Description
Factory-direct welded square steel tube supply — raw steel production and tube fabrication under one roof, eliminating material traceability gaps for Q235 Q345 welded square steel tube manufacturer orders.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235/Q345/A36/SS400 Welded Square Steel Tube |
| Product Type | Welded Square Steel Tube |
| Steel Grade | Q235, Q345, A36, SS400, Q195 |
| Standard | ASTM, GB/T 6728 |
| Section Shape | Square / Rectangular |
| Size Range | 10×10mm – 600×600mm |
| Wall Thickness | 0.5mm – 12.0mm |
| Length | 1m – 12m or customized |
| Technique | ERW / Welded |
| Surface Treatment | Hot DIP Galvanized / Black / Color Painting / PVC Coated |
| Tolerance | ±1% |
| Ends | Plain |
| Application | Steel structures / Construction frames / Machinery / Scaffolding / Furniture / Fences / Container frames / Engineering supports |
| MOQ | 1 Ton |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Industrial Construction | Warehouse portal frames, factory column grids, mezzanine platforms |
| Infrastructure & Civil Engineering | Bridge handrail posts, sound barrier supports, highway sign gantries |
| Machinery & Equipment | Conveyor frames, crane boom sections, equipment base structures |
| Logistics & Storage | Pallet racking uprights, container corner castings, modular shed frames |
| Agricultural & Fencing | Greenhouse skeleton tubes, livestock pen frames, perimeter security fencing |
What Negative Tolerance Actually Costs on a 600×600 Frame Order
A few tenths of a millimeter in wall thickness can shift an entire container’s invoiced weight by over a ton.
I once shipped a batch of 600×600 square tubes to a West African client. The wall thickness sat at the lower edge of negative tolerance — technically within spec on paper, but the theoretical weight came out more than two tons short per container. The client’s site inspector re-measured every piece, rejected the lot, and the full container sat at the port for weeks. That kind of mismatch between invoiced weight and actual weight doesn’t just eat margin; it destroys trust on a project that may span years. [NEED_CITE: EN 10219 tolerance requirements for cold-formed welded hollow sections] For buyers sourcing a Q235 Q345 welded square steel tube manufacturer, dimensional consistency and transparent weight calculation matter as much as the steel grade itself.
Matching Section Dimensions to Structural Load Paths
Square and rectangular hollow sections in the 10×10mm to 600×600mm range serve fundamentally different structural roles. Small-section tubes under 100mm typically function as secondary bracing, furniture frames, or fence posts, where formability and surface finish take priority. Mid-range sections from 100mm to 300mm carry primary loads in warehouse frames, scaffolding systems, and machinery bases — demanding consistent weld integrity and predictable dimensional accuracy. The 300mm to 600mm range handles heavy column and beam applications in industrial buildings, where the Q235 Q345 welded square steel tube manufacturer must guarantee flatness of bearing surfaces and weld penetration across the full section. Our ERW process with in-line dimensional monitoring keeps the ±1% tolerance meaningful across this entire span, not just on paper.
Engineering Compliance Across Export Markets
European EPC contractors specifying EN 10219 cold-formed hollow sections need mill test certificates with heat-number traceability back to the raw slab, plus CE marking documentation for customs clearance. [NEED_CITE: steel grade equivalence between GB, EN, and ASTM systems] North American projects referencing ASTM A500 or A53 require separate chemical and mechanical reporting aligned to those standards. Middle East and African infrastructure tenders often accept GB/T 6728 with third-party inspection from SGS or BV. The key is having all certification streams ready before the contract is signed — not scrambling after production is finished. We maintain in-house chemical composition and mechanical property testing, so MTC packages are generated at the mill, not assembled from subcontractor scraps.
Steel Grade Selection and ERW Welding Fundamentals
Q235 and Q345 represent the two most widely specified grades in Chinese structural steel. Q235 offers adequate strength for general construction frames, fencing, and non-critical supports, while Q345 provides higher yield capacity for loaded columns, crane beams, and heavy industrial platforms. A36 and SS400 serve as functional equivalents for projects designed to ASTM or JIS frameworks respectively. [NEED_CITE: Q235 A36 S235JR grade equivalence in structural applications] The ERW welding process forms the tube by rolling flat strip into a closed section and fusing the seam through high-frequency electric resistance — producing a clean, narrow weld zone suitable for subsequent galvanizing or painting. For hot-dip galvanized finishes, the zinc coating class ranges from Z10 to Z29 depending on the corrosion environment, from indoor warehouse framing to outdoor coastal infrastructure. Wall thickness from 0.5mm to 12.0mm covers everything from light-gauge furniture tubes to heavy structural hollow sections, and the ±1% tolerance applies across the full range.
The Hidden Price of Unverified Material Claims
Ordering structural tubes without verified mill test certificates or third-party inspection creates risks that surface only at the construction site. Weld seams with insufficient penetration fail during bending or drilling operations. Undocumented steel grades cannot be validated against EN 10219 or ASTM A500 requirements, triggering rejection by the project’s quality auditor. Negative tolerance pushed beyond acceptable limits reduces actual load-bearing capacity while the invoice still charges for theoretical weight. [NEED_CITE: consequences of non-compliant hollow section procurement in international construction projects] These failures don’t show up in the supplier’s factory — they appear during customs inspection, during the engineer’s on-site复检, or when a connection plate doesn’t fit because the outer dimension drifted.
