Description
Factory-Direct ERW Square Tubes — Every batch of Q235B Q345B ERW square steel tube ships with original mill test certificates and ASTM compliance documentation, eliminating middlemen markups for bulk buyers.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B / Q345B ERW Square Steel Tube |
| Product Type | Welded Square and Rectangular Steel Tube (ERW) |
| Steel Grade | Q195, Q235, Q235B, Q345, Q345B, SS400, ASTM/AISI, SGCC, CGCC, TDC51DZM, TDC52DTS350GD, TS550GD, DX51D+Z |
| Standard | ASTM, API, JIS, ISO 9001, TISI |
| Section Shape | Square / Rectangular |
| Size Range | 20×20 mm – 200×200 mm |
| Wall Thickness | 0.5 – 40 mm |
| Length | 1 – 12 m (standard: 6 m / 6.4 m / 12 m) |
| Technique | ERW (Electric Resistance Welded) |
| Surface Treatment | Cold Rolled / Galvanized Coating |
| Tolerance | ±1% |
| Ends | Plain |
| Application | Construction Structure, Boiler, Fluid Transport, Drill, Hydraulic, Gas, Oil, Chemical Fertilizer, Structural Frame |
| MOQ | 25 Tons (full 20ft container) |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Infrastructure | Building columns, structural frames, scaffolding supports, bridge railings |
| Industrial Equipment | Machinery frames, hydraulic cylinder housings, conveyor structures |
| Energy Sector | Oil & gas pipeline supports, drilling platform structures, chemical plant frameworks |
| Agricultural & Storage | Greenhouse framing, silo structures, equipment shelters |
Where Dimensional Tolerance Decides Structural Acceptance on Site
±1% tolerance on Q235B Q345B ERW square steel tube prevents field rejections during assembly.
I once watched a Thai contractor reject an entire container of square tubes because wall thickness ran negative beyond acceptable limits. The beams looked fine visually, but when they tried bolting connection plates, nothing aligned. That shipment came back to Jinan for rework — a loss nobody needed. Carbon Cold Rolled ERW Square Steel Tube Supplier operations that skip in-house dimensional checks pass these problems downstream. Project buyers in Southeast Asia and Africa face customs delays when mill test certificates don’t match physical specs [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance requirements].
How ERW Square Tubes Match Structural Frame Requirements
Carbon Cold Rolled ERW Square Steel Tube in Q235B and Q345B grades delivers the flat surface profile and consistent corner geometry that structural frames demand. The electric resistance welding process produces a seam that matches base metal strength, allowing these tubes to carry compressive and bending loads in building columns and machinery frames without secondary reinforcement. For projects requiring corrosion resistance in coastal or chemical environments, the galvanized coating option extends service life without field painting. Our 2,800+ specification inventory means contractors can source both 20×20 mm light gauge and 200×200 mm heavy structural sections from one shipment.
Engineering Compliance and Certification for Global Projects
Structural engineers specifying Carbon Cold Rolled ERW Square Steel Tube to ASTM standards require documented proof that material properties meet design calculations. Q235B conforms to general structural applications, while Q345B provides higher yield strength for load-bearing frames and industrial equipment supports [NEED_CITE: ASTM A500 structural tubing grade requirements]. The TISI certification we maintain opens Thai market access without additional testing, and ISO 9001 documentation satisfies most EPC contractor procurement protocols. For European projects, our CE marking under EN 10210/EN 10219 covers the same ERW square tube range, though buyers should confirm specific grade equivalence before ordering [NEED_CITE: steel grade equivalence between Chinese GB and international standards].
Steel Grade Selection and ERW Welding Process
Q235B remains the default choice for general construction because it balances formability with adequate strength for non-critical structural members. Q345B steps up yield capacity for frames carrying dynamic loads or supporting heavy equipment — the manganese content increase improves toughness without sacrificing weldability. The ERW process fuses tube edges through high-frequency current resistance, creating a weld zone that undergoes the same cold rolling reduction as the parent metal. This eliminates the visible bead found in spiral-welded pipe and produces uniform wall thickness around the entire section. Cold rolled surface finish delivers a smooth appearance for architectural exposure, while galvanized coating adds 40-80 μm zinc layer for outdoor or humid environments [NEED_CITE: ERW welding quality control in structural hollow sections].
Hidden Costs of Unverified Steel Tube Procurement
Ordering Carbon Cold Rolled ERW Square Steel Tube without third-party verification invites three failure modes: material substitution where Q195 ships as Q235B, wall thickness running 10-15% below nominal, and missing heat number traceability that blocks customs clearance. Engineering inspectors reject shipments lacking original mill test certificates, and project owners face liability exposure if structural members fail without documented compliance. The cost of re-inspection, air freight replacements, and delayed handover typically exceeds any initial price savings from unverified suppliers [NEED_CITE: structural steel procurement quality assurance requirements].
Why Bulk Buyers Source from Shandong Xin Jiyuan
We operate three production lines running simultaneously, producing 20,000+ tons monthly across square, rectangular, and round sections — this volume supports factory-direct pricing without broker margins. Every Carbon Cold Rolled ERW Square Steel Tube batch undergoes three-stage inspection in our in-house lab covering dimensional accuracy, visual weld quality, and mechanical sampling. Original mill test certificates ship with every container, documenting chemical composition and tensile properties by heat number. Third-party SGS or BV inspection arranges on request for buyers requiring independent verification. Our export team handles container loading optimization, combining multiple specifications in single shipments to reduce per-ton freight costs. Long-term partners receive volume discount reviews every six months and dedicated account management for repeat orders.
Documentation & Compliance
- Mill test certificate documenting Q235B/Q345B chemical composition and mechanical properties per ASTM standards, issued by original producing mill
- CE certificate covering EN 10210/EN 10219 compliance for European market structural applications
- ISO 9001:2015 quality management system certificate valid across all production lines
- SGS or BV third-party inspection report available upon request for independent quality verification
- Full material traceability by heat number linking each tube bundle to production batch and test results
- Complete customs documentation package including packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- Q235B Q345B ERW square tubes bundled with steel strips at 1.5-ton intervals, wrapped in waterproof cloth for ocean transit protection
- Galvanized coated tubes include edge protectors and plastic caps to preserve zinc layer during handling and shipping
- Container loading plans optimize 20ft and 40ft shipments by combining 6m and 12m lengths to maximize payload per TEU
- Custom cutting to project-specified lengths available, with 50mm tolerance on cut-to-size orders
- Each bundle marked with heat number, steel grade, size specification, and production date for site identification
- FOB Qingdao port standard, with CIF and DDP options available to major destinations across Southeast Asia, Middle East, and Africa
Getting Your Bulk Quote Started
Submit your specification sheet covering tube dimensions, wall thickness, steel grade, total tonnage, and destination port — we respond within 12 hours with pricing, production timeline, and available mill test certificate samples. For non-standard sizes outside our 20×20 to 200×200 mm range, share your drawing or engineering requirements and we confirm feasibility and lead time.
Request Your Carbon Cold Rolled ERW Square Steel Tube Quote
Email your specifications to admin@sdxinjiyuan.com or message +86 188 5315 7756 (WhatsApp/WeChat) for factory-direct pricing and certification documentation.
