ThePipingMart Blog Grades 21-6-9 Stainless Steel (UNS S21900) – Composition, Properties, and Uses

21-6-9 Stainless Steel (UNS S21900) – Composition, Properties, and Uses

21-6-9 Stainless Steel

When choosing the right type of stainless steel, various options are available. One option that stands out is 21-6-9 stainless steel. While many people have heard of it, only some understand what it is and why it is an excellent choice for certain applications. This article will examine everything you need to know about 21-6-9 stainless steel, including its composition, properties, and applications.

What is 21-6-9 stainless Steel?

21-6-9 stainless steel is a type of austenitic steel alloy that consists of 21% chromium, 6% nickel, and 9% manganese. This alloy combines corrosion resistance, excellent strength, and weldability properties. It possesses great heat-resisting qualities, which make it an ideal material for industrial applications such as food processing and medical equipment.

21-6-9 Stainless Steel Composition

21-6-9 stainless steel is austenitic stainless steel composed of iron, chromium, nickel, and manganese. However, what makes it unique is the addition of nitrogen and molybdenum, which give it exceptional properties that make it ideal for many applications. It has a higher nitrogen content than most other austenitic stainless steels, which makes it highly resistant to pitting and crevice corrosion. Additionally, the molybdenum enhances its overall toughness, improves its weldability, and maintains its strength at elevated temperatures.

Element Content (%)
Iron, Fe 64
Chromium, Cr 20
Manganese, Mn 9
Nickel, Ni 6
Silicon, Si 1
Nitrogen, N 0.23
Carbon, C 0.080
Phosphorous, P 0.060
Sulfur, S 0.030

21-6-9 Stainless Steel Physical Properties

21-6-9 stainless steel is an excellent choice due to its unique physical properties such as its high strength, excellent corrosion resistance, and impressive heat resistance at high temperatures. It can withstand extreme environments and remains durable over time. This makes it perfect for use in chemical and petrochemical industries, aerospace, and marine applications. Not to mention, 21-6-9 stainless steel is super easy to maintain, making it a popular choice for many projects. Whether it’s for structural or decorative applications, this stainless steel alloy won’t disappoint.

Properties Metric Imperial
Density 7.83 g/cm3 0.283 lb/in³

21-6-9 Stainless Steel Mechanical Properties

With a tensile strength of over 200 ksi and elongation of 30%, 21-6-9 SS is able to withstand high stress and deformation without bending or breaking. Plus, it has a high resistance to corrosion and oxidation, making it a popular choice in industries like aerospace and chemical processing.

Properties Metric Imperial
Tensile strength, ultimate 883 MPa 128000 psi
Tensile strength, yield (@0.2%) 745 MPa 108000 psi
Elongation at break (in 50 mm) 56% 56%
Modulus of elasticity (typical for stainless steel) 200 GPa 29000 ksi
Machinability (based on 100 machinability for AISI 1212 steel) 30 30

21-6-9 Stainless Steel Thermal Properties

Properties Metric Imperial
Thermal expansion co-efficient (@ 25-95°C/77-203°F) 16.7 µm/m°C 9.28 µin/in°F
Thermal conductivity (@-180°C/-292°C) 7.80 W/mK 54.1 BTU in/hr.ft².°F

21-6-9 Stainless Steel Equivalent

Other designations that are equivalent to grade 21-6-9 stainless steel include the following:

  • AMS 5561
  • AMS 5562
  • AMS 5656
  • ASTM A269 (XM-10)
  • ASTM A276 (XM-10)
  • ASTM A312 (XM-10)
  • ASTM A314 (XM-10)
  • ASTM A412 (XM-10)
  • ASTM A479 (XM-10)
  • ASTM A580 (XM-10)
  • ASTM A813 (XM-10)
  • ASTM A814 (XM-10)

21-6-9 Stainless Steel Uses

21-6-9 stainless steel is an excellent choice for high-stress applications, as it is highly resistant to corrosion, wear, and heat. Its corrosion resistance makes it an ideal choice for marine applications, such as boat fittings and fixtures and oil and gas applications. Furthermore, its superb mechanical properties make it suitable for aerospace applications, such as jet engines and missile components. Additionally, it is used in industrial applications, such as power generation turbines and pump components. Any application that requires a strong, durable, and corrosion-resistant material could benefit from 21-6-9 stainless steel.

21-6-9 Stainless Steel Welding

While 21-6-9 stainless steel is highly weldable, welding requires specific pre- and post-welding procedures to ensure the best results. Welding must follow the correct procedures to avoid undesirable results, such as reducing corrosion resistance or cracking. As a result, it is important to consult with welding experts to ensure that the appropriate welding techniques are used to achieve optimal results.


21-6-9 stainless steel is an excellent choice for applications that require a strong, durable, and corrosion-resistant material. Its unique composition, properties, and applications perform exceptionally in high-stress environments. Whether you want to use it in marine, aerospace or industrial applications, 21-6-9 stainless steel is an excellent choice you can trust to get the job done right.

Related Post