Description
Factory-Direct ERW Hollow Sections — Q235 and Q345 welded square and rectangular steel tubes rolled and dispatched from our Jinan mill with original mill test certificates for every heat.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235 / Q345 Welded Square and Rectangular Steel Tube |
| Product Type | Welded Square and Rectangular Steel Tube (ERW) |
| Steel Grade | Q195, Q215, Q235, Q345, S235JR, S355JR, SS400 |
| Standard | ASTM A213, DIN EN 10217-1 |
| Section Shape | Square / Rectangular |
| Size Range | 30×30 mm, 30×40 mm, 50×50 mm (custom sizes available) |
| Wall Thickness | 1 mm – 3 mm |
| Length | 6 m / 6.4 m / 12 m (custom length available) |
| Technique | ERW (Cold Rolled / Hot Rolled) |
| Surface Treatment | Hot Rolled / Slightly Oiled / Non-oiled |
| Tolerance | ±1% |
| Ends | Plain |
| Application | Construction building material / Steel structures / Machinery / Furniture manufacturing / Architectural decoration |
| MOQ | 5 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Building | Column frames, roof trusses, portal frame bracing, mezzanine supports |
| Steel Structures | Welded portal frames, bracing members, purlin systems, equipment skids |
| Machinery Manufacturing | Machine bases, conveyor supports, guarding frames, hydraulic stands |
| Furniture & Interior | Exposed structural legs, shelving uprights, decorative screen frames |
| Architectural Decoration | Canopy structures, façade sub-frames, canopy bracing tubes |
What Negative Tolerance Actually Costs on a Q235 Square Tube Order
A wall thickness that reads 0.8 mm instead of 1.0 mm on a 30×30 Q235 tube means the entire container fails acceptance at the project site.
I learned this the hard way on a Riyadh job where 30×30 square tubes came in below minimum wall. The client pulled a caliper off the first piece, rejected the lot, and the whole container went back to the mill for re-rolling. On thin-wall ERW sections in the 1–3 mm range, even a small tolerance drift changes the section modulus and load-bearing capacity — and no amount of paperwork fixes a physical shortcoming. Fragmented sourcing from multiple traders makes this worse: you get mixed heats, inconsistent chemistry, and certificates that don’t match the steel in the bundle. [NEED_CITE: EN 10219 cold-formed welded hollow section dimensional tolerance requirements]
How Q235 and Q345 Grades Match Structural Frame Requirements
Q235 Q345 welded square rectangular steel tube sections in 30×30, 30×40, and 50×50 mm cover the majority of light-to-medium structural framing across construction, machinery bases, and architectural sub-structures. The Q235 grade handles general bracing and non-critical framing where formability and weldability matter more than raw strength, while Q345 steps up for load-bearing columns and equipment skids that demand higher yield. Our mill holds 2,800+ specifications in rolling schedule, so when a project calls for a non-standard 30×40×1.2 in Q345 at 6.4 m length, we pull from ready stock or roll to order rather than forcing you into a substitute section.
Structural Compliance and Surface Protection for ERW Hollow Sections
Load-bearing frames designed to EN 1993 or AISC require traceable chemistry and verified mechanical properties — not just a supplier’s word. Q235 and Q345 grades under DIN EN 10217-1 give you a recognized standard path for European and Middle Eastern projects, while S235JR and S355JR equivalence opens doors for spec-driven tenders. [NEED_CITE: steel grade equivalence between Chinese GB, European EN, and American ASTM standards] The hot rolled surface with slight oiling protects against transit corrosion without adding cost; for coastal or high-humidity sites, upgrading to galvanized finish extends service life significantly. Plain ends arrive ready for on-site welding, punching, or bending — no secondary machining needed before erection.
Steel Grade Selection and ERW Process Explained for Buyers
Q-series grades (Q195 through Q345) follow the Chinese GB system where the number indicates minimum yield strength in MPa — Q235 yields at 235 MPa, Q345 at 345 MPa. For international projects, S235JR maps closely to Q235 in yield and chemistry, while S355JR aligns with Q345. SS400 from JIS sits in the same general family. ERW welding produces a longitudinal seam that, on thin-wall sections in the 1–3 mm range, delivers consistent dimensional accuracy and smooth internal finish — critical when tubes serve as structural columns or visible architectural elements. The ±1% tolerance on our Q235 Q345 welded square rectangular steel tube production keeps section properties within design assumptions, avoiding the weight-and-strength shortfalls that come from unchecked negative tolerance. [NEED_CITE: ERW welded hollow section manufacturing process and quality control]
The Hidden Cost of Unverified Steel Grades on Thin-Wall Tubes
Accepting Q235 tubes without original mill test certificates means you cannot prove chemistry or yield strength to the project engineer — and that stops payment release. Missing CE or EN 10219 documentation triggers customs holds at EU and Middle Eastern ports, turning a routine shipment into a weeks-long delay. [NEED_CITE: customs clearance requirements for structural steel imports with CE certification] Negative tolerance beyond ±1% reduces actual weight and section modulus, so a tube that looks right on paper fails load testing on site. Re-rolling, re-shipping, and re-certifying a rejected container costs multiples of the original price difference between a verified supplier and an unverified one.
