Description
Direct Mill Supply, Full Traceability — Q235B and Q345B square and rectangular steel tubes produced from our own steel mill with mill test certificates covering every heat number.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B/Q345B Square and Rectangular Steel Tube |
| Product Type | Square / Rectangular Steel Tube (SHS/RHS) |
| Steel Grade | Q195, Q235, Q235B, Q345, Q345B, SS400, SS330, SS540 |
| Standard | ASTM |
| Section Shape | Square / Rectangular / Round |
| Wall Thickness | 0.5–200 mm |
| Length | 12 m |
| Technique | Hot Rolled / Cold Rolled |
| Surface Treatment | Hot Rolled / Galvanized / Consumer’s Requirement |
| Tolerance | ±1% |
| Ends | As per consumer requirement |
| Application | Fluid Pipe / Boiler Pipe / Drill Pipe / Hydraulic Pipe / Gas Pipe / Steel Structures / Construction Frames / Machinery |
| MOQ | 5 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Building | Column and beam frames, portal structures, mezzanine platforms, stairway supports |
| Industrial Infrastructure | Hydraulic piping circuits, gas distribution lines, boiler feed systems, fluid transfer networks |
| Machinery & Equipment | Conveyor frame structures, crane booms, equipment base frames, drill string components |
| EPC & General Contracting | Prefabricated steel modules, warehouse racking systems, infrastructure support assemblies |
What Negative Tolerance Overruns Cost on a Q345B Frame Order
A wall thickness that reads within spec on paper but fails caliper measurement on site turns a delivered bundle into scrap.
When buyers source ASTM Q235B Q345B square rectangular steel tube supplier products through trading intermediaries, the material chain breaks at the mill gate. Certificates get copied, heat numbers go unverified, and the ±1% tolerance becomes a one-directional allowance — always minus. I once watched a 50×50 SHS shipment to Dubai get rejected at third-party inspection because the wall thickness ate through the negative tolerance limit on nearly every piece. The entire container came back for re-measurement and sorting. [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance requirements]
The real cost is not the re-inspection fee. It is the crane idle time, the welder standing by, and the RFI chain that follows when a structural engineer questions whether the as-delivered sections can carry the design load.
Matching Section Geometry to Structural Load Paths
Square and rectangular hollow sections from the Q235B and Q345B grade range serve load-bearing frames where torsional rigidity matters more than circular alternatives. The flat faces of SHS and RHS allow direct bolted or welded connections without gusset plates, reducing joint complexity on construction frames and machinery bases. When an ASTM Q235B Q345B square rectangular steel tube supplier provides both hot rolled and cold rolled options, the buyer can match forming method to application — hot rolled for thicker structural columns, cold rolled for tighter-tolerance machine frames.
Engineering Compliance and Surface Protection Choices
Structural frames in corrosive environments require surface treatment decisions before fabrication, not after. Hot rolled Q235B sections suit painted or fireproofed indoor applications, while galvanized Q345B RHS protects outdoor infrastructure from atmospheric corrosion without ongoing maintenance. For projects targeting EU markets, EN 10219 compliance governs cold-formed hollow sections; for North American specs, ASTM A500 Grade B or C equivalence must be documented. [NEED_CITE: steel grade equivalence mapping between GB/T and ASTM standards] Dimensional tolerance at ±1% across the 0.5–200 mm wall thickness range ensures shop drawings translate to as-built accuracy without field rework.
Understanding Q-Series Grade Selection and Rolling Process
The Q235B and Q345B designations follow the Chinese GB/T 1591 system where the number indicates minimum yield strength in MPa. Q235B covers general structural applications where moderate strength suffices — warehouse frames, scaffolding, and non-critical machinery supports. Q345B steps up to higher yield for load-bearing columns, crane beams, and bridge components where weight-to-strength ratio drives section selection. SS400 and SS330 from JIS G3101 offer Japanese-standard alternatives for projects specifying JIS compliance. Hot rolling produces thicker walls with mill scale surface, suited for structural work where coating follows. Cold rolling delivers tighter dimensional control and smoother finish for visible architectural applications. [NEED_CITE: hot rolled versus cold formed structural hollow section mechanical property differences]
Hidden Costs of Unverified Material Procurement
Sourcing ASTM Q235B Q345B square rectangular steel tube supplier products without verified mill test certificates creates three failure modes. First, grade substitution — Q235 shipped as Q345B passes visual inspection but fails structural calculations under design load. Second, tolerance abuse — wall thickness at the extreme negative limit reduces section modulus below engineering assumptions. Third, documentation gaps — missing heat numbers block customs clearance in markets requiring EN 1090 or AISC compliance. [NEED_CITE: material traceability requirements for structural steel in international construction projects] Each failure mode surfaces not at the mill, but at the job site, where rework costs multiply by the square of project progress.
