ASTM A500 Grade B & C · Metric sections for bulk export
We manufacture square steel tubing for distributors, fabricators and structural projects. The metric range below covers 40 × 40 to 400 × 400 mm, in 6 m, 12 m or cut lengths. Choose mill finish, paint or hot-dip galvanizing, with cutting and fabrication quoted alongside the tubing.
Square tubing is supplied for frames, platforms and machine bases with connections on several faces. For close-fitting inserts, we also review the corner shape, internal seam and required clearance.
When the tube is being selected for equipment-support columns, compare HSS and wide-flange column arrangements before fixing the connection details.
The 6 m and 12 m formats suit workshops that plan their own cutting and welding. Each bundle retains its section, grade and wall so stock can be allocated to the correct frame members.
Repeated machine bases and platforms need consistent lengths, angles and hole positions. Prepared tubing can include those features, deburring and the specified surface finish.
| Item | Supply Range |
|---|---|
| Product | Square carbon steel hollow structural sections (HSS / SHS) |
| Manufacturing route | Cold-formed welded tube with a longitudinal seam |
| Material specification | ASTM A500/A500M; Grade B or Grade C to the order |
| Outside section size | 40 × 40 to 400 × 400 mm in the published metric catalog |
| Wall selection | Size-dependent nominal wall ranges; see the catalog table |
| Length formats | 6 m, 12 m or finished cut lengths |
| Base finish | Black mill finish or oiled tube for further fabrication |
| Protective finishes | Painted or hot-dip galvanized to the specified finish requirement |
| Ends & cut geometry | Plain square-cut ends; miter cuts or weld preparation to drawing |
| Fabrication options | Cutting, deburring, punching and welded assembly to order |
| Inspection records | Material identity, section dimensions and ordered inspection documents |
| Order packing | Bundles separated by section, wall, grade and finished length |
Each quoted item lists its size, wall, grade, finish and quantity.
The table lists metric outside sizes and nominal wall ranges. Inch values are conversions; 63.5 mm equals 2.5 in.
Swipe left to see all columns.
| Outside size (mm) | Outside size (in., converted) | Wall range (mm) | Wall range (in., converted) |
|---|---|---|---|
| 40 × 40 | 1.575 × 1.575 | 1.0–3.5 | 0.039–0.138 |
| 50 × 50 | 1.969 × 1.969 | 1.0–5.0 | 0.039–0.197 |
| 60 × 60 | 2.362 × 2.362 | 1.0–6.0 | 0.039–0.236 |
| 63.5 × 63.5 | 2.500 × 2.500 | 1.0–6.0 | 0.039–0.236 |
| 75 × 75 | 2.953 × 2.953 | 1.5–6.0 | 0.059–0.236 |
| 80 × 80 | 3.150 × 3.150 | 2.0–6.0 | 0.079–0.236 |
| 100 × 100 | 3.937 × 3.937 | 2.3–6.0 | 0.091–0.236 |
| 125 × 125 | 4.921 × 4.921 | 4.0–6.0 | 0.157–0.236 |
| 150 × 150 | 5.906 × 5.906 | 4.0–8.0 | 0.157–0.315 |
| 200 × 200 | 7.874 × 7.874 | 6.0–12.0 | 0.236–0.472 |
| 250 × 250 | 9.843 × 9.843 | 6.0–12.0 | 0.236–0.472 |
| 300 × 300 | 11.811 × 11.811 | 6.0–12.0 | 0.236–0.472 |
| 400 × 400 | 15.748 × 15.748 | 6.0–12.0 | 0.236–0.472 |
Each selected outside size is quoted with one nominal wall, grade, finished length and quantity.
View our BAOLAI square-section catalog (PDF, pages 65–66)
Finished lengths, miter cuts and prepared holes can be supplied with the tubing. The drawing’s reference face and revision are retained for each prepared frame part.
A cutting list defines finished lengths and quantities; the part drawing adds angles, holes and joining details. We follow the specified drawing revision and keep left- and right-hand parts distinct when the assembly requires them.
Choose black or oiled tubing for further workshop fabrication, or the specified painted or galvanized finish. Cutting, holes, welds and mating surfaces are coordinated with that finish.
We check section size, wall, finished cuts and the features that meet plates or brackets. Surface and packing checks follow the processing work; material records identify the supplied grade and batch.
Steel strip passes through forming, longitudinal welding and sizing to become square tube. Cutting and any ordered fabrication or finishing follow. The specified grade and section size remain linked to the material through these operations.
We check section dimensions, finished length and straightness against the ordered requirements. Fabricated parts also need checks at the cut angles, holes and mating features shown on the drawing. The final inspection includes surface condition after processing.
The specified grade and heat or batch reference link the supplied tube to its material documents.
Section checks cover the stated tolerances and any corner or fit requirements on the drawing.
Finished lengths and prepared features are checked against the applicable part drawing and revision.
Material reports identify the supplied grade and batch. For prepared frame parts, dimensional records follow the released drawing revision so receiving can distinguish a tube-size check from a finished-part check.
The factory reference library linked here is published under BAOLAI. It contains general QC procedures and earlier pipe reports; your square-tubing order has its own grade, batch and agreed dimensional records.
BAOLAI QC procedures & published reportsThe standard production lead time is 15–30 days, depending on the specification and order quantity. Cutting, fabrication and finishing affect the schedule. The confirmed dispatch date is separate from ocean transit and destination clearance.
FOB, CFR and CIF are available with a named port. Full lengths, cut pieces and coated sections have different packing and loading needs, which are included in the quoted shipment scope.
Size, wall, grade and length identify each bundle. Timber supports and secured bands hold the load, with contact protection for coated surfaces. A packing list by specification helps your receiving team check mixed-size shipments without sorting every piece.
Tubing, cutting, fabrication, finish and freight are priced separately. This lets you compare full-length material with parts prepared for assembly.
Yes. List the quantity, wall, grade and length for each section separately. Each combination remains a separate order line for production and packing, even when the bundles travel in the same shipment.
We review trial and mixed-size orders by section, wall and preparation. Any production or processing minimum appears against that item in the quote, before the order is placed.
We work with third-party inspection organizations. Include the inspection scope and any witness points in the purchase requirements so access, testing and document review can be arranged before dispatch.
No. A 20 ft length is 6.096 m, and 40 ft is 12.192 m. If the cut list is in feet, keep that unit and the finished-length tolerance on the inquiry so the order is checked against the correct length.
The quote and order need the same drawing revision. Mark changes to lengths, holes, angles or finish on the revised drawing; they can affect material use, processing cost and the dispatch schedule.
Compare the same outside size, nominal wall, grade, length and finish first. Then check quantity units, cutting or fabrication, inspection documents, packing, delivery term and named port. Price per ton alone does not describe the same delivered order.
Upload your material list and add a short note with the destination, or enter the sizes and quantities in your inquiry. For prepared parts, a drawing adds the cuts, holes and finish. We return the tube, processing and delivery scope as separate quote items.