Stainless Steel Industrial Welded Tubes
An industrial welded austenitic stainless steel pipe to ASTM A312/A312M, longitudinally welded, for high-temperature and corrosive chemical piping.
Product Introduction
ASTM A312 / A312M Industrial Welded Austenitic Stainless Steel Round Pipe
Full Standard Name: ASTM A312/A312M
Scope: Longitudinally welded stainless steel round pipe (WLD), Heavy Cold-worked welded pipe (HCW), seamless pipe. Widely applied for high-temperature service and corrosive chemical piping (compliant with ASME B31.3, pressure vessels).
Dimensional supporting standard: ASME B36.19M (Stainless Steel Pipe Outside Diameter & Schedule Wall Thickness)
1. Core Manufacturing Requirements for Welded Pipe (WLD)
- Automatic longitudinal welding without filler metal.
- Pipes NPS 14 and smaller shall have only one longitudinal weld seam. Pipes larger than NPS14 may adopt double longitudinal welds upon purchaser’s approval.
- Finished pipes shall be delivered after solution heat treatment (conventional grades: ≥1040°C with rapid cooling).
- HCW (Heavy Cold-worked welded pipe): Wall thickness reduction ≥35% after welding; 100% radiographic inspection (RT) prior to welding.
- Each pipe shall undergo either hydrostatic test OR eddy current non-destructive test.
2. Common Material Grades (TP Series, Mainstream for Industrial Welded Pipe)
| Grade | UNS No. | Key Features | Typical Service Conditions |
|---|---|---|---|
| TP304 | S30400 | General-purpose austenitic stainless steel | Water supply & drainage, mild acid & alkali, low-temperature piping |
| TP304L | S30403 | Low carbon grade, resistance to intergranular corrosion | Pipelines without post-weld solution treatment, chemical piping |
| TP304H | S30409 | High carbon grade, excellent high-temperature creep resistance | Boilers, high-temperature flue gas ducts |
| TP316 | S31600 | Molybdenum-bearing grade, anti-chloride corrosion | Seawater, organic acid, petrochemical media |
| TP316L | S31603 | Low-carbon molybdenum stainless steel, preferred for welding | Marine environment, pharmaceutical & fine chemical industry (most popular grade for welded pipe in market) |
| TP321 | S32100 | Titanium stabilized, resistant to sensitization | Medium & high-temperature welded piping |
| TP347 | S34700 | Niobium stabilized grade | High-temperature boilers, hydrogenation units |
| TP310S | S31008 | High chromium & nickel, outstanding high-temperature oxidation resistance | Furnace tubes, high-temperature flue gas piping |
3. Mechanical Properties (Minimum Room Temperature Requirements for Welded Pipe)
| Item | General Grades: TP304 / 304L / 316 / 316L |
|---|---|
| Minimum Tensile Strength | 485 MPa |
| Minimum Yield Strength | 170 MPa |
| Minimum Elongation | 40 % |
4. Dimensional System (NPS Nominal Size + Schedule Wall Thickness, Fixed Outside Diameter)
Outside diameter strictly follows ASME B36.19. Same NPS shares identical OD; wall thickness increases with higher Schedule number.
Common wall thickness series: 5S, 10S, 40S, 80S (Stainless steel dedicated Schedule, do NOT confuse with carbon steel ASME B36.10 SCH).
Common Specification Summary (NPS, DN, OD mm)
| Nominal Size NPS | DN | Outside Diameter OD (mm) | Available Standard Schedule Wall Thickness |
|---|---|---|---|
| 1/2" | DN15 | 21.3 | 5S / 10S / 40S / 80S |
| 3/4" | DN20 | 26.7 | 5S / 10S / 40S / 80S |
| 1" | DN25 | 33.4 | 5S / 10S / 40S / 80S |
| 1.5" | DN40 | 48.3 | 5S / 10S / 40S / 80S |
| 2" | DN50 | 60.3 | 5S / 10S / 40S / 80S |
| 3" | DN80 | 88.9 | 5S / 10S / 40S / 80S |
| 4" | DN100 | 114.3 | 5S / 10S / 40S / 80S |
| 6" | DN150 | 168.3 | 5S / 10S / 40S / 80S |
| 8" | DN200 | 219.1 | 5S / 10S / 40S / 80S |
| 10" | DN250 | 273.1 | 10S / 40S / 80S |
| 12" | DN300 | 323.9 | 10S / 40S / 80S |
Standard dimensional coverage range: NPS 1/8" ~ NPS48"
Standard fixed lengths: 6m, 12m; random lengths negotiable.
Surface finish: Pickled & passivated; Bright Annealed (BA) surface available upon request.
5. Tolerance Requirements for Welded Round Pipe
- Outside Diameter Tolerance
OD ≤114.3 mm: +0.80 / -0.80 mm
114.3 mm ＜ OD ≤219.1 mm: +1.60 / -0.80 mm
- Wall Thickness Tolerance: Nominal wall thickness ±12.5% (Weld seam area is not restricted by upper tolerance limit)
- Straightness and end squareness comply with general requirements specified in A999.