Description
Factory-Direct Sharp-Corner RHS/SHS — 41 patented sharp-corner forming technologies with wall thickness up to 40 mm, shipped to 50+ countries.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B / Q345B Sharp Corner Square & Rectangular Steel Tube |
| Product Type | Square and Rectangular Steel Tube (Sharp Corner / Right-Angle) |
| Steel Grade | Q235B, Q345B |
| Standard | GB/T 6728; EN 10219; EN 10210; ASTM A500 |
| Section Shape | Square / Rectangular (Sharp Corner, Right-Angle) |
| Size Range | 150–625 mm (side length) |
| Wall Thickness | Up to 40 mm |
| Length | 5.8 m / 6 m / 12 m (standard); 5–15 m (custom) |
| Technique | ERW (Electric Resistance Welded) |
| Surface Treatment | Hot Rolled / HDG (Hot-Dip Galvanized) |
| Tolerance | ±1% |
| Ends | Plain |
| Processing Service | Bending, Cutting, Decoiling, Punching, Welding |
| Application | Steel structures / Construction building frames / Machinery fabrication / Scaffolding / Industrial project procurement |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| EPC Contractors & Steel Structure Fabricators | Modular industrial frames, equipment support structures, plant roof trusses |
| Construction Companies | High-rise building columns, bridge cross-beams, infrastructure scaffolding |
| Machinery Manufacturers | Conveyor system frames, automation equipment bases, crane boom sections |
| System Integrators | Warehouse racking uprights, solar panel mounting structures, pipeline support brackets |
When a 12% Negative Tolerance Lands Your Container in Customs Limbo
Sharp-corner Q235B Q345B square rectangular steel tube supplier tolerance control decides whether your cargo clears the port or sits for re-inspection.
I watched a full container of right-angle rectangular tubes get rejected at Dubai port because the site supervisor pulled out a caliper and found wall thickness negative tolerance running at 12%. The entire shipment was stuck — too expensive to return, too risky to use. That kind of failure doesn’t come from bad intent; it comes from suppliers who don’t run in-house physical and chemical labs and can’t verify what they’re shipping. [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance requirements] When you’re sourcing a Q235B Q345B sharp corner square rectangular steel tube supplier for structural frames, ±1% tolerance backed by original mill test certificates isn’t a luxury — it’s the baseline that separates a deliverable project from a customs nightmare.
How Sharp-Corner Geometry Matches Precision Structural Connections
Standard rounded-corner hollow sections leave gaps at moment connections that require additional gusset plates or welding filler. The proprietary sharp-corner forming process on these Q235B and Q345B tubes eliminates that R-angle gap, allowing direct bolted or welded contact between members. On modular steel frame projects across Southeast Asia and the Middle East, this means faster assembly and cleaner load transfer at joints. As a Q235B Q345B sharp corner square rectangular steel tube supplier running 2,800+ specifications from a single factory, we produce non-standard side lengths and wall thicknesses that match your connection details — not the other way around.
Structural Compliance and Surface Protection for Field Conditions
Load-bearing frames for high-rise construction and industrial plants must conform to EN 1993 or AISC design codes, which reference material standards like EN 10219 for cold-formed welded hollow sections. [NEED_CITE: steel grade equivalence between GB Q-series and EN S-series standards] Q235B maps broadly to S235JR, while Q345B aligns with S355JR — but the equivalence must be documented on the mill test certificate for EU customs and engineer approval. For outdoor or corrosive industrial environments, hot-dip galvanized (HDG) finish provides zinc coating protection that hot-rolled black surface cannot. Standard lengths of 5.8 m, 6 m, and 12 m ship efficiently in containers; custom 5–15 m cuts reduce on-site welding joints. CE certification under EN 10210 and EN 10219 is mandatory for European import, and every batch leaves the factory with full chemical and mechanical test data.
Steel Grade Selection and ERW Welding Fundamentals
Q235B and Q345B belong to China’s GB/T 700 and GB/T 1591 grade systems respectively. Q235B offers adequate yield strength for general structural frames, scaffolding, and non-critical load paths. Q345B delivers higher yield strength for heavy-duty columns, bridge components, and machinery bases where deflection limits are tighter. The ERW (Electric Resistance Welded) process forms the tube from coil through continuous rolling and fuses the seam using electrical resistance heat — producing a clean weld line suitable for structural applications up to 40 mm wall thickness. [NEED_CITE: ERW versus seamless steel tube manufacturing process comparison] For surface treatment, hot-rolled black finish suits indoor or painted applications, while HDG galvanizing extends service life in coastal, chemical, or high-humidity environments without additional coating maintenance. The ±1% dimensional tolerance ensures that theoretical weight calculations match actual delivered weight — critical for both structural engineering calculations and freight cost accuracy.
The Real Cost of Buying the Wrong Grade or Missing Paperwork
Specifying Q235B when the structural engineer calculated for Q345B means the frame deflects beyond allowable limits — and the fix is cutting out and replacing members, not adding paint. Missing CE certificates under EN 10210 or EN 10219 means the container cannot clear EU customs, regardless of whether the steel itself is perfectly sound. [NEED_CITE: customs clearance documentation requirements for structural steel imports to EU] Unverified negative tolerance compounds the problem: the tube passes visual inspection but fails load testing on site. Every one of these failures traces back to a procurement decision made on price alone, without requiring original mill test certificates or third-party SGS/BV inspection before shipment.
