Description
Factory-Direct Square Hollow Sections — 2,800+ specifications in stock with in-house lab testing
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235/Q345 Carbon Steel Square/Rectangular Hollow Section |
| Product Type | Square / Rectangular Steel Tube (Hollow Section, SHS/RHS) |
| Steel Grade | Q195, Q235, Q235B, Q345, Q345B, Q460, SS330, SS400, SS540, DC51D+Z, DC52D+Z, DC53D+Z |
| 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 (Z coating: DC51D+Z, DC52D+Z, DC53D+Z) / Bare / Consumer’s Requirement |
| Tolerance | ±1% |
| Ends | As per customer requirement |
| Application | Fluid Pipe / Boiler Pipe / Drill Pipe / Hydraulic Pipe / Gas Pipe / Steel Structures / Construction Frames / Machinery |
| MOQ | 5 Tons |
| Origin | China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| EPC Contractors & Steel Structure Fabricators | Structural frames, industrial buildings, modular construction, warehouse columns |
| Machinery Manufacturers | Hydraulic systems, equipment frames, conveyor structures, crane booms |
| Construction Companies | High-rise building columns, bridge components, infrastructure supports, scaffolding |
What Wall-Thickness Tolerance Costs on a Structural Frame Order
Negative tolerance beyond ±1% means re-cut beams, rejected welds, and delayed handover.
When square hollow sections arrive at site with wall thickness running 8–12% below nominal, fabricators discover the problem only after cutting begins. Weld prep dimensions shift, connection plates no longer align, and structural engineers must recalculate load capacity mid-project. For EPC contractors working under EN 1993 or AISC compliance, material certificates that don’t match physical measurements trigger third-party inspection holds — sometimes freezing an entire container at port [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance requirements]. The cost isn’t just the steel; it’s crane idle time, re-welding labor, and schedule penalties.
Matching Structural Load Paths and Connection Geometry
Square and rectangular hollow sections in Q235/Q345 grades serve as primary load-bearing members where bidirectional bending resistance matters more than unidirectional I-beam performance. The Hot Rolled Carbon Steel Square Hollow Section Pipe Supplier delivers wall thickness from 0.5 mm to 200 mm, covering both light-gauge purlin applications and heavy-duty column sections for multi-story frames. Hot rolled technique produces thicker walls suitable for primary structures, while cold rolled achieves tighter tolerances for precision machinery frames. Galvanized coatings DC51D+Z through DC53D+Z extend service life in coastal or industrial atmospheres where corrosion allowance would otherwise require oversizing the section.
Engineering Code Compliance and Certification Pathways
Structural hollow sections must satisfy both material chemistry and dimensional standards before engineers sign off on load calculations. Q235/Q345 grades meet Chinese GB standards but require equivalence mapping for projects specifying ASTM A500 or EN 10219 [NEED_CITE: steel grade equivalence between EN and ASTM standards]. EU projects demand CE certification under EN 10210/EN 10219 for hot-formed or cold-formed hollow sections respectively — without this mark, customs clearance fails regardless of mill test quality. Singapore FPC certification opens Southeast Asian infrastructure tenders. The ±1% tolerance specification ensures sections fit within connection detailing assumptions; tighter tolerances reduce field adjustment but increase production cost.
Steel Grade Selection and Manufacturing Process Trade-offs
Q235 and Q345 represent the workhorse grades for general structural applications, with Q345 offering higher yield strength for weight-optimized designs. The SS series (SS330, SS400, SS540) follows Japanese industrial standards common in Southeast Asian projects. DC51D+Z, DC52D+Z, and DC53D+Z denote galvanized coating grades where the Z suffix indicates zinc coating weight — selection depends on corrosion environment severity rather than structural load. Hot rolled hollow sections suit heavy wall thickness applications above 6 mm where internal corner radii are less critical, while cold rolled sections achieve sharper corners and thinner walls for architectural exposure. The proprietary sharp-corner rectangular tube technology fills a gap where standard EN 10219 products cannot achieve the 90-degree internal corners required for flush-mounted connection plates.
Hidden Costs When Material Certificates Don’t Match Physical Reality
Ordering Q345 hollow sections that arrive with Q235 chemistry means the entire batch fails structural verification — not just the tested samples. Engineers cannot approve as-built conditions when mill test certificates show one grade but portable XRF analysis reveals another. Projects in EU markets face customs rejection without proper CE marking, regardless of whether the steel itself meets mechanical requirements. Negative tolerance stacking across wall thickness, width, and length dimensions compounds into weight shortages that trigger contractual disputes. The Hot Rolled Carbon Steel Square Hollow Section Pipe Supplier provides in-house physical and chemical laboratory testing with original mill test certificates per heat number, eliminating grade substitution risk before shipment [NEED_CITE: material traceability requirements for structural steel certification].
