Description
Factory-Direct SHS & RHS Supply — Q235B Q355B square rectangular steel tube supplier producing to EN10219 and ASTM A500 with original mill test certificates for every heat.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B / Q355B Square and Rectangular Carbon Steel Tube |
| Product Type | Square / Rectangular Steel Tube (Hollow Section) |
| Steel Grade | Q195, Q235, Q355, S195, S235JR, S355JR, A53 Grade A, A53 Grade B, A500 Grade A, A500 Grade B, A500 Grade C, STK400, SS400, ST42.2 |
| Standard | EN10219, EN10210, GB/T 6728, JIS G3466, ASTM A500, ASTM A36 |
| Section Shape | Square / Rectangular |
| Size Range (Square) | 20×20mm – 500×500mm |
| Size Range (Rectangular) | 20×40mm – 300×500mm |
| Wall Thickness | 1.2mm – 20mm |
| Length | 3m – 12m (random or cut-to-length) |
| Technique | Hot Rolled / Welded (ERW) |
| Surface Treatment | Black (Hot Rolled), Pre-galvanized (40–80g/m²), Hot Dipped Galvanized (200–600g/m²) |
| Tolerance | ±1% |
| Ends | Plain |
| Application | Construction, Steel Structures, Solar Structures, Fence Posts, Greenhouse Frames, Machinery, Shipbuilding, Power Engineering |
| MOQ | 1 Ton |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Building | Building frames, structural columns, load-bearing supports, scaffolding uprights |
| Infrastructure & Energy | Solar panel mounting structures, fence posts, greenhouse frames, power transmission towers |
| Industrial & Machinery | Equipment base frames, conveyor structures, shipbuilding internal supports, power engineering brackets |
What Negative Wall Tolerance Costs on a Structural Frame Order
A tube that passes visual inspection but fails thickness measurement will not hold up at the engineering acceptance stage.
When procurement teams source Q235B Q355B square rectangular steel tube supplier products without verifying actual wall thickness against mill certificates, the gap between theoretical weight and real load-bearing capacity becomes a silent project risk. I once shipped a full container of rectangular tubes to Dubai — the third-party inspector measured wall thickness on arrival and found it beyond permissible negative tolerance. The entire container was returned for re-rolling, and the freight loss alone ran into tens of thousands of dollars. That kind of cost does not show up in the initial quotation.
Fragmented sourcing makes this worse. When pipes, plates, and sections come from different yards, each with their own tolerance habits, the structural engineer cannot guarantee uniform performance. [NEED_CITE: EN 10219 cold-formed structural hollow section tolerance requirements]
Matching Hollow Section Dimensions to Structural Load Paths
Square and rectangular hollow sections from 20×20mm up to 500×500mm cover the full range from light-duty greenhouse frames to primary building columns. The closed cross-section of SHS and RHS provides higher torsional rigidity compared to open profiles, making them suitable for moment-resisting frames where lateral stability matters. For solar mounting structures and fence post applications, the smaller dimensions (20×20mm to 100×100mm) with 1.2–3.0mm wall thickness offer an optimal weight-to-strength ratio. As a Q235B Q355B square rectangular steel tube supplier, we produce these sections across three rolling lines, holding ready stock in standard sizes while custom lengths and non-standard dimensions follow typical production lead times.
Engineering Compliance and Surface Protection Selection
Structural applications in Europe require CE marking under EN10210 (hot-finished) or EN10219 (cold-formed) — without valid certificates, customs clearance fails regardless of product quality. For projects following ASTM A500, the grade equivalence mapping from Q235B to A500 Grade B or Q355B to A500 Grade C must be documented in the mill test certificate. [NEED_CITE: steel grade equivalence mapping between GB/T, EN, and ASTM standards] Surface treatment selection depends on the exposure environment: black (hot rolled) tubes suit indoor structural frames where painting will follow; pre-galvanized coatings at 40–80g/m² protect against light atmospheric corrosion during construction phases; hot dipped galvanizing at 200–600g/m² is necessary for outdoor infrastructure such as solar structures and fence posts in coastal or industrial zones. Cut-to-length delivery reduces on-site welding and secondary processing.
Steel Grade Selection and Welding Process Fundamentals
The Q-series (Q195, Q235, Q355) follows the Chinese GB/T system where the number indicates minimum yield strength in MPa. The S-series (S235JR, S355JR) follows EN standards, while ASTM A500 Grades A, B, C represent the North American specification system. All three systems are represented in our grade coverage, allowing a single Q235B Q355B square rectangular steel tube supplier order to serve projects across different regulatory regions. The ERW welding process used for these hollow sections produces a longitudinal weld seam suitable for structural applications up to moderate pressure levels — for high-pressure fluid conveyance, seamless alternatives would be specified instead. Wall thickness tolerance of ±1% applies across the 1.2mm to 20mm range, but buyers should verify that the mill test certificate documents actual measured values rather than nominal specifications. Hot rolled black finish retains the mill scale and is typically chosen when the tube will receive further surface treatment on-site.