Why Project Buyers Source Q235 Q345 Welded Square Rectangular Steel Tube from Xin Jiyuan
We roll and ship from our own Jinan mill — no trading company markup, no middleman inventory games. Every Q235 Q345 welded square rectangular steel tube bundle leaves with an original mill test certificate showing heat number, chemistry, and mechanical test results. Our in-house lab runs three-stage inspection before dispatch, and we welcome SGS or BV third-party inspection for projects that require it. With 2,800+ specifications in stock, we fill mixed-container orders combining square, rectangular, and round sections in a single shipment — cutting your logistics cost and coordination overhead. Custom lengths up to 12 m, non-standard sizes, and processing services (welding, punching, bending) reduce your on-site preparation time. Our export team handles full documentation, container loading optimization, and customs paperwork for 50+ destination countries.
Documentation & Compliance
- Mill test certificate documenting Q235 or Q345 chemical composition and mechanical properties per DIN EN 10217-1, with heat number traceability
- CE certificate covering EN 10219 cold-formed welded structural hollow sections for European and Middle Eastern project compliance
- ISO 9001:2015 quality management certificate covering full production and inspection process
- SGS or BV third-party inspection report available on request for independent verification of dimensions, surface quality, and mechanical properties
- Material traceability by heat number linking each bundle to its original mill test certificate
- Full customs documentation package including packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- Q235 and Q345 ERW tubes bundled with steel strips and edge protectors to prevent surface damage during ocean transit
- Slightly oiled surface treatment applied before bundling to prevent rust formation during container shipping
- Container loading optimized for 6 m, 6.4 m, and 12 m lengths to maximize weight utilization and minimize shipping cost per ton
- Custom length cutting available to project specification, reducing on-site waste and preparation time
- Each bundle marked with heat number, steel grade (Q235 / Q345), section size, and length for clear site identification
- FOB, CIF, and DDP terms available with door-to-door logistics coordination to major ports worldwide
Getting Your Q235 Q345 Welded Square Rectangular Steel Tube Quote Started
Send your specification list — section size, wall thickness, length, steel grade, quantity, and destination port — and we return a competitive bulk quote with volume pricing, production lead time, and payment terms within 12 hours. For non-standard sizes or custom lengths outside the 30×30 to 50×50 mm range, we provide a feasibility check and rolling schedule confirmation before you commit.
Frequently Asked Questions
Q: How do Q235 and Q345 grades compare to S235JR and S355JR for international projects?
A: Q235 and S235JR share similar yield strength and chemical composition ranges, making them interchangeable for most general structural applications. Q345 and S355JR follow the same equivalence pattern at higher yield levels. We supply both Chinese GB and European EN designations from the same production line, with mill test certificates referencing the standard your project requires.
Q: Can you provide mill test certificates and third-party inspection for Q235 Q345 welded square rectangular steel tube orders?
A: Yes. Every shipment includes an original mill test certificate showing heat number, chemical composition, and mechanical test results per DIN EN 10217-1. SGS or BV third-party inspection is available on request for independent verification before loading.
Q: What is the minimum order quantity for custom sizes outside 30×30, 30×40, and 50×50 mm?
A: Standard sizes in Q195 through Q345 grades carry a 5-ton MOQ. For non-standard sections or custom lengths up to 12 m, we confirm rolling feasibility and MOQ based on your specific requirement — trial orders from 1 ton are accepted for new customers evaluating quality.
Q: How do you handle surface protection for hot rolled ERW tubes during shipping?
A: Tubes receive slight oiling after production to prevent transit corrosion. For projects in coastal or high-humidity environments, we can supply galvanized finish on request. Each bundle is packed with edge protectors to preserve surface condition during ocean freight.
Q: What documentation do you provide for customs clearance on structural steel tube imports?
A: We supply a complete documentation package including mill test certificates, packing list, bill of lading, certificate of origin, and CE certificate where required. Our export team coordinates directly with your forwarder to ensure smooth customs clearance at destination port.
Request Your Q235 Q345 Welded Square Rectangular Steel Tube Quote Today
Submit your section sizes, wall thickness, steel grade, quantity, and destination port to receive factory-direct pricing with original mill test certificates and full export documentation.
Contact: Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Mobile / WhatsApp / WeChat: +86 188 5315 7756
Email: admin@sdxinjiyuan.com
Website: www.sdxinjiyuan.com
