Overview of ASTM A778 Stainless Steel Pipe
ASTM A778 is a technical standard for stainless steel welded pipes, which is mainly applicable to pipeline systems in corrosion-resistant environments.
ASTM A778 Stainless Steel Pipe Specification
| Nomal Diameter | Outside diameter(mm) | Wall Thickness(mm) | |||
| NB | NPS | SCH 5S | SCH 10S | SCH 40S | |
| 8 | 1/4″ | 13.70 | 1.65 | 2.24 | |
| 10 | 3/8″ | 17.15 | 1.65 | 2.31 | |
| 15 | 1/2″ | 21.34 | 1.65 | 2.11 | 2.77 |
| 20 | 3/4″ | 26.67 | 1.65 | 2.11 | 2.87 |
| 25 | 1″ | 33.40 | 1.65 | 2.77 | 3.38 |
| 32 | 1 1/4″ | 42.16 | 1.65 | 2.77 | 3.56 |
| 40 | 1 1/2″ | 48.26 | 1.65 | 2.77 | 3.68 |
| 50 | 2″ | 60.33 | 1.65 | 2.77 | 3.91 |
| 65 | 2 1/2″ | 73.03 | 2.11 | 3.05 | 5.16 |
| 80 | 3″ | 88.90 | 2.11 | 3.05 | 5.49 |
| 90 | 3 1/2″ | 101.60 | 2.11 | 3.05 | 5.74 |
| 100 | 4″ | 114.30 | 2.11 | 3.05 | 6.02 |
| 125 | 5″ | 141.30 | 2.77 | 3.40 | 6.55 |
| 150 | 6″ | 168.28 | 2.77 | 3.40 | 7.11 |
| 200 | 8″ | 219.08 | 2.77 | 3.76 | 8.18 |
| 250 | 10″ | 273.05 | 3.40 | 4.19 | 9.27 |
| 300 | 12″ | 323.85 | 3.96 | 4.57 | 9.52 |
ASTM A778 Welded Pipe Tolerance Requirements
- Outer Diameter Tolerance: ±0.1%.
- Wall Thickness Tolerance: ±10%, minimum wall thickness ≥ 87.5% of the nominal wall thickness.
ASTM A778 vs A312/A358
- No heat treatment required: Different from ASTM A312/A358 (solution treatment after welding is required).
- Basic inspection: Only the minimum testing is required. When additional inspections are needed, supplementary standards such as A312 shall be referenced.
Material Composition of ASTM A778
| Type | Chemical Composition | ||||||||
| ASTM | JIS | C | Si | Mn | P | S | Ni | Cr | Mo |
| 304 | SUS 304 | ≤0.08 | ≤0.75 ≤1.00 |
≤2.00 | ≤0.045 ≤0.045 |
≤0.03 | 8.0~11.0 | 18.0~20.0 | / |
| 304L | SUS 304L | ≤0.03 | ≤0.75 ≤1.00 |
≤2.00 | ≤0.045 ≤0.045 |
≤0.03 | 8.0~13.0 9.0~13.0 |
18.0~20.0 | / |
| 316L | SUS 316L | ≤0.03 | ≤0.75 ≤1.00 |
≤2.00 | ≤0.045 ≤0.045 |
≤0.03 | 10.0~14.0 12.0~15.0 |
16.0~18.0 | 2.0~3.0 |
ASTM A778 Stainless Production Process
- Use straight-seam welding or spiral butt welding. Form stainless steel coils/sheets by shielded arc welding.
- Weld defects need to be repaired manually or automatically to the intact metal layer.
- No annealing heat treatment is required, as the material’s corrosion resistance is relied upon.
Mechanical and Physical Properties
| Type | Mechanical and physical properties | ||||
| ASTM | JIS | Tensile Strength | Elongation | Yeild Strength | Hardness |
| Mpa | % | Mpa | HRB | ||
| 304 | SUS 304 | ≥520 ≥515 |
≥40 ≥40 |
≥210 ≥205 |
≤92 ≤90 |
| 304L | SUS 304L | ≥480 ≥485 |
≥40 ≥40 |
≥175 ≥170 |
≤92 ≤90 |
| 316L | SUS 316L | ≥480 ≥485 |
≥40 ≥40 |
≥175 ≥170 |
≤95 ≤90 |
ASTM A778 Pipe Applications
- It is mainly used in scenarios for transporting corrosive media:
- Chemical/Petrochemical: Acid- and alkali-resistant liquid pipelines.
- Water Treatment/Paper Manufacturing: Chloride ion corrosion-resistant systems.
- Food Hygiene Equipment: Meeting pollution-free requirements.
- Electroplating Equipment: Customized thickened pipes (e.g., with a specification of 12.7×0.8 mm).