The Hidden Cost of Unverified Material Documentation
Ordering structural hollow sections without original mill test certificates means the engineering team cannot confirm chemical composition or mechanical properties — a gap that surfaces during project inspection or customs audit. Missing CE EN10219 documentation for European shipments leads to cargo held at port, with demurrage charges accumulating daily. Material that does not conform to the specified grade may pass initial visual checks but fail during structural load testing, forcing costly replacement of installed sections. [NEED_CITE: consequences of missing mill test certificates in international steel procurement] When wall thickness falls outside the specified ±1% tolerance, the theoretical weight calculation used in structural design no longer matches actual performance, creating liability exposure for the project engineer.
Procurement Confidence Through Direct Factory Control
As a Q235B Q355B square rectangular steel tube supplier operating our own production facility since 2013, we control the entire process from raw material input to final container loading. Every batch undergoes three-stage inspection in our in-house laboratory before release, with chemical composition and mechanical properties documented in original mill test certificates traceable by heat number. Our factory-direct model eliminates intermediary markups, and volume discount programs apply for repeat procurement partners. We maintain ready stock across 2,800+ standard specifications for urgent requirements, while custom orders in non-standard dimensions or specific grade combinations follow defined production schedules. Third-party inspection through SGS or BV is available upon request before shipment, providing independent verification for projects requiring additional assurance. Professional export documentation handling covers customs clearance requirements across 50+ destination countries.
Documentation & Compliance
- Mill test certificate documenting Q235B/Q355B chemical composition and mechanical properties per GB/T 6728, traceable by heat number
- CE certificate under EN10219 (cold-formed) or EN10210 (hot-finished) for European market customs clearance
- ISO 9001:2015 quality management system certificate covering production and inspection processes
- SGS or BV third-party inspection report available upon request for independent quality verification
- Material traceability documentation linking each tube to its heat number and production batch
- Complete customs document package including packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- Q235B and Q355B tubes bundled with steel strips in seaworthy packaging, with bundle weight optimized for 20ft and 40ft container capacity
- Hot dipped galvanized tubes (200–600g/m² zinc coating) packed with edge protectors to prevent coating damage during ocean transit
- Container loading plans optimized for mixed-size orders combining 20×20mm small sections with 500×500mm large sections to maximize weight utilization
- Cut-to-length service available for 3m–12m requirements, reducing on-site cutting waste for construction projects
- Heat number and steel grade stenciled on each tube bundle for site identification and traceability verification
- FOB, CIF, and DDP shipping terms available with professional documentation handling for destination customs
Starting Your Structural Tube Procurement
Submit your specification requirements — section dimensions, wall thickness, steel grade, quantity, and destination port — to receive a competitive quotation with volume pricing and delivery schedule. For non-standard dimensions or specific grade requirements beyond standard stock, our engineering team will provide custom production options with confirmed lead times. All quotations include documentation confirmation for mill test certificates and any required third-party inspection arrangements.
Request Your Quotation with Mill Test Certificates
Send your specifications via email or WhatsApp to receive bulk pricing, certification confirmation, and container loading plans within 12 hours.
Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Website: www.sdxinjiyuan.com
Tel: +86 531 8573 6315
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@sdxinjiyuan.com
Address: No.11889, Jingshi West Road, Lulian Group, Jinan City, Shandong Province, China
Frequently Asked Questions
Q: How do Q235B and Q355B map to international standards like S235JR, S355JR, and ASTM A500?
A: Q235B corresponds to S235JR in the EN system and is comparable to ASTM A500 Grade B in mechanical properties. Q355B maps to S355JR under EN standards and aligns with ASTM A500 Grade C. Our mill test certificates document the actual chemical composition and mechanical test results, allowing your engineer to verify equivalence for your specific project code.
Q: Do you provide CE EN10219 or EN10219 certificates for European market clearance?
A: Yes, our production carries Lloyd’s CE certification under both EN10210 for hot-finished hollow sections and EN10219 for cold-formed sections. The CE certificate and Declaration of Performance are included in the shipping documentation package for customs clearance in EU member states.
Q: What is the minimum order quantity for trial orders or non-standard sizes?
A: The MOQ is 1 ton, which supports trial orders for quality verification before committing to larger volumes. For non-standard dimensions outside our 2,800+ ready-stock specifications, custom production is available with typical lead times confirmed at the quotation stage.
Q: What are the differences between black, pre-galvanized, and hot dipped galvanized surface options?
A: Black (hot rolled) finish retains the mill scale and suits indoor applications where painting or further coating will follow. Pre-galvanized tubes carry a zinc coating of 40–80g/m², providing protection during transport and short-term outdoor exposure. Hot dipped galvanized tubes feature 200–600g/m² zinc coating for long-term corrosion resistance in outdoor infrastructure applications such as solar structures and fence posts.
Q: How do you handle container loading optimization for heavy steel tube shipments?
A: Our export team prepares container loading plans that maximize weight utilization while respecting port weight limits. For mixed-size orders, smaller sections are nested within larger hollow sections where structurally safe, and loading sequences are planned to ensure balanced weight distribution. Professional documentation and customs clearance support is provided for destination port requirements.
