Description
Factory-direct ERW square and rectangular steel tubes — raw material from our own steel mill, fabricated and tested under one quality system before shipment.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B/Q345B ERW Square and Rectangular Steel Tube |
| Product Type | Welded Square and Rectangular Steel Tube (ERW) |
| Steel Grade | Q195, Q235, Q235B, Q345, Q345B, SS400, SGCC, CGCC, TDC51DZM, TDC52DTS350GD, TS550GD, DX51D+Z |
| Standard | ASTM, API, JIS, ISO 9001, TISI |
| Section Shape | Square / Rectangular |
| Size Range | 20×20 mm – 200×200 mm |
| Wall Thickness | 0.5 – 40 mm |
| Length | 1 – 12 m |
| Technique | ERW (Electric Resistance Welded) |
| Surface Treatment | Cold Rolled / Galvanized Coating |
| Tolerance | ±1% |
| Ends | Plain (default) |
| Application | Construction Structure, Boiler, Fluid Transport, Drill, Hydraulic, Gas, Oil, Chemical Fertilizer, Structure Pipe |
| MOQ | 25 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Building | Steel frame structures for warehouses, industrial platforms, and commercial buildings |
| Infrastructure & EPC | Support structures for Belt & Road projects, bridge components, and utility frames |
| Fluid & Energy Transport | Gas and oil pipelines, hydraulic systems, and chemical fertilizer distribution lines |
| Industrial Manufacturing | Boiler frames, drill structures, and conveyor support assemblies |
What Wall-Thickness Tolerance Costs on a Structural Frame Order
A ±1% tolerance on a Q235B Q345B ERW square rectangular steel tube supplier order means the difference between passing site inspection and scrapping an entire container.
Overseas buyers routinely discover that fabricators sourcing steel from third-party mills cannot guarantee consistent wall thickness. When negative tolerance exceeds project limits, structural connections fail dimensional checks, welding joints misalign, and rework delays cascade across the construction schedule. The cost of air-freighting replacement tubes often exceeds the original order profit — a lesson learned the hard way on a Thai warehouse project where 0.3mm over-tolerance triggered full batch rejection at port.
Matching ERW Tubes to Structural and Fluid Applications
Q235B Q345B ERW square rectangular steel tube supplier products in the 20×20–200×200 mm range with 0.5–40 mm walls serve dual roles: structural frames requiring load-bearing capacity and fluid transport lines needing pressure integrity. The ERW welding process with certified WPS procedures ensures weld seam strength matches the base metal, while galvanized coating options protect against corrosion in outdoor infrastructure or chemical environments. Our vertically integrated supply chain — from raw steel production to finished tube fabrication — eliminates the material traceability gaps that plague multi-source procurement.
Engineering Compliance and Certification Requirements
Structural applications demand compliance with ASTM, API, and JIS standards, while TISI certification is mandatory for Thai market imports. The Q235B and Q345B grades meet international equivalence requirements for S235JR and S355JR respectively, enabling cross-standard project specification [NEED_CITE: steel grade equivalence between EN and ASTM standards]. Third-party inspection by SGS or BV verifies dimensional accuracy and coating thickness before shipment, while complete mill test documentation — including chemical composition, mechanical properties, and heat number traceability — satisfies customs and engineering approval requirements [NEED_CITE: EN 10219 cold-formed hollow section requirements].
Steel Grade Selection and ERW Process Fundamentals
Q195 through Q345B grades offer progressive yield strength increases for load-bearing applications, while SGCC and CGCC galvanized grades provide corrosion resistance for outdoor exposure. The ERW (Electric Resistance Welded) process creates a continuous weld seam through electrical resistance heating, producing tubes with consistent dimensional accuracy and cost efficiency compared to seamless alternatives. Surface treatment flexibility — cold rolled for indoor applications, galvanized coating for corrosion protection, or oiled for temporary rust prevention — allows project-specific selection. The ±1% tolerance on wall thickness and outer dimensions ensures precision fit-up for welded connections and bolted assemblies.
