Tianjin Lefin Industrial Co., Ltd is one of the most experienced manufacturers and suppliers of as/nzs 3679.1 grade 300 hot-rolled bars, flat and sections in China. Please feel free to buy high quality as/nzs 3679.1 grade 300 hot-rolled bars, flat and sections from our factory. Good service and reasonable price are available.
I. Standard Positioning (Clearly define the boundaries)
AS/NZS 3679.1 "Structural Steel - Part 1: Hot-Rolled Bars and Sections" (the current version is : 2016, replaced by : 2010) is one of the three core material standards for structural steel in Australia/New Zealand. It only covers hot-rolled open-section steel and bars:
| Standard | Coverage |
| AS/NZS 3679.1 | Hot-Rolled Bars, Plates, and Open Sections (the current topic) |
| AS/NZS 3678 | Hot-Rolled Plates and Patterned Plates |
| AS/NZS 3679.2 | Stitched H-Sections (Welded Beams/Columns) |
| AS/NZS 1163 | Cold-Rolled/Hot-Rolled Hollow Sections (SHS/RHS/CHS, not covered by 3679.1) |
Grade 300 is applicable for structures designed according to AS 4100, AS 5100.6, and NZS 3404. It is weldable (AS/NZS 1554) and can be bolted or riveted.
II. Grade 300 Steel Grade System
The number "300" represents the nominal minimum yield strength (MPa) of this steel grade. Under the same 300 classification, based on the impact toughness requirements, there are four subgrades:
| Subgrade | Impact Requirements | Applicable Scenarios |
| 300 (Base Grade) | No Charpy Requirements | General structural frames, beams and columns |
| 300L0 | 27 J @ 0℃ (average), single value ≥ 20 J | Low temperature/dynamic load-sensitive conditions |
| 300L15 | 27 J @ −15℃ (average), single value ≥ 20 J | More severe low-temperature conditions |
| 300S0 | 70 J (Seismic Grade, only in New Zealand, in conjunction with NZS 3404) | New Zealand seismic/fault critical structures |
When placing an order, please write the full subgrade, for example, AS/NZS 3679.1-300L0. Do not just write "300", otherwise it will be defaulted to no impact acceptance.
III. Types of Section Steel (Core) under Grade 300 Steel Grade
| Category | Code | Section Characteristics | Example Name | Typical Applications |
| Universal Beam | UB | Parallel flange H-shaped, height > flange width, strong in bending | 310 UB 46.2 (310 represents nominal height in mm, 46.2 is weight in kg/m) | Beams, purlins, primary and secondary load-bearing components |
| Universal Column | UC | Flange width ≈ height, approximately square section, stable in compression | 200 UC 46.2 | Columns, axial compression components |
| Parallel Flange Channel | PFC | Flange inner surface parallel, C-shaped opening | 300 PFC | Trusses, connecting beams, supports |
| Tapered Flange Channel | TFC | Flange with taper (old type channel steel) | - | General structures, trusses |
| Equal Angle Steel | EA | L-shaped, two limbs of equal length, symmetrical strength | 100×100×10 EA | Supports, trusses, connections |
| Unequal Angle Steel | UA | L-shaped, two limbs of unequal length | 150×90×10 UA | Truss chords, secondary structures |
| T-Section Steel | Tee | Formed from universal section sections | Extracted from UB/UC | Connectors, light-duty trusses |
|
Flat Steel / Round Steel / Square Steel / Hexagonal Steel |
Flat/Round/Square/Hexagon | Bar materials | Like 100×10 Flat | Connecting plates, anchoring, general processing |
Key Points:
- The section dimensions of UB/UC/PFC are unique to Australian standards and cannot be directly interchanged with British Standard BS4, European Standard IPE/HE (EN 10365). When reporting specifications, the dimensions must be in accordance with the Australian standard table.
- Common specification range reference: UB from 150 UB to 610 UB; UC from 100 UC to 310 UC; Angle steel 20×20×3 to 250×250×28;
IV. Grade 300 Technical Requirements
1. Chemical Composition (Fore-runners' Analysis, Maximum Percentage by Mass)
| Element | C | Mn | Si | P | S | CEV |
| Grade 300 | 0.22 | 1.60 | 0.50 | 0.040 | 0.040 | 0.44 - 0.46 |
CEV = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15.
- Microalloying: Microalloying elements are not allowed in the base grade 300. They can only be added when the thickness is ≥ 15 mm, with a total of ≤ 0.15% (Nb ≤ 0.02%, V ≤ 0.03%, Ti ≤ 0.04%), and the content of each element must be indicated in the certificate.
- Intentional addition of boron is not allowed (unless agreed by the buyer); the total of residual elements is ≤ 1.00%.
- Grain refinement elements Al/Ti can be added, with a total of ≤ 0.15%.
2. Mechanical Properties (Classified by thickness of inspected part, minimum value)
|
Thickness t (mm) |
Yield Strength ReH (MPa) |
Tensile Strength Rm (MPa)
|
Tensile Elongation A5 (%) |
| t ≤ 11 | 320 | 440 | 22 |
| 11 < t ≤ 17 | 310 | 430 | 22 |
| 17 < t ≤ 40 | 300 | 430 | 22 |
| t > 40 | 280 | 410 | 22 |
That is: The thicker the steel, the lower the yield/ tensile requirements. This is the law of strength attenuation of the steel type as the section thickness increases. When placing orders and calculating strength, it is essential to take the actual flange thickness grade as the value.
3. Dimension and weight tolerance (Key item)
| Item | Tolerance |
| Single piece weight | Not less than nominal value 97.5% (i.e. -2.5%) |
| Batch (≥1 t) | total mass Nominal value ±2.5% |
| UB/UC | height ±3 mm |
| Flange width | +6 / -5 mm |
| Flange/ web thickness | ±0.7~1.5 mm (depending on the specification) |
| Straightness | Universal steel 1 mm/m, total bend ≤4 mm for 6 m |
| Flange perpendicularity (non-perpendicularity) | 1% of flange width |
4. Surface quality, marking and certificates
- The surface must not have harmful defects that affect use (cracks, heavy skin, folding, etc.).
- New 2016 regulations: All products must be traceable to the test certificate. The marking requirement for steel sections has been changed from "forced rolled marking >150 mm" to a permanent marking requirement based on performance; the label must correspond to the corresponding furnace number and certificate.
- Each batch of delivery must be accompanied by a quality certificate (MTC), including furnace number, chemical composition (C/Mn/Si/P/S/Cr/Mo/V/Ni/Cu/Al/Ti/Nb/B/CE), mechanical properties, impact results (such as L0/L15), etc.
- In engineering projects, ACRS certification (Australian New Zealand Steel Reinforcement and Structural Steel Certification Body) products are usually required.
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