What is the carbon equivalent value (CEV) of AS/NZS 3679.1 Grade 300PLUS?

Grade 300PLUS has a guaranteed maximum CEV of 0.40 per AS/NZS 3679.1. The CEV is calculated as C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15. This low CEV ensures excellent weldability without preheat for most thicknesses. Standard Grade 300 also has CEV 0.40 max but without the guaranteed compliance that 300PLUS provides.

Australian Steel Properties — AS/NZS 3679.1 Yield & Tensile Strength by Grade

Q: What is the difference between Grade 300 and Grade 300PLUS in AS/NZS 3679.1?

Grade 300PLUS has the same minimum yield (300 MPa) and tensile (430 MPa) strength as Grade 300 but with guaranteed tighter chemical composition limits — specifically a guaranteed maximum CEV of 0.40 for improved weldability. In practice, Grade 300PLUS is the default structural steel grade supplied in Australia.

Q: What is the yield strength of AS/NZS 3679.1 Grade 350 steel?

The minimum yield strength of Grade 350 is 340 MPa for thicknesses up to 12 mm, reducing to 330 MPa for 12-20 mm, 310 MPa for 20-40 mm, and 280 MPa for 40-80 mm. Despite the name '350', the tabulated minimum Fy is 340 MPa because the grade designation refers to the nominal yield, while the specified minimum varies by thickness bracket.

Q: When is Charpy V-notch testing required for Australian structural steel?

AS 4100 Clause 5.4.2 requires CVN testing when the minimum service temperature is below 0 C, for tension members thicker than 25 mm, or for welded tension connections thicker than 12 mm in service below 10 C. The Charpy test temperature must be at or below the adjusted service temperature. For most indoor commercial buildings in temperate Australian cities, CVN testing is not required.

Q: How do AS/NZS 3679.1 grades compare to ASTM and EN standards?

Grade 350 is approximately equivalent to ASTM A992 (Fy = 345 MPa) and EN 10025 S355 JR (Fy = 355 MPa). Grade 300PLUS is comparable to ASTM A572 Grade 42 or EN S275 JR. The Australian grades have slightly lower Fy values in thicker sections compared to international equivalents.

Complete reference for AS/NZS 3679.1 structural steel mechanical properties. Yield strength Fy, tensile strength Fu, elongation, and Charpy V-notch impact values for hot-rolled steel sections and plates used in Australian steel design per AS 4100:2020.

Quick access: AS 4100 steel design guide → | Beam capacity calculator → | Steel section properties →

AS/NZS 3679.1 Structural Steel Grades

AS/NZS 3679.1 (Hot-Rolled Structural Steel Sections and Bars) is the Australian and New Zealand standard that covers universal beams (UB), universal columns (UC), parallel flange channels (PFC), equal and unequal angles, and welded sections (WB, WC). The standard defines five primary structural grades.

Grade 300

Grade 300 is the base structural steel grade used for lightly loaded members where strength requirements are modest. It has a minimum yield strength of 300 MPa for thicknesses up to 12 mm.

Minimum yield strength (Fy): 300 MPa (t <= 12 mm), reducing to 280 MPa for thicker sections
Minimum tensile strength (Fu): 430 MPa
Minimum elongation: 22% (5.65 x sqrt(So) gauge length)
Typical CEV: 0.40 max
Use: Light framing, secondary members, non-structural components, and general fabrication

Grade 300PLUS

Grade 300PLUS is the most common structural steel grade specified in Australia. It has the same minimum yield and tensile properties as Grade 300 but with tighter chemical composition limits and improved weldability, resulting in a guaranteed carbon equivalent value (CEV) of 0.40 max for superior welding performance.

Minimum yield strength (Fy): 300 MPa (t <= 12 mm), reducing with thickness
Minimum tensile strength (Fu): 430 MPa
Minimum elongation: 22%
Typical CEV: 0.40 max (guaranteed)
Use: The default grade for most structural applications in Australia — beams, columns, bracing, trusses, and connections. Grade 300PLUS is what you get when you order "structural steel" in Australia.