Why Procurement Teams Consolidate Sharp-Corner Tube Orders Here
Factory-direct pricing eliminates trading company markups — we operate three dedicated production lines and ship from our own warehouse in Jinan. Every heat of steel passes through our in-house physical and chemical laboratory before forming; the mill test certificate you receive matches the actual batch chemistry and mechanical results, not a template. Our 41 patented technologies include the proprietary sharp-corner rectangular tube process that fills specification gaps unavailable from standard catalog suppliers. With 2,800+ specifications covering side lengths from 150 mm to 625 mm and wall thickness up to 40 mm, plus custom non-standard sizes, you source pipes, plates, beams, and fabrication from one factory instead of coordinating five vendors. CE certification under EN 10210 and EN 10219, ISO 9001:2015, Singapore FPC, and SGS/BV third-party verification are standard documentation — not upgrade packages. Professional loading plans optimize container weight distribution for heavy-wall tubes, and we handle FOB, CIF, and DDP logistics to 50+ countries.
Documentation & Compliance
- Mill test certificate documenting Q235B and Q345B chemical composition (C, Mn, Si, P, S) and mechanical properties per GB/T 700 and GB/T 1591, with heat number traceability
- CE certificate under EN 10210 (hot-finished) and EN 10219 (cold-formed) for structural hollow section compliance in EU markets
- ISO 9001:2015 quality management system certificate covering full production from coil incoming inspection to final dimensional check
- SGS or BV third-party inspection report available upon request, covering visual, dimensional, and mechanical testing before shipment
- Material traceability by heat number linking each tube bundle to its original steelmaking chemistry and rolling record
- Customs document package including commercial invoice, packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- Q235B and Q345B sharp-corner tubes bundled with galvanized steel strips at both ends and mid-span, with edge protectors preserving sharp-corner geometry during transit
- HDG galvanized tubes wrapped with waterproof cloth and separated by rubber spacers to prevent zinc coating abrasion between nested members
- Container loading plans optimized for 5.8 m, 6 m, and 12 m standard lengths to maximize payload within 20 GP and 40 HC weight limits for heavy-wall sections up to 40 mm
- Custom cut-to-length service available for 5–15 m requirements, with cut ends deburred and marked with heat number, steel grade, and section dimensions
- Each bundle labeled with weather-resistant tags showing steel grade (Q235B or Q345B), section size, wall thickness, length, heat number, and gross/net weight
- FOB Jinan/Qingdao, CIF, and DDP delivery options with real-time container tracking to ports across EU, North America, Middle East, Southeast Asia, and South America
Start Your Sharp-Corner Tube Procurement With Verified Data
Send your section dimensions, wall thickness, steel grade, quantity, and destination port — we return a detailed quotation with unit price, production lead time, applicable certifications, and a sample mill test certificate within 12 hours. For non-standard sizes outside the 2,800+ catalog range, we provide custom forming feasibility confirmation and tooling lead time before you commit.
Request Your Quotation and Mill Test Certificate Today
Submit your Q235B or Q345B sharp-corner square and rectangular tube specifications via email at admin@sdxjysteel.com or contact us on WhatsApp at +86 188 5315 7756 to receive pricing, original mill test certificates, and CE EN 10210/EN 10219 compliance documentation.
Frequently Asked Questions
Q: How do Q235B and Q345B compare to European and American steel grade standards?
A: Q235B corresponds broadly to S235JR (EN 10025) and ASTM A36 in yield strength range, while Q345B aligns with S355JR and ASTM A572 Grade 50. Full chemical composition and mechanical property cross-reference tables are included with every mill test certificate we issue, and our CE documentation under EN 10219 confirms equivalence for EU structural design code compliance.
Q: Can you produce sharp-corner rectangular tubes in non-standard sizes outside your catalog range?
A: Yes. Our 41 patented forming technologies cover 2,800+ standard specifications, and we produce custom non-standard side lengths and wall thicknesses up to 40 mm based on your engineering drawings. Custom orders require a feasibility review and tooling confirmation before production begins.
Q: What certifications are included for EU customs clearance?
A: Every shipment to EU markets includes CE certification under EN 10210 and EN 10219, ISO 9001:2015 quality certificate, original mill test certificates with full chemical and mechanical data, and a complete customs document package (packing list, bill of lading, certificate of origin). Third-party SGS or BV inspection reports are available upon request.
Q: How is the sharp-corner geometry maintained during shipping and handling?
A: Sharp-corner tubes are bundled with galvanized steel strips and edge protectors that contact the flat surfaces rather than the corner radii. HDG galvanized orders receive additional waterproof wrapping and rubber spacers between layers. Our loading plans distribute weight to prevent bundle shifting during ocean transit, preserving both corner geometry and zinc coating integrity.
Q: What is the difference between hot-rolled black finish and HDG galvanized for these tubes?
A: Hot-rolled black finish suits indoor structural applications or projects where the tubes will receive paint or powder coating on site. Hot-dip galvanized (HDG) finish provides a zinc coating that protects against corrosion in outdoor, coastal, or high-humidity industrial environments without additional surface treatment, extending service life significantly in aggressive conditions.
