Description
Direct Mill Supply, Zero Traceability Gaps — Q235 and Q345 ERW square and rectangular steel tubes produced, fabricated, and documented under a single quality system from our own steel mill in Jinan.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235/Q345 ERW Square and Rectangular Steel Tube |
| Product Type | Welded Square and Rectangular Steel Tube (Hollow Section) |
| Steel Grade | Q195, Q215, Q235, Q345 |
| Standard | ASTM A213-2001, DIN EN 10217-1-2005 |
| Section Shape | Square / Rectangular |
| Size Range | 300×300 mm (other sizes available per request) |
| Length | 6 m (customizable) |
| Technique | ERW (Electric Resistance Welded) |
| Surface Treatment | Slightly Oiled / Hot Rolled |
| Tolerance | ±1% |
| Ends | Plain (default) |
| Processing Service | Welding, Punching, Cutting, Bending, Decoiling |
| Application | Structure Pipe, Fluid Pipe, Boiler Pipe, Drill Pipe, Gas Pipe, Oil Pipe, Chemical Fertilizer Pipe |
| MOQ | 5 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Building | Column and beam frames, mezzanine platforms, stairway supports for commercial and industrial buildings |
| Infrastructure & EPC | Bridge support structures, conveyor gantries, equipment skids for petrochemical and power plants |
| Fluid & Gas Transmission | Low-pressure gas distribution lines, chemical fertilizer plant piping, water conveyance systems |
| Industrial Facilities | Warehouse roof trusses, crane runway beams, machinery base frames |
Dimensional Tolerance on a 300 mm Square Tube — Where ±1% Decides Site Acceptance
A 3 mm deviation on a 300×300 section can misalign an entire bolted connection.
When structural frames arrive on site with flange out-of-square beyond tolerance, field crews either burn hours reaming holes or wait for replacement sections — both eating into float time that projects rarely have. On an ERW square and rectangular steel tube ASTM standard supplier order, buyers sourcing through trading companies face an extra layer of uncertainty: the fabricator did not roll the material, the mill did not see the fabrication drawings, and nobody owns the full dimensional chain. I once watched a container of 300×300 sections get rejected at port because wall-thickness readings drifted past the negative tolerance limit — the mill certificate said one thing, the caliper said another, and the trading company had already left the country. [NEED_CITE: dimensional tolerance requirements for cold-formed structural hollow sections]
Matching Structural Load Paths in Frame and Bracing Systems
For column-to-beam moment connections and bracing nodes, the ±1% tolerance on our 300×300 mm ERW square and rectangular steel tube ASTM standard supplier sections keeps gusset plates flush without field grinding. Q345 grade delivers higher yield capacity where bracing members resist lateral wind or seismic loads, while Q235 remains cost-effective for secondary framing and purlin supports. Because our own mill produces the raw coil and our fabrication shop welds and drills the finished assembly, connection plates and stiffeners are matched to the parent tube from the same heat — no supply-chain gap between material certificate and as-built component.
Engineering Code Compliance and Corrosion Environment Selection
Structural projects targeting EU or Middle East markets must demonstrate conformity with EN 1090 execution classes, which demands full material traceability back to the melt and certified welding procedures. [NEED_CITE: EN 1090 structural fabrication execution class requirements] Our Q235 and Q345 ERW square and rectangular steel tube ASTM standard supplier tubes ship with mill test certificates tied to individual heat numbers, and every weld on fabricated assemblies follows qualified WPS/PQR procedures. For outdoor or coastal installations, the slightly oiled hot-rolled surface provides short-term transit protection; for long-term corrosion resistance, we coordinate galvanizing or painting after fabrication — the choice depends on whether the tube serves as a structural member or a fluid conveyance line.
ERW Weld Integrity and Steel Grade Selection Logic
Electric Resistance Welding produces a longitudinal seam with a narrow heat-affected zone, making it suitable for structural hollow sections where internal pressure is low but dimensional accuracy matters. Compared with seamless processes, ERW on 300×300 mm sections offers tighter wall-thickness uniformity at lower cost — a trade-off that works for frame structures but requires full ultrasonic weld inspection for pressurized fluid lines. Q345 versus Q235 is a yield-strength decision: Q345 carries roughly 40% more load per unit area, which translates into lighter sections or longer spans for the same design force. [NEED_CITE: steel grade equivalence between Chinese GB and international ASTM/EN systems] The slight oiling on hot-rolled surfaces prevents rust during storage and ocean transit without interfering with subsequent painting or galvanizing.
