A358 Vs A312 Stainless Steel Round Pipe – What’s The Difference?
Jun 11, 2025
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What Is ASTM A358 Electric-Fusion-Welded (EFW) pipe?
ASTM A358 covers Electric-Fusion-Welded (EFW) austenitic stainless steel pipe, typically used in high-temperature or corrosive applications. This standard includes large-diameter pipes that are welded from stainless steel plates or coils.
Key points:
Material: Austenitic stainless steels (e.g. 304/304L, 316/316L, 321, 347)
Form: Welded only (usually large OD: > 8" or DN200)
Process: Electric-fusion welding with or without filler metal
Classes: Class 1 to Class 5 depending on testing, weld inspection, and heat treatment
Application: Oil & gas, chemical processing, structural columns, pressure lines
What Is ASTM A312 Seamless and welded steel pipe?
ASTM A312 is the standard specification for seamless, welded, and heavily cold-worked austenitic stainless steel pipes used for high-temperature and general corrosion-resistant service.
Key points:
Material: Austenitic grades like 304/304L, 316/316L, etc.
Form: Seamless or welded
Available sizes: Common in SCH 10–SCH 80, from 1/8" to 24" NPS
Testing: Hydrostatic, NDT, dimensional
Application: Water systems, pressure piping, food & pharma process lines
A358 vs A312 stainless steel pipe: What's the Difference?
| Feature | ASTM A358 | ASTM A312 |
|---|---|---|
| Pipe Type | Welded (EFW) | Seamless or Welded |
| Size Range | Large diameter (typically > 8") | Broad range (1/8" – 24") |
| Weld Method | Electric fusion welded | Fusion welded or seamless |
| Use Case | High-temp, large OD piping | General pressure piping |
| Classes | Class 1 to 5 (depending on QA requirements) | No class-based subdivisions |
| Inspection Level | Higher (especially Class 1/3) | Standard NDT & hydrostatic |
| Cost | Higher for large OD or Class 1–2 | More economical for general use |
ASTM A358 or A312 Stainless Steel Pipes?
We supply a full range of:
A312 TP304 / TP316 Seamless & Welded Pipes
A358 Class 1–3 Large Diameter EFW Pipes
Mill Test Certificates (EN 10204 3.1 / 3.2), surface finishes, NACE compliance, and third-party inspection available.
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