Description
Factory-Direct Welded Tubes — Q235B carbon steel welded square rectangular hollow tube supplier producing EN standard sections from 20×20 mm to 100×150 mm with original mill certificates on every heat.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B Carbon Steel Welded Square & Rectangular Hollow Tube |
| Product Type | Square / Rectangular Steel Tube (Welded ERW / Hot Rolled) |
| Steel Grade | Q195, Q215, Q235, Q235B |
| Standard | EN |
| Section Shape | Square / Rectangular |
| Size Range | 20×20 mm – 100×150 mm |
| Length | 6–12 m |
| Technique | ERW / Hot Rolled |
| Surface Treatment | Non-oiled, Hot Rolled finish |
| Tolerance | ±1% / ±10% |
| Ends | Plain |
| Application | Structure Pipe, Construction Building Material, Building frames, Steel structures, Machinery, Scaffolding |
| Processing Service | Welding, Punching, Cutting, Bending, Decoiling |
| Invoicing | By Theoretical Weight |
| Package | Seaworthy Standard Package |
| MOQ | 1 Ton |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Building | Building frames, structural columns, roof trusses, scaffolding systems |
| Machinery Manufacturing | Equipment base frames, conveyor structures, machine guards |
| Infrastructure Projects | Bridge support structures, utility pole bases, industrial platform framing |
| Steel Fabrication | Welded assemblies, modular structures, load-bearing frameworks |
What Wall-Thickness Tolerance Costs on a Q235B Carbon Steel Welded Square Rectangular Hollow Tube Order
Tolerance drift beyond ±1% turns a theoretical-weight invoice into a structural liability.
I once watched a container of 20×50 mm welded tubes get rejected at the port because the buyer’s inspector found wall thickness negative tolerance exceeding 15%. The entire shipment had to be pulled, re-sorted, and reloaded — costing weeks of delay and thousands in rework. On a Q235B carbon steel welded square rectangular hollow tube order, even minor tolerance deviations compound across hundreds of tons: underweight sections fail load calculations, over-thick walls inflate material costs, and inconsistent dimensions wreck welding fit-up on site. [NEED_CITE: EN 10219 dimensional tolerance requirements for cold-formed welded hollow sections]
Matching EN Standard Sections to Structural Frame Loads
Q235B carbon steel welded square rectangular hollow tube in EN standard covers 20×20 mm to 100×150 mm — the exact range needed for light-to-medium structural frames in building construction and scaffolding. The hot rolled non-oiled surface accepts primer and paint systems without additional degreasing, while the ERW process delivers consistent wall thickness across the 6–12 m length range. For machinery base frames and conveyor structures, the square and rectangular profiles provide predictable moment of inertia in both axes, simplifying connection design.
Engineering Compliance and Certification Requirements
Structural hollow sections for building frames and scaffolding must comply with EN 1993 design codes, which reference EN 10219 for cold-formed welded sections and EN 10210 for hot-formed welded sections. Q235B steel grade meets the chemical composition and mechanical property requirements for S235JR equivalence under European standards, enabling CE certification and customs clearance across EU markets. [NEED_CITE: steel grade equivalence between Chinese Q series and European S series standards] Third-party inspection by SGS or BV before loading verifies dimensional accuracy and weld integrity, while original mill test certificates document heat-by-heat traceability for project auditors.
Steel Grade Selection and ERW Welding Process
Q195, Q215, Q235, and Q235B represent a carbon steel family with incrementally higher yield strength — Q195 suits light non-structural applications, while Q235B delivers the yield point required for load-bearing building frames and machinery structures. The ERW (Electric Resistance Welding) process joins the formed edges under heat and pressure without filler metal, producing a narrow weld zone that maintains uniform mechanical properties across the tube cross-section. Hot rolled finish means the tubes emerge from the final rolling pass at elevated temperature, resulting in a mill scale surface that provides baseline corrosion resistance during storage and transit. The ±1% tolerance on wall thickness ensures that theoretical weight invoicing aligns with actual delivered weight — critical when procurement budgets are locked to tonnage pricing.
Hidden Costs of Tolerance Deviation and Certification Gaps
Purchasing Q235B carbon steel welded square rectangular hollow tube without verified mill test certificates risks customs holds at destination ports — EU importers routinely face delays when CE documentation or EN 10219 compliance proof is missing. Negative tolerance beyond specification limits means the buyer pays for steel that isn’t there: a 3.0 mm nominal wall delivered at 2.5 mm reduces load capacity and may fail structural inspection. [NEED_CITE: consequences of dimensional non-compliance in structural steel procurement] Rejection, re-sorting, and replacement shipments erase any upfront price savings from unverified suppliers.
