ASTM A990 is a standard specification for duplex stainless steel castings used in pressure-containing applications such as valves, flanges, and fittings. This standard covers five different grades of duplex stainless steel castings, each with unique properties and characteristics.
The five grades covered by ASTM A990 include CD3MN, CD4MCu,
CD4MCuN, CE3MN, and CE8MN. CD3MN is a duplex stainless steel with a high
chromium content and moderate amounts of nickel, molybdenum, and nitrogen. It
offers good corrosion resistance in various environments, including seawater,
and is often used in valves, pumps, and other pressure-containing components.
CD4MCu is a duplex stainless steel with higher levels of
chromium, molybdenum, and copper than CD3MN. It has excellent resistance to
pitting and crevice corrosion and is commonly used in marine and chemical
processing applications.
CD4MCuN is a modified version of CD4MCu that also contains
nitrogen for improved corrosion resistance. This grade is well-suited for
applications in harsh environments, such as offshore oil and gas production.
CE3MN is a duplex stainless steel with a high nitrogen
content and low nickel content. It offers good resistance to corrosion and
stress corrosion cracking in chloride-containing environments and is often used
in chemical processing and pulp and paper production.
CE8MN is a duplex stainless steel with higher levels of
nitrogen and molybdenum than CE3MN. It has excellent resistance to pitting and
crevice corrosion and is often used in seawater applications.
The mechanical properties of the duplex stainless steel castings
specified in ASTM A990 depend on the grade and the heat treatment process. The
minimum tensile strength and yield strength requirements for each grade are
specified in the standard, as well as the maximum hardness values.
ASTM A990 also specifies the chemical composition and testing
requirements for each grade of duplex stainless steel castings. The chemical
composition requirements ensure that the castings meet the specified corrosion
resistance and mechanical properties, while the testing requirements ensure
that the castings meet the quality standards set forth in the specification.
In conclusion, ASTM A990 is an important standard
specification for duplex stainless steel castings used in pressure-containing
applications. Understanding the different grades and their properties can help
engineers and designers select the appropriate material for their specific
application. By following the requirements set forth in ASTM A990,
manufacturers can ensure that their duplex stainless steel castings meet the
necessary quality and performance standards
