Description
Factory-direct Q235 welded square steel tube — mill-produced to ASTM and JIS standards with full dimensional tolerance control and mill test certificates for every shipment.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235 Welded Square Steel Tube |
| Product Type | Welded Square Steel Tube |
| Steel Grade | Q195, Q235, Q345 |
| Standard | ASTM, JIS, DIN |
| Section Shape | Square |
| Size Range | 300×300 mm / 500×500 mm |
| Wall Thickness | 0.5–30 mm |
| Length | 6–12 m |
| Technique | Welded (Hot Rolled / Cold Rolled) |
| Surface Treatment | Black / Oiled (as produced) |
| Tolerance | ±1% |
| Ends | Plain |
| Application | Steel structures / Construction frames / Bridges / Roofing / Building material |
| MOQ | 5 Tons |
| Origin | China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Steel Structure Fabrication | Column and beam frames for industrial warehouses and commercial buildings |
| Construction & Infrastructure | Scaffolding systems, bridge support members, roofing purlins |
| Civil Engineering | Foundation piles, retaining wall bracing, utility pole structures |
| Building Material Supply | Load-bearing frames for pre-engineered buildings and modular construction |
What Dimensional Tolerance Actually Means for a 500×500 Structural Frame Order
A ±1% tolerance on a Q235 welded square steel tube determines whether your frame passes structural inspection or gets rejected at the job site.
When buyers source large-section welded tubes for steel structures, the gap between nominal and actual dimensions directly affects bolt-hole alignment, weld joint fit-up, and overall frame geometry. Standard welded square tubes with loose tolerance control can accumulate dimensional drift across multiple connection points — turning a straightforward assembly into weeks of rework. Buyers who have experienced container arrivals with bent corners or out-of-spec wall thickness know that tolerance is not a catalog number; it is a cost variable embedded in every ton of steel shipped. [NEED_CITE: dimensional tolerance requirements for structural hollow sections per ASTM A500]
Matching 300–500 mm Square Sections to Structural Load Paths
The 300×300 mm and 500×500 mm size range covers the mid-to-heavy load spectrum in building frames and bridge components. At 300×300 mm, these Q235 welded square steel tubes serve as secondary beams and bracing members where moderate load capacity is required. Stepping up to 500×500 mm shifts the application to primary columns and transfer girders carrying concentrated loads from upper floors. The wall thickness range from 0.5 mm to 30 mm allows engineers to optimize weight versus section modulus — thin-wall sections for non-load-bearing cladding supports, heavy-wall sections for seismic-resisting frames. Our production lines cover this full range with consistent ±1% tolerance, verified by in-house dimensional testing before each shipment leaves the mill.
Engineering Compliance and Steel Grade Selection for Structural Projects
Structural projects governed by ASTM, JIS, or DIN standards require documented proof that the steel grade meets specified chemical and mechanical thresholds. Q235, as a carbon structural steel, provides adequate yield strength for general construction frames and non-critical infrastructure members. For projects requiring higher load capacity or seismic performance, Q345 offers increased yield strength while maintaining weldability and formability. The welded manufacturing process — whether hot rolled or cold rolled — must conform to the dimensional and surface quality requirements of the applicable standard. [NEED_CITE: steel grade equivalence between GB Q-series and ASTM/JIS standards] Third-party inspection through SGS or BV is available for buyers who need independent verification before container loading, ensuring that mill test certificates match the physical product and that customs documentation satisfies importing country requirements.
Understanding Welded Square Tube Manufacturing and Grade Behavior
The welded process for square steel tubes begins with coil or plate material formed into the required cross-section and joined by longitudinal or spiral weld seams. Hot rolled welded tubes are produced at elevated temperatures, resulting in a mill scale surface that is typically left as-produced or oiled for short-term corrosion protection. Cold rolled welded tubes undergo additional forming at room temperature, achieving tighter dimensional accuracy and smoother surface finish. The choice between Q195, Q235, and Q345 grades reflects the structural demand: Q195 suits light-duty applications such as fencing and handrails; Q235 covers the majority of building frames and scaffolding; Q345 is specified for heavy structural members, bridge components, and equipment supports requiring higher strength-to-weight ratios. Wall thickness directly influences section properties — a 500×500 mm tube at 30 mm wall carries substantially more load than the same outer dimension at 10 mm wall, but also weighs significantly more per meter, affecting transportation cost and crane capacity on site.
Hidden Costs of Incorrect Grade Specification and Tolerance Failure
Specifying Q235 when the structural calculation requires Q345 does not show up as a price saving — it shows up as a failed load test, a rejected inspection report, or a structural deficiency discovered during commissioning. Similarly, accepting wall thickness below the specified tolerance to reduce unit cost creates a cascade of problems: reduced section modulus, lower buckling resistance, and potential non-compliance with the engineer of record’s specifications. [NEED_CITE: consequences of dimensional non-compliance in structural steel procurement] Buyers who have dealt with customs holds due to missing or incorrect mill test certificates understand that documentation is not paperwork — it is the legal basis for the steel to enter the country and be used in the structure.
