BS 4360 Grade 43 Double-Sided Submerged Arc Welding (DSAW) Steel Pipe
✅ Basic Overview
BS 4360 Grade 43 DSAW (Double-Sided Submerged Arc Welded) steel pipe is a standard structural steel product that combines the now-withdrawn British Standard material grade with a robust, high-integrity welding process . While BS 4360 has been superseded by EN 10025 (with the modern equivalent being S275JR), Grade 43 remains a widely recognized specification in legacy projects and in regions where familiarity with the British standard persists . DSAW is the preferred manufacturing method for large-diameter, thick-wall pipes used in demanding structural and low-pressure fluid applications .
📋 Name Explanation
| Part | Meaning |
|---|---|
| BS | British Standard |
| 4360 | The withdrawn British Standard specification for weldable structural steels |
| Grade 43 | A common carbon steel grade with a minimum yield strength of approximately 275 MPa (40 ksi) – the modern equivalent is S275JR |
| DSAW | Double-Sided Submerged Arc Welding – both inside and outside welds are applied; the welding arc is submerged in granular flux; separate welds consume a portion of each other forming a single high-quality weld nugget |
🔧 DSAW Manufacturing Process
Double-Sided Submerged Arc Welding 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 |
|---|---|
| JCOE / JCO | Progressive J-C-O forming steps (J-shape → C-shape → O-shape), expanded after welding; this is the most common method for LSAW/DSAW pipes |
| UOE | Plate pressed into U-shape, then O-shape, expanded after welding |
Cold Expansion
Pipe may be expanded up to 1.5% to obtain final OD dimension
This process can result in a gain of yield strength
Expansion is most often utilized in UOE mills due to the need to recover yield strength lost during forming
📊 Key Specifications
| Attribute | Description |
|---|---|
| Standard (Historical) | BS 4360 (withdrawn, replaced by EN 10025) |
| Modern Equivalent | S275JR (EN 10025-2) – minimum yield strength 275 MPa |
| Grade | Grade 43 – minimum yield strength approximately 275 MPa (40 ksi) |
| Manufacturing Process | DSAW (Double-Sided Submerged Arc Welding) / LSAW (Longitudinal Submerged Arc Welding) |
| Forming Methods | JCOE or UOE |
| Size Range | 16" to 72" OD (406 mm to 1829 mm) |
| Wall Thickness | 6.0 mm to 40 mm (up to 60 mm for piling applications) |
| Length | 6 m to 12.3 m standard; up to 18 m available |
🔬 Chemical Composition & Mechanical Properties
Note: BS 4360 Grade 43 is a structural steel grade. Its chemical and mechanical properties are equivalent to the modern standard EN 10025 S275JR .
| Element | Maximum % |
|---|---|
| Carbon (C) | 0.21-0.25% |
| Manganese (Mn) | 1.50% max |
| Silicon (Si) | 0.05-0.40% |
| Phosphorus (P) | 0.040-0.050% max |
| Sulfur (S) | 0.040-0.050% max |
| Property | Minimum Value |
|---|---|
| Yield Strength (t ≤ 16mm) | 275 MPa |
| Tensile Strength | 410-560 MPa |
| Elongation | 20-23% |
| Charpy Impact | 27 J at +20°C (JR equivalent) |
📏 Dimensional Specifications
| Parameter | Range / Tolerance |
|---|---|
| Outside Diameter | 16" to 72" (406 mm to 1829 mm) |
| Wall Thickness | 6.0 mm to 40 mm (up to 60 mm for piling) |
| Diameter Tolerance | ±0.75% of specified OD (typical) |
| Wall Thickness Tolerance | +15% / -12.5% of nominal (typical) |
| Length | 6 m to 12.3 m standard; up to 18 m available |
Wall Thickness Availability by Diameter (X52 grade example – similar for Grade 43):
| 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 |
| 72" | 1829 | 10.0 - 30.0 |
🧪 Testing & Inspection Requirements
| Test Type | Requirement | Notes |
|---|---|---|
| Chemical Analysis | Per heat lot | Verifies composition limits |
