CD6MN duplex stainless steel


CD6MN duplex stainless-steel overview

CD6MN is a duplex stainless-steel alloy containing more chromium, molybdenum, and nitrogen than standard austenitic stainless steel. It also includes small amounts of nickel and copper. CD6MN steel offers excellent corrosion resistance and strength properties in harsh operating conditions.

Duplex stainless steels like CD6MN have a unique microstructure that provides a combination of high strength, corrosion resistance, and toughness. The two-phase structure consists of both austenite and ferrite phases, which helps to improve the alloy’s resistance to stress corrosion cracking, pitting, and crevice corrosion.

CD6MN is often used in applications that require high resistance to chloride-induced stress corrosion cracking and pitting corrosion. It is also commonly used in pumps, valves, and other chemical, petrochemical, and oil and gas equipment. Its strength and toughness make it ideal for high-pressure and high-temperature applications.

Overall, CD6MN is a versatile and reliable duplex stainless steel alloy that combines strength, toughness, and corrosion resistance, making it a popular choice for various industries and applications.

The characteristics of ASTM A890 grade 3A

ASTM A890 grade 3A is a high-strength corrosion-resistant duplex stainless steel. Some key characteristics of this grade include:

  • High strength: ASTM A890 grade 3A offers high yield and tensile strengths, making it suitable for applications where strength is crucial.
  • Corrosion resistance: This grade is highly resistant to corrosion, especially in acidic, chloride-rich environments, making it ideal for use in the chemical, petrochemical, and oil and gas industries.
  • Good weldability: ASTM A890 grade 3A is easily weldable using standard welding techniques and equipment.
  • Excellent toughness: This grade has excellent toughness and impact resistance, which makes it suitable for use in harsh environmental conditions.
  • Good creep resistance: ASTM A890 grade 3A has good creep resistance at high temperatures, making it suitable for use in applications where high-temperature strength is required.
  • Good formability: This grade is easily formed into different shapes and sizes using standard forming and machining techniques.
  • Low thermal expansion: ASTM A890 grade 3A has a low thermal expansion coefficient, which makes it suitable for use in applications where dimensional stability is important.

CD6MN chemical composition

Carbon:                                                                  0.06% Max

Manganese:                                                          1.00% Max

Silicon:                                                                   1.00% Max

Phosphorus:                                                          0.04% Max

Sulfur:                                                                     0.04% Max

Chromium:                                                        24.00-27.00%

Nickel:                                                                  4.00 – 6.00%

Molybdenum:                                                     1.75 – 2.50%

Nitrogen:                                                             0.15 – 0.25%

CD6MN duplex
A890 Grade 3A

Physical properties

  • Yield Strength:                        80 ksi Min
  • Tensile Strength:                   110 – 135 ksi
  • Elongation at 2 in:                   15% Min
  • Reduction of Area:                   35% Min

Casting standards

CD6MN (UNS J93371) Casting Typical Application

CD6MN is a type of duplex stainless steel that offers excellent corrosion resistance, high strength and toughness, and good weldability. This material is commonly used in the following applications:

  • Subsea control lines – CD6MN is well-suited for subsea applications due to its resistance to chloride stress corrosion cracking and pitting corrosion.
  • Heat exchangers – CD6MN’s high strength and corrosion resistance make it ideal for use in heat exchangers that handle corrosive fluids.
  • Water systems – CD6MN can be used for piping and fittings in water systems as it is resistant to corrosion and biofouling.
  • Offshore platforms – CD6MN is often used in offshore platforms due to its high strength, resistance to corrosion, and ability to withstand harsh marine environments.
  • Fire-fighting systems – CD6MN can be used in fire-fighting systems due to its corrosion resistance and ability to withstand high temperatures.
  • Pump and valve industry – CD6MN is used in the pump and valve industry for its excellent resistance to corrosion and ability to withstand high pressure and temperature environments.

Overall, CD6MN is a versatile material that finds applications in a wide range of industries including oil and gas, chemical processing, and marine engineering.

Casting Material Grades:

ASTM A995 Grade 3A; ASTM A890 Grade 3A; Type 25Cr-5Ni-Mo-N; Casting UNS J93371; ACI CD6MN;

Stainless Steel CD6MN (UNS J93371) Casting Heat treatment process:

The heat treatment process for CD6MN stainless steel casting (UNS J93371) involves the following steps:

Solution Annealing: The casting is heated to a temperature of 1070-1100℃ and held at that temperature for a period of 1-2 hours. This process helps to dissolve all the alloying elements uniformly within the austenitic matrix.

Rapid Quenching: The casting is then rapidly quenched in water or rapidly cool by other means. which helps to trap the alloying elements within the austenitic matrix.

The heat treatment process is crucial for achieving the desired mechanical properties of the CD6MN stainless steel casting. The solution annealing and rapid quenching steps help to create a homogeneous austenitic structure, while the tempering process helps to improve the steel’s mechanical properties. Proper heat treatment can result in a CD6MN casting with excellent corrosion resistance, high strength, and good ductility.