Description
Factory-Direct ERW Hollow Sections — Q235B welded square and rectangular steel tube produced on our own forming lines, shipped with full mill test certificates to 50+ countries.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B Welded Square and Rectangular Steel Tube |
| Product Type | Welded Square and Rectangular Steel Tube |
| Steel Grade | Q195, Q215, Q235, Q345B, S235JR, S355JR, SS400 |
| Standard | ASTM, ASTM A213, DIN EN 10217-1 |
| Section Shape | Square, Rectangular |
| Size Range | 300×300 mm |
| Wall Thickness | 1 mm – 3 mm |
| Length | 6 m / 6.4 m / 12 m, or Customers’ Request |
| Technique | ERW (Cold Rolled / Hot Rolled) |
| Surface Treatment | Hot Rolled, Non-oiled |
| Tolerance | ±1% |
| Invoicing | By Theoretical Weight |
| Processing Service | Welding, Punching, Cutting, Bending, Decoiling |
| Application | Construction Building Material, Structural frames, Architectural decoration, Furniture manufacturing |
| MOQ | 5 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Building | Structural frames, column supports, beam-to-column connections for mid-rise commercial buildings |
| Architectural Facade | Curtain wall mullions, decorative cladding supports, exposed steel framing for commercial lobbies |
| Furniture Manufacturing | Table legs, shelving frames, display rack structures requiring clean surface finish |
| Steel Structure Fabrication | Truss members, bracing tubes, purlin systems for warehouses and industrial sheds |
What Tight Wall Tolerance Means When You Order 300×300 ERW Tubes
A ±1% tolerance on a 300×300 welded square and rectangular steel tube keeps connection plates flush and weld gaps predictable across the entire order.
When wall thickness drifts beyond ±1%, fabricators face misaligned gusset plates, inconsistent weld penetration, and rejected inspections on structural frames. For a 300×300 section at 3 mm wall, even a 0.1 mm deviation compounds across a 12 m length — enough to throw off bolt-hole alignment on site. We have seen orders from other mills arrive with wall variation exceeding 0.3 mm, forcing contractors to re-cut every piece before assembly. [NEED_CITE: EN 10219 dimensional tolerance requirements for cold-formed hollow sections]
How 300×300 ERW Sections Match Structural Frame Demands
A 300×300 welded square and rectangular steel tube at 1–3 mm wall serves as primary framing for light-to-medium structural systems. The ERW process produces a continuous weld seam with consistent strength along the full length, while the ±1% tolerance ensures that end-plate connections and base-plate details fit without field rework. For architectural applications, the hot-rolled non-oiled surface accepts primer and paint directly, eliminating the degreasing step that oiled tubes require. Our forming lines hold corner radii within tight bounds, so the tube sits flat against mating surfaces — critical when the architect specifies exposed steel framing.
Engineering Compliance for Q235B and Equivalent Grades in Global Projects
When a project calls for S235JR per EN 10219, the equivalent Q235B from Chinese mills must meet matching chemical composition and tensile requirements. [NEED_CITE: steel grade equivalence between EN 10219 and GB/T standards] For EU-bound shipments, CE certification per EN 10210 or EN 10219 is mandatory — without it, customs holds the container regardless of physical quality. North American projects referencing ASTM A213 require mill test certificates showing heat-by-heat chemistry and mechanical test results. Our in-house laboratory tests every heat for yield strength, tensile strength, elongation, and chemical composition, then issues certificates that align with the destination standard. For projects in seismic zones or cold climates, the grade selection from Q195 up to Q345B or S355JR allows engineers to match ductility and toughness requirements without switching suppliers.
ERW Process and Grade Selection for Welded Hollow Sections
The ERW (Electric Resistance Welding) process forms the tube from hot-rolled or cold-rolled coil, then welds the seam through electrical resistance — no filler metal, no visible bead on the exterior after trimming. This makes ERW welded square and rectangular steel tube cost-effective for structural applications where seamless pricing is prohibitive. Q235B offers a balanced yield point suitable for general construction, while Q345B provides higher strength for long-span frames. The S-series grades (S235JR, S355JR) follow EN specifications with guaranteed impact energy at 0°C, essential for outdoor structures in temperate climates. SS400, the Japanese industrial standard grade, matches Q235B closely and is specified across Southeast Asian projects. Wall thickness from 1 mm to 3 mm covers light gauge framing up to medium structural members — thin enough for weight-sensitive applications, thick enough to resist local buckling in compression zones.
