Quick Answer
Quick Answer
AS/NZS 3679.2 covers welded I-sections — Welded Beams (WB) and Welded Columns (WC) — in grades 300, 350, and 400. The flange and web plates are manufactured to AS/NZS 3678, then submerged arc welded. Grade 350 delivers a minimum yield strength of 340 MPa for flanges > 17 mm and 360 MPa for flanges ≤ 17 mm.
AS/NZS 3679.2 governs the manufacture and supply of welded I-sections — fabricated structural members consisting of two flange plates connected to a web plate by longitudinal fillet welds. Unlike hot-rolled sections (AS/NZS 3679.1), welded sections allow larger depths, greater versatility in flange-to-web proportions, and the use of higher-strength plate grades. Welded Beams (WB) are optimised for bending, with wider flanges relative to the web; Welded Columns (WC) are proportioned for axial and combined loading with wide, stocky flanges.
The constituent plates are manufactured to AS/NZS 3678 in the relevant grade, and the fabricated section is required to meet AS/NZS 3679.2 compositional, mechanical, dimensional, and weld quality requirements.
Scope and Applicability
AS/NZS 3679.2 applies to:
- Welded I-sections produced by continuous or intermittent longitudinal submerged arc welding (SAW) or other approved processes
- Welded Beams (WB) — deep, slender web with wide flanges for moment resistance
- Welded Columns (WC) — compact proportions for axial and bi-axial loading
- Grades 300, 350, and 400
- Section depths from approximately 200 mm to 1200 mm
The standard does not cover plate girders fabricated in accordance with AS/NZS 1554 (welding standard) unless also certified to AS/NZS 3679.2. Custom-fabricated welded beams outside the listed section sizes are not covered.
Grade Coverage
| Grade | Sub-grades | Impact Requirement | Typical Use |
|---|---|---|---|
| 300 | (none), L0, L15 | None / 27 J @ 0 °C / 27 J @ −15 °C | Low-rise building frames |
| 350 | (none), L0, L15 | None / 27 J @ 0 °C / 27 J @ −15 °C | General structural frames, bridges |
| 400 | (none), L0, L15 | None / 27 J @ 0 °C / 27 J @ −15 °C | Long-span structures, heavy crane runways |
Grade 350 is the most widely supplied grade for WB and WC sections in Australia. Grade 400 is used for long-span or high-load applications where weight reduction is important.
Chemical Composition Requirements
The flange and web plates used in manufacturing must comply with AS/NZS 3678. The following requirements apply to the constituent plates as verified by the section manufacturer's quality records.
Grade 300 — Plate Composition
| Element | Flange ≤ 17 mm | Flange > 17 mm |
|---|---|---|
| C max | 0.22 | 0.22 |
| Mn max | 1.70 | 1.70 |
| Si max | 0.50 | 0.50 |
| P max | 0.040 | 0.040 |
| S max | 0.040 | 0.040 |
| CEV max | 0.46 | 0.46 |
Grade 350 — Plate Composition
| Element | Flange ≤ 17 mm | Flange > 17 mm |
|---|---|---|
| C max | 0.20 | 0.20 |
| Mn max | 1.70 | 1.70 |
| Si max | 0.50 | 0.50 |
| P max | 0.040 | 0.040 |
| S max | 0.040 | 0.040 |
| CEV max | 0.48 | 0.50 |
Grade 400 — Plate Composition
| Element | Flange ≤ 17 mm | Flange > 17 mm |
|---|---|---|
| C max | 0.20 | 0.20 |
| Mn max | 1.70 | 1.70 |
| Si max | 0.50 | 0.50 |
| P max | 0.035 | 0.035 |
| S max | 0.035 | 0.035 |
| CEV max | 0.50 | 0.53 |
CEV = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15. Constituent plates may include microalloying additions of Nb, V, or Ti within limits.
Mechanical Properties
Mechanical properties are tested on specimens taken from the flange of the welded section. The governing thickness is the flange plate thickness.