Why Bulk Buyers Source Q235B Welded Tubes from Xin Jiyuan
Factory-direct pricing eliminates trading company markups — Xin Jiyuan operates three production lines with monthly capacity exceeding 20,000 tons, enabling volume discounts for long-term partners. Every batch ships with original mill test certificates documenting chemical composition and mechanical properties per heat number; third-party SGS/BV inspection is available on request before container loading. The company maintains ready stock across 2,800+ specifications, supporting urgent orders and split shipments without waiting for production scheduling. Flexible MOQ from 1 ton trial orders to full-container bulk quantities accommodates both project procurement and trader inventory building. Professional export teams handle documentation, customs clearance, and container loading optimization — consolidating square tubes, rectangular tubes, and other steel products into single shipments to reduce freight costs.
Documentation & Compliance
- Mill test certificate documenting Q235B chemical composition (C, Mn, Si, P, S) and yield strength per EN standard, issued per heat number for full traceability
- CE certificate (EN 10210 / EN 10219) confirming compliance with European structural hollow section requirements for EU project acceptance
- ISO 9001:2015 quality management certificate covering production processes, inspection protocols, and documentation control
- SGS or BV third-party inspection report verifying dimensional accuracy, weld quality, and surface condition before loading
- Material traceability by heat number linking each tube bundle to its original billet and rolling records
- Customs documents including packing list, bill of lading, and certificate of origin for destination port clearance
Packaging, Loading & Delivery
- Q235B welded square and rectangular tubes bundled with steel straps and edge protectors to prevent surface damage during ocean transit
- Non-oiled hot rolled finish requires no special coating protection but benefits from covered storage or tarpaulin wrapping in humid climates
- 6–12 m lengths loaded into 20ft or 40ft containers with optimized nesting — rectangular sections 50×100 mm and 100×150 mm nest efficiently to maximize container payload
- Cutting service available to produce exact project lengths from standard 6–12 m stock, reducing on-site waste and handling
- Heat number and steel grade (Q235B) stenciled on each bundle for site identification and inspection traceability
- FOB, CIF, and DDP shipping terms available with professional logistics coordination from Shandong ports to destination
Getting Your Q235B Welded Tube Quote
Submit your specification sheet — section size, wall thickness, length, steel grade, quantity, and destination port — via email or WhatsApp to receive a competitive bulk quote within 12 hours. Xin Jiyuan’s engineering team will confirm dimensional feasibility, suggest EN standard alternatives if needed, and provide mill test certificate samples for your quality verification. For non-standard dimensions or custom processing (cutting, punching, bending), share your drawings for a tailored production plan.
Frequently Asked Questions
Q: How does Q235B compare to S235JR or ASTM A500 Grade B?
A: Q235B is the Chinese national standard carbon steel grade with yield strength and chemical composition closely matching S235JR under EN 10219 and ASTM A500 Grade B under American standards. Xin Jiyuan provides mill test certificates documenting the actual chemical analysis and mechanical test results for each heat, enabling your engineering team to verify equivalence for project specifications.
Q: Do your CE and EN 10210/10219 certificates work for EU project compliance?
A: Yes. Xin Jiyuan holds Lloyd’s CE certification covering EN 10210 (hot-formed welded structural hollow sections) and EN 10219 (cold-formed welded structural hollow sections). Every shipment includes the CE declaration of conformity and factory production control (FPC) certificate required for EU customs clearance and project acceptance.
Q: Can you produce non-standard dimensions and what is the minimum order quantity?
A: Xin Jiyuan maintains ready stock in 2,800+ standard specifications from 20×20 mm to 100×150 mm. For non-standard sizes outside the stock range, custom production is available with typical lead times of 15–25 days depending on specifications. The minimum order quantity is 1 ton, supporting both trial orders and full-container bulk procurement.
Q: How is invoicing by theoretical weight calculated and what tolerances apply?
A: Theoretical weight is calculated using the nominal outer dimensions and wall thickness specified in your order, multiplied by the steel density (7.85 g/cm³) and total length. Xin Jiyuan maintains wall thickness tolerance within ±1% of nominal, ensuring that actual delivered weight closely matches theoretical weight — protecting buyers from the hidden cost of negative tolerance deviations common in unverified supply chains.
Q: What is the production lead time and do you handle shipping with optimized container loading?
A: Standard specifications ship from ready stock within days of deposit receipt. Custom orders typically require 15–25 days for production. Xin Jiyuan’s export team handles FOB, CIF, and DDP shipping terms, with professional container loading plans that maximize payload for rectangular sections and coordinate documentation for smooth customs clearance at destination ports.
Request Your Q235B Welded Tube Quote Today
Send your specifications — section size, wall thickness, length, quantity, and destination — to receive factory-direct pricing and mill test certificate samples within 12 hours.
Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Website: www.sdxinjiyuan.com
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@sdxinjiyuan.com
