When sourcing cold-formed structural steel hollow sections, one question comes up repeatedly among procurement managers and small business owners alike: should you go with C250 or C350? The AS/NZS 1163 C250 pipe is a cost-efficient, weldable structural grade with a minimum yield strength of 250 MPa and tensile strength ranging from 320 to 510 MPa. C350, by contrast, delivers a minimum yield of 350 MPa, making it better suited for heavier loads. Choosing between them is not about picking the "better" grade — it is about matching the right material to your actual structural demands and budget.
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Understanding AS/NZS 1163 C250 and C350 Pipes
AS/NZS 1163 is the standard that both Australia and New Zealand agree on for cold-formed structural steel hollow sections. The "C" before the number means it was made by cold-forming, and the number itself means the minimum yield strength in megapascals. For structural engineering use, both grades come in a wide range of shapes and sizes, including Circular Hollow Sections (CHS), Square Hollow Sections (SHS), and Rectangular Hollow Sections (RHS).
Mechanical and Chemical Properties Compared
At the design stage, the differences in how these two grades work mechanically are important. C250 has a minimum yield strength of 250 MPa, a tension range of 320–510 MPa, and an elongation range of 18–22%. The yield point goes up to 350 MPa at C350, and the tensile range goes from 430 to 530 MPa. The elongation is slightly lower because of the higher cold-working intensity.
Chemically, both grades keep their carbon equivalents (CEV) low so that they can be welded. Manganese levels can reach 1.50%, and carbon levels are between 0.20 and 0.25%. Because AS/NZS 1163 C250 pipe has a low CEV, it has a slight advantage in cold-forming flexibility and surface finish accuracy. This is why it is still the best choice for fabricators who need to make tight bends or complex joint designs.
Dimensional Tolerances and Grade Suffixes
AS/NZS 1163 sets very tight limits for wall thickness, straightness, and mass for both grades. One important thing to keep in mind is that grades ending in "L0," like C250L0 or C350L0, show a certain Charpy impact energy at 0°C. These types can't be switched out for their non-suffixed counterparts, and the right one should be chosen based on the project's needs, especially in cold places like southern New Zealand or high-altitude Australia.
Strength and Performance Differences
The difference of 100 MPa in yield strength between C250 and C350 is important to know when designing structures. According to AS 4100 (Steel Structures), engineers can use a better yield grade to make sections smaller while keeping their load capacity the same. This is known as "section optimization." In high-stress situations, this means that C350 parts can be lighter and use less material.
Load Capacity and Durability
When bending, axial compression, and combined loading are all taken into account, C350 is clearly stronger. In real life, a 75x75x3 SHS in C350 can hold about 40% more vertical load than the same piece in C250. But AS/NZS 1163 C250 pipe is more flexible because it has a higher stretch ratio (up to 22%). This makes it better for uses that need to absorb energy or structures that are loaded and unloaded quickly.
Corrosion Resistance and Weldability
For outdoor use, neither type is naturally resistant to rust; the surfaces need to be treated with hot-dip galvanizing (which meets AS/NZS 4680), powder coating, or epoxy primer. Because C250 has a lower carbon equivalent, it is slightly easier to weld without preheating. This speeds up the production process for small structural jobs. As per AS/NZS 1163 quality assurance, products must go through required mechanical testing, chemical makeup verification, and dimensional checking at the mill level. This gives buyers a record of the product's performance that can be tracked and verified.
Applications and Use Cases
When procurement teams know where each grade works best, they can avoid over-specification, which often leads to extra costs in light structural projects.
C250 hollow sections work well in the following situations where modest load requirements and ease of manufacturing are important:
- Greenhouse and agricultural framing: Purlins, rafters, and perimeter frames for polytunnels and shade structures benefit from C250's light weight and easy weld behavior.
- Fencing and guardrails: Perimeter fencing for homes and farms, where looks and cost are more important than structural redundancy.
- Furniture frames and display fixtures: C250 RHS and SHS are used to make table legs, shelves, and modular rack systems for light furniture production.
- Equipment support brackets: General-purpose industry support structures that can handle light to moderate loads.
From small fabricators to farm operators to light building companies in Australia, New Zealand, and Southeast Asia, these uses meet most of their needs.
