Quick Answer
Quick Answer
AS/NZS 3678 covers hot-rolled structural steel plates, floorplates, and slabs in grades 200, 250, 300, 350, 400, and WR350. Each grade above 200 offers L0 (0 °C Charpy) and L15 (−15 °C Charpy) sub-grades. Grade 350 has a minimum yield strength of 360 MPa at ≤ 11 mm and 340 MPa at 11–17 mm, with 480 MPa tensile strength.
AS/NZS 3678 is the primary Australian and New Zealand standard for hot-rolled structural steel flat products — plates, floorplates, and slabs. Published jointly by Standards Australia and Standards New Zealand, it sets compositional and mechanical requirements for steels used in structural engineering applications such as bridges, buildings, pressure vessels, and marine structures. The standard is published in SI units and applies to products produced in Australia or imported for Australian and New Zealand projects.
Scope and Applicability
AS/NZS 3678 applies to:
- Hot-rolled flat products: plates (thickness ≥ 3 mm), floorplates (chequer plate), and slabs
- Structural applications in buildings, bridges, cranes, and offshore platforms
- Products with nominal thickness from 3 mm to 140 mm
- All grades supplied in the as-rolled or normalised condition
The standard does not cover structural sections (universal beams, columns, channels, angles) — those are addressed by AS/NZS 3679.1 (hot-rolled bars and sections) and AS/NZS 3679.2 (welded I-sections). Hollow sections are covered by AS/NZS 1163.
Grade Coverage
AS/NZS 3678 specifies six grade families. The numeric designator approximates the minimum yield strength in MPa for thin product. Sub-grades L0 and L15 indicate the Charpy impact test temperature.
| Grade | Sub-grades | Impact Test Temperature | Typical Application |
|---|---|---|---|
| 200 | (none) | Not required | Light structural, general fabrication |
| 250 | L0, L15 | 0 °C (L0) / −15 °C (L15) | General structural, building frames |
| 300 | L0, L15 | 0 °C (L0) / −15 °C (L15) | Medium structural, bridges |
| 350 | L0, L15 | 0 °C (L0) / −15 °C (L15) | Heavy structural, high-rise buildings |
| 400 | L0, L15 | 0 °C (L0) / −15 °C (L15) | High-strength structural, crane booms |
| WR350 | L0, L15 | 0 °C (L0) / −15 °C (L15) | Weathering steel, exposed structures |
Grade 200 does not have sub-grades and has no impact test requirement. WR350 is a weathering (atmospheric corrosion-resistant) grade with copper and chromium additions.
Chemical Composition Requirements
All values are wt% maximum unless a range is shown. Composition is governed by ladle analysis. CEV = carbon equivalent value per formula: CEV = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15.
Grade 200
| Element | ≤ 11 mm | > 11 mm |
|---|---|---|
| C max | 0.22 | 0.22 |
| Mn max | 1.60 | 1.60 |
| Si max | 0.50 | 0.50 |
| P max | 0.040 | 0.040 |
| S max | 0.040 | 0.040 |
| CEV max | 0.43 | 0.43 |
Grade 250
| Element | ≤ 11 mm | 11–17 mm | 17–40 mm | > 40 mm |
|---|---|---|---|---|
| C max | 0.22 | 0.22 | 0.22 | 0.22 |
| Mn max | 1.70 | 1.70 | 1.70 | 1.70 |
| Si max | 0.50 | 0.50 | 0.50 | 0.50 |
| P max | 0.040 | 0.040 | 0.040 | 0.040 |
| S max | 0.040 | 0.040 | 0.040 | 0.040 |