Why Procurement Teams Choose Our Mill Direct
Factory-direct pricing eliminates trading company margins on every ton shipped. Our in-house physical and chemical laboratory tests every heat before release, with mill test certificates documenting actual chemistry and mechanical properties — not catalogue specifications. The 2,800+ specification range covers non-standard dimensions that force buyers to source from multiple suppliers elsewhere. Proprietary sharp-corner rectangular tube technology holds 41 invention patents and fills gaps in global supply where standard mills cannot achieve true 90-degree internal corners. Lloyd’s Register EU CE certification under EN 10210/EN 10219 plus Singapore FPC clears customs in regulated markets without third-party re-inspection delays. Professional loading plans optimize container utilization for 12-meter lengths, reducing freight cost per ton compared to LCL shipments. Door-to-door logistics coordination handles export documentation, customs clearance, and final delivery in 50+ countries.
Documentation & Compliance
- Mill test certificate documenting Q235/Q345 chemical composition and mechanical properties per heat number
- CE certificate under EN 10210 for hot-formed hollow sections or EN 10219 for cold-formed sections
- ISO 9001:2015 quality management system certificate covering production and inspection processes
- SGS or BV third-party inspection report available upon request for projects requiring independent verification
- Material traceability report linking each bundle to heat number, chemical analysis, and mechanical test results
- Customs documentation package including packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- Hot rolled Q235/Q345 square hollow sections bundled with steel strips and edge protectors to prevent coating damage during ocean transit
- Galvanized DC51D+Z/DC52D+Z/DC53D+Z tubes wrapped in waterproof paper with plastic caps on ends to preserve zinc coating integrity
- 12-meter standard lengths loaded in dedicated 20ft or 40ft containers with professional stowage plans maximizing weight utilization
- Custom cut-to-length service available for non-standard dimensions, with cutting marks and heat numbers preserved on each piece
- Bundle identification tags showing steel grade, wall thickness, heat number, and purchase order reference for site traceability
- FOB, CIF, and DDP shipping terms available with real-time tracking from Jinan port to destination in 50+ countries
Getting Your Quote and Material Certification Started
Submit your specification sheet including section dimensions, wall thickness, steel grade, quantity, and destination port to receive pricing within 12 hours. Request mill test certificates and third-party inspection options upfront to confirm compliance with your project’s engineering codes. Non-standard dimensions and custom lengths are quoted separately with typical production lead times confirmed before order placement.
Start Your Steel Procurement Today
Send your requirements via email to admin@sdxjysteel.com or contact us at +86 188 5315 7756 (WhatsApp/WeChat) to receive detailed quotations with material certifications.
Frequently Asked Questions
Q: How do Q235 and Q345 grades compare to ASTM A500 or EN 10219 specifications?
A: Q235 and Q345 are Chinese standard grades with equivalent mechanical properties to international specifications, though exact chemical composition ranges differ. We provide grade equivalence documentation and can supply material meeting ASTM A500 Grade B/C or EN 10219 S235/S355 requirements upon request, with corresponding mill test certificates.
Q: Can you provide third-party inspection and what documentation supports customs clearance?
A: Yes, SGS and BV third-party inspections are available for any order. We supply CE certificates under EN 10210/EN 10219 for EU markets, Singapore FPC for Southeast Asian projects, plus standard customs documents including packing list, bill of lading, and certificate of origin.
Q: What is the minimum order quantity for custom non-standard dimensions?
A: The standard MOQ is 5 tons. Custom non-standard sizes beyond our 2,800+ specification range are available with quantity requirements depending on section dimensions and wall thickness — we confirm exact MOQ during quotation based on your specific requirements.
Q: How does invoicing by theoretical weight work with ±1% tolerance?
A: Invoicing uses calculated theoretical weight based on nominal dimensions and standard steel density. The ±1% tolerance applies to actual production dimensions. For projects requiring actual weight invoicing or tighter tolerance control, we discuss options during quotation to match your project’s measurement and payment terms.
Q: When should I specify galvanized DC51D+Z/DC52D+Z/DC53D+Z versus hot rolled bare finish?
A: Galvanized coatings suit outdoor exposure, coastal environments, or industrial atmospheres where corrosion protection extends service life without maintenance. DC51D+Z provides standard corrosion resistance, while DC53D+Z offers enhanced forming capability for post-delivery fabrication. Hot rolled bare finish works for interior applications or projects where field painting or additional coating will be applied after installation.
