Description
Factory-Direct Welded SHS Supply — Q235 and Q355 welded square steel tubes produced from our own steel mill with full heat-number traceability to raw slab.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235 / Q355 Welded Square Steel Tube |
| Product Type | Welded Square Steel Tube (SHS) |
| Steel Grade | Q195, Q235, Q345 (Q355) |
| Standard | ASTM |
| Section Shape | Square |
| Size Range | 10×10 mm – 500×500 mm |
| Wall Thickness | 0.5 – 25 mm |
| Length | 6 – 12 m |
| Technique | Hot Rolled / Welded |
| Surface Treatment | Hot Rolled finish, Oiled or Non-oiled |
| Tolerance | ±1% |
| Ends | Plain ends |
| Application | Steel structures, Construction frames, Building material, Machinery, Scaffolding |
| MOQ | 5 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Commercial Construction | Building frames, column and beam assemblies, mezzanine platforms |
| Industrial Facilities | Warehouse roof trusses, factory support structures, equipment platforms |
| Infrastructure | Bridge access frameworks, utility support gantries, sound barrier posts |
| Machinery & Equipment | Conveyor structures, crane booms, machine base frames |
| Scaffolding & Temporary Works | Scaffold towers, shoring props, access stairway frames |
What Wall-Thickness Tolerance Costs on a Structural Frame Order
A ±1% tolerance on a Q235 Q355 welded square steel tube is not a marketing line — it is the difference between passing site inspection and shipping the whole container back.
When overseas buyers source welded square tubes from fragmented suppliers, material certificates often arrive without heat-number linkage to actual production batches. Wall thickness drifting beyond ±1% means theoretical weight calculations no longer match physical delivery, triggering disputes at customs weigh-in or structural engineer sign-off. I have seen entire shipments rejected because ultrasonic thickness testing caught walls sitting below the lower deviation limit — and the return freight cost more than the steel itself. [NEED_CITE: ASTM A500 dimensional tolerance requirements for structural hollow sections]
How Q235 and Q355 Grades Match Structural Frame Demands
Q235 serves general construction frames where moderate load-bearing is required, while Q355 steps up yield capacity for heavier industrial structures and longer-span trusses. The Q235 Q355 welded square steel tube range from 10×10 mm to 500×500 mm covers everything from light scaffolding uprights to primary column sections. Wall thickness from 0.5 mm to 25 mm allows precise matching to calculated load requirements without over-specifying material cost. Our own steel mill produces both grades under one quality system, so every tube carries traceable chemistry from slab to finished section.
Meeting ASTM Compliance for North American and International Projects
ASTM-standard welded square tubes must demonstrate conforming chemistry and dimensional accuracy across every heat lot. For projects in North America, ASTM compliance determines whether the material clears customs and passes third-party inspection at the fabrication shop. Wall thickness tolerance of ±1% ensures that shop drawing calculations for connection design remain valid — a critical factor when CNC-cutting and welding are sequenced before delivery. [NEED_CITE: ASTM A500 cold-formed welded structural tubing specifications] Surface treatment in hot rolled finish with oiled or non-oiled options provides baseline corrosion protection during transit and allows downstream painting or galvanizing per project specification.
Understanding Q-Series Steel Grades and Welded SHS Production
Q235 and Q355 belong to the Chinese GB/T steel grade system, where the number indicates minimum yield strength in MPa. Q235 is broadly equivalent to ASTM A36 and S235JR in international standards, while Q355 aligns with ASTM A572 Grade 50 and S355JR. The welded square steel tube production process involves forming hot-rolled coil into square profile through continuous welding, followed by sizing and cutting to length. This method delivers consistent corner geometry and weld integrity across the full 10×10 mm to 500×500 mm range. Wall thickness from 0.5 mm to 25 mm covers thin-wall decorative sections through heavy structural members. Hot rolled finish with optional oiling provides mill-scale surface suitable for further coating or direct use in protected environments.
The Hidden Cost of Sourcing Welded Square Tubes Without Traceability
Purchasing Q235 Q355 welded square steel tubes from traders or brokers who source from unknown mills creates documentation gaps that surface at the worst moments. Missing heat numbers mean mill test certificates cannot be verified against physical material. Negative tolerance exceeding ±1% reduces actual load-bearing capacity below engineering design assumptions. [NEED_CITE: structural steel material traceability requirements for international construction projects] Customs authorities in strict markets may hold or reject shipments lacking proper certification packages. Rework at the fabrication shop — re-welding, re-drilling, or scrapping non-conforming sections — multiplies project costs far beyond the original material savings.