| CEV max | 0.43 | 0.43 | 0.43 | 0.43 |
Grade 300
| Element | ≤ 11 mm | 11–17 mm | 17–40 mm | > 40 mm |
|---|---|---|---|---|
| C max | 0.20 | 0.20 | 0.20 | 0.20 |
| Mn max | 1.70 | 1.70 | 1.70 | 1.70 |
| Si max | 0.50 | 0.50 | 0.50 | 0.50 |
| P max | 0.040 | 0.040 | 0.040 | 0.040 |
| S max | 0.040 | 0.040 | 0.040 | 0.040 |
| CEV max | 0.46 | 0.46 | 0.46 | 0.46 |
Grade 350
| Element | ≤ 11 mm | 11–17 mm | 17–40 mm | > 40 mm |
|---|---|---|---|---|
| C max | 0.20 | 0.20 | 0.20 | 0.20 |
| Mn max | 1.70 | 1.70 | 1.70 | 1.70 |
| Si max | 0.50 | 0.50 | 0.50 | 0.50 |
| P max | 0.040 | 0.040 | 0.040 | 0.040 |
| S max | 0.040 | 0.040 | 0.040 | 0.040 |
| CEV max | 0.48 | 0.48 | 0.48 | 0.50 |
Grade 400
| Element | ≤ 11 mm | 11–17 mm | 17–40 mm | > 40 mm |
|---|---|---|---|---|
| C max | 0.20 | 0.20 | 0.20 | 0.20 |
| Mn max | 1.70 | 1.70 | 1.70 | 1.70 |
| Si max | 0.50 | 0.50 | 0.50 | 0.50 |
| P max | 0.035 | 0.035 | 0.035 | 0.035 |
| S max | 0.035 | 0.035 | 0.035 | 0.035 |
| CEV max | 0.50 | 0.50 | 0.50 | 0.53 |
Grade WR350 (Weathering Steel)
| Element | ≤ 11 mm | > 11 mm |
|---|---|---|
| C max | 0.17 | 0.17 |
| Mn max | 1.30 | 1.30 |
| Si | 0.15–0.50 | 0.15–0.50 |
| P max | 0.040 | 0.040 |
| S max | 0.040 | 0.040 |
| Cu min | 0.25 | 0.25 |
| Cr | 0.40–0.80 | 0.40–0.80 |
| Ni | 0.10–0.50 | 0.10–0.50 |
| CEV max | 0.48 | 0.48 |
WR350 must also meet: Al ≥ 0.015% when fine grain practice is used. The combination of Cu + Cr + Ni + Mo ≥ 0.60% is required for weathering classification.
Mechanical Properties
Minimum tensile properties from transverse test specimens per AS 1391. ReH = upper yield strength (or Rp0.2 for grades without a defined yield point), Rm = ultimate tensile strength.
Grade 200
| Thickness (mm) | ReH min (MPa) | Rm (MPa) | Elongation A5 min % |
|---|---|---|---|
| ≤ 11 | 200 | 300–400 | 22 |
| > 11 to 17 | 200 | 300–400 | 22 |
| > 17 to 40 | 200 | 300–400 | 22 |
Grade 250
| Thickness (mm) | ReH min (MPa) | Rm (MPa) | Elongation A5 min % |
|---|---|---|---|
| ≤ 11 | 260 | 410–530 | 22 |
| > 11 to 17 | 250 | 410–530 | 22 |
| > 17 to 40 | 250 | 410–530 | 22 |
| > 40 to 50 | 240 | 400–520 | 22 |
| > 50 to 65 | 230 | 400–520 | 22 |
| > 65 to 80 | 220 | 380–510 | 22 |
| > 80 to 110 | 210 | 380–510 | 22 |
| > 110 to 140 | 200 | 360–480 | 22 |
Grade 300
| Thickness (mm) | ReH min (MPa) | Rm (MPa) | Elongation A5 min % |
|---|---|---|---|
| ≤ 11 | 320 | 430–560 | 22 |
| > 11 to 17 | 310 | 430–560 | 22 |
| > 17 to 40 | 300 | 430–560 | 22 |
| > 40 to 50 | 290 | 420–550 | 22 |
| > 50 to 65 | 280 | 420–550 | 22 |
| > 65 to 80 | 270 | 400–530 | 22 |
| > 80 to 110 | 260 | 400–530 | 22 |
| > 110 to 140 | 250 | 380–510 | 22 |
Grade 350
| Thickness (mm) | ReH min (MPa) | Rm (MPa) | Elongation A5 min % |
|---|---|---|---|
| ≤ 11 | 360 | 480–620 | 22 |
| > 11 to 17 | 340 | 480–620 | 22 |
| > 17 to 40 | 340 | 480–620 | 22 |
| > 40 to 50 | 330 | 460–600 | 22 |
| > 50 to 65 | 320 | 460–600 | 22 |
| > 65 to 80 | 310 | 450–590 | 22 |
| > 80 to 110 | 300 | 450–590 | 22 |
| > 110 to 140 | 280 | 430–570 | 22 |
Grade 400
| Thickness (mm) | ReH min (MPa) | Rm (MPa) | Elongation A5 min % |