Hidden Costs of Incorrect Material Procurement
Specifying the wrong steel grade or accepting undocumented negative tolerance creates cascading failures: customs clearance delays due to missing certification, on-site rework when dimensional checks fail, and structural safety risks when material properties don’t match engineering calculations. A Q235B Q345B ERW square rectangular steel tube supplier order without proper mill test certificates risks rejection at destination port, while inconsistent coating thickness accelerates corrosion in aggressive environments. The true cost of cheap procurement includes project delays, replacement shipping, and reputational damage with end clients [NEED_CITE: material certification requirements for international steel procurement].
Why Procurement Teams Choose Our Vertically Integrated Supply
Our own steel mill produces 2,800+ specifications of raw material, feeding directly into the tube fabrication workshop — eliminating the quality gaps when fabricators source from third-party suppliers. Every Q235B Q345B ERW square rectangular steel tube supplier order includes full mill test documentation with heat number traceability, certified welding procedures per AWS/EN standards, and dimensional inspection reports. Third-party inspection by SGS or BV is available for every shipment, while professional export packing and oversized cargo loading ensure damage-free delivery. We serve general contractors and EPC firms across the EU, Middle East, Southeast Asia, and Africa with consistent quality and complete accountability from raw material to finished product.
Documentation & Compliance
- Mill test certificate documenting Q235B/Q345B chemical composition and mechanical properties per ASTM standards
- ISO 9001 quality management certificate covering the entire production process from steelmaking to tube fabrication
- SGS or BV third-party inspection report verifying dimensional accuracy, coating thickness, and weld quality
- Material traceability by heat number linking each tube to its original steel batch and production records
- Customs documentation package including packing list, bill of lading, and certificate of origin for destination clearance
- TISI certification available for Thai market projects requiring local compliance approval
Packaging, Loading & Delivery
- ERW square and rectangular tubes bundled with steel strips and edge protectors to preserve galvanized coating during ocean transit
- Custom length cutting from 1–12 m range to match project specifications and reduce on-site waste
- Container loading optimization for 20×20–200×200 mm sections to maximize weight utilization within shipping limits
- Heat number and steel grade marking on each tube for site identification and quality verification
- FOB, CIF, and DDP shipping terms available with professional oversized cargo handling and lashing
- Complete export documentation provided for customs clearance at destination port
Initiating Your Q235B Q345B ERW Square Rectangular Steel Tube Inquiry
Submit project drawings, steel grade requirements, quantity, and destination port to receive a detailed quotation including material, fabrication, coating, and shipping costs. Our engineering team reviews specifications within 24 hours and provides shop drawing confirmation before production begins. Third-party inspection and mill test certificate packages are confirmed at the inquiry stage to ensure compliance with your project standards.
Frequently Asked Questions
Q: What is the steel grade equivalence between Q235B, Q345B, and international standards?
A: Q235B corresponds to S235JR in EN standards and SS400 in JIS, while Q345B matches S355JR. We provide full mill test certificates documenting chemical composition and mechanical properties to support cross-standard project specifications.
Q: Can you provide third-party inspection for Q235B Q345B ERW square rectangular steel tube orders?
A: Yes, SGS and BV third-party inspection is available for every shipment. Inspection covers dimensional accuracy, coating thickness, weld quality, and surface treatment verification before loading.
Q: What is the MOQ for custom sizes outside the standard 20×20–200×200 mm range?
A: Standard MOQ is 25 tons. Custom non-standard sizes are available with extended production lead times. Submit specifications for a tailored quotation.
Q: How do you ensure wall thickness tolerance meets ±1% requirements?
A: Our vertically integrated production from raw steel to finished tubes allows direct process control. Every batch undergoes dimensional inspection with ultrasonic thickness testing, and results are documented in the mill test certificate package.
Q: What surface treatment options are available for corrosion protection?
A: We offer cold rolled finish for indoor applications, galvanized coating for outdoor corrosion resistance, and oiled surface for temporary rust prevention during storage and transit. Selection depends on project environment and service life requirements.
Get Your Q235B Q345B ERW Square Rectangular Steel Tube Quotation
Send project specifications, steel grade, quantity, and destination port to receive a detailed offer with mill test certificate confirmation within 24 hours.
Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Website: www.xjystructure.com
Tel: +86 531 8573 6315
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@xjystructure.com
Address: No.11889, Jingshi West Road, Lulian Group, Jinan City, Shandong Province, China