Why Project Teams Source Through XJY Structure
Our fabrication division operates under the same roof as the steel production facility, meaning every Q235B and Q345B section leaving Jinan carries a continuous material chain from liquid steel to finished tube. The mill test certificate references the same heat number stamped on each piece. We maintain over 2,800 specifications in inventory, covering the full 0.5–200 mm wall thickness range and square-to-rectangular section spectrum, so project teams sourcing an ASTM Q235B Q345B square rectangular steel tube supplier avoid splitting orders across multiple vendors. In-house CNC cutting, drilling, bending, and welding services transform raw tubes into fabrication-ready components per approved shop drawings. Certified welding procedures and qualified welders hold AWS and EN credentials. Every shipment includes complete QC documentation — WPS, PQR, dimensional inspection reports, and coating thickness records.
Documentation & Compliance
- Mill test certificate documenting Q235B and Q345B chemical composition and mechanical properties per GB/T 1591, with heat number traceability from raw slab to finished tube
- CE certificate covering EN 10219 cold-formed structural hollow sections for EU market customs clearance and EN 1090 execution class compliance
- ISO 9001 quality management certificate covering the integrated steel production and fabrication workflow
- SGS or BV third-party inspection report available for wall thickness verification, dimensional checks, and coating adhesion testing upon buyer request
- Material traceability report linking each bundle to its heat number, chemical analysis, and rolling schedule
- Export customs documentation including packing list, bill of lading, and certificate of origin for destination-country import clearance
Packaging, Loading & Delivery
- Hot rolled Q235B and Q345B square rectangular tubes bundled with steel strips at six points, with edge protectors preventing zinc coating damage on galvanized sections during ocean transit
- 12-meter standard length loaded in 20ft and 40ft containers with optimized nesting for rectangular sections, maximizing payload per shipment
- Galvanized surfaces wrapped in waterproof paper with desiccant packs to prevent white rust formation during humid climate transport
- Custom cut-to-length service available per consumer requirement, with each piece marked by heat number, steel grade, and section dimensions
- Shipping terms FOB, CIF, and DDP supported, with professional lashing plans for oversized structural sections exceeding standard container dimensions
Starting Your Procurement Process
Submit project drawings in PDF or DWG format along with required steel grades, section dimensions, wall thickness, surface treatment preference, and destination port. Our engineering team reviews shop drawings, confirms ASTM Q235B Q345B square rectangular steel tube supplier availability against your specification, and returns a detailed quotation covering material, fabrication, coating, packing, and logistics within 24 hours.
Request a Quotation with Mill Test Certificate
Send your specifications and drawings to receive pricing, material certification, and production lead time confirmation.
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: How do Q235B and Q345B grades compare to ASTM A500 equivalents?
A: Q235B generally maps to ASTM A500 Grade B for structural applications, while Q345B aligns with ASTM A500 Grade C in terms of minimum yield strength. We provide grade equivalence documentation for projects requiring cross-standard compliance verification.
Q: Can you produce non-standard dimensions with a low minimum order quantity?
A: Yes. Our integrated mill and fabrication facility supports custom section sizes and wall thicknesses within the 0.5–200 mm range. The minimum order quantity is 5 Tons, and we accommodate project-specific cutting, drilling, and bending per approved shop drawings.
Q: What surface treatment options are available for corrosion protection?
A: We supply hot rolled bare tubes for indoor or painted applications, hot-dip galvanized sections for outdoor atmospheric exposure, and custom coating per consumer requirement including primer and topcoat systems for aggressive industrial environments.
Q: Do you provide cutting, bending, and welding services to drawing specifications?
A: Yes. Our fabrication division offers CNC cutting, plasma and flame cutting, drilling, bending, and MIG/MAG/SAW welding per approved shop drawings. All welding follows certified WPS procedures with qualified welders holding AWS and EN certifications.
Q: What is the production lead time and how do you handle international shipping?
A: Typical production lead times apply once drawings and deposit are confirmed. We provide professional packing, oversized cargo loading plans, complete export documentation, and tracking through to site delivery under FOB, CIF, or DDP terms.
