Quick Answer
Quick Answer
AS/NZS 1163 covers cold-formed structural steel hollow sections — RHS (rectangular), SHS (square), and CHS (circular) — in three grades: C250L0, C350L0, and C450L0. The "C" prefix denotes cold-formed; "L0" denotes 0 °C Charpy impact testing. C350L0 delivers a minimum yield strength of 350 MPa and 430 MPa tensile strength.
AS/NZS 1163 is the joint Australian and New Zealand standard for cold-formed structural steel hollow sections. It applies to rectangular hollow sections (RHS), square hollow sections (SHS), and circular hollow sections (CHS) produced by cold-forming from strip or plate, with or without subsequent annealing or stress-relieving treatment. Hollow sections produced to this standard are widely used for columns, trusses, bracing members, portal frame purlins, and architectural structures throughout Australia and New Zealand.
The "C" prefix in the grade designation distinguishes cold-formed hollow sections from hot-rolled flat products. All three grades include the L0 sub-designation, meaning Charpy impact testing at 0 °C is mandatory for all grades.
Scope and Applicability
AS/NZS 1163 applies to:
- Cold-formed structural steel hollow sections in RHS, SHS, and CHS profiles
- Wall thicknesses from 1.6 mm to 16.0 mm
- Nominal outside dimensions up to 400 mm × 400 mm (RHS/SHS) and up to 508 mm outside diameter (CHS)
- Sections supplied in straight lengths from 6.0 m to 12.5 m (standard mill lengths)
- Grades C250L0, C350L0, and C450L0
The standard does not cover:
- Hot-finished hollow sections (produced by hot-rolling or hot-extrusion)
- Structural tube for pressure or fluid applications (refer AS 1074, AS 1579)
- Mechanical tube without structural certification
Grade Coverage
| Grade | Charpy Sub-grade | Yield Strength (min) | Tensile Strength (min) | Typical Use |
|---|---|---|---|---|
| C250L0 | L0 (0 °C) | 250 MPa | 320 MPa | Light structures, secondary members, frames |
| C350L0 | L0 (0 °C) | 350 MPa | 430 MPa | General structural use, trusses, columns |
| C450L0 | L0 (0 °C) | 450 MPa | 500 MPa | High-load columns, long-span trusses |
All grades have the L0 designation built into the grade name. Impact testing at 0 °C to 27 J average is a standard requirement — there are no variants without impact testing, unlike AS/NZS 3678/3679.1 base grades. There is no L15 (−15 °C) variant in AS/NZS 1163.
Chemical Composition Requirements
Composition applies to the strip or coil material used in manufacture. All values are wt% maximum unless a range is shown.
Grade C250L0
| Element | Limit |
|---|---|
| C max | 0.22 |
| Mn max | 1.70 |
| Si max | 0.50 |
| P max | 0.040 |
| S max | 0.040 |
| CEV max | 0.43 |
Grade C350L0
| Element | Limit |
|---|---|
| C max | 0.22 |
| Mn max | 1.70 |
| Si max | 0.50 |
| P max | 0.040 |
| S max | 0.040 |
| CEV max | 0.43 |
Grade C450L0
| Element | Limit |
|---|---|
| C max | 0.22 |
| Mn max | 1.70 |
| Si max | 0.50 |
| P max | 0.040 |
| S max | 0.040 |
| CEV max | 0.46 |
CEV = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15. The higher strength of C450L0 is achieved through cold-working strain hardening, not primarily through composition differences. The microstructure and work-hardening during the cold-forming process increase the effective yield strength above that of the parent strip. This means welding can partially anneal the cold-worked zone, reducing strength in the HAZ.
