Description
Factory-Direct Carbon Steel Hollow Sections — ASTM standard Q235B and Q345B square hollow pipes rolled in-house with wall thickness reaching 200 mm, shipped without trading margins.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B/Q345B Carbon Steel Square Hollow Pipe |
| Product Type | Square / Rectangular Steel Tube (Hollow Section) |
| Steel Grade | Q195, Q235, Q235B, Q345, Q345B, SS400, SS330-SS540 |
| Standard | ASTM |
| Section Shape | Square / Rectangular / Round |
| Size Range | Wall thickness 0.5–200 mm |
| Length | 12 m |
| Technique | Hot Rolled / Cold Rolled |
| Surface Treatment | Hot Rolled / Galvanized / Consumer’s Requirement |
| Tolerance | ±1% |
| Ends | As per customer requirement |
| Application | Steel structures / Construction frames / Machinery / Fluid transport / Scaffolding |
| MOQ | 5 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| EPC Contractors | Industrial plant steel frames, pipe rack supports, conveyor gantries |
| Construction Companies | Building column frames, scaffolding uprights, mezzanine beams |
| Machinery Manufacturers | Equipment base frames, crane boom sections, hydraulic cylinder housings |
| Infrastructure Developers | Bridge handrail posts, sound barrier columns, solar mounting structures |
What Wall-Thickness Tolerance Costs on a Structural Frame Order
A ±1% tolerance on a 200 mm wall section is the difference between a mill test passing and a site re-cut.
When EPC contractors receive hot rolled carbon steel square hollow pipe with oversized negative tolerance, the theoretical weight no longer matches the declared weight — and the load-bearing calculation collapses at the engineer’s desk. I have seen containers held at destination ports because the inspector’s ultrasonic reading fell outside the tolerance band declared on the mill test certificate. The re-inspection fee alone can eat the margin on the entire order. Fragmented sourcing makes this worse: buying beams from one mill and hollow sections from another means mismatched chemistry, mismatched certificates, and a customs broker who does not know which document belongs to which container [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance requirements].
How Q345B Hollow Sections Match Structural Frame Loads
Hot rolled carbon steel square hollow pipe in Q345B delivers higher yield strength than Q235B, making it the default choice for primary load-bearing columns and long-span beams in industrial plants. The 0.5–200 mm wall range covers everything from light scaffolding uprights to heavy machinery base frames, and the ±1% tolerance keeps fabrication shops from rejecting material at the incoming inspection gate. Our in-house bending and cutting service means the 12 m length arrives on site pre-sized for the connection node, eliminating the secondary cutting cost that erodes project margins on large-tonnage orders.
Engineering Compliance and Certification Path
For projects designed to AISC or EN 1993, the steel grade equivalence between the Chinese Q-series and international standards must be documented on the mill test certificate — not assumed from the purchase order [NEED_CITE: steel grade equivalence between EN and ASTM standards]. Q235B maps broadly to S235 / ASTM A36, while Q345B aligns with S355 / ASTM A572 Gr 50 in most structural applications, but the exact chemical composition and mechanical property values must be verified per heat. Hot rolled surface finish is suitable for indoor structural frames, while galvanized treatment is specified for outdoor scaffolding and solar mounting where corrosion resistance extends service life. CE certification under EN 10210 or EN 10219 is mandatory for EU customs clearance, and third-party inspection by SGS or BV closes the audit trail for EPC main contractors.
Steel Grade Selection and Rolling Process Explained
The Q-series (Q195 through Q345B) follows the Chinese GB standard system where the number after “Q” indicates the minimum yield strength in MPa — Q345B therefore offers roughly 50% higher yield capacity than Q195, which directly reduces the section size needed for the same load. SS400 and SS330-SS540 are JIS G3101 general structural grades widely specified in Southeast Asian and Middle Eastern projects, and their chemistry overlaps sufficiently with Q235B to allow substitution in many non-critical applications. Hot rolling produces a mill scale surface that is acceptable for painted or concealed structural members, while cold rolling delivers tighter dimensional accuracy and a cleaner surface for exposed architectural frames. Galvanized coating adds corrosion protection for outdoor scaffolding and coastal infrastructure, but the coating thickness must be verified per root with a coating thickness gauge — a lesson I learned the hard way when a Southeast Asian photovoltaic支架 order was rejected at destination because the zinc layer fell below the specified 80 microns [NEED_CITE: hot-dip galvanized coating thickness testing per ASTM A123].
Hidden Costs of Wrong Grade or Missing Certification
Specifying Q235B on the purchase order when the structural drawing calls for Q345B means the entire batch fails the engineer’s load calculation — and replacement tonnage arrives weeks after the crane is already on site. Missing CE documentation on an EU-bound shipment triggers customs holds that incur port storage fees calculated per container per day, often exceeding the product value within a month. Negative tolerance beyond the declared ±1% range inflates the theoretical weight versus actual weight, which the buyer discovers only when the third-party inspector measures the wall thickness at the destination yard — at which point the only options are costly air-freight replacement or on-site structural re-engineering [NEED_CITE: structural steel acceptance criteria per EN 10204 inspection documents].
Why Project Procurement Teams Source Here
Shandong Xin Jiyuan Special Steel Tube Co., Ltd operates three dedicated production lines covering over 2800 specifications, meaning the Q345B square hollow section in a non-standard wall thickness does not require a separate supplier search. The in-house physical and chemical laboratory issues mill test certificates per heat number before the container is sealed, so the project engineer receives traceable chemistry and mechanical data — not a generic template. Forty-one invention patents include proprietary sharp-corner rectangular tube technology that fills a gap in global supply for architectural frames requiring tight corner radii. CE certification under EN 10210 and EN 10219, ISO 9001:2015 registration, and SGS/BV third-party inspection availability remove the certification gap that delays EU and North American customs clearance. Professional loading plans optimize container utilization for 12 m lengths, and door-to-door logistics coordination covers FOB, CIF, and DDP terms to 50+ countries.
Documentation & Compliance
- Mill test certificate documenting Q235B or Q345B chemical composition and yield strength per ASTM standard, issued per heat number
- CE certificate covering EN 10210 hot-finished or EN 10219 cold-formed hollow sections for EU market customs clearance
- ISO 9001:2015 quality management system certificate covering the full production and inspection process
- SGS or BV third-party inspection report verifying wall thickness, coating thickness, and dimensional tolerance at the loading port
- Material traceability sheet linking each bundle to its heat number, chemical analysis, and mechanical test results
- Customs document package including packing list, bill of lading, and certificate of origin for destination port clearance
Packaging, Loading & Delivery
- Hot rolled Q235B and Q345B square hollow pipes bundled with high-tensile steel strips and seaworthy wrapping to prevent shifting during ocean transit
- Galvanized hollow sections packed with edge protectors and plastic caps to preserve the zinc coating and prevent white rust formation
- 12 m standard lengths loaded in dedicated containers with wooden chocks and steel dividers to optimize 20ft and 40ft GP utilization
- Custom cutting to project-specified lengths performed before packing, with each bundle labeled by heat number, steel grade, and section size
- Shipping marks stenciled on both ends of each bundle showing steel grade (Q235B/Q345B), wall thickness, and purchase order reference
- FOB, CIF, and DDP terms available with real-time container tracking from Jinan inland port to destination
Getting Your Quote and Mill Test Certificate
Submit your section size, wall thickness, steel grade (Q235B or Q345B), total tonnage, and destination port to receive a detailed quotation including unit price, production lead time, and applicable certification scope within 12 hours. Non-standard dimensions and custom cutting or bending requirements are quoted separately with engineering drawings confirmed before production. The mill test certificate and third-party inspection report are provided as draft copies for your engineer’s review before the deposit is transferred.
Frequently Asked Questions
Q: What steel grades are available for the hot rolled square and rectangular hollow pipes?
A: The range covers Q195, Q235, Q235B, Q345, Q345B under Chinese GB standards, plus SS400 and SS330-SS540 under JIS G3101, all produced to ASTM standard requirements.
Q: Can you provide custom cutting and bending services to specific dimensions?
A: Yes, in-house cutting and bending services are available for the 12 m standard length, with engineering drawings confirmed before production begins.
Q: What certifications do the steel tubes carry for EU and international markets?
A: Products are certified under CE (EN 10210/EN 10219), ISO 9001:2015, Singapore FPC, and third-party verified by SGS and BV upon request.
Q: What is the minimum order quantity and typical delivery time?
A: The minimum order quantity is 5 tons, and typical production lead times apply once the deposit is received and drawings are confirmed.
Q: How is quality consistency ensured across large-volume orders?
A: The in-house physical and chemical laboratory conducts incoming, in-process, and final inspections per heat number, with a full inspection report provided before shipment.
Request Your Quotation and Mill Test Certificate Today
Send your section size, steel grade, quantity, and destination port to receive a detailed quotation with certification scope within 12 hours.
Shandong Xin Jiyuan Special Steel Tube Co., Ltd | Tel: +86 531 8573 6315 | Mobile/WhatsApp/WeChat: +86 188 5315 7756 | Email: admin@sdxjysteel.com