Integrated Mill and Fabrication Under One Quality System
XJY Structure operates as the fabrication division of Shandong Xin Jiyuan Special Steel Tube Co., Ltd, meaning the raw steel strip that forms your Q235 Q345 welded square steel tube manufacturer order comes from our own production lines — not from spot-market purchases with uncertain chemistry. Our facility maintains over 2,800 raw material specifications in stock, so standard and custom sizes can be scheduled without waiting for external mill rolling campaigns. Every heat number is traceable from slab to finished tube, and our in-house laboratory generates mill test certificates documenting chemical composition and mechanical properties before shipment. For projects requiring CE marking under EN 10219 or third-party inspection by SGS and BV, the documentation chain is prepared as part of the standard production workflow, not as an afterthought. We also provide shop drawing review, custom cut-to-length, drilling, and welding preparation — services that typically require a separate subcontractor when sourcing from a standalone tube mill.
Documentation & Compliance
- Mill test certificate documenting Q235/Q345/A36 chemical composition and mechanical properties per GB/T 6728 or ASTM, with heat number traceability from raw slab to finished tube
- CE certificate and Declaration of Performance for EN 10219 cold-formed welded hollow sections, required for European Union customs clearance and project handover
- ISO 9001 quality management system certificate covering the full production process from strip forming through ERW welding, galvanizing, and final inspection
- SGS or BV third-party inspection report available at any production stage — dimensional checks, weld seam testing, coating thickness measurement
- Material traceability report linking each bundle to its heat number, steel grade, and production batch for project audit compliance
- Full export documentation package including packing list, bill of lading, certificate of origin, and fumigation certificate for destination port customs
Packaging, Loading & Delivery
- Q235 and Q345 welded square tubes bundled with galvanized steel strips at intervals sized to the section dimension, preventing bundle shift during ocean transit
- Hot-dip galvanized tubes packed with edge protectors and waterproof interleave to preserve zinc coating integrity from the galvanizing bath to the project site
- Container loading plans optimized for 10m and 12m lengths across 20ft and 40ft open-top or flat-rack containers, maximizing payload for 600×600 heavy-wall sections
- Custom cut-to-length service available for any length between 1m and 12m, reducing on-site waste and cutting labor for scaffold and fencing applications
- Each bundle labeled with heat number, steel grade, size specification, and gross/net weight for immediate identification at the construction yard
- FOB, CIF, and DDP shipping terms available with professional oversized cargo lashing for heavy-wall 600×600 tubes destined for Middle East, Southeast Asia, and African ports
Getting Your Quotation Moving
Send your project drawings in PDF or DWG format along with the required steel grade, section dimensions, wall thickness, surface treatment, and destination port. We respond within 24 hours with a detailed quotation covering material, fabrication, coating, packing, and shipping costs — including the shop drawing timeline and production schedule. If your project specifies EN 10219 or ASTM compliance, confirm the certification requirements upfront so the mill test certificate and third-party inspection can be scheduled into the production plan.
Start Your Q235 Q345 Welded Square Steel Tube Inquiry
Share your specifications, steel grade, and quantity to receive a detailed quotation with mill test certificate documentation.
Company: 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
Frequently Asked Questions
Q: What is the steel grade equivalence between Q235, Q345, A36, and European S grades?
A: Q235 is broadly equivalent to S235JR and ASTM A36 in yield strength range, while Q345 corresponds to S355JR/J2 and ASTM A572 Grade 50. Exact equivalence depends on the specific chemical composition and impact testing requirements of your project standard. We provide cross-reference documentation with every mill test certificate to support your engineer’s material approval process.
Q: How do you verify material authenticity and traceability for exported tubes?
A: Every bundle carries a unique heat number that traces back to the original steel slab. The mill test certificate documents chemical composition and mechanical properties for that specific heat. Third-party inspection by SGS, BV, or TÜV can be arranged at any production stage — from strip incoming inspection through welding, galvanizing, and final dimensional checks.
Q: Can you provide custom cut-to-length, drilling, and welding preparation services?
A: Yes. As a vertically integrated fabrication facility, we offer cut-to-length to any dimension between 1m and 12m, along with CNC drilling, beveling for weld preparation, and custom punching per your shop drawings. These services are quoted together with the tube supply, eliminating the need for a separate processing subcontractor.
Q: How do you calculate pricing weight — theoretical or actual?
A: We are transparent about this. For standard orders, pricing can be based on theoretical weight calculated from nominal dimensions, or on actual weighed weight — your choice. We clearly state which method applies in the quotation. Negative tolerance is controlled within ±1% per the product specification, and we never push tolerance to the extreme to gain weight advantage at the buyer’s expense.
Q: What surface treatment options are available and how do I choose?
A: Hot-dip galvanized is recommended for outdoor or corrosive environments — coastal infrastructure, agricultural buildings, and industrial plants with chemical exposure. Black (uncoated) tubes suit indoor structural frames where painting will be done on-site. PVC coated and color painted finishes are available for architectural applications where appearance matters. We advise on coating class selection based on your project’s corrosion environment.