The Hidden Cost of Unverified Material on a Structural Order
Accepting an ERW square and rectangular steel tube ASTM standard supplier quote without verified mill certificates may save a few percent on unit price — until customs holds the container for missing documentation, or the site engineer rejects sections because the heat number on the stamp does not match the test report. Negative tolerance abuse is another silent cost: a tube that measures 1.5 mm thin on a 10 mm nominal wall carries less load than the structural calculation assumed, and no amount of re-inspection restores the missing steel. [NEED_CITE: consequences of material non-conformance in structural steel procurement]
Why Project Teams Source This Tube from Our Mill and Fabrication Shop
We roll the coil, weld the tube, and fabricate the connection — all inside one facility in Jinan, which means the mill test certificate, the weld map, and the dimensional inspection report come from a single quality system rather than three separate vendors. Our own理化实验室 tests every heat for chemical composition and mechanical properties before the tube leaves the line, and third-party inspectors such as SGS or BV are welcome to witness testing at any stage. With over 2,800 specifications in raw material inventory, we can pull Q235 or Q345 coil for a 5-ton MOQ order without waiting for a third-party mill’s production slot. Custom cutting, punching, and bending to shop-drawing dimensions reduces on-site labor, and our loading crews plan container stowage around the 6 m length to maximize payload per shipment.
Documentation & Compliance
- Mill test certificate documenting Q235 or Q345 chemical composition and mechanical properties per ASTM A213-2001 and DIN EN 10217-1-2005, linked to individual heat numbers
- CE marking and declaration of performance for EN 10219 hollow sections where project specification requires European conformity
- ISO 9001 quality management certificate covering the full scope from steel production through fabrication and surface treatment
- SGS or BV third-party inspection report available for pre-shipment witness of dimensional checks, weld NDT, and coating thickness
- Full material traceability package: WPS, PQR, weld maps, and dimensional inspection reports for each fabricated assembly
- Export customs documentation including packing list, bill of lading, and certificate of origin for destination-country clearance
Packaging, Loading & Delivery
- Q235 and Q345 ERW square and rectangular steel tubes bundled with steel strips and edge protectors to prevent surface damage to the slightly oiled hot-rolled finish during ocean transit
- 6 m standard length loaded in layered stacks with timber dunnage to distribute weight evenly and avoid point contact on the tube corners
- Custom-cut sections packed separately with heat-number tags attached for on-site identification and traceability verification
- Container stowage optimized for 300×300 mm profiles to maximize payload within 20 GP or 40 HC units, reducing per-ton freight cost
- FOB Jinan or Qingdao port with CIF and DDP options available; door-to-door logistics coordinated for project sites in the Middle East, Southeast Asia, and Africa
Starting Your Procurement Process
Share your project drawings in PDF or DWG format along with the required steel grade, section size, quantity, and destination port. Our engineering team responds within 24 hours with a preliminary assessment, shop-drawing timeline, and a detailed quotation covering material, fabrication, coating, and freight — so you can evaluate total landed cost before committing.
Frequently Asked Questions
Q: How do Q235 and Q345 grades compare to ASTM A36 or S235/S355 in international specifications?
A: Q235 roughly corresponds to ASTM A36 and S235 in yield strength, while Q345 aligns with ASTM A572 Grade 50 and S355. We provide grade equivalence tables with every quotation so your engineer can verify compliance with the project’s governing standard.
Q: Can you supply mill test certificates and arrange third-party inspection for customs clearance?
A: Yes. Every shipment includes a mill test certificate tied to the specific heat number, and we welcome SGS, BV, or client-nominated inspectors to witness testing and dimensional checks before loading.
Q: What is the minimum order quantity for custom-cut and fabricated sections?
A: The MOQ is 5 tons. For fabricated assemblies with cutting, punching, or bending to shop-drawing dimensions, we review the drawing set and confirm feasibility before quoting.
Q: What surface treatment options are available for corrosion protection?
A: Standard delivery is slightly oiled or hot-rolled finish. For projects requiring enhanced corrosion resistance, we coordinate galvanizing or industrial painting after fabrication, depending on the service environment.
Q: Do you provide quality documentation packages for EN 1090 or AISC compliance?
A: Yes. We supply WPS, PQR, weld maps, dimensional inspection reports, and coating reports as a complete documentation package for international project compliance.
Get Your Quotation with Full Material Traceability
Send your section sizes, steel grade, quantity, and destination port to receive a detailed quotation and mill test certificate sample within 24 hours.
Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Website: www.xjystructure.com
Tel: +86 531 8573 6315
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@xjystructure.com
Address: No.11889, Jingshi West Road, Lulian Group, Jinan City, Shandong Province, China