|---|---|---|---|
| ≤ 11 | 420 | 480–650 | 20 |
| > 11 to 17 | 400 | 480–650 | 20 |
| > 17 to 40 | 380 | 480–650 | 20 |
| > 40 to 50 | 360 | 460–630 | 20 |
| > 50 to 65 | 350 | 460–630 | 20 |
Grade WR350
| Thickness (mm) | ReH min (MPa) | Rm (MPa) | Elongation A5 min % |
|---|---|---|---|
| ≤ 11 | 360 | 480–620 | 22 |
| > 11 to 17 | 340 | 480–620 | 22 |
| > 17 to 40 | 340 | 480–620 | 22 |
| > 40 to 80 | 320 | 460–600 | 22 |
Impact Test Requirements
Charpy V-notch impact tests are required for all grades except Grade 200. Tests are conducted per AS 1544.2.
| Grade | Sub-grade | Test Temperature | Minimum Average Energy | Individual Minimum |
|---|---|---|---|---|
| 250 | L0 | 0 °C | 27 J | 20 J |
| 250 | L15 | −15 °C | 27 J | 20 J |
| 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 |
| WR350 | L0 | 0 °C | 27 J | 20 J |
| WR350 | L15 | −15 °C | 27 J | 20 J |
Tests are conducted on sets of three transverse Charpy specimens. The average of three specimens must meet the minimum average; not more than one specimen may fall below the individual minimum. Grade 200 has no impact test requirement and no L-sub-grade designation.
Additional Tests
- Bend test: All grades must pass a guided bend test with mandrel diameter as specified per grade and thickness.
- Ultrasonic testing: Optional (supplementary requirement S1). Plates thicker than 40 mm may be subject to UT per AS 2207 when specified on the purchase order.
- Through-thickness (Z) properties: Lamellar tearing resistance (Z25, Z35 per supplementary requirement) may be specified for plates loaded in the through-thickness direction.
- Surface quality: Plates must be free from cracks, seams, laps, and other injurious defects. Minor surface imperfections may be ground to a smooth contour.
Australian Steel Mill Certification Requirements
Mill test certificates (MTCs) for AS/NZS 3678 material supplied to Australian and New Zealand projects must comply with the requirements of AS/NZS 3678 Clause 9 and typically include:
- Standard designation:
AS/NZS 3678with grade and sub-grade (e.g.,350L0) - Steel maker's name and works
- Cast (heat) number and product identification
- Product form, dimensions, and mass
- Ladle (heat) analysis for C, Mn, Si, P, S, Al (when fine-grain), and CEV
- Tensile test results: ReH, Rm, and elongation
- Charpy impact test results (temperature, individual and average values) for L0/L15 grades
- Statement of compliance with AS/NZS 3678
- Authorised signatory and date
ACRS Certification: The Australasian Certification Authority for Reinforcing and Structural Steels (ACRS) provides third-party product certification for structural steels in Australia and New Zealand. ACRS-certified mills undergo audited surveillance to confirm ongoing compliance with AS/NZS 3678. Specifiers and engineers should verify that steel for structural applications is sourced from ACRS-certified suppliers, particularly for projects under the National Construction Code (NCC) or governed by AS 4100 (Steel Structures). The ACRS certificate number and expiry date should be recorded as part of project quality documentation.