Mechanical Properties
All tensile tests per AS 1391. Test specimens are taken from the face of the hollow section (not the corner region).
| Grade | Wall Thickness (mm) | ReH min (MPa) | Rm min (MPa) | Elongation A5 min % |
|---|---|---|---|---|
| C250L0 | 1.6 to 6.0 | 250 | 320 | 20 |
| C250L0 | > 6.0 to 16.0 | 250 | 320 | 20 |
| C350L0 | 1.6 to 6.0 | 350 | 430 | 16 |
| C350L0 | > 6.0 to 16.0 | 350 | 430 | 16 |
| C450L0 | 1.6 to 6.0 | 450 | 500 | 12 |
| C450L0 | > 6.0 to 16.0 | 450 | 500 | 12 |
Note: Elongation requirements for hollow sections are lower than for plate/sections of equivalent grade due to the work-hardening in the cold-forming process. For C450L0, the elongation minimum of 12% is adequate for most structural applications but restricts use in applications requiring high ductility.
Impact Test Requirements
Charpy V-notch impact tests per AS 1544.2 are mandatory for all grades (L0 is built into the grade designation).
| Grade | Test Temperature | Average Minimum | Individual Minimum |
|---|---|---|---|
| C250L0 | 0 °C | 27 J | 20 J |
| C350L0 | 0 °C | 27 J | 20 J |
| C450L0 | 0 °C | 27 J | 20 J |
Three specimens per test. The average must be ≥ 27 J; no more than one individual result may fall below 20 J. Specimens are taken from the flat face of the section, not the corner zone. Corner regions are excluded because cold-bending work-hardens the material and can reduce toughness in corner zones relative to the flat faces.
Section Size Ranges
Rectangular Hollow Sections (RHS)
| Category | Outside Width (mm) | Outside Height (mm) | Wall Thickness (mm) |
|---|---|---|---|
| Light | 50 × 25 to 75 × 50 | — | 1.6 to 4.0 |
| Standard | 100 × 50 to 200 × 100 | — | 2.5 to 9.0 |
| Heavy | 250 × 150 to 400 × 200 | — | 6.0 to 16.0 |
Square Hollow Sections (SHS)
| Category | Outside Size (mm × mm) | Wall Thickness (mm) |
|---|---|---|
| Light | 20 × 20 to 65 × 65 | 1.6 to 4.0 |
| Standard | 75 × 75 to 200 × 200 | 2.5 to 12.5 |
| Heavy | 250 × 250 to 400 × 400 | 6.0 to 16.0 |
Circular Hollow Sections (CHS)
| Category | Outside Diameter (mm) | Wall Thickness (mm) |
|---|---|---|
| Light | 21.3 to 88.9 | 1.6 to 6.0 |
| Standard | 101.6 to 219.1 | 3.2 to 12.5 |
| Heavy | 244.5 to 508.0 | 6.0 to 16.0 |
Exact available sizes depend on the manufacturer. InfraBuild (formerly OneSteel) and Orrcon Steel publish complete size tables for Australian-stocked product.
Dimensional Tolerances
| Parameter | RHS/SHS | CHS |
|---|---|---|
| Outside width/height | ±1% or ±0.5 mm (whichever greater) | — |
| Outside diameter | — | ±1% or ±0.5 mm (whichever greater) |
| Wall thickness | −10% to +10% | −10% to +10% |
| Mass per metre | ±6% (individual), ±4% (lot) | ±6% (individual), ±4% (lot) |
| Straightness | 1 mm per metre | 1 mm per metre |
| Squareness of end | 2° | — |
| Corner radius (outer) | 2.0 to 3.0× wall thickness | — |
Welding Considerations
Because C350L0 and C450L0 achieve part of their strength through cold-working:
- Welding in the corner zone should be avoided where possible; structural welds should be located on flat faces.
- HAZ softening adjacent to welds reduces the yield strength locally. Design to AS 4100 accounts for this by treating welded regions conservatively.
- Preheat requirements per AS/NZS 1554.1: for C350L0 with CEV ≤ 0.43, preheat is generally not required for wall thicknesses up to ~12 mm; C450L0 with CEV ≤ 0.46 may require preheat for thicker walls or high-restraint joints.
- Electrodes and consumables should match the base grade. For C450L0, use E48 or E49 series electrodes (480–490 MPa deposited weld metal tensile strength).
