameter | Required outside diameter |
| Wall Thickness | Required wall thickness |
| Length | Required tube length |
| Quantity | Required order quantity |
| Manufacturing Method | Seamless manufacturing requirement |
| Dimensional Tolerances | If specifically required |
| Heat Treatment | If specified |
| Testing | Hydraulic / NDT requirements |
| U-Bend Dimensions | If applicable |
| Documentation | Inspection documentation requirements |
| Third-Party Inspection | If required |
| Delivery | Delivery destination |
For an accurate quotation, please send your required grade, outside diameter, wall thickness, length and quantity.
For heat exchanger projects requiring U-bent tubes, please also provide the bend radius, leg length and drawing.
For project enquiries, attach your tube list, technical specification or drawing for technical review, together with testing, inspection documentation and delivery requirements.