Cross-Standard Equivalents
AS/NZS 3678 grades are broadly equivalent to grades in other international standards. Equivalency is approximate — direct substitution requires verification of specific composition, mechanical, and impact requirements.
| AS/NZS 3678 Grade | ASTM Equivalent | EN 10025 Equivalent | IS 2062 Equivalent | JIS G3101 |
|---|---|---|---|---|
| 250 | A36 | S235JR / S235J0 | E250 (Fe 410-W) | SS400 |
| 300 | A572 Gr 42 | S275JR / S275J0 | E300 | SM400 |
| 350 (L0) | A572 Gr 50 | S355JR | E350 (Fe 490-W) | SM490 |
| 350 (L15) | A572 Gr 50 | S355J2 | E350 | SM490 |
| 400 (L0) | A572 Gr 60 | S420ML | — | SM520 |
| WR350 | A588 Gr A/B | S355J0WP / S355J2WP | — | SMA400 |
Note: EN 10025-3 S355NL and S355ML have additional normalised or thermo-mechanically rolled conditions that do not directly correspond to AS/NZS 3678 as-rolled product. Verify CEV, impact energy, and delivery condition before substitution.
MTC Verification Checklist
When receiving AS/NZS 3678 material on a project, verify:
- Standard shown as
AS/NZS 3678(not simplyAS 3678— the joint edition is the current version) - Grade and sub-grade match purchase order (e.g.,
350L0not just350) - Heat number traceable to physical plate markings (colour code or stencil)
- C, Mn, Si, P, S values within grade limits for the supplied thickness range
- CEV calculated or stated and within limit for grade/thickness
- ReH ≥ minimum for the thickness range ordered
- Rm within the specified range (not just above minimum)
- Elongation ≥ 22% (or 20% for Grade 400)
- Charpy results (L0/L15): three individual values and average reported, all compliant
- ACRS certificate number noted in project quality file (if applicable)
- MTC signed by authorised mill representative
Frequently Asked Questions
What does the L suffix mean in AS/NZS 3678 grade designations?
The L suffix indicates the Charpy V-notch impact test temperature. L0 means the steel passes the 27 J average Charpy test at 0 °C; L15 means it passes at −15 °C. Grade 200 has no L sub-grade because impact testing is not required. For projects in cold climates or where fracture toughness is critical (e.g., bridges, offshore structures), L15 grades are typically specified.
What is the yield strength of AS/NZS 3678 Grade 350?
For thickness ≤ 11 mm, the minimum yield strength (ReH) is 360 MPa. For thicknesses from 11 mm to 40 mm it is 340 MPa, dropping progressively for thicker plates: 330 MPa (40–50 mm), 320 MPa (50–65 mm), 310 MPa (65–80 mm), 300 MPa (80–110 mm), and 280 MPa (110–140 mm). The tensile strength (Rm) range for Grade 350 is 480–620 MPa for thicknesses up to 65 mm.
Is AS/NZS 3678 Grade 350 equivalent to ASTM A572 Grade 50?
They are broadly comparable in yield strength (350 MPa vs 345 MPa) and tensile range, but there are differences in chemical composition limits, CEV requirements, and impact testing provisions. A572 Gr 50 does not mandate Charpy impact testing in its base specification, whereas AS/NZS 3678 350L0/L15 mandates 27 J at 0 °C or −15 °C. Direct substitution requires design engineer approval and documentation.
What is WR350 and when is it used?
WR350 is a weathering steel grade equivalent in strength to Grade 350 but with added Cu, Cr, and Ni to form a stable, adherent patina when exposed to the atmosphere. This patina significantly retards further corrosion, eliminating the need for paint in many outdoor applications. It is used for exposed bridge girders, architectural features, and structures in rural or semi-industrial environments. It is not suitable in marine splash zones or environments with persistent moisture.
Does AS/NZS 3678 require ACRS certification?
AS/NZS 3678 itself does not mandate ACRS certification — it is a product standard, not a procurement policy. However, the Australian Building Codes Board and many state government procurement policies require or strongly recommend ACRS-certified steel for structural applications under AS 4100. Engineers should check project specifications and relevant authority requirements. ACRS certification provides independent third-party assurance that the steel consistently meets AS/NZS 3678.
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