Grade 300
| Flange Thickness (mm) | ReH min (MPa) | Rm min (MPa) | Elongation A5 min % |
|---|---|---|---|
| ≤ 11 | 320 | 440 | 22 |
| > 11 to 17 | 310 | 430 | 22 |
| > 17 to 40 | 300 | 430 | 22 |
| > 40 to 63 | 280 | 410 | 22 |
Grade 350
| Flange Thickness (mm) | ReH min (MPa) | Rm min (MPa) | Elongation A5 min % |
|---|---|---|---|
| ≤ 11 | 380 | 480 | 22 |
| > 11 to 17 | 360 | 480 | 22 |
| > 17 to 40 | 340 | 480 | 22 |
| > 40 to 63 | 330 | 460 | 22 |
Grade 400
| Flange Thickness (mm) | ReH min (MPa) | Rm min (MPa) | Elongation A5 min % |
|---|---|---|---|
| ≤ 11 | 420 | 480 | 20 |
| > 11 to 17 | 400 | 480 | 20 |
| > 17 to 40 | 380 | 480 | 20 |
| > 40 to 63 | 360 | 460 | 20 |
Impact Test Requirements
Charpy V-notch tests per AS 1544.2 are required only when L0 or L15 is specified.
| Grade | Sub-grade | Test Temperature | Average Minimum | Individual Minimum |
|---|---|---|---|---|
| 300 | L0 | 0 °C | 27 J | 20 J |
| 300 | L15 | −15 °C | 27 J | 20 J |
| 350 | L0 | 0 °C | 27 J | 20 J |
| 350 | L15 | −15 °C | 27 J | 20 J |
| 400 | L0 | 0 °C | 27 J | 20 J |
| 400 | L15 | −15 °C | 27 J | 20 J |
Specimens are taken from the flange. Average of three must be ≥ 27 J; no more than one individual result may fall below 20 J.
Welding Requirements
AS/NZS 3679.2 imposes weld-quality requirements on the longitudinal fillet welds joining flanges to the web. Key provisions:
- Weld process: Submerged arc welding (SAW) is the standard process. Other processes (GMAW, FCAW) require pre-qualified procedure qualification records per AS/NZS 2980.
- Weld size: Minimum fillet weld size is specified based on the web and flange thickness combination.
- Internal defects: Weld defects are assessed per AS/NZS 3679.2 Table limits; radiographic or ultrasonic testing of welds may be required under supplementary clauses.
- HAZ properties: The heat-affected zone (HAZ) adjacent to the flange-to-web weld must not exhibit hardness exceeding 350 HV10 when tested per AS 1817.
- Weld procedure: The welding consumable and procedure must be qualified to achieve the required weld metal tensile and impact properties.
- Residual stress: Residual stresses from welding are acknowledged; thermal straightening after welding must not exceed specified temperature limits (typically ≤ 650 °C for Grade 350).
Dimensional Tolerances
| Parameter | Tolerance |
|---|---|
| Overall depth (d) | ±3 mm |
| Flange width (bf) | ±3 mm |
| Flange thickness (tf) | −5% to +12% of nominal |
| Web thickness (tw) | −5% to +12% of nominal |
| Squareness of flange | 1% of flange width |
| Sweep (lateral bow) | 1 mm per metre, 4 mm per 6 m |
| Camber (vertical bow) | Per purchase agreement; typically ≤ L/1000 |
| Mass per metre | ±3.0% on individual, ±1.5% on lots |
Key Section Properties — Welded Beams (WB), Grade 350
| Designation | d (mm) | bf (mm) | tf (mm) | tw (mm) | Mass (kg/m) |
|---|---|---|---|---|---|
| 200 WB 22.3 | 196 | 134 | 7.0 | 4.5 | 22.3 |
| 250 WB 25.7 | 244 | 146 | 6.0 | 4.0 | 25.7 |
| 300 WB 32.0 | 290 | 165 | 6.5 | 4.5 | 32.0 |
| 350 WB 48.0 | 340 | 200 | 8.0 | 6.0 | 48.0 |
| 400 WB 67.0 | 390 | 230 | 10.0 | 7.0 | 67.0 |
| 500 WB 74.0 | 490 | 250 | 8.0 | 6.0 | 74.0 |
| 500 WB 92.0 | 494 | 250 | 10.0 | 7.0 | 92.0 |
| 500 WB 115 | 500 | 250 | 14.0 | 8.0 | 115 |
| 700 WB 115 | 686 | 300 | 12.0 | 8.0 | 115 |
| 700 WB 150 | 692 | 300 | 16.0 | 9.5 | 150 |
| 900 WB 175 | 880 | 350 | 14.0 | 10.0 | 175 |
| 900 WB 218 | 890 | 350 | 18.0 | 12.0 | 218 |
| 1200 WB 249 | 1196 | 350 | 14.0 | 10.0 | 249 |
| 1200 WB 317 | 1204 | 350 | 20.0 | 12.0 | 317 |
Key Section Properties — Welded Columns (WC), Grade 350
| Designation | d (mm) | bf (mm) | tf (mm) | tw (mm) | Mass (kg/m) |
|---|---|---|---|---|---|
| 200 WC 52.0 | 200 | 200 | 8.0 | 6.0 | 52.0 |
| 250 WC 73.0 | 250 | 250 | 10.0 | 7.0 | 73.0 |
| 250 WC 89.0 | 254 | 256 | 12.0 | 8.0 | 89.0 |
| 350 WC 197 | 350 | 350 | 20.0 | 12.0 | 197 |
| 350 WC 230 | 356 | 352 | 25.0 | 13.0 | 230 |
| 400 WC 181 | 400 | 400 | 18.0 | 10.0 | 181 |
| 400 WC 212 | 402 | 400 | 22.0 | 12.0 | 212 |
Cross-Standard Equivalents
Welded sections to AS/NZS 3679.2 are broadly comparable to fabricated welded sections in other standards. Plate grades used in manufacture are equivalent per AS/NZS 3678.
