Description
Let me work through this step by step.
Step 1: Gate Check
The identifier is “Gr.B / Q235B / Q345B Welded Rectangular Hollow Section” — not empty/null. Gate passes.
Step 2: Bold positioning statement
Identifier: “Gr.B / Q235B / Q345B Welded Rectangular Hollow Section”
Sum of digits: No digits in identifier… Let me re-read. “identifier: Gr.B / Q235B / Q345B Welded Rectangular Hollow Section”
Digits: 2, 3, 5, 3, 4, 5 → 2+3+5+3+4+5 = 22 → 22 mod 3 = 1 → Direction 1: 全规格一站采购方向
Step 3: Main keyword
“ASTM A500 Gr.B rectangular hollow section supplier” — must appear 3-6 times exactly as-is.
Step 4: Title language
Title is in English → entire output in English.
Step 5: Author persona
Started on rolling floor in Foshan, learned RHS tube forming/welding, moved to export sales. Pitfall: Malaysian warehouse contractor, 300×100 RHS, wall thickness negative tolerance 8% lighter than theoretical, SGS flagged, 20GP re-sorted, client lost 3 weeks.
Step 6: Check specs available
- Steel grades: Gr.B, S355JRH, Q235B, Q345B, S235, S275, S355, STK400
- Size: 15mm×20mm – 700mm×800mm
- Wall thickness: 1–30mm
- Length: 5.8m/6m/11.8m/12m/Random
- Technique: ERW Welded
- Surface: Black Painting/Galvanized/Varnish/Bare/Oiled
- Standard: ASTM A500/ASTM A53/GB/T3091/DIN
- Tolerance: ±12.5%
- Ends: Plain
Step 7: Draft all 16 sections, ensuring no forbidden words, no Chinese characters, no template repetition.
Now let me write the full output:
—
Full-Range RHS Procurement from One Factory — Over 2,800 welded rectangular hollow section specifications in stock from 15×20mm to 700×800mm, eliminating the need to coordinate multiple suppliers for structural steel projects.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Gr.B / Q235B / Q345B Welded Rectangular Hollow Section |
| Product Type | Welded Rectangular Steel Tube (RHS Hollow Section) |
| Steel Grade | Gr.B, S355JRH, Q235B, Q345B, S235, S275, S355, STK400 |
| Standard | ASTM A500, ASTM A53, GB/T3091, DIN |
| Section Shape | Rectangular |
| Size Range | 15mm × 20mm – 700mm × 800mm |
| Wall Thickness | 1 – 30 mm |
| Length | 5.8m / 6m / 11.8m / 12m / Random Length |
| Technique | ERW Welded |
| Surface Treatment | Black Painting / Galvanized / Varnish / Bare / Oiled |
| Tolerance | ±12.5% |
| Ends | Plain |
| Application | Construction, Building, Curtain Wall, Support Tubes, Steel Structures, Scaffolding |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| EPC Contractors | Industrial warehouse frames, plant support structures, pipe rack columns |
| Construction Companies | High-rise building columns, curtain wall mullions, floor beam systems |
| Infrastructure Developers | Bridge handrail posts, scaffolding uprights, sound barrier frames |
| Machinery Manufacturers | Conveyor system frames, equipment base platforms, lifting arm supports |
What Wall-Thickness Tolerance Costs on a Structural Frame Order
A 300×100 RHS that weighs 8% less than theoretical can shut down an entire job site for weeks.
I learned this the hard way on the rolling floor years ago. A Southeast Asian warehouse contractor received a shipment of rectangular hollow sections where the wall thickness had drifted deep into negative tolerance. The theoretical weight on paper looked right, but actual piece weight told a different story. The third-party inspector flagged every single tube. The whole container had to be pulled apart, re-sorted, and reloaded — three weeks of idle crane time and rescheduled crews. [NEED_CITE: EN 10219 dimensional tolerance requirements for cold-formed hollow sections] When you source from an ASTM A500 Gr.B rectangular hollow section supplier without in-house lab verification, that tolerance gap becomes your risk, not theirs.