Why Project Buyers Choose Our Integrated Mill and Fabrication
Our vertically integrated operation combines raw steel production with dedicated structural tube fabrication, eliminating the sourcing gap between material supplier and processor. Every Q235 Q355 welded square steel tube we deliver carries mill test certificates traceable to specific heat numbers from our own production facility. With over 2,800 specifications in our inventory system, we fulfill mixed-size orders without forcing buyers to source from multiple vendors. Our certified welding procedures and qualified welders ensure that every longitudinal seam meets ASTM requirements. Third-party inspection through SGS or BV is available for buyers who require independent verification before shipment. Professional loading and lashing plans account for the specific dimensions and weight of square tube bundles, preventing transit damage and optimizing container utilization.
Documentation & Compliance
- Mill test certificate documenting Q235 and Q355 chemical composition and mechanical properties per ASTM, with heat-number traceability to raw slab
- ASTM compliance certificate confirming dimensional accuracy and tolerance verification for welded square steel tubes
- ISO 9001 quality management system certificate covering the full production process from coil reception to finished tube
- SGS or BV third-party inspection report available for wall thickness verification, visual weld inspection, and dimensional checks
- Material traceability report linking each bundle to specific heat numbers, production dates, and test results
- Complete customs documentation package including packing list, bill of lading, and certificate of origin for smooth import clearance
Packaging, Loading & Delivery
- Q235 and Q355 welded square steel tubes bundled with high-tensile steel strips at regular intervals to prevent shifting during ocean transit
- Oiled surface treatment applied to hot rolled finish tubes to prevent rust formation during extended shipping periods
- Mixed-size loading plans optimized for 6 m and 12 m lengths to maximize container payload while protecting corner geometry
- Custom cutting to project-specific lengths available within the 6–12 m range, with cut ends deburred and marked per bundle
- Heat number and steel grade stenciled on each bundle tag for immediate site identification and inspection verification
- FOB, CIF, and DDP shipping terms available with professional oversized cargo handling and door-to-door tracking
Start Your Procurement with Drawings and Specifications
Submit your project drawings, required steel grades, size specifications, and destination port to receive a detailed quotation including material, fabrication, coating, and shipping costs. Our engineering team will review shop drawings and confirm ASTM compliance requirements before production begins. Request mill test certificate samples and third-party inspection procedures to verify our documentation package meets your project standards.
Get Your Q235 Q355 Welded Square Steel Tube Quote Today
Share your specifications, steel grades, and quantity requirements to receive pricing with complete mill test certificates and export documentation within 24 hours.
Contact:
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 difference between Q235 and Q355 steel grades for welded square tubes?
A: Q235 offers moderate yield strength suitable for general construction frames and light structural applications, while Q355 provides higher yield capacity for heavy industrial structures and longer-span members. Both grades are produced in our own mill with full ASTM compliance and traceable mill test certificates.
Q: Can you provide third-party inspection for wall thickness and dimensional accuracy?
A: Yes, SGS and BV third-party inspections are available for wall thickness verification using ultrasonic testing, dimensional checks against ±1% tolerance, and visual weld seam inspection. Inspection reports are included in the export documentation package.
Q: What surface treatment options are available for welded square steel tubes?
A: We supply hot rolled finish with oiled or non-oiled surface treatment as standard. The oiled option provides rust prevention during ocean shipping, while non-oiled tubes are suitable for immediate downstream processing such as galvanizing or painting per project requirements.
Q: Do you offer custom cutting and processing services for project-specific lengths?
A: Yes, CNC cutting services are available to produce tubes in custom lengths within the 6–12 m standard range. Additional processing including drilling, bending, and end preparation can be coordinated with our fabrication workshop based on your shop drawings.
Q: How do you ensure material traceability from raw steel to finished tubes?
A: As a vertically integrated producer with our own steel mill, we maintain complete heat-number traceability from raw slab through coil production to finished welded square tubes. Every bundle carries mill test certificates linking chemistry and mechanical properties to specific production heats.
