JIS G3101 SS400 Double-Sided Submerged Arc Welding (DSAW/LSAW) Steel Pipe
Basic Overview
JIS G3101 SS400 DSAW (Double-Sided Submerged Arc Welding) steel pipe is a large-diameter welded pipe manufactured from carbon structural steel conforming to the Japanese Industrial Standard JIS G3101. The "SS400" designation indicates a minimum tensile strength of 400 MPa (58,000 psi) , with yield strength of approximately 245 MPa (35,500 psi) for thicknesses ≤ 16mm .
The DSAW process-also known as LSAW (Longitudinal Submerged Arc Welding)-is a high-integrity welding method where both inside and outside welds are applied, forming a single high-quality weld nugget. This process is specifically designed for large-diameter, thick-wall pipes used in structural, piling, and low-pressure fluid applications .
Name Explanation
| Part | Meaning |
|---|---|
| JIS | Japanese Industrial Standards |
| G3101 | Standard for "Rolled Steels for General Structure" |
| SS400 | Grade designation: "SS" = Structural Steel, "400" = minimum tensile strength (MPa) |
| DSAW/LSAW | Double-Sided/Longitudinal Submerged Arc Welding – pipe formed from steel plate and welded longitudinally on both inside and outside surfaces |
Key Specifications
| Attribute | Description |
|---|---|
| Material Standard | JIS G3101 – Rolled Steels for General Structure |
| Steel Grade | SS400 – Minimum tensile strength 400 MPa |
| Manufacturing Process | DSAW (Double-Sided Submerged Arc Welding) / LSAW (Longitudinal Submerged Arc Welding) |
| Forming Methods | JCOE (progressive J-C-O forming) or UOE (U-ing, O-ing, Expanding) |
| Size Range | 219 mm to 1625 mm (8" to 64") OD – typical for LSAW; up to 3048 mm available |
| Wall Thickness | 6.35 mm to 60 mm (up to 120 mm for special applications) |
| Length | 3 m to 18 m standard; up to 32 m available |
| End Finishes | Plain ends, beveled ends (30° bevel angle), threaded |
| Coating Options | Black paint, varnish, anti-rust oil, galvanized, FBE, 3LPE |
Chemical Composition (JIS G3101 SS400)
| Element | Maximum % | Notes |
|---|---|---|
| Carbon (C) | 0.16-0.25% (typical) | Low carbon for good weldability |
| Manganese (Mn) | 1.40% max | Provides strength |
| Silicon (Si) | 0.35% max | Deoxidizer |
| Phosphorus (P) | 0.050% max | Controlled for weldability |
| Sulfur (S) | 0.050% max | Controlled for toughness |
| Copper (Cu) | 0.20% min (when specified) | Improves corrosion resistance |
Note: JIS G3101 does not specify mandatory limits for carbon and manganese. Values shown are typical from manufacturer data. Other alloying elements may be added as necessary .
Mechanical Properties (JIS G3101 SS400)
Yield Strength (min)
| Thickness (mm) | Yield Strength (MPa) |
|---|---|
| ≤ 16 | 245 (≥) |
| 16 < t ≤ 40 | 235 |
| 40 < t ≤ 100 | 215 |
| > 100 | 205 |
Tensile Strength
| Property | Value |
|---|---|
| Tensile Strength (min) | 400 MPa |
| Tensile Strength Range | 400-510 MPa |
Other Properties
| Property | Value |
|---|---|
| Elongation (min) | 17-21% (depends on thickness) |
| Hardness | 150-180 HB typical |
| Impact Testing | Not required by JIS G3101 |
SS400 Grade Comparison with International Equivalents
| Standard | Equivalent Grade | Notes |
|---|---|---|
| JIS G3101 | SS400 | Original standard |
| GB/T 700 | Q235B | Most direct Chinese equivalent |
| ASTM | A36 | Slightly higher yield (250 MPa) |
| EN 10025 | S235JR | Similar properties |
| DIN 17100 | ST37-2 | Historical German equivalent |
Key Differences between SS400 and Q235B :
SS400 has higher tensile strength lower limit (400 MPa vs. 370 MPa)
SS400 allows wider manganese upper limit (1.40% vs. 1.40% similar)
SS400 has slightly higher phosphorus/sulfur allowances (0.050% vs. 0.045%)
Dimensional Specifications
| Parameter | Range / Tolerance |
|---|---|
| Outside Diameter | 219 mm to 1625 mm (8" to 64") – typical LSAW range; up to 3048 mm available |
| Wall Thickness | 6.35 mm to 60 mm (up to 120 mm for special applications) |
| Diameter Tolerance | ±0.75% of specified OD (typical) |
| Wall Thickness Tolerance | +15% / -12.5% of nominal (typical) |
| Length | 3 m to 18 m standard; up to 32 m available |
| Out-of-Roundness | ≤ 1% of specified OD |
Typical Size Availability (SS400):
| OD (inch) | OD (mm) | Wall Thickness Range (mm) |
|---|---|---|
| 16" | 406 | 6.0 - 14.0 |
| 20" | 508 | 6.0 - 16.0 |
| 24" | 610 | 6.0 - 18.0 |
| 30" | 762 | 7.0 - 21.0 |
| 36" | 914 | 8.0 - 24.0 |
| 40" | 1016 | 8.0 - 26.0 |
| 48" | 1219 | 9.0 - 28.0 |
| 56" | 1422 | 10.0 - 29.0 |
| 60" | 1524 | 10.0 - 29.0 |
| 64" | 1626 | 10.0 - 30.0 |
DSAW/LSAW Manufacturing Process
Double-Sided Submerged Arc Welding (DSAW), also known as Longitudinal Submerged Arc Welding (LSAW), is a high-efficiency process used primarily for large-diameter steel pipes .
