ASTM A312 TP316L Seamless Tube Hex Outer Round Inner, UNS S31603 / 1.4404 Stainless Steel Hollow Bar

TP316L (UNS S31603, W.Nr 1.4404) seamless tube features a hexagonal outer profile and precision concentric round inner bore, manufactured by cold drawing and solution annealing. As a low-carbon molybdenum-bearing austenitic stainless steel, it provides superior resistance to pitting, crevice corrosion and intergranular corrosion compared with 304, performing well in saltwater, chloride and mild acidic environments. The hex outer surface prevents slipping while the smooth round inner bore ensures stable fluid flow. Custom across-flat size, inner diameter, wall thickness, cutting length and tight tolerances are available. Material test certificates EN 10204 3.1 / 3.2 can be supplied; third-party inspection by SGS, BV is acceptable.

Equivalent Grades

• UNS: S31603
• ASTM: A312 TP316L
• EN / W.Nr: 1.4404
• GB: 022Cr17Ni12Mo2
• JIS: SUS316L

Chemical Composition (wt%, ASTM A312 TP316L)

Mechanical Properties (Solution Annealed, Room Temperature, ASTM A312)

表格

Product Specifications

• Shape: Hexagonal outer, concentric round inner bore, fully seamless, no longitudinal weld
• Surface: Pickled No.1 finish, cold drawn bright finish, or mirror polishing on request
• Size: Custom across-flat, inner diameter, wall thickness; standard length 6 m or cut-to-length
• Tolerance: Standard tolerance for hex flats, inner bore and concentricity; precision tight tolerance available with extra charge
• Marking: Heat number, material grade, dimension marked on each piece / bundle
• Packaging: Waterproof wrapping + solid wooden crates for sea shipment
• Certificates: EN 10204 3.1 standard; 3.2 certificate and third-party inspection negotiable

Applications

• Hollow bolt & stud blanks for marine and chemical equipment
• Hydraulic / pneumatic fittings working in chloride environments
• Anti-twist hollow shafts for offshore, food and pharmaceutical machinery
• Instrument tubing, valve and pump component blanks
• Seawater service parts, desalination equipment
• Chemical pipeline fittings, waste water treatment components
• Food, beverage and sanitary processing equipment

FAQ for TP316L Outer Hex Inner Round Seamless Tube

Q1: What material standard does this tube follow?

 A: It meets ASTM A312 TP316L, UNS S31603, W.Nr 1.4404, GB 022Cr17Ni12Mo2 and JIS SUS316L, delivered in solution annealed condition.

Q2: Is it seamless or welded?

A: It is fully cold-drawn seamless hollow bar without longitudinal weld, featuring hexagonal outer surface and concentric round inner bore.

Q3: What is the main advantage of 316L compared with 304?

A: 316L contains molybdenum and has ultra-low carbon. It provides superior resistance to pitting, crevice corrosion and intergranular corrosion, suitable for chloride, seawater and mild acidic environments.

Q4: Can you produce custom sizes?

 A: Yes. Across-flat, inner diameter, wall thickness, tolerance and cut length can be customized. MOQ depends on the specific dimension.

Q5: What surface options are available?

A: Pickled No.1 finish, cold drawn bright finish and mirror polishing are available as customer requests.

Q6: What certificates can you provide?

 A: EN 10204 3.1 MTC is standard. 3.2 certificate, SGS, BV and other third-party inspections can be arranged before shipment.

Q7: How long is your lead time?

 A: Regular sizes: 7–15 working days. Non-standard profiles or precision tight tolerance items: 20–30 working days.

Q8: What payment terms do you accept?

 A: T/T and sight L/C are acceptable. We support payment in two installments: 50% deposit in advance, balance before shipment. Other terms can be negotiated.

Q9: How about packaging?

A: Wrapped with waterproof paper, bundled and packed into solid wooden crates for ocean transport. Each bundle is marked with heat number, grade and dimensions.

Q10: Can you supply samples?

A: Small samples are free of charge; buyers only bear the courier freight.

Q11: What are the typical applications?

A: Widely used for marine hollow stud blanks, desalination parts, chemical fittings, food & pharmaceutical machinery, anti-twist hollow shafts, pump and valve blanks, wastewater treatment components.

Q12: Can you guarantee tight tolerances?

A: Standard tolerances for hex flats, inner bore and concentricity are offered. Precision tight tolerances for mechanical parts are available at an extra cost.

Q13: Is this grade weldable?

A: Yes. Thanks to its low carbon content, 316L avoids intergranular corrosion after welding and shows good weldability.