How ERW Welded RHS Matches Structural Frame Requirements
Welded rectangular hollow sections in the 15×20mm to 700×800mm range serve as load-bearing columns, beam members, and bracing elements across commercial and industrial projects. The flat faces of RHS provide direct bearing surfaces for bolted and welded connections — unlike round pipes, no saddle plates are needed at intersection joints. For an ASTM A500 Gr.B rectangular hollow section supplier covering wall thicknesses from 1mm to 30mm, the engineering range spans from light-gauge curtain wall mullions to heavy structural columns in multi-story frames. ERW welding produces a continuous longitudinal seam that, when inspected through in-house physical and chemical testing, delivers weld integrity consistent with the parent metal.
Engineering Compliance and Surface Protection Choices
Structural steel used in load-bearing frames must conform to recognized standards — ASTM A500 for North American projects, EN 10219 for European construction, and GB/T3091 for domestic Chinese specification jobs. [NEED_CITE: steel grade equivalence between ASTM A500 and EN 10219 standards] Galvanized surface treatment extends service life in coastal or high-humidity environments where black painted or oiled finishes would degrade within months. For indoor warehouse structures with controlled atmospheres, bare or oiled RHS offers cost efficiency without sacrificing structural performance. Plain ends allow on-site cutting and welding without additional edge preparation, reducing secondary fabrication time at the erection stage.
Steel Grade Selection and ERW Welding Fundamentals
The Gr.B grade under ASTM A500 sits at the entry level of structural carbon steel, offering adequate strength for non-critical frames and light support structures. Moving to Q345B or S355JRH increases yield capacity significantly — essential for multi-story building columns and heavy industrial crane runways where load calculations demand higher design stress. The Q-series (Chinese GB standard) and S-series (European EN standard) map to similar mechanical property tiers, allowing grade substitution when project documentation permits. [NEED_CITE: structural steel grade comparison between ASTM, EN, and GB standards]
ERW welding forms the tube by rolling a steel strip into rectangular profile and welding the longitudinal seam through high-frequency electric resistance. This process suits production of RHS in the 15×20mm to 700×800mm range with wall thicknesses from 1mm to 30mm, balancing production speed with dimensional consistency. The ±12.5% wall thickness tolerance aligns with international cold-formed hollow section standards, though projects requiring tighter control should request mill test certificates confirming actual measurements per heat number.
The Hidden Cost of Sourcing Without Verified Mill Certificates
Ordering welded RHS without confirmed material certification creates a cascade of downstream failures. Steel grade misidentification means the structural engineer’s load calculations no longer apply — a Q235B tube substituted for Q345B reduces design capacity without visible warning. Missing CE documentation under EN 10210/EN 10219 triggers customs holds at EU ports, turning a routine delivery into a weeks-long storage liability. [NEED_CITE: CE marking requirements for structural steel hollow sections in European construction] Negative tolerance beyond acceptable limits reduces actual load-bearing capacity while the invoice still charges for theoretical weight. An ASTM A500 Gr.B rectangular hollow section supplier providing original mill test certificates per heat number eliminates these risks before the container leaves the factory floor.
Why Project Procurement Teams Source Welded RHS Directly from Our Mill
Every welded rectangular hollow section we produce passes through an in-house physical and chemical laboratory — incoming raw material inspection, in-process weld seam testing, and final dimensional verification before shipment. Our three dedicated production lines cover over 2,800 specifications across the 15×20mm to 700×800mm range, meaning a single purchase order can combine small-gauge curtain wall tubes and heavy structural columns without splitting across multiple vendors. We hold 41 invention patents including proprietary sharp-corner rectangular tube technology, and our products carry CE certification under EN 10210/EN 10219 for European market compliance alongside ISO 9001:2015 quality management. Third-party inspection through SGS and BV is available on request, and our professional loading team optimizes container stowage for mixed-size shipments to 50+ countries — reducing per-unit freight cost on every 20GP and 40HQ dispatched.
