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Magnetic Notes on Austenitic Stainless Steels

Austenitic stainless steel is commonly used in the manufacturing of a variety of industrial valves due to its excellent mechanical properties, corrosion resistance, and versatility.
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    The practice of using a magnet to test the quality and authenticity of stainless steel valves is a one-sided and impractical method of judgment.

    There are various types of stainless steel, classified by their structure at room temperature, such as martensitic stainless steel, austenitic stainless steel, ferritic, and duplex stainless steel. Austenitic stainless steel exhibits no or weak magnetism, whereas other stainless steel alloys are strongly magnetic.

    austenitic stainless steels
    austenitic stainless steels

    What are Austenitic Stainless Steels

    Austenitic stainless steels are a category of stainless steels characterized by their austenite crystal structure at room temperature. This group of steels includes types 302, 304, 316, and others. The austenitic structure is achieved through the addition of elements like nickel, manganese, and nitrogen that stabilize the austenite phase at room temperature.

    Austenitic stainless steels are known for their excellent corrosion resistance, formability, and weldability. These properties make them a popular choice for a wide range of applications, from kitchen utensils to chemical processing equipment, and from architectural applications to components in the automotive industry.

    The primary elements in austenitic stainless steels are iron, chromium, and nickel. The high nickel and chromium contents enable this type of steel to resist a wide range of corrosive environments and makes it the most stainless of the stainless steels. They also often contain additional alloying elements, such as manganese and molybdenum, to further enhance specific properties.

    A key feature of austenitic stainless steel is that it is non-magnetic in its solution annealed condition. However, it can become slightly magnetic when cold-worked.

    Why do Austenitic Stainless Steels with Magnetism

    CF8 (304), CF8M (316), CF3 (304L), CF3M (316L), and others all belong to austenitic stainless steel and are either non-magnetic or weakly magnetic. However, during smelting, a small amount of martensitic or ferritic structure may recombine in the austenite, unevenly distributed, as little as 5% or as much as 40%. If these proportions increase, the casting will exhibit magnetism. In general, castings with a higher content of ferrite will have better strength.

    AlloyASTM StandardUNS StandardCarbon (C)Manganese (Mn)Silicon (Si)Chromium (Cr)Nickel (Ni)Molybdenum (Mo)
    CF8 (304)A351J92600≤0.08%≤2.00%≤2.00%18.0–21.0%8.0–11.0%≤0.75%
    CF8M (316)A351J92900≤0.08%≤2.00%≤2.00%18.0–21.0%9.0–12.0%2.0–3.0%
    CF3 (304L)A351J92500≤0.03%≤2.00%≤2.00%18.0–21.0%8.0–12.0%≤0.75%
    CF3M (316L)A351J92800≤0.03%≤2.00%≤2.00%18.0–21.0%10.0–15.0%2.0–3.0%
    In addition, each alloy contains other elements such as phosphorus (P), sulfur (S), and copper (Cu) in small amounts. Nitrogen (N) may also be added to some specifications of these alloys. It’s important to consult the specific material specification for the exact composition.


    Currently, there is no process either domestically or internationally that achieves 100% austenite. During the solution treatment of austenitic stainless steel castings, only carbides are dissolved into the austenite, enhancing the casting’s corrosion resistance. It is impossible to change the content of martensite or ferrite, merely changing the structure slightly, which doesn’t significantly reduce magnetism.

    The raw casting will also exhibit slight magnetism during cold processing. The key to reducing magnetism in stainless steel materials such as CF8 (304), CF8M (316), CF3 (304L), CF3M (316L), and others is to control the content of martensite or ferrite. The lower the content, the weaker the magnetism, or the aim could be to fracture their structure and distribute them evenly.

    duplex stainless steel valve casting
    duplex stainless steel valve casting

    ASTM A351 stainless steel valves, chemical composition


    Tubes and plates are produced from steel blanks through many rounds of heating, extruding, and cooling. This process disrupts the structure of the martensite and ferrite, distributing them very evenly. Therefore, the magnetism of tubes and plates is minimal or undetectable.

    austenitic stainless steel2
    austenitic stainless steel

    Mechanical Properties Table of Cast Steel Valves

    ASTM CAST GRADE Tensile strength(psi)Yield strength(psi min)Elongation(at 2 inches) Reduction of Area (%)
    Minimum Steel Mechanical PropertiesModulusApproximate
    ASTM A216 Grade WCB70,00036,000223527.9137-187
    ASTM A352 Grade LCB65,00035,000243527.9137-187
    ASTM A217 Grade C590,00060,000183527.4241 Max.
    ASTM A217 Grade WC165,00035,000243529.9215 Max.
    ASTM A217 Grade WC670,00040,000203529.9215 Max.
    ASTM A217 Grade WC970,00040,000203529.9241 Max.
    ASTM A352 Grade LC365,00040,000243527.9137
    ASTM A217 Grade C1290,00060,000183527.4180-240
    ASTM A351 Grade CF-865,00028,0003528140
    ASTM A351 Grade CF-8M70,00030,0003028.3156-170
    ASTM A126 Class B31,000160-220
    ASTM A126 Class C41,000160-220
    ASTM A395 Type 60-45-1560,00045,0001523-26143-207
    ASTM A439 Type D-2B58,00030,0007148-211
    ASTM B6230,00014,000201713.555-65*
    ASTM B143 Alloy 1A40,00018,00020201575-85*
    ASTM B147 Alloy 8A65,00025,000202015.498*
    ASTM B148 Alloy 9C75,00030,00012 min.1217150
    (Weldable Grade)65,00032,5002523120-170
    ASTM A494 (Hastelloy B)72,00046,0006
    ASTM A494 (Hastelloy C)72,00046,0004
    Stellite No. 6121,00064,00001.feb30.4
    ASTM B211 Alloy 20911-T344,00036,0001510.295
    ASTM B16 1/2 Hard45,00015,00075014
    ASTM B21 Alloy 46460,00027,0002255
    AISI 12L 1479,00071,0001652163
    ASTM A108 Grade 101869,00048,0003862143
    (Suitable for ASTM A193 Grade B7 bolt material)135,000115,000226329.9255
    ASTM A276 Type 30285,00035,000607028150
    ASTM A276 Type 30485,00035,0006070149
    ASTM A276 Type 31680,00030,000607028149
    ASTM A276 Type 316L81,00034,00055146
    ASTM A276 Type 41075,00040,000357029155
    ASTM A461 Grade 630135,000105,000165029275-345
    Alloy K500 (K Monel)100,00070,0003526175-260
    ASTM B335 (Hastelloy B)100,00046,00030
    ASTM B336 (Hastelloy C)100,00046,00020

    Neither domestic nor international standards typically include magnetism testing for austenitic stainless steel. It is not a standard for determining the quality of stainless steel. It should be emphasized that the magnetism of austenitic stainless steel, caused by various factors, is not at the same level as that of other stainless steel materials or carbon steel. In other words, the magnetism of austenitic stainless steel is always weak.

    Recommended Applications (Casting Valve Materials)

    Materials GroupMaterial GradeRECOMMENDED SERVICE
    High-temperature Carbon SteelASTM A216 Grade WCBNon-corrosive fluids such as water, oil, and gases at temperatures range -20°F (-30°C) and +1100°F (+593°C).
    Low-temperature Carbon SteelNon-corrosive fluids such as water, oil, and gases at temperatures range -20°F (-30°C) and +800°F (+425°C)Low temperature to -50°F (-46°C). Use excluded above +650°F (+340°C).
    Low-temperature Carbon SteelASTM A352 Grade LC1Low temperature to -75°F (-59°C). Use excluded above +650°F (+340°C).
    Low-temperature Carbon SteelASTM A352 Grade LC2Low temperature to -100°F (-73°C). Use excluded above +650°F (+340°C).
    3.1/2% Nickel SteelASTM A352 Grade LC3Low temperature to -150°F (-101°C). Use excluded above +650°F (+340°C).
    1.1/4% Chrome 1/2% Moly SteelASTM A217 Grade WC6Non-corrosive fluids such as water, oil&gases at temperatures range -20°F (-30°C) and +1100°F (+593°C).
    2.1/4% ChromeASTM A217 Grade C9Non-corrosive fluids such as water, oil&gases at temperatures range -20°F (-30°C) and +1100°F (+593°C).
    5% Chrome 1/2% MolyASTM A217 Grade C5Mild corrosive or erosive applications and non-corrosive applications at temperatures between -20°F (-30°C) and +1200°F (+649°C).
    9%ChromeASTM A217 Grade C12Mild corrosive or erosive applications and non-corrosive applications at temperatures between -20°F (-30°C) and +1200°F (+649°C).
    1% Moly
    12% Chrome SteelASTM A487 Grade CA6NMCorrosive application at temperatures between -20°F (-30°C) and +900°F (+482°C).
    12% ChromeASTM A217 Grade CA15Corrosive application at temperatures up to +1300°F (+704°C)
    Stainless steel 316ASTM A351 Grade CF8MCorrosive or either extremely low or high-temperature non-corrosive services between -450°F (-268°C) and +1200°F (+649°C). Above +800°F (+425°C) specify carbon content of 0.04% or greater.
    Stainless steel 347ASTM 351 Grade CF8CMainly for high temperature, corrosive applications between -450°F (-268°C) and +1200°F (+649°C). Above +1000°F (+540°C) specify carbon content of 0.04% or greater.
    Stainless steel 304ASTM A351 Grade CF8Corrosive or extremely high temperatures non-corrosive services between -450°F (-268°C) and +1200°F (+649°C). Above +800°F (+425°C) specify carbon content of 0.04% or greater.
    Stainless steel 304LASTM A351 Grade CF3Corrosive or non-corrosive services to +800F (+425°C).
    Stainless steel 316LASTM A351 Grade CF3MCorrosive or non-corrosive services to +800F (+425°C).
    Alloy-20ASTM A351 Grade CN7MGood resistance to hot sulfuric acid to +800F (+425°C).
    MonelASTM 743 Grade M3-35-1Weldable grade. Good resistance to corrosion by all common organic acids and salt water. Also highly resistant to most alkaