Description
Factory-Direct Pricing, No Middlemen — Q235B and Q345B carbon steel square and rectangular tubes produced on our own lines, shipped directly from Jinan to your project site.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B / Q345B Carbon Steel Square and Rectangular Tube |
| Product Type | Square / Rectangular Steel Tube (Hollow Section) |
| Steel Grade | Q195, Q235, Q235B, Q345, Q345B, SS400, SS330–SS540 |
| Standard | ASTM, JIS |
| Section Shape | Square, Rectangular, Round |
| Size Range | Wall thickness 0.5–200 mm |
| Length | 12 m standard, customizable |
| Technique | Cold Rolled / Hot Rolled |
| Surface Treatment | Hot Rolled, Galvanized, Oiled, Bare, Painted |
| Tolerance | ±1% |
| Ends | Plain (default) |
| Processing Service | Welding, Punching, Cutting, Bending, Decoiling |
| Application | Construction, Petrochemicals, Fluid Pipe, Boiler Pipe, Drill Pipe, Hydraulic Pipe, Gas Pipe, Machinery, Steel Structures |
| MOQ | 5 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| EPC Contractors | Steel structure frames for industrial plants, pipe racks, equipment supports |
| Construction Companies | High-rise building columns, bridge supports, scaffolding systems |
| Machinery Manufacturers | Hydraulic cylinders, fluid transmission lines, conveyor frames |
| Infrastructure Developers | Highway guardrail posts, sound barrier frames, foundation piles |
| System Integrators | Automation conveyor structures, material handling frames |
What Wall-Thickness Tolerance Costs on a Structural Frame Order
A ±1% tolerance gap can mean the difference between passing third-party inspection and an entire container held at port.
When procurement teams source ASTM JIS Carbon Steel Square Rectangular Hollow Section Tube products from fragmented suppliers, inconsistent wall thickness is the most frequent cause of on-site rejection. I have seen batches where negative tolerance exceeded acceptable limits — the material looked right on the outside, but ultrasonic testing revealed thin walls that could not carry design loads. The result: customs delays, re-order costs, and weeks of schedule slip. Every tube we roll goes through our in-house physical and chemical laboratory before it leaves the floor, with real-time data logged per heat number. [NEED_CITE: EN 10219 cold-formed hollow section tolerance requirements]
How Q235B and Q345B Match Structural Load Requirements
For load-bearing frames in industrial buildings and bridge supports, Q345B delivers higher yield strength than Q235B while maintaining weldability and formability. When the ASTM JIS Carbon Steel Square Rectangular Hollow Section Tube is specified for hydraulic or fluid systems, the ±1% wall tolerance ensures consistent internal pressure ratings. Our production lines cover wall thickness from 0.5 mm to 200 mm, so whether you need thin-walled tubes for conveyor frames or thick-walled sections for heavy equipment bases, the same supplier handles the full range without quality variation.
Engineering Compliance and Certification Pathways
Structural steel procurement for EU markets requires CE marking under EN 10210 or EN 10219, while North American projects typically reference ASTM A500 or A53. The Q235B grade roughly corresponds to S235JR in EN standards, and Q345B aligns with S355JR — but equivalence is not automatic. Mill test certificates must document chemical composition and mechanical properties per the specified standard, or customs will reject the shipment. [NEED_CITE: steel grade equivalence between GB, EN, and ASTM standards] For projects in Southeast Asia, Singapore FPC certification adds another compliance layer that many suppliers overlook until the last minute.
Steel Grade Selection and Processing Fundamentals
The Q-series (Q195, Q235B, Q345B) follows the Chinese GB standard system where the number indicates minimum yield strength in MPa. SS400 and SS330–SS540 belong to the JIS G3101 general structure steel family, widely used in Japanese-spec projects across Southeast Asia. Hot rolled surface finish is suitable for indoor structural applications, while galvanized coating extends service life in corrosive environments — coastal construction, chemical plants, or outdoor scaffolding. Bending and cutting services reduce secondary fabrication costs at your site, but the key is ensuring the base material meets the specified grade before any downstream processing begins. [NEED_CITE: JIS G3101 SS400 mechanical properties and applications]
Hidden Costs of Unverified Material Sources
Purchasing from trading companies without mill test certificates creates a cascade of risks: material traceability gaps, unknown negative tolerance, and missing certification for customs. When a batch fails third-party inspection at destination port, the buyer absorbs demurrage charges, return freight, and project delays — costs that far exceed any initial price savings. Engineering specifications require documented proof of steel grade and chemical composition; verbal assurance from a supplier means nothing to the inspecting authority. [NEED_CITE: third-party inspection requirements for structural steel imports]
Why Engineering Teams Source Directly from Our Lines
We operate three dedicated production lines covering 2,800+ specifications, including proprietary sharp-corner rectangular tube technology that holds 41 invention patents. Every order ships with mill test certificates generated from our in-house laboratory — not forwarded documents from unknown mills. Our CE certification under EN 10210/10219 and Singapore FPC clear customs in EU and Southeast Asian markets without additional testing. For non-standard sizes or custom lengths, we adjust production parameters directly rather than sourcing from external mills. Professional loading plans optimize container space for 12 m standard lengths, and our logistics team coordinates FOB, CIF, or DDP delivery to 50+ countries.
Documentation & Compliance
- Mill test certificate documenting Q235B chemical composition and mechanical properties per GB/T 700
- CE certificate confirming EN 10210/EN 10219 compliance for European market entry
- ISO 9001:2015 quality management certificate covering production and inspection processes
- SGS or BV third-party inspection report available for independent quality verification
- Material traceability by heat number linking each tube to its production batch and test results
- Customs documents including packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- Q235B and Q345B tubes bundled with steel strips and edge protectors to prevent surface damage during ocean transit
- Hot rolled surface tubes coated with anti-rust oil before bundling to preserve finish quality
- 12 m standard length tubes loaded with optimized stowage plans maximizing container payload
- Custom cut-to-length tubes packaged separately with clear heat number and grade identification marks
- FOB, CIF, and DDP shipping options with real-time tracking from Jinan port to destination
- Galvanized tubes wrapped with protective film to maintain zinc coating integrity during handling
Start Your Procurement with Verified Specifications
Submit your required steel grade, section dimensions, wall thickness, quantity, and destination port — we respond within 12 hours with pricing, mill test certificate samples, and delivery timeline. For non-standard sizes or custom bending and cutting, our technical team provides fabrication drawings and production feasibility confirmation before you commit.
Request Pricing and Material Certification
Send your specifications to admin@sdxjysteel.com or contact us via WhatsApp at +86 188 5315 7756 for immediate quotation and mill test certificate review.