When the loads on the structure are too high for C250 pipes to safely handle, C350 pipes step in. For heavy-duty mezzanine floors, steel frames with more than one story, crane runway beams, and big infrastructure brackets, you need C350 of more. Because the grade has a higher yield, smaller wall sections can carry the same loads, which is important for designs that need to be light.
Procurement and Supplier Considerations
For buyers who care about costs, price is often the deciding factor. C250 always costs less than C350 because it requires less alloying and is easier to process. For small orders, like those made by farm owners or small fabricators, this price difference can mean big savings on the total cost of the project's materials.
Before placing an order, pay close attention to the following factors when evaluating suppliers:
- Certification documentation: Make sure that every package comes with an AS/NZS 1163 mill certificate that includes a heat number that can be tracked. Inspection reports from a third party add another level of proof.
- Lead time and stock availability: Reliable AS/NZS 1163 C250 pipe suppliers keep common sizes in stock, such as 25x25, 50x50, 75x75 SHS and 25NB to 150NB CHS. This means that standard orders can be sent out within 10 to 20 days.
- Minimum order quantity: Buyers of small projects should make sure that the MOQ is flexible right away. Some makers can handle orders for only part of a box, which keeps capital from being stuck in extra inventory.
- Packaging integrity: For long-haul shipping by sea, pieces that are bundled and strapped with end caps and moisture-barrier wrapping greatly lower the risk of damage during transport.
Before placing large orders, buyers using Alibaba or Google search terms like "AS/NZS 1163 C250 pipe manufacturer" should compare the credentials of the supplier with certified mill paperwork and ask for samples of MTCs (Material Test Certificates).
Making the Right Choice: C250 or C350?
There are three things that determine which grade to use: the load requirement, the budget, and the local code. If your engineering plans use AS 4100 and say that light framing or secondary structural parts must have a minimum yield of 250 MPa, then C250 is technically enough and will save you money. Upgrading to a C350 without a good reason from an engineering point of view costs more and doesn't help the structure.
That being said, future-proofing is important. If a building could be used for something bigger or if local building rules are going to get stricter, planning with C350 from the start saves a lot of money on upgrades later on. In the same way, projects in cold places should decide if the L0 impact variant is necessary.
The safest thing to do is to give your steel supplier your load calculations and project scope as early as possible in the buying process. A skilled provider can help you find the most cost-effective compliant grade, which will help you avoid both the risk of not meeting requirements and spending too much on materials that aren't needed.
Conclusion
Both C250 and C350 are reliable grades that meet the requirements of AS/NZS 1163, but they have different structural roles. The AS/NZS 1163 C250 pipe is great for light framing, farming structures, fences, and making furniture, all of which need to be easy to work with and cost-effective. When higher load demands call for more structural capacity in a given section size, C350 is the right choice. Instead of automatically choosing the higher grade, it is better for the project's cost and for the structure's long-term dependability to match the grade to the application.
FAQ
What is the main difference between C250 and C350 pipe?
At least 250 MPa of yield strength is reached by C250, and 350 MPa is reached by C350. For light structure work, C250 is better at being bendable and weldable, while C350 can handle heavy loads in the same section size.
Is C250 pipe compliant with Australian building codes?
Yes. Under AS 4100, AS/NZS 1163 C250 pipe can be used in structural uses where the intended yield strength is at least 250 MPa.
What does the "L0" suffix mean on C250L0?
The L0 suffix means that the Charpy impact performance is guaranteed at 0°C. The C250 and C250L0 are not the same; choose the one that fits your project's temperature and design needs.
How do I verify pipe quality from a new supplier?
Ask for the mill certificate (MTC) with a heat number that can be tracked, make sure that the pipe surface has continuous stencil markings, and if they are available, ask for third-party inspection reports.
Can C250 hollow sections be hot-dip galvanized?
Yes, C250 can be galvanized according to AS/NZS 4680. However, the steel should have a silicon percentage that stays within the guidelines to make sure the zinc coating sticks well.
Get a Competitive Quote from Longma Group Today
Since 2003, Longma Group has sold approved structural steel hollow parts to customers in more than 90 countries. As a reliable AS/NZS 1163 C250 pipe supplier, we offer full mill certification, small-batch ordering, and reliable 10–20 day dispatch on sizes that are in stock. Whether your project needs C250 or C350, our team offers competitive CIF prices and full documentation, which includes MTC, ITP, and MPS. To get a quote right away, email us at info@longma-group.com or go to longma-group.com.
