Description
Factory-direct pricing, zero middlemen — every Q235B and Q345B ASTM carbon steel square rectangular hollow section ships from our Jinan production lines with original mill test certificates attached.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B/Q345B Carbon Steel Square/Rectangular Pipe |
| Product Type | Square / Rectangular Steel Tube (Hollow Section) |
| Steel Grade | Q195, Q235, Q235B, Q345, Q345B, SS400 |
| Standard | ASTM |
| Section Shape | Square, Rectangular, Round |
| Wall Thickness | 0.5–200 mm |
| Length | 12 m |
| Technique | Cold Rolled / Hot Rolled |
| Surface Treatment | Hot Rolled / Galvanized / Bare |
| Tolerance | ±1% |
| Ends | Plain |
| Processing Service | Welding, Punching, Cutting, Bending, Decoiling |
| Application | Construction frames, steel structures, petrochemicals, marine industries, fluid transport, machinery |
| MOQ | 5 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Infrastructure | Building frames, scaffolding supports, column structures, roof trusses |
| Petrochemical & Marine | Pipeline supports, platform handrails, corrosion-resistant structural members |
| Machinery & Equipment | Conveyor frames, crane booms, hydraulic cylinder housings |
| Steel Fabrication | Welded assemblies, base plates, equipment skids |
What Wall-Thickness Tolerance Costs on a Structural Frame Order
A ±1% tolerance on a 200 mm wall section is the difference between a frame that passes inspection and one that gets rejected at the gate.
When procurement teams source an ASTM carbon steel square rectangular hollow section from fragmented suppliers, wall thickness variance compounds across hundreds of members. A batch that measures 0.3 mm under spec on a critical load-bearing column triggers structural engineer rejections, forces on-site rework, and delays project handover by weeks. We have seen entire container loads held at customs because the mill test certificate did not match the physical gauge readings — a problem that traces back to suppliers who cannot guarantee tolerance consistency across production runs. [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance requirements]
Matching Hollow Section Geometry to Structural Load Paths
Square and rectangular profiles distribute load across four flat faces, making them ideal for column and beam connections where welding access matters. The Q235B grade provides adequate yield strength for standard building frames, while Q345B steps up for heavier spans in industrial sheds and bridge supports. Our production lines hold 2,800+ specification combinations in stock, so when a project engineer calls for a 150×100×6 rectangular tube in Q345B, we pull from ready inventory rather than waiting for a custom roll. This matters when site crews are standing by and every day of delay burns crane rental costs.
Engineering Compliance and Certification Requirements
ASTM standard hollow sections must carry traceable mill test certificates showing chemical composition and mechanical test results per heat number. For projects in North America, ASTM conformance is non-negotiable — customs authorities and structural inspectors both verify documentation before approving material for installation. Galvanized finishes add corrosion resistance for marine and petrochemical environments, while bare or oiled surfaces suit indoor structural applications where painting follows on-site. Third-party inspection from SGS or BV provides an independent verification layer that satisfies both the project owner and the insurance underwriter. [NEED_CITE: ASTM A500 structural tubing certification and testing requirements]
Steel Grade Selection and Manufacturing Process
The Q-series grades (Q195 through Q345B) follow the Chinese GB/T standard system, where the “Q” denotes yield strength and the number indicates the minimum yield value in MPa. Q235B remains the workhorse grade for general construction — it welds easily, forms cleanly, and costs less than higher-strength alternatives. Q345B delivers higher yield strength for structures carrying heavier loads, reducing section size and overall weight. SS400, the Japanese equivalent, appears frequently in projects sourced for Southeast Asian markets. Hot rolled production suits thicker walls above 6 mm, while cold rolled achieves tighter tolerances and smoother surfaces on thinner sections. Galvanizing adds a zinc coating that protects against atmospheric corrosion for twenty years or more in moderate environments, making it the default choice for outdoor structural steel in coastal regions.