Process Description
Welding arc is submerged in granular flux during welding, protecting the weld from atmospheric contamination
Both inside and outside welds are required, usually accomplished in separate processes
The separate welds consume a portion of the other, resulting in a single high-quality weld nugget
Forming Methods
| Method | Description | Typical Diameters |
|---|---|---|
| JCOE | Progressive J-C-O forming steps (J-shape → C-shape → O-shape), expanded after welding | 406-1626 mm (16"-64") |
| UOE | Plate pressed into U-shape, then O-shape, expanded after welding | 508-1118 mm (20"-44") |
Process Steps
Plate Selection – Steel plates meeting JIS G3101 SS400 requirements
Edge Preparation – Edges are beveled to create a V-shaped groove
Forming – Steel plates are formed into cylindrical shapes using JCOE or UOE presses
Tack Welding – Formed plates are tack-welded to maintain shape
Double Submerged Arc Welding – Pipe seam welded on both interior and exterior surfaces
Cold Expansion – Pipe may be expanded up to 1.5% to achieve final OD dimension
Ultrasonic Inspection – Seam inspected by continuous ultrasonic automatic flaw detection
Hydrostatic Pressure Test – Each pipe undergoes hydrostatic pressure testing (if specified)
Finishing – End processing, beveling, coating, and marking according to specifications
Testing & Inspection Requirements
| Test Type | Requirement | Notes |
|---|---|---|
| Chemical Analysis | Per heat lot | Verifies composition limits per JIS G3101 |
| Tensile Test | Per lot | Verifies yield and tensile strength |
| Flattening Test | Required | Checks ductility and weld integrity |
| Bend Test | Required | Verifies weld integrity |
| Charpy Impact Test | Not required by JIS G3101 | May be specified for SM grades |
| Hydrostatic Test | Per project/standard | Pressure integrity verification |
| Ultrasonic Inspection | 100% of weld seam | Continuous automatic flaw detection |
| X-ray Inspection | For "T" joints | Where strip butt welds intersect spiral seams |
| Dimensional Inspection | 100% | Per standard tolerances |
| Mill Test Certificate | EN 10204 Type 3.1B | Provided with full test results |
Common Applications
| Application | Description |
|---|---|
| Building Construction | Beams, columns, floor slabs, stairs in factories, residential, and commercial buildings |
| Bridge Engineering | Bridge railings, bridge piers, bridge decks for medium and small-span bridges |
| Piling Foundations | Load-bearing piles for buildings and deep foundations |
| Infrastructure Projects | Tunnel supports, retaining walls, highway structures |
| Mechanical Manufacturing | Light machinery bases, bearing supports, gearbox housings, agricultural machinery brackets |
| Transportation | Vehicle chassis, frames, truck body panels, non-critical ship structural components |
| Other Fields | Power transmission towers, communication towers, scaffolding, pipe supports, municipal guardrails |
Product Standards for Finished DSAW Pipe
Since JIS G3101 defines the material grade, the finished DSAW pipe product is typically manufactured to additional product standards:
| Product Standard | Application | Notes |
|---|---|---|
| JIS G3444 | Carbon steel pipes for general structural purposes | Specifies dimensional tolerances, hydrostatic test pressure |
| Project Specification | Large-diameter custom pipes (penstocks, piles) | Directly calls for JIS G3101 SS400 plate |
| EN 10219 | Cold-formed structural hollow sections | European standard equivalent |
| ASTM A53 | General service pipe | American standard equivalent |
Key Advantages
| Advantage | Description |
|---|---|
| Excellent Weldability | Low carbon content (≤0.25%) ensures good field weldability |
| Good Formability | Suitable for cold bending, flanging, and shaping without cracking |
| Cost-Effective | Most economical choice for general structural applications |
| Large Diameter Capability | DSAW produces pipes from 8" to 64" OD – ideal for large-diameter applications |
| High Weld Integrity | Double-sided welding creates a single high-quality weld nugget with 100% UT inspection |