Cross-Standard Equivalents
| AS/NZS 1163 Grade | EN 10219 Equivalent | ASTM A500 Equivalent | JIS G3466 | Notes |
|---|---|---|---|---|
| C250L0 | S250NH | Grade A (CHS) / Grade A (RHS) | STKR400 | EN impact test at 0 °C for J0 sub-grade |
| C350L0 | S355NH (CHS) / S355NH (RHS) | Grade C (CHS/RHS) | STKR490 | S355NH = 355 MPa min yield, 0 °C Charpy |
| C450L0 | S420MH | Grade D | — | EN 10219 Grade S420 is hot-finished; no direct cold-formed equivalent in EN |
ASTM A500 is the US standard for cold-formed structural hollow sections. Grade C (317 MPa yield for RHS/SHS, 317 MPa for CHS) is the closest match to C350L0 by tensile properties, though impact testing is not required by A500 in its base edition.
MTC Verification Checklist
- Standard shown as
AS/NZS 1163 - Grade matches purchase order:
C250L0,C350L0, orC450L0(note: grade includes the L0 suffix — it is not separate) - Section profile (RHS, SHS, CHS) and nominal size match ordered product
- Heat (cast) number traceable to physical section markings
- C, Mn, P, S, CEV values within grade limits
- ReH ≥ grade minimum for the wall thickness range
- Rm ≥ grade minimum
- Elongation ≥ 20% (C250L0), ≥ 16% (C350L0), ≥ 12% (C450L0)
- Charpy: three individual values and average reported at 0 °C; average ≥ 27 J
- Dimensional inspection report or mill tolerance compliance statement present
- ACRS certificate number noted (if applicable)
- MTC signed by authorised mill representative
Frequently Asked Questions
Why does the grade designation in AS/NZS 1163 always include 'L0'?
Unlike AS/NZS 3678 and 3679.1 where impact testing is optional (base grade with no L suffix has no Charpy requirement), AS/NZS 1163 mandates Charpy testing at 0 °C for all grades. The L0 is therefore not an optional sub-grade but a standard requirement built into the grade name. There is no equivalent to a base grade without impact testing, and there is no L15 (−15 °C) sub-grade in AS/NZS 1163.
What is the yield strength of AS/NZS 1163 C350L0?
The minimum yield strength (ReH) for C350L0 is 350 MPa for all wall thicknesses from 1.6 mm to 16.0 mm. The minimum tensile strength is 430 MPa. Elongation must be at least 16% on a gauge length of 5.65√A₀. These properties are consistent across the grade regardless of section size.
Can cold-formed hollow sections be hot-dip galvanised?
Yes. AS/NZS 1163 hollow sections are regularly hot-dip galvanised to AS/NZS 4680. However, venting holes must be provided in closed sections before galvanising to allow zinc to flow in and trapped air/steam to escape, preventing explosion in the galvanising bath. Corner regions with high residual stress from cold-forming can be susceptible to liquid metal embrittlement — the zinc bath temperature (445–465 °C) and residual stresses can interact. This risk is managed by ensuring the section chemistry (silicon and phosphorus content) is within limits specified by the galvaniser, and by avoiding excessively sharp bends.
Is C450L0 equivalent to Grade 450 structural plate?
Broadly comparable in yield strength, but they are different product forms with different ductility requirements. AS/NZS 3678 Grade 400 plate has a 20% elongation minimum versus 12% for C450L0 hollow sections. The cold-forming process in C450L0 raises yield strength through strain hardening, which also reduces ductility. For applications requiring high toughness or significant plastic deformation, Grade 400/350 plate or hot-finished hollow sections should be considered over C450L0.
What is the difference between cold-formed (AS/NZS 1163) and hot-finished hollow sections?
Cold-formed hollow sections (AS/NZS 1163) are formed from flat strip at ambient temperature, creating residual stresses in corner regions and relying on strain hardening for strength in C350/C450 grades. Hot-finished hollow sections (no Australian standard — sourced to EN 10210) are formed while the steel is hot and then allowed to cool, relieving residual stresses and producing a more uniform microstructure. Hot-finished sections have better ductility, more uniform corner properties, and improved weldability, but are more expensive and less commonly stocked in Australia.
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