ASTM A666 vs ASTM A240 standards: differences

What is ASTM A240?
ASTM A240 is a standard specification for chromium and chromium-nickel stainless steel plate, sheet, and strip, covering various grades used for pressure vessels and general applications. It defines the required chemical composition, mechanical properties, and other specifications to ensure consistency and quality for products like those made from grades 304, 316, and 321 stainless steel. This standard is widely used across industries such as food processing, construction, and petrochemicals.

 

What is ASTM A666?
ASTM A666 is a standard specification for annealed or cold-worked austenitic stainless steel sheet, strip, plate, and flat bar. It sets the requirements for the steel's chemical composition and mechanical properties, such as tensile strength, yield strength, hardness, and elongation. This standard is used for a variety of applications, including structural, pressure vessel, magnetic, cryogenic, and heat-resisting purposes.

 

What is the difference between ASTM A240 and A666?

ASTM A240 covers a broad range of stainless steel plates, sheets, and strips for general and pressure vessel applications, while ASTM A666 specifically covers austenitic stainless steel in sheet, strip, plate, or flat wire forms for applications requiring higher structural strength. The key difference is that A666 is intended for higher structural strength, whereas A240 is a more general standard for corrosion and temperature resistance in pressure vessels.

Feature	ASTM A240	ASTM A666
Primary Application	General and pressure vessel applications	Higher structural strength applications
Material Covered	A wide range of stainless steel alloys, including ferritic, austenitic, martensitic, and duplex	Austenitic stainless steel only
Product Forms	Plates, sheets, and strips	Sheet, strip, plate, or flat wire
Key Requirement	Covers chemical composition and mechanical properties	Focuses on the heat treatment and cooling requirements for achieving higher structural strength

 

What is the difference between ASTM A240 and ASTM A167?
The main difference between ASTM A240 and ASTM A167 is the chemical composition. ASTM A240 steel contains chromium, molybdenum, and nickel, while ASTM A167 only contains chromium and molybdenum. This means that ASTM A240 steel will resist corrosion better than ASTM A167. 

 

What is the thickness tolerance of ASTM A240?

Thickness tolerances in ASTM A240 vary depending on the sheet thickness, width, and manufacturing process (hot-rolled or cold-rolled). Tolerances are specified in the form of ranges; for example, tolerances of ±0.002 inches are available for certain sizes, or +0.050 inches / -0.010 inches for certain widths and thicknesses.

For Stainless Steel Plates and Sheets (Hot-Rolled / Cold-Rolled)

Nominal Thickness (mm)	Thickness Tolerance (mm)
Up to 6 mm	±0.15
Over 6 mm to 13 mm	±0.20
Over 13 mm to 25 mm	±0.25
Over 25 mm to 50 mm	±0.35
Over 50 mm to 75 mm	±0.45
Over 75 mm to 100 mm	±0.55

Note: Cold-rolled sheet typically has tighter tolerances than hot-rolled. For example, a 2B finish cold-rolled sheet may have ±0.10 mm tolerance for thin gauges (<3 mm).

 

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ASTM A240 Standard Specification.pdf