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A stainless steel component manufacturer located in Thailand's Eastern Economic Corridor has placed a repeat order with us for ASTM A312 TP316L (UNS S31603 / EN 1.4404) seamless stainless steel hexagonal tube in size S45×32mm, produced by the cold drawn process. The hex tube is machined by the client into hex nuts, valve body components, and instrumentation fittings supplied to petrochemical and food processing plants across Southeast Asia.
The buyer operates a precision machining workshop in Rayong, Thailand, serving refinery, chemical, and food-grade process equipment contractors. Their product range includes stainless hex fittings, instrumentation valve bodies, and custom machined sleeves — all components that must comply with ASME and ASTM pressure-retaining standards and remain traceable to the original mill heat.
- Hex profile accuracy: The client machines the tube directly on automatic lathes, so the across-flats dimension and concentricity of the bore had to be held tightly to avoid eccentric wall thickness and scrap.
- Seamless requirement: Pressure-retaining parts cannot tolerate a welded seam, which would create a preferential corrosion path and fail hydrostatic testing.
- Corrosion resistance: The molybdenum-bearing 316L grade was mandatory for chloride-bearing process media and for welded assemblies where intergranular corrosion resistance is required.
- Traceability and certification: Every shipment had to arrive with an EN 10204 3.1 mill test certificate and full heat number identification for the client's own customer audits.
- Cold drawn finish: A bright, scale-free cold drawn surface was needed to reduce machining passes and improve final electropolishing results.
We supplied cold drawn seamless 316L hexagonal tube to the client's exact S45×32mm specification — 45mm across flats with a 32mm internal diameter — produced from a seamless mother tube, then cold drawn over a hexagonal mandrel and finally solution annealed and pickled/passivated. Each production lot was dimensionally inspected, eddy-current tested, and hydrostatically tested before packing.
Key features delivered to the Thai client:
- Seamless Construction: No longitudinal weld, satisfying ASME pressure-retaining requirements and eliminating preferential weld corrosion.
- TP316L / 1.4404 Chemistry: Low-carbon molybdenum-bearing austenitic grade for chloride environments and post-weld intergranular corrosion resistance.
- Cold Drawn Hex Profile: Sharp corners, consistent across-flats dimension, and bright surface finish that reduces machining time per part.
- Annealed & Passivated: Solution annealed to restore corrosion resistance after cold working, then pickled and passivated for a clean, oxide-free surface.
- Full Certification: EN 10204 3.1 MTC with heat number traceability on every bundle and each cut length.
| Parameter | Specification |
|---|---|
| Standard | ASTM A312 / A312M, ASTM A269 |
| Grade | TP316L / UNS S31603 / EN 1.4404 |
| Type | Seamless, cold drawn hexagonal tube |
| Size | S45×32mm (45mm across flats, 32mm ID) |
| Wall Thickness | 6.5mm nominal |
| Length | 3–6m random or fixed cut to order |
| Surface | Bright cold drawn, pickled and passivated |
| Straightness | ≤ 1.5 mm/m |
| Testing | Hydrostatic / eddy current / PMI on request |
| Certification | EN 10204 3.1 Mill Test Certificate per heat |
| Element | C | Si | Mn | P | S | Cr | Ni | Mo |
|---|---|---|---|---|---|---|---|---|
| Range | ≤0.030 | ≤1.00 | ≤2.00 | ≤0.045 | ≤0.030 | 16.0–18.0 | 10.0–14.0 | 2.0–3.0 |
| Property | Requirement |
|---|---|
| Tensile Strength | ≥ 485 MPa |
| Yield Strength (0.2%) | ≥ 170 MPa |
| Elongation | ≥ 35% |
| Hardness | ≤ 90 HRB |
For hex nuts and hex-bodied fittings, machining from a hexagonal tube eliminates the largest single cost driver in the shop: turning a round bar down to a hex profile. Using a cold drawn hex tube means the six flats are already formed to tolerance, the bore is already sized close to the finished thread minor diameter, and the machinist only needs to face, chamfer, and thread. In this project the switch reduced roughing time per part and cut swarf volume significantly, while a seamless body kept the parts compliant for pressure service.
- Dimensional consistency of the hex profile eliminated eccentric-wall scrap on the client's automatic lathes.
- Seamless 316L body passed the client's hydrostatic and PMI inspection on every received lot.
- Cold drawn bright finish reduced machining passes and improved downstream electropolishing yields.
- Complete heat number traceability satisfied end-customer audit requirements in the refinery sector.
- The client consolidated hex tube purchasing with us and has since extended the order range to additional across-flats sizes.
This Thailand project illustrates why the choice of raw stock form matters as much as the material grade. A correctly specified ASTM A312 TP316L 1.4404 seamless stainless steel hexagonal tube, S45×32mm cold drawn, delivers certified corrosion resistance together with real machining cost savings. We supply 316L and 304L seamless hex tube across a wide range of across-flats sizes and wall thicknesses, with solution annealing, pickling and passivation, and third-party inspection available on request for shipment to Laem Chabang and other Southeast Asian ports.