Why Buyers Choose SD XJY Pipe for Welded Square Steel Tube Procurement
Our mill operates three dedicated production lines covering over 2,800 specifications in square and rectangular hollow sections, with wall thickness capability up to 40 mm. The Q235 welded square steel tube in 300×300 mm and 500×500 mm sizes is produced in-house with full dimensional control, chemical analysis, and mechanical testing performed in our own laboratory before shipment. Every order is accompanied by a mill test certificate documenting heat number, chemical composition, and mechanical properties. For buyers requiring third-party verification, we arrange SGS or BV inspection at the mill prior to container loading. Our export experience covers 50+ countries, with professional loading procedures designed to prevent bending and surface damage during ocean transit. Custom lengths, non-standard sizes, and specific surface treatment requirements are accommodated within standard production schedules.
Documentation & Compliance
- Mill test certificate documenting Q235 chemical composition (C, Mn, Si, S, P) and mechanical properties (yield strength, tensile strength, elongation) per ASTM or JIS standard
- CE certificate confirming compliance with EN 10219 for cold-formed welded structural hollow sections, required for EU market entry
- ISO 9001:2015 quality management system certificate covering the full production and inspection process
- SGS or BV third-party inspection report verifying dimensional accuracy, surface quality, and marking before container loading
- Material traceability documentation linking each tube to its heat number and production batch for project quality records
- Complete customs documentation including packing list, bill of lading, and certificate of origin formatted for the destination country
Packaging, Loading & Delivery
- Q235 welded square steel tubes bundled with steel strips and edge protectors to maintain bundle integrity during crane handling and ocean transit
- Black or oiled surface treatment applied at the mill to prevent rust formation during storage and shipping; additional protection available for extended sea voyages
- Container loading optimized for 6 m and 12 m lengths to maximize payload per 20ft or 40ft container, reducing per-ton freight cost
- Custom cutting to project-specific lengths available to reduce on-site waste and labor cost for scaffolding and framing applications
- Heat number and steel grade marked on each tube end for on-site identification and traceability during installation
- FOB, CIF, and DDP shipping terms available with door-to-door logistics coordination for project sites in 50+ countries
Requesting a Quotation for Your Welded Square Steel Tube Requirement
Submit your specification including outer dimension, wall thickness, steel grade, total quantity, and destination port to receive a detailed quotation with unit price, production lead time, and shipping terms. We provide mill test certificates and arrange third-party inspection for buyers who require independent quality verification before shipment.
Get Your Q235 Welded Square Steel Tube Quote with Mill Test Certificate
Send your specification and quantity to receive pricing, production schedule, and documentation package within 12 hours.
Contact:
- Tel: +86 531 8573 6315
- Mobile/WhatsApp/WeChat: +86 188 5315 7756
- Email: admin@sdxjypipe.com
Frequently Asked Questions
Q: What is the difference between Q235 and Q345 steel grades for welded square tubes?
A: Q235 is a standard carbon structural steel suitable for general construction frames, scaffolding, and non-critical structural members. Q345 offers higher yield strength for heavy-load applications such as primary columns, bridge components, and seismic-resisting frames. Both grades maintain good weldability and formability.
Q: Can you provide mill test certificates for ASTM and JIS standards?
A: Yes, every shipment includes a mill test certificate documenting chemical composition and mechanical properties. We produce Q235 welded square steel tubes to meet ASTM, JIS, and DIN standards as specified in your purchase order. Third-party inspection through SGS or BV is available for additional verification.
Q: What is the minimum order quantity for 500×500 mm welded square tubes?
A: The minimum order quantity is 5 tons. We can mix different sizes and wall thicknesses within the 300×300 mm to 500×500 mm range to reach the MOQ, allowing flexibility for projects requiring multiple specifications.
Q: Do you offer custom lengths and cutting services?
A: Yes, standard lengths are 6–12 m, but we provide custom cutting to your project-specific requirements. This reduces on-site cutting waste and labor cost, particularly for scaffolding and repetitive framing applications.
Q: How do you prevent damage during container loading and ocean shipping?
A: We use professional loading procedures with steel strip bundling, edge protectors, and strategic weight distribution to prevent bending and surface damage. Tubes are secured to prevent movement during transit, and surface treatment (black or oiled) provides corrosion protection during ocean shipping.
Need Q235 Welded Square Steel Tube with Full Certification?
Submit your dimension, wall thickness, grade, and quantity to receive a quotation with mill test certificate and production schedule.
Contact:
- Tel: +86 531 8573 6315
- Mobile/WhatsApp/WeChat: +86 188 5315 7756
- Email: admin@sdxjypipe.com