| 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 | When specified | For low-temperature applications (typically 27J at +20°C for JR equivalent) |
| Hydrostatic Test | Per project/standard | For pressure applications |
| NDT (Ultrasonic/X-ray) | Weld seam inspection | Standard practice for DSAW |
| Mill Test Certificate | EN 10204 Type 3.1B | Provided with full test results |
🏭 Common Applications
| Application | Description |
|---|---|
| Structural Engineering | Building frames, columns, trusses for high-rise buildings, stadiums, exhibition halls |
| Piling Foundations | Load-bearing piles for buildings and structures |
| Bridge Construction | Structural members, supports, pedestrian bridges |
| Offshore Projects | Marine structures, port facilities |
| Low-Pressure Fluid Transmission | Water, gas, and oil pipelines (non-critical) |
| Infrastructure Projects | Tunnel supports, retaining walls, highway structures |
📝 Important Considerations
1. Standard Status
BS 4360 has been withdrawn and replaced by EN 10025. The direct modern equivalent of Grade 43 is S275JR (EN 10025-2) . For new projects, specifying S275JR is recommended.
2. Grade 43 vs. Grade 50
| Grade | Yield Strength | Modern Equivalent |
|---|---|---|
| Grade 43 | ~275 MPa | S275JR |
| Grade 50 | ~355 MPa | S355JR / S355J2H |
3. Product Standard
While BS 4360 defines the material grade, the finished DSAW pipe product is typically manufactured to product standards such as:
EN 10219 (cold-formed welded structural hollow sections) – for structural applications
EN 10217 (welded tubes for pressure purposes) – for pressure applications
ASTM A252 (pipe piles) – for piling applications
4. Impact Properties
The "Grade 43" designation does not specify impact test temperature. For applications requiring guaranteed toughness:
S275JR – 27 J at +20°C
S275J0 – 27 J at 0°C
S275J2 – 27 J at -20°C
5. Coating Options
DSAW pipe can be supplied with various coatings for corrosion protection :
FBE (Fusion Bonded Epoxy) – for buried pipelines
3LPE (3-layer polyethylene) – for buried applications
Coal Tar Epoxy – for marine environments
Varnish/Anti-rust oil – temporary protection
Bitumen coating – for buried service
Galvanizing – for outdoor applications
6. End Finishes
Plain ends – standard for most applications
Beveled ends – for field welding (30° bevel angle)
Threaded ends – for mechanical connections
7. Third-Party Inspection
Available inspection services include SGS, BV, Lloyds, TUV .
📝 Summary
BS 4360 Grade 43 Double-Sided Submerged Arc Welded (DSAW) steel pipe is a standard product for large-diameter structural and low-pressure fluid applications . While the BS 4360 standard has been withdrawn, Grade 43 remains widely recognized, with its modern equivalent being EN 10025 S275JR .
Key features:
Grade 43 offers minimum yield strength of approximately 275 MPa (40 ksi)
DSAW manufacturing produces pipes from 16" to 72" OD with wall thickness up to 40 mm (60 mm for piling)
Double-sided welding creates a single high-quality weld nugget
JCOE or UOE forming methods ensure precise dimensional accuracy
Cold expansion (up to 1.5%) may be applied, which can increase yield strength
Common applications include:
Structural engineering (building frames, columns, trusses)
Piling foundations and bridge construction
Offshore projects and marine structures
Low-pressure fluid transmission (water, gas, oil)
Infrastructure projects (tunnels, retaining walls)
When ordering, specify: BS 4360 Grade 43 (or modern equivalent EN 10025 S275JR), DSAW (Double-Sided Submerged Arc Welded), Size (OD x WT), Length, End Finish (plain/beveled), and Coating Requirements. For new projects, EN 10025 S275JR is the recommended material specification .