| Wide Availability | Commonly stocked by manufacturers globally |
| Globally Recognized | Equivalent to Q235B, A36, and S235JR – widely accepted worldwide |
| Balanced Properties | Good combination of strength, ductility, and weldability for general structural use |
Important Considerations
1. SS400 vs. Higher Grades
JIS G3101 includes multiple grades :
| Grade | Tensile Strength (MPa) | Yield Strength (≤16mm) | Typical Application |
|---|---|---|---|
| SS330 | 330-430 | ≥205 | Light structural, general use |
| SS400 | 400-510 | ≥245 | Most common – general structural |
| SS490 | 490-610 | ≥285 | Heavy-duty structural |
| SS540 | ≥540 | ≥400 | High-strength applications |
2. Yield Strength Not Guaranteed by Standard
JIS G3101 does not specify mandatory yield strength for SS400. The yield values (≥245 MPa for ≤16mm) are provided as reference values . Manufacturers typically supply to these reference values.
3. SM Grades for Higher Toughness
For applications requiring guaranteed impact toughness, specify SM400 grades instead:
SM400B: 27 J at 0°C
SM400C: 27 J at 0°C (improved toughness)
SM400 series also specifies minimum yield strength (245 MPa)
4. Impact Testing
JIS G3101 SS400 does not require Charpy impact testing by the standard . For applications requiring low-temperature toughness, specify SM400 grades.
5. Temperature Limitations
Maximum recommended service temperature: 350°C (662°F)
Short-term exposure up to 450°C possible
No guaranteed low-temperature toughness – not suitable for sub-zero applications without evaluation
6. Corrosion Protection
SS400 has limited corrosion resistance. For buried or exposed applications, specify protective coatings :
3LPE (3-layer polyethylene) – for buried pipelines
FBE (Fusion Bonded Epoxy) – for oil & gas pipelines
Hot-dip galvanized – for outdoor applications
Varnish / Anti-rust oil – temporary protection
7. Pressure Applications
SS400 is primarily designed for structural applications, not high-pressure fluid transmission. For pressure applications, API 5L grades are recommended .
8. Third-Party Inspection
Available inspection services include SGS, BV, Lloyds
9. Weldability
Low carbon content ensures excellent weldability
Suitable for all standard welding methods (SMAW, GTAW, GMAW, SAW)
No post-weld heat treatment required for most thicknesses
Preheat: 100-150°C recommended for thicker sections
Summary
JIS G3101 SS400 Double-Sided Submerged Arc Welded (DSAW/LSAW) steel pipe is the most common large-diameter structural steel pipe manufactured to Japanese Industrial Standards. With minimum tensile strength of 400 MPa (58,000 psi) , yield strength of approximately 245 MPa (35,500 psi) for thicknesses ≤ 16mm, and excellent weldability, this material is the standard choice for general structural applications worldwide .
Key features:
Material standard: JIS G3101 SS400 – Japanese Industrial Standard for general structural steel
Tensile strength: 400-510 MPa – defines the SS400 designation
Yield strength (reference) : ≥245 MPa for thickness ≤ 16mm
Globally recognized equivalents: Q235B (China), A36 (USA), S235JR (Europe), ST37-2 (Germany)
DSAW/LSAW manufacturing produces pipes from 8" to 64" OD with wall thickness up to 60 mm
Double-sided welding creates a single high-quality weld nugget
JCOE or UOE forming methods ensure precise dimensional accuracy
100% ultrasonic inspection of weld seam ensures quality
Excellent weldability and good formability
Most economical choice for general structural applications
Common applications include:
Building construction (beams, columns, frames)
Bridge engineering (piers, railings, decks)
Piling foundations and infrastructure projects
Mechanical manufacturing and transportation
Power transmission towers and scaffolding
When ordering, specify: JIS G3101, Grade SS400, DSAW/LSAW (Double-Sided/Longitudinal Submerged Arc Welded), Size (OD x WT), Length, End Finish (plain/beveled), Coating Requirements, and Mill Test Certificate to EN 10204 Type 3.1B .
For applications requiring guaranteed impact toughness, specify SM400B (0°C) or SM400C instead. For high-strength structural applications, consider SS490 or SS540 grades .
