What is the difference between ASTM A790 and A789?

What is ASTM A790 material?

ASTM A790 is the standard specification for seamless and weldable ferritic/austenitic (duplex) stainless steel tubes, designed for high-strength, corrosion-resistant applications. It covers a variety of duplex steel grades, including high-strength, standard, super, and ultra-hard steels, and is widely used in the oil and gas, chemical, and marine industries.

 

What is ASTM A789 material?

ASTM A789 is a standard specification for seamless and welded ferritic/austenitic (duplex) stainless steel tubing designed for high-strength, corrosion-resistant service. It is widely used in chemical, oil/gas, and marine industries, particularly for heat exchangers, condensers, and in chloride-rich environments, often under names like 2205 (UNS S31803/S32205) or Super Duplex.

 

What is the difference between ASTM A790 and A789?

ASTM A790 and ASTM A789 are both standards for duplex stainless steel, but they differ primarily by application: A790 covers pipe (larger diameter, structural piping), while A789 covers tubing (smaller diameter, heat exchangers). A790 is designed for general corrosive service piping systems, while A789 is focused on resistance to chloride stress corrosion cracking.

 

ASTM A790 vs. ASTM A789: Key Differences

Feature	ASTM A790	ASTM A789
Product Type	Pipe (Seamless and Welded)	Tubing (Seamless and Welded)
Common Application	High-pressure fluid transport, structural use, oil & gas pipelines.	Heat exchangers, condensers, evaporators, and general corrosion service.
Dimensional Standard	ASME B36.19 / B36.10 (NPS & Schedule)	Exact OD and Wall Thickness (Inches or mm)
Size Designation	Based on Nominal Pipe Size (NPS) and Schedule (e.g., NPS 2" Sch 40S).	Based on Outer Diameter (OD) and actual wall thickness (e.g., 1" OD x 0.065" WT).
General Requirements	Governed by ASTM A999	Governed by ASTM A1016 (formerly A450)
Wall Thickness Tolerance	Generally -12.5% of the nominal wall.	Stricter tolerances; usually specified as Average Wall or Minimum Wall.
Mechanical Tests	Tensile, Yield, Elongation, Flattening, and Hydrostatic/NDT.	Tensile, Yield, Elongation, Flattening, Flaring, Flanging, Hardness, and Hydrostatic/NDT.
Mandatory Tube Tests	N/A	Flaring and Flanging tests are critical for tube-to-tubesheet connections.
Surface Finish	Usually Pickled/Annealed; finish is less critical than tubes.	Often more precise; can be Bright Annealed (BA) or Polished for heat transfer efficiency.

 

ASTM A790 vs. ASTM A789 ：Dimensional Tolerances

Parameter	ASTM A790 (Pipe)	ASTM A789 (Tube)
Outside Diameter (OD)	±0.75% of OD	±0.10 mm (OD ≤ 38 mm) ±0.25% of OD (OD > 38 mm)
Wall Thickness (WT)	-12.5% / +Not specified (typically +20% allowed)	±10% of nominal wall thickness
Length Tolerance	-0 / +6 mm (for random lengths) Cut lengths: ±3 mm	Cut lengths: ±3 mm U-tubes: tighter control per agreement
Straightness	Max 0.2% of length	Typically tighter than pipe (e.g., ≤ 1/1000 of length)
Ovality (Out-of-Roundness)	Included within OD tolerance	Limited to OD tolerance; stricter control
End Squareness (Cutting Angle)	Not explicitly strict	Ends shall be reasonably square (stricter for heat exchanger use)

 

 What is the difference between ASTM A790 and ASTM A928?

ASTM A790 and ASTM A928 are both standards for duplex stainless steel pipes, but they differ primarily in manufacturing method and application. ASTM A790 covers both seamless and welded pipes (usually autogenous), while ASTM A928 specifically covers Electric Fusion Welded (EFW) pipe using filler metal, often intended for more corrosive or higher-pressure service.

 

What is the difference between ASTM A312 and A790?

The main difference is that ASTM A312 covers austenitic stainless steel tubes (such as 304/316) for high-temperature and generally corrosive environments, while ASTM A790 covers ferritic/austenitic (duplex) stainless steel tubes (such as S31803/S32205) designed for superior corrosion resistance.

 

 

ASTM A789 ASTM A790 Stainless Steel Tubes Supplier

 

Common Grades

Duplex: S31803, S32205 (2205)
Super Duplex: S32750 (2507), S32760
Lean Duplex: S32304, S32101

 

Standard End Finishes

Plain Ends (PE): Square cut for mechanical couplings or socket welding.
Beveled Ends (BE): Prepared for butt-welding (per ASME B16.25).
Threaded Ends: Male/Female threads for specific fittings.

 

Standard	Product Form	Manufacturing Process	Typical Size Range
ASTM A790	Seamless Pipe	Hot Rolled / Cold Drawn	NPS 1/8" to 24" (Sch 10S - XXS)
ASTM A790	Welded Pipe	Automatic Weld / EFW	NPS 2" to 48" (Sch 5S - 80S)
ASTM A789	Seamless Tubing	Cold Drawn / Cold Rolled	OD 6mm to 219.1mm (WT 0.5 - 20mm)
ASTM A789	Welded Tubing	Continuous Weld (Laser/TIG)	OD 12.7mm to 323.9mm
ASTM A789	Heat Exchanger Tubes	Seamless / Welded	OD 12.7mm to 76.2mm (Precise WT)
ASTM A789	U-Bent Tubes	Cold Bent from Straight Tube	Based on Heat Exchanger design
ASTM A789	Instrumentation Tubes	Precision Cold Drawn	OD 1/16" to 1-1/2"
ASTM A789	Coiled Tubing	Seamless / Welded (Orbitally)	Long lengths (up to 1000m+)