Documentation & Compliance
- Mill Test Certificate documenting Gr.B chemical composition and mechanical properties per ASTM A500, issued per heat number
- CE Certificate under EN 10210/EN 10219 confirming compliance for structural hollow sections in European construction markets
- ISO 9001:2015 Quality Management System certificate covering the full welded RHS production process
- SGS or BV Third-Party Inspection Report verifying dimensional accuracy, wall thickness, and surface quality before shipment
- Material Traceability Report linking each bundle to its heat number, steel grade (Q235B/Q345B/S355JRH), and production batch
- Customs Documentation Package including packing list, Bill of Lading, and Certificate of Origin for import clearance
Packaging, Loading & Delivery
- Welded RHS bundled with steel strips and edge protectors, sized to match the 15×20mm–700×800mm range to prevent surface damage during transit
- Galvanized rectangular tubes wrapped with waterproof film to preserve zinc coating integrity during ocean freight
- Container loading optimized by our professional team for mixed-dimension orders — combining 6m structural columns with shorter 5.8m bracing tubes to maximize 40HQ payload
- Cut-to-length service available for 11.8m and 12m random lengths, reducing on-site waste for construction projects requiring specific span measurements
- Each bundle marked with heat number, steel grade (Gr.B/Q345B/S355JRH), and dimensional identification for traceability at the erection stage
- FOB, CIF, and DDP shipping terms available with real-time tracking for deliveries to EU, North America, Southeast Asia, Middle East, and African ports
Getting Your Welded RHS Quote Started
Submit your specification list — section dimensions, wall thickness, steel grade, total tonnage, and destination port — and our team responds within 12 hours with unit pricing, production lead time, and applicable certification details. For non-standard dimensions outside the 15×20mm to 700×800mm catalog range, share your drawing and we confirm feasibility and tooling requirements. Request original mill test certificates and third-party inspection arrangements at the inquiry stage to lock compliance into your procurement timeline before production begins.
Frequently Asked Questions
Q: Can ASTM A500 Gr.B be substituted with Q345B or S355JRH for the same project?
A: These grades belong to different standard systems — ASTM A500 (American), GB (Chinese), and EN (European) — but share similar structural carbon steel characteristics. Grade substitution depends on your structural engineer’s approval and project specification requirements. We supply all three grades from the same production facility and can provide mill test certificates for whichever grade your documentation requires.
Q: What is the wall thickness tolerance for welded rectangular hollow sections?
A: Our welded RHS follows ±12.5% wall thickness tolerance per international cold-formed hollow section standards. Every shipment includes a mill test certificate documenting actual measured wall thickness per heat number. For projects requiring tighter tolerance control, discuss your specific requirements at the inquiry stage so we can confirm production capability.
Q: Do you provide CE certification for European construction projects?
A: Yes. Our welded rectangular hollow sections carry CE certification under EN 10210 and EN 10219, covering the full range of sizes and steel grades we produce. The CE certificate, along with Declaration of Performance and mill test certificates, is included in the shipping documentation package for EU customs clearance and project compliance.
Q: What surface treatment options are available for different environments?
A: We offer black painting, hot-dip galvanized, varnish, bare, and oiled finishes. Galvanized treatment suits coastal, high-humidity, or outdoor infrastructure applications where corrosion resistance is critical. Black painted or oiled finishes work for indoor structural frames and warehouse construction where the steel will be enclosed or further coated after erection.
Q: Can you produce non-standard rectangular hollow section dimensions?
A: Yes. Beyond our standard catalog of over 2,800 specifications covering 15×20mm to 700×800mm, we accept custom non-standard dimension orders. Share your required section size, wall thickness, and quantity — we confirm feasibility, production timeline, and any tooling requirements before you commit to the order.
Request Your ASTM A500 Gr.B Rectangular Hollow Section Quote Today
Send your specification sheet — dimensions, steel grade, quantity, and destination — to receive pricing, mill test certificate samples, and production scheduling within 12 hours.
Company: Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Website: www.sdxjysteel.com
Tel: +86 531 8573 6315
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@sdxjysteel.com
Address: No.11889, Jingshi West Road, Lulian Group, Jinan City, Shandong Province, China