| AS/NZS 3679.2 Grade | ASTM Plate Equivalent | EN 10025 Plate Equivalent | Notes |
|---|---|---|---|
| 300 | A36 | S275JR | Welded section standard-specific requirements differ |
| 350 | A572 Gr 50 | S355JR | Common grade for WB/WC in Australia |
| 400 | A572 Gr 60 | S420ML | Higher-strength; restricted availability |
Note: There is no direct ASTM standard for welded structural sections equivalent to AS/NZS 3679.2. In North American practice, welded built-up sections are designed per AISC and use ASTM plate material. EN 10025-2 covers the plate; EN 10034 and EN 10162 govern hot-rolled section tolerances but not welded sections.
MTC Verification Checklist
- Standard shown as
AS/NZS 3679.2 - Grade and sub-grade match purchase order (e.g.,
350L0) - Section designation matches ordered product (e.g.,
700 WB 150) - Constituent plate heat numbers traceable to AS/NZS 3678 MTCs
- C, P, S, CEV values within grade limits for flange thickness
- ReH ≥ minimum for flange thickness; Rm ≥ minimum
- Elongation ≥ 22% (Grade 300/350) or ≥ 20% (Grade 400)
- Charpy results reported if L0 or L15 ordered
- Weld procedure reference or qualification number recorded
- Dimensional inspection records available
- ACRS certificate number noted
- MTC signed by authorised manufacturer representative
Frequently Asked Questions
What is the difference between WB and WC sections in AS/NZS 3679.2?
Welded Beams (WB) are proportioned with a deeper web relative to flange width, optimised for bending moment resistance in beams and girders spanning horizontally. Welded Columns (WC) have a compact cross-section with nearly equal depth and flange width, providing good resistance to both axial compression and bending in both axes. WC sections are used as columns in multi-storey building frames where bi-axial loading is significant.
Are WB sections stronger than UB sections of the same mass?
Not necessarily stronger — it depends on the application. WB sections typically have greater depth for the same mass compared to equivalent UB sections, giving higher section modulus for bending applications. However, hot-rolled UB sections are manufactured to tighter dimensional tolerances and have more predictable residual stress distributions. For heavily loaded long-span beams, WB sections offer greater economy; for standard framing, UB sections are often preferred for consistency.
Do welded sections require additional weld quality documentation on the MTC?
Yes. An AS/NZS 3679.2 MTC should reference the weld procedure specification (WPS) or procedure qualification record (PQR) used in manufacture, and include a statement that welding was performed in accordance with AS/NZS 3679.2 weld requirements. For L0/L15 grades, weld HAZ hardness compliance should be documented. Supplementary UT or radiographic inspection reports, if required, should also be referenced.
Can AS/NZS 3679.2 Grade 400 welded sections be used without additional approvals?
Grade 400 is a listed grade within AS/NZS 3679.2. However, designers using Grade 400 in AS 4100 designs should note that some code capacity tables and design aids are based on Grade 350. Grade 400 can be used with the appropriate yield strength values, but the higher CEV (up to 0.53) means more stringent preheat requirements per AS/NZS 1554.1 for welded connections, and these must be reflected in the project welding procedures.
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