English
A stainless steel distributor and precision machining group based in South Korea has appointed us as its offshore supply partner for ASTM A511 TP304 (UNS S30400 / EN 1.4301) seamless stainless steel hexagonal tube, cold drawn, with a hairline surface finish, covering an across-flats range from 19mm to 90mm. The material supports the client's production of hex fittings, valve trim, food equipment components, and architectural hardware for domestic and export programmes.
The buyer operates a distribution network in Gyeonggi Province and supplies machined stainless components to Korean valve manufacturers, food processing equipment builders, and architectural metalwork contractors. Korean industrial buyers enforce strict documentation discipline: every incoming lot is verified against the mill certificate, dimensions are gauge-checked, and surface condition is compared to a photographic reference before release.
- Multi-size procurement: The client needed one source able to cover a continuous 19–90mm across-flats range, avoiding split orders across several mills.
- Hairline surface requirement: Unlike standard pickled or bright finishes, the hairline (fine linear grain) finish had to be uniform in direction and depth, visible on all six flats, and free of cross-grain scratches.
- Seamless and mechanical-grade: Mechanical tubing to ASTM A511 was specified rather than welded tube, to preserve wall integrity during deep machining and thread rolling.
- Dimensional control: Across-flats tolerance, corner radius consistency, and bore concentricity all had to hold through the full size range, not only in stock sizes.
- Traceability: Heat-number marking per bundle plus an EN 10204 3.1 mill test certificate, with Korean-language packing lists for customs clearance.
We supplied cold drawn seamless TP304 hexagonal tube to ASTM A511, produced from seamless mother tube, drawn over a hexagonal mandrel, solution annealed, straightened, and hairline finished on all six flats.
Key features delivered to the Korean client:
- ASTM A511 Mechanical Tubing: Seamless construction specified for mechanical and pressure-adjacent applications with consistent wall thickness for machining.
- Full Size Range: A continuous 19–90mm across-flats programme from one production source, simplifying the client's procurement and inventory planning.
- Hairline Finish: Uniform linear grain applied across all flats, matching the client's reference sample for both appearance and paint/adhesive adhesion.
- TP304 Chemistry: General-purpose austenitic grade equivalent to SUS304 and EN 1.4301, suitable for food contact and architectural service.
- Documentation Package: EN 10204 3.1 MTC per heat, dimensional inspection report per size, and Korean-language packing list.
| Parameter | Specification |
|---|---|
| Standard | ASTM A511 / A511M (seamless mechanical tubing) |
| Grade | TP304 / UNS S30400 / EN 1.4301 / SUS304 |
| Type | Seamless, cold drawn hexagonal tube |
| Size Range | 19mm – 90mm across flats (AF) |
| Wall Thickness | 2mm – 12mm, per size |
| Length | 3–6m random or fixed cut to order |
| Surface Finish | Cold drawn + hairline grain, all flats |
| Straightness | ≤ 1.5 mm/m |
| Testing | Eddy current / hydrostatic / PMI on request |
| Certification | EN 10204 3.1 Mill Test Certificate per heat |
| Element | C | Si | Mn | P | S | Cr | Ni |
|---|---|---|---|---|---|---|---|
| Range | ≤0.08 | ≤1.00 | ≤2.00 | ≤0.045 | ≤0.030 | 18.0–20.0 | 8.0–11.0 |
| Property | Requirement |
|---|---|
| Tensile Strength | ≥ 515 MPa |
| Yield Strength (0.2%) | ≥ 205 MPa |
| Elongation | ≥ 35% |
| Hardness | ≤ 90 HRB |
A hairline finish is a fine, directional grain produced by controlled abrasive treatment after cold drawing. It differs from a mirror polish in that the surface retains a subtle linear texture rather than full reflectivity. For this Korean client the finish served three purposes: it masked minor handling marks that would be obvious on a mirror surface, it provided a consistent decorative appearance for exposed architectural hardware, and it created a uniform key for subsequent painting or adhesive bonding. The grain must run consistently along the tube axis on every flat, so finishing is performed per flat rather than by circumferential brushing.
- A single-source 19–90mm programme removed the need for multi-mill sourcing and cut the client's procurement lead time.
- Hairline finish passed the client's photographic reference inspection on arrival, with no cross-grain rejects.
- Seamless A511 body held up through thread rolling and deep boring without wall cracking.
- Complete documentation package cleared Korean customs and internal quality audit without a single query.
- First-shipment sizes were re-ordered within the same quarter, with two additional across-flats sizes added.
This Korea project demonstrates that for mechanical and decorative hex components, the finish specification is a functional requirement, not a cosmetic extra. A properly executed ASTM A511 TP304 seamless stainless steel hexagonal tube, 19–90mm across flats, cold drawn with hairline surface, removes secondary finishing operations at the customer's plant while satisfying audit-grade documentation requirements. We supply 304 and 316L seamless hex tube across the full 19–90mm range with pickled, bright, satin, or hairline finishes.