The Hidden Cost of Unverified Material Sources
Purchasing an ASTM carbon steel square rectangular hollow section from an unverified supplier means accepting material that may carry incorrect grade markings, exceed negative tolerance limits, or lack proper heat treatment. When a galvanized tube arrives on-site with a zinc coating thinner than specified, corrosion begins within months — not decades. When a Q345B certificate turns out to be forged or transferred from a different heat, the structural engineer must order destructive testing on every member, halting construction. These failures do not show up in the purchase price; they surface months later as warranty claims, structural remediation, and reputational damage with the project owner. [NEED_CITE: consequences of non-conforming structural steel in construction projects]
Why Procurement Teams Source Hollow Sections From Us
We run three production lines simultaneously in Jinan, producing over 20,000 tons monthly across square, rectangular, and round sections. Every ASTM carbon steel square rectangular hollow section leaving our facility carries an original mill test certificate tied to its heat number — no transferred documents, no photocopies. Our in-house laboratory conducts three-stage inspection: incoming raw material verification, in-process dimensional checks, and final mechanical testing before dispatch. For buyers needing mixed containers — say, square tubes for columns, rectangular tubes for beams, and channel steel for bracing — we consolidate into a single shipment with optimized loading plans that maximize container weight without exceeding port limits. Long-term partners receive volume-based pricing reviews every six months, and our export team handles all documentation, customs clearance, and logistics coordination from factory floor to destination port.
Documentation & Compliance
- Mill test certificate documenting Q235B and Q345B chemical composition and mechanical properties per ASTM standard, issued with unique heat number traceability
- ISO 9001:2015 quality management certificate covering full production process from raw material incoming to final dispatch
- SGS or BV third-party inspection report available upon request, verifying dimensional accuracy, surface coating thickness, and mechanical test results
- Material traceability report linking each bundle to its production heat number, rolling date, and test batch
- Complete customs documentation package including commercial invoice, packing list, bill of lading, and certificate of origin
- CE certification available for EN 10210/EN 10219 standard hollow sections shipped to European markets
Packaging, Loading & Delivery
- Q235B and Q345B square and rectangular tubes bundled with high-tensile steel strips, wrapped in waterproof cloth for ocean transit protection
- Galvanized hollow sections packed with edge protectors and separator pads to prevent zinc coating damage during handling and shipping
- 12-meter standard length tubes loaded with optimized stowage plans maximizing 20ft and 40ft container payload while respecting port weight restrictions
- Custom cut-to-length service available, with cut ends deburred and protected against corrosion during transport
- Each bundle tagged with heat number, steel grade, specification, and net weight for site identification and traceability
- FOB, CIF, and DDP shipping terms available with door-to-door logistics coordination to major ports across Southeast Asia, Middle East, Africa, and South America
Starting Your Hollow Section Procurement
Send your specification sheet — section dimensions, wall thickness, steel grade, quantity, and destination port — and receive a detailed quotation within twelve hours, complete with mill test certificate samples and loading plans. For non-standard sizes or custom cut lengths, our technical team reviews your drawings and confirms feasibility with production timelines.
Request Your ASTM Hollow Section Quotation
Submit your specifications via email at admin@sdxinjiyuan.com or contact us on WhatsApp at +86 188 5315 7756 to receive pricing, mill test certificates, and delivery schedules for your next project.
Frequently Asked Questions
Q: What is the difference between Q235B and Q345B for structural applications?
A: Q235B offers lower yield strength suitable for general construction frames and non-critical structural members, while Q345B provides higher yield strength for load-bearing columns, heavy-span beams, and industrial structures where weight reduction matters. Both grades weld readily and comply with ASTM equivalence standards.
Q: Can you provide mill test certificates for every shipment?
A: Yes, every bundle of ASTM carbon steel square rectangular hollow section ships with an original mill test certificate documenting chemical composition and mechanical properties, traceable to the specific heat number. We also accommodate SGS or BV third-party inspection requests.
Q: What surface treatment options are available for outdoor structural applications?
A: We offer hot rolled bare finish for indoor or painted applications, hot-dip galvanized coating for long-term corrosion protection in outdoor and marine environments, and oiled surfaces for temporary protection during transit and storage.
Q: Do you support custom cut-to-length and processing services?
A: Yes, our processing capabilities include cutting, bending, punching, welding, and decoiling. We produce custom lengths beyond the standard 12-meter option, with tight tolerance control and deburred cut ends ready for site installation.
Q: What is the minimum order quantity for trial purchases?
A: The standard MOQ is 5 tons, which accommodates trial orders for new buyers and small-batch project requirements. We also support split shipments and consolidated multi-product container loading for ongoing procurement programs.