Hidden Costs When Tolerance and Certification Fall Short
Ordering welded square and rectangular steel tube without verified tolerance claims risks dimensional rejection at the fabrication shop. A tube that measures 2.6 mm instead of the specified 3 mm wall may pass visual inspection but fails load calculations — forcing the engineer to redesign or the contractor to replace the entire batch. Missing CE marks on EN-specified grades trigger customs holds in EU ports, adding demurrage costs that exceed the tube price itself. [NEED_CITE: customs clearance requirements for structural steel in EU markets] Mill test certificates that list only “conforms to standard” without heat-by-heat data cannot satisfy audited quality systems, leaving the buyer exposed during project handover.
Why Source Your Welded Square and Rectangular Steel Tube From Us
We operate three dedicated forming lines in Jinan, Shandong, producing welded square and rectangular steel tube across 2,800+ specifications — including the 300×300 section you need, in wall thicknesses from 1 mm to 3 mm. Every heat passes through our in-house physical and chemical laboratory before shipment, so the mill test certificate you receive reflects actual test data, not template values. Our 41 invention patents include China’s original sharp-corner rectangular tube technology, giving you tight corner radii that standard tooling cannot achieve. For EU projects, we hold CE certification per EN 10210 and EN 10219, verified by Lloyd’s Register — no last-minute scrambling for compliance documents. We also arrange SGS or BV third-party inspection at our facility before loading, so your surveyor sees the product in our yard, not at the destination port. Custom cutting, punching, and bending services let you receive fabrication-ready lengths, reducing waste and labor at your site.
Documentation & Compliance
- Mill test certificate documenting Q235B chemical composition and mechanical properties per GB/T 6728, with heat number traceability
- CE certificate per EN 10219 for S235JR and S355JR grades, issued by Lloyd’s Register for EU customs clearance
- ISO 9001:2015 quality management certificate covering the full production process from coil input to final inspection
- SGS or BV third-party inspection report available upon request, covering dimensional checks, visual inspection, and witness testing
- Material traceability report linking each bundle to its heat number, chemical analysis, and mechanical test results
- Export documentation including packing list, bill of lading, and certificate of origin formatted for destination customs
Packaging, Loading & Delivery
- Q235B welded square and rectangular steel tube bundled with steel strips, separated by rubber pads to prevent surface scratching on the hot-rolled non-oiled finish
- 6 m and 12 m lengths loaded in dedicated containers with timber chocks and edge protectors, optimized for 300×300 section dimensions to maximize payload per shipment
- Heat number and steel grade stenciled on each bundle end, matching the mill test certificate for on-site verification by your QA team
- Custom cut-to-length service available — specify your required lengths and we deliver ready-to-weld pieces, reducing your scrap rate on 1–3 mm wall sections
- FOB, CIF, and DDP shipping terms available from Qingdao port, with professional container loading supervised by our export team to prevent transit damage
Start Your Procurement With Verified Specifications
Send us your required dimensions, steel grade, quantity, and destination port — we return a detailed quotation with unit price, lead time, and shipping terms within 12 hours. Request the mill test certificate format upfront so your engineering team can confirm compliance before placing the order. For non-standard sizes or custom processing, share your drawings and we provide a fabrication-ready solution with confirmed tolerances.
Get Your Q235B ERW Tube Quotation With Mill Test Certificate
Submit your specifications via email at admin@sdxjypipe.com or contact us on WhatsApp at +86 188 5315 7756 to receive pricing, certification documents, and delivery schedule for your welded square and rectangular steel tube order.
Frequently Asked Questions
Q: How does Q235B compare to S235JR and SS400 in chemical composition and mechanical properties?
A: Q235B, S235JR, and SS400 are considered equivalent grades across Chinese GB, European EN, and Japanese JIS standards respectively. They share similar carbon content ranges and yield strength levels, making them interchangeable for general structural applications. We supply all three grades from the same production lines and provide mill test certificates showing the specific chemistry and mechanical results for each heat.
Q: Can you produce non-standard sizes outside the 300×300 specification?
A: Yes. Our production lines cover 2,800+ specifications across square, rectangular, and round sections. If your project requires dimensions outside standard catalog sizes, share your drawing or specification and we confirm feasibility, tooling requirements, and minimum order quantity.
Q: What surface treatment options are available for welded square and rectangular steel tube?
A: We supply hot-rolled non-oiled as the standard finish, suitable for painting or powder coating after fabrication. Galvanized finish is available for corrosion-prone environments. Specify your requirement at inquiry stage so we include the correct pricing and lead time.
Q: Do you provide CE certification for European projects?
A: Yes. Our CE certificate per EN 10210 and EN 10219 is issued by Lloyd’s Register and covers S235JR and S355JR grades. The certificate accompanies each shipment to EU destinations, ensuring customs clearance without delay.
Q: What is the minimum order quantity for custom-cut lengths?
A: The standard MOQ is 5 tons. For custom cutting, punching, or bending services, the MOQ depends on the processing complexity and final dimensions. Share your requirements and we confirm the exact quantity and pricing.
