Round Tube — Tube specification
Round tube — tube ordered by exact OD and wall thickness. Round tube is used for heat exchangers, boilers and instruments, with tighter tolerances than pipe.
- Tube specification
- 22 grades
- EN 10204 3.1 / 3.2
Reviewed by the Kanak Steel & Engineering Co. technical team · Updated October 2026
What is a round tube?
A round tube is tube ordered by exact OD and wall thickness. Round tube is used for heat exchangers, boilers and instruments, with tighter tolerances than pipe.
Standards for round tubes
| Dimensions | Tube specification |
|---|---|
| Material — stainless | ASTM A312 · tube ASTM A269 / ASTM A213 |
| Material — duplex | ASTM A790 · tube ASTM A789 |
| Material — nickel alloys | ASTM B423 (825) · ASTM B444 (625) · ASTM B622 (C276) |
| Material — carbon & Cr-Mo | ASTM A106 · ASTM A333 · ASTM A335 |
| Certificate | EN 10204 3.1, or 3.2 with third-party inspection |
Round Tube: What to Know Before Ordering
- OD × wall ordering
- Seamless or welded
- Straight or U-bent
Round Tube Materials & Grades
| Grade | Material standard | Best for |
|---|---|---|
| Inconel 825 round tube | ASTM B163 · B423 | Sulphuric and phosphoric acid service, chloride stress-corrosion cracking and sour gas |
| SS 904L round tube | ASTM A269 · A213 where supported (N08904) | Dilute sulphuric acid, phosphoric acid and chloride-bearing cooling water |
| SS 304 round tube | ASTM A213 · A269 · A249 | General corrosion resistance, food, water and architectural work |
| SS 304L round tube | ASTM A213 · A269 · A249 | Welded tanks, piping and vessels in general corrosive service |
| SS 310 / 310S round tube | ASTM A213 | Furnaces, burners and heat treatment at high temperature |
| SS 316 / 316L round tube | ASTM A213 · A269 · A249 | Chloride-bearing process fluids, marine air and pharmaceutical service |
| SS 321 round tube | ASTM A213 | High-temperature service between 425 and 815 °C |
| SS 347 round tube | ASTM A213 | Welded high-temperature piping in refineries and power plants |
| Duplex 2205 round tube | ASTM A789 | Strength with chloride resistance at a stainless-steel budget |
| Super Duplex 2507 round tube | ASTM A789 | Seawater and high-chloride service where strength also matters |
| Inconel 600 round tube | ASTM B163 · B167 | High-temperature oxidation, caustic and nuclear service |
| Inconel 625 round tube | ASTM B444 · B704 | Seawater, high strength and high temperature in one alloy |
| Inconel 718 round tube | a specification not yet established | Very high strength at temperatures up to about 650 °C |
| Incoloy 800 / 800H / 800HT round tube | ASTM B163 · B407 | Furnaces, petrochemical heaters and high-temperature piping |
| Hastelloy C276 round tube | ASTM B622 · B626 | The most aggressive mixed acids, wet chlorine and hypochlorite |
| Hastelloy C22 round tube | ASTM B622 · B626 | Mixed oxidising and reducing acids, and weld overlays |
| Monel 400 round tube | ASTM B163 · B165 | Seawater, hydrofluoric acid and marine service |
| Super Duplex S32760 round tube | ASTM A789 | Seawater firewater, injection and offshore piping |
| ASTM A335 P11 round tube | ASTM A335 P11 | Steam and hot-oil piping up to about 550 °C |
| ASTM A335 P22 round tube | ASTM A335 P22 | High-pressure steam and hydrogen service up to about 580 °C |
| S275JR round tube | EN 10219 square & rectangular sections | General structures, frames and fabrication |
| S355J2+N round tube | EN 10219 square & rectangular sections | Heavy structures, cranes and offshore frames |
Round tube — questions buyers ask
What is a round tube?
A round tube is tube ordered by exact OD and wall thickness. Round tube is used for heat exchangers, boilers and instruments, with tighter tolerances than pipe.
What is the difference between tube and pipe?
Tube is specified by exact OD and wall; pipe by nominal size and schedule.
Which grades are round tubes available in?
Inconel 825, SS 904L, SS 304, SS 304L, SS 310 / 310S, SS 316 / 316L, SS 321, SS 347, Duplex 2205, Super Duplex 2507, Inconel 600, Inconel 625, Inconel 718, Incoloy 800 / 800H / 800HT, Hastelloy C276, Hastelloy C22, Monel 400, Super Duplex S32760, ASTM A335 P11, ASTM A335 P22, S275JR, S355J2+N.
Which standard covers round tube dimensions?
Tube specification. The material standard depends on the grade.
Sources: the ASTM / ASME specifications named on this page and producer datasheets · Last updated October 2026