Grade 350

Grade 350 offers higher strength than Grade 300PLUS with Fy = 340 MPa for thicknesses up to 12 mm. It is used when member weight reduction or higher load capacity is needed.

Minimum yield strength (Fy): 340 MPa (t <= 12 mm)
Minimum tensile strength (Fu): 450 MPa
Minimum elongation: 22%
Typical CEV: 0.44 max
Use: Heavily loaded beams and columns, long-span structures, cantilevers, and where self-weight reduction is beneficial

Grade 400

Grade 400 is a higher-strength steel used for specialised applications where significant weight reduction is required.

Minimum yield strength (Fy): 380 MPa (t <= 12 mm)
Minimum tensile strength (Fu): 500 MPa
Minimum elongation: 20%
Typical CEV: 0.48 max
Use: Heavy-duty transport structures, mining equipment, crane runways

Grade 450

Grade 450 is the highest-strength grade in AS/NZS 3679.1, offering substantial weight savings at higher material cost.

Minimum yield strength (Fy): 430 MPa (t <= 12 mm)
Minimum tensile strength (Fu): 540 MPa
Minimum elongation: 18%
Typical CEV: 0.50 max
Use: Lightweight structures, mobile equipment, specialised industrial applications

Complete Fy and Fu Table — AS/NZS 3679.1

The following table presents mechanical properties for all grades. Fy reduces with increasing thickness due to the reduced effect of rolling.

Grade	t <= 12 mm Fy MPa	12 < t <= 20 mm Fy MPa	20 < t <= 40 mm Fy MPa	40 < t <= 80 mm Fy MPa	Fu MPa (all t)	Elongation % min
300	300	280	260	240	430	22
300PLUS	300	280	260	240	430	22
350	340	330	310	280	450	22
400	380	360	340	320	500	20
450	430	410	390	370	540	18

Plate Grades — AS/NZS 3678

Structural steel plates are covered under AS/NZS 3678 (Structural Steel — Hot-Rolled Plates, Floorplates and Slabs). The grades and strengths differ from AS/NZS 3679.1 sections.

Grade	Type	t <= 12 mm Fy MPa	Fu MPa	CEV max	Typical Use
250	Mild steel	250	410	0.38	Base plates, stiffeners, gussets
250L15	Low-temp	250	410	0.38	Low-temperature service
300	Structural	300	430	0.40	General platework
300PLUS	Structural+	300	430	0.40	Default plate grade
350	High strength	340	450	0.44	Heavy platework
400	High strength	380	500	0.48	Wear applications

Charpy V-Notch Impact Requirements

AS 4100 Clause 5.4 requires Charpy V-notch (CVN) impact testing for certain applications to ensure fracture toughness. The requirements depend on the minimum service temperature, member thickness, and stress level.

Charpy Requirements Per AS/NZS 3679.1

Grade	CVN Test Temp	Min Avg Energy (longitudinal)	Min Single Energy
300	0 °C	27 J	20 J
300PLUS	0 °C	27 J	20 J
350	0 °C	27 J	20 J
350 (optional)	-20 °C	27 J	20 J
400	0 °C (unless specified)	27 J	20 J
450	0 °C (unless specified)	27 J	20 J

When CVN Testing is Required Per AS 4100

AS 4100 Clause 5.4.2 requires Charpy V-notch testing when:

Minimum service temperature below 0 °C — for all tension members and members subject to stress reversal
Member thickness exceeds 25 mm — in tension or stress reversal applications
Welded connections in tension — with thickness exceeding 12 mm and service temperature below 10 °C
Ductility-critical connections — such as moment connections in seismic frames

The Charpy test temperature must be equal to or lower than the minimum service temperature minus a temperature adjustment based on member thickness and stress level.

