What is Alloy 20 & Cn7m Material?

When talking about what is Alloy 20 & CN7M material, Alloy 20 is an austenitic stainless steel which has been created for use in applications and industries that use sulfuric acid. Because of its resistance to corrosion, Alloy 20 is used in various industries like plastics, chemicals, power generation, petrochemicals, etc. The cast equivalent of Alloy 20 is CN7M. CN7M is the designation for this material and this designation is used in the ASTM system, as well as in the ACI system. Alloy 20 & CN7M are austenitic stainless steels of a speciality grade and they are referred to as ‘super’ stainless steels.

904l vs Alloy 20

When considering 904L vs Alloy 20, 904L has UNS N08904, whereas Alloy 20 has UNS N08020. 904L has a Density of 0.288 lb/in³ (7.97 g/cc). Alloy 20 has a Density of 0.291 lb/in3 (8.05 g/cm3). 904L has a Yield Tensile Strength of 214 MPa (31000 psi). Alloy 20 has a Yield Tensile Strength of 515 MPa (74700 psi). 904L has an Elongation at Break of 35%. Alloy 20 also has an Elongation at Break of 35%. 904L has a linear CTE of 5.80 µin/in-°F (10.4 µm/m-°C). The linear CTE of Alloy 20 is 6.61 µin/in-°F (11.9 µm/m-°C). 

Why alloy 20 is casting grade

To understand why Alloy 20 is casting grade, one has to go right back to the origins of Alloy 20. It has its origins in the year 1951, in relation to the invention by Carpenter Steel. Initially, Alloy 20 was known as Carpenter Stainless 20. At this time, Alloy 20 was representative of a wrought alloy, which was akin to the cast alloy CN7M. But this cast composition could not be hot worked. Albeit, it was Carpenter’s invention of Alloy 20 that made possible various wrought forms like pipes, bars, plates, wires, sheets, forgings, etc.  This is why Alloy 20 is known as casting grade.

Alloy 20 Composition

Alloy 20, also known as Carpenter® 20 and Incoloy® 20, is an austenitic nickel-iron-chromium alloy.

Other trade name: Alloy 20, Incoloy 20, UNS N08020, Carpenter 20, 20Cb-3