Description
Factory-Direct Welded SHS Without Middlemen — Q235B and S-series grades roll off our own ERW lines at 757 USD/ton baseline, shipped with original mill certificates.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Carbon Steel Q235B Welded Square Steel Tube |
| Product Type | Welded Square Steel Tube (Square Hollow Section / SHS) |
| Steel Grade | Q235B, Gr.B, S235, S275, S355, STK400 |
| Standard | ASTM A500, ASTM A53, GB/T 3091 |
| Section Shape | Square |
| Size Range | 19mm×19mm – 800mm×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 |
| Tolerance | ±1% |
| Ends | Plain |
| Application | Construction structures / Building frames / Curtain wall systems / Support tubes / Structural pipe / Machinery frames |
| MOQ | 5 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| EPC Contractors & Construction | Steel structure frames, curtain wall supports, building scaffolding, column bracing |
| Machinery Manufacturers | Equipment frames, conveyor system structures, industrial support bases |
| Infrastructure Developers | Bridge support columns, industrial platform structures, foundation piles |
| System Integrators | Automation gantry frames, material handling racks, modular support assemblies |
What Wall-Thickness Tolerance Actually Costs on a Square Tube Order
A ±1% tolerance on a 30mm wall is the difference between a clean weld prep and a rejected batch at the port.
I still remember a Middle East shipment where negative tolerance on wall thickness slipped past our outgoing check. Third-party re-inspection at destination flagged the entire lot — customs held it, the contractor missed a crane window, and we absorbed the re-rolling cost. Since then, every High Quality Carbon Steel Q235B Welded Square Steel Tube leaving Jinan is measured against the drawing before the container doors close [NEED_CITE: EN 10219 cold-formed and welded hollow section dimensional tolerance requirements].
When specs are fragmented across three suppliers, one of them will cut tolerance to win price. The buyer pays later — in re-welding, in structural re-calculation, or in a failed audit.
Matching Section Sizes to Structural Load Paths
Square hollow sections from 19×19mm up to 800×800mm cover everything from light-gauge curtain wall mullions to heavy column bases. The 1–30mm wall range lets engineers tune weight versus moment of inertia without switching suppliers mid-project. For a High Quality Carbon Steel Q235B Welded Square Steel Tube destined for a warehouse frame, Q235B or S235 handles typical gravity loads; once the span grows or seismic category rises, S355 or STK400 keeps the section compact. Our ERW lines hold the ±1% tolerance across that full range, so the welder on site sees a consistent prep edge from the first tube to the last.
Compliance Pathways for EU, North America, and Belt & Road Sites
European projects demand CE marking under EN 10210 or EN 10219 — without it, the tube cannot be structurally certified, regardless of how good the steel looks [NEED_CITE: CE marking requirements for structural hollow sections under EN 10210 and EN 10219]. North American tenders typically call for ASTM A500 Grade B or C, while Gulf and Southeast Asian infrastructure often accepts GB/T 3091 with mill test backup. A single order mixing grades and standards is routine for our EPC clients; we mark each bundle with heat number, grade, and standard so the site inspector can trace it back to the ladle analysis without guessing.
Reading the Steel Grade Line: Q235B vs S235 vs Gr.B
Q235B is the Chinese workhorse — widely available, weldable, and cost-effective for non-critical frames. Its European near-equivalent S235 follows EN 10025 chemistry, while ASTM Gr.B sits in the A500 family with slightly different elongation rules. Moving up to S275 or S355 raises yield strength for longer spans or heavier point loads, letting designers shrink the section and save on handling weight. STK400, a JIS structural tube grade, appears frequently in Southeast Asian and Japanese-spec projects. The ERW process fuses the strip edges under pressure, producing a weld seam that, when paired with in-house physical and chemical lab checks, matches the parent metal in both tensile and bend tests. Surface options — black painted, hot-dip galvanized, varnished, or bare — are chosen against the corrosion exposure: galvanized for outdoor bracing, bare for indoor frames that will be fire-proofed later.
The Hidden Price of Wrong Grade or Missing Certificate
Ordering S235 when the drawing calls for S355 does not show up until the structural engineer signs off — or refuses to. A missing CE mark on an EU-bound shipment means the container sits at Rotterdam while the importer scrambles for paperwork, burning demurrage by the day. Negative tolerance beyond the ±1% band thins the wall just enough to fail ultrasonic thickness checks at the port, turning a routine delivery into a customs dispute [NEED_CITE: steel grade equivalence between EN 10219 and ASTM A500 standards]. The cost is never the tube price — it is the crane idle time, the re-order freight, and the lost contract.
Why Procurement Teams Return to Jinan for SHS
We roll the High Quality Carbon Steel Q235B Welded Square Steel Tube on three dedicated ERW lines, so the price you see is the mill price — no trading markup. Every heat runs through our own physical and chemical lab before it leaves the bay, and the resulting mill test certificate travels with the cargo. With 2,800+ specifications in our rolling program, you can consolidate square tubes, rectangular tubes, round pipes, and beams into one shipment instead of juggling four vendors. Our sharp-corner rectangular tube patent — one of 41 in our portfolio — fills a gap that standard mills cannot close, giving architects clean 90-degree joints without extra machining. CE certification under EN 10210 and EN 10219, ISO 9001:2015 registration, and SGS or BV third-party inspection are standard documentation, not upsells. Custom non-standard sizes and fixed-length cutting are handled on-site, so your 11.8m columns arrive without field trimming.
Documentation & Compliance
- Mill test certificate documenting Q235B or S355 chemical composition and mechanical properties per GB/T 3091 or EN 10219
- CE certificate covering EN 10210 hot-finished or EN 10219 cold-formed structural hollow sections for EU customs
- ISO 9001:2015 quality management certificate tied to the production batch
- SGS or BV third-party inspection report confirming dimensional tolerance and surface quality before shipment
- Full heat-number traceability from slab to finished High Quality Carbon Steel Q235B Welded Square Steel Tube
- Export documents including packing list, bill of lading, and certificate of origin for destination clearance
Packaging, Loading & Delivery
- Black-painted Q235B square tubes bundled with steel strips and edge protectors to prevent coating damage during ocean transit
- Galvanized SHS wrapped in waterproof paper with wooden cradles at 6m and 12m lengths to preserve the zinc layer
- Container loading plans optimized for 19×19mm through 400×400mm sections, maximizing 20ft and 40ft OT payload without overhang
- Random or fixed-length cutting to 5.8m, 6m, 11.8m, or 12m per site requirement, with kerf allowance confirmed before rolling
- Each bundle stenciled with heat number, steel grade, standard, and dimensions for instant site identification
- FOB Jinan, CIF destination port, or DDP door-to-door options with real-time container tracking
Getting Your Quote and Mill Test Package Ready
Send the section size, wall thickness, steel grade, tonnage, and destination port — we return a detailed offer with unit price, delivery window, and applicable certificates within 12 hours. If your drawing calls for a non-standard dimension or a mixed-grade container, we confirm feasibility and tooling before you commit. Third-party inspection via SGS or BV can be booked at the production stage so the report ships with the cargo.
Frequently Asked Questions
Q: How do Q235B, S235, and Gr.B compare across standards?
A: They occupy similar yield-strength bands but follow different national standards — GB/T 3091, EN 10025, and ASTM A500 respectively. We supply all three and provide cross-reference documentation so your engineer can approve the substitution.
Q: Can I get a mill test certificate before the container loads?
A: Yes. Original MTC showing chemical composition and mechanical test data is issued per heat number and shared before shipment. SGS or BV third-party reports can be arranged at the same stage.
Q: Do you produce non-standard sizes outside the 19×19 to 800×800mm range?
A: Custom dimensions are available against drawing. MOQ and lead time depend on the section and quantity — we confirm both before rolling.
Q: Which surface treatment suits outdoor coastal structures?
A: Hot-dip galvanized provides the longest corrosion resistance for exposed environments. Black painted or varnished finishes work for indoor or temporarily protected frames, while bare tubes are typically used when the buyer applies their own coating system on site.
Q: What certificates do I need for EU customs clearance?
A: CE marking under EN 10210 or EN 10219 is mandatory for structural use. We supply the CE certificate, mill test certificate, and full export documents so your forwarder clears without delay.
Send Your Specification, Get the Mill Test Package
Email your drawing or size list to admin@sdxjysteel.com or message on WhatsApp at +86 188 5315 7756 — we return pricing, certificates, and a loading plan within 12 hours.