Chemical Composition Requirements

AS/NZS 3679.1 specifies maximum chemical composition limits to ensure weldability and mechanical performance. The carbon equivalent value (CEV) is the primary weldability parameter.

Grade	C max	Si max	Mn max	P max	S max	CEV max
300	0.22	0.50	1.50	0.040	0.040	0.40
300PLUS	0.22	0.50	1.50	0.040	0.040	0.40
350	0.22	0.50	1.60	0.040	0.040	0.44
400	0.22	0.50	1.60	0.040	0.040	0.48
450	0.22	0.50	1.70	0.040	0.040	0.50

CEV is calculated as: C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15

AS 4100 Capacity Factors for Australian Steel

When using AS 4100:2020 for design, the following capacity factors (phi) apply to member design using the steel properties above:

Design Check	phi (Capacity Factor)
Section capacity (tension, compression, bending)	0.90
Member buckling capacity (compression, bending)	0.90
Bolt shear and tension	0.80
Weld capacity	0.80
Concrete bearing (base plates)	0.60
Anchor bolt tension	0.80
Anchor bolt shear	0.80

Cross-Reference to International Standards

AS/NZS Grade	Approx Equivalent ASTM	Approx Equivalent EN	Approx Equivalent CSA
300	A572 Gr 42	S235	260W
300PLUS	A572 Gr 42	S275 JR	300W
350	A572 Gr 50 / A992	S355 JR	350W
400	A572 Gr 60	S420 N	400W
450	A572 Gr 65	S460 N	480W

Design Resources

Australian Steel Design Guide — AS 4100 overview
AS 4100 Base Plate Design — Base plate reference
Beam Capacity Calculator
Column Capacity Calculator
Section Properties
Australian Bolt Grades

Frequently Asked Questions

What is the difference between Grade 300 and Grade 300PLUS in AS/NZS 3679.1? Grade 300PLUS has the same minimum yield (300 MPa) and tensile (430 MPa) strength as Grade 300 but with guaranteed tighter chemical composition limits — specifically a guaranteed maximum CEV of 0.40 for improved weldability. In practice, Grade 300PLUS is the default structural steel grade supplied in Australia. If you order "structural steel" in Australia without specifying a grade, you will typically receive Grade 300PLUS.

What is the yield strength of AS/NZS 3679.1 Grade 350 steel? The minimum yield strength of Grade 350 is 340 MPa for thicknesses up to 12 mm, reducing to 330 MPa for 12-20 mm, 310 MPa for 20-40 mm, and 280 MPa for 40-80 mm. Despite the name "350", the tabulated minimum Fy is 340 MPa because the grade designation refers to the nominal yield, while the specified minimum varies by thickness bracket.

When is Charpy V-notch testing required for Australian structural steel? AS 4100 Clause 5.4.2 requires CVN testing when the minimum service temperature is below 0 °C, for tension members thicker than 25 mm, or for welded tension connections thicker than 12 mm in service below 10 °C. The Charpy test temperature must be at or below the adjusted service temperature based on the thickness and stress-level factors. For most indoor commercial buildings in temperate Australian cities (Sydney, Melbourne, Brisbane), CVN testing is not required.

How do AS/NZS 3679.1 grades compare to ASTM and EN standards? AS/NZS 3679.1 Grade 350 (Fy = 340 MPa, Fu = 450 MPa) is approximately equivalent to ASTM A992 (Fy = 345 MPa, Fu = 450 MPa) used in the US and EN 10025 S355 JR (Fy = 355 MPa, Fu = 470-630 MPa) used in Europe. Grade 300PLUS is comparable to ASTM A572 Grade 42 or EN S275 JR. The Australian grades have slightly lower Fy values in thicker sections compared to their international equivalents.

Educational reference only. All design values must be verified against the current edition of AS/NZS 3679.1 and AS 4100 before use. This information does not constitute professional engineering advice. Always consult a qualified structural engineer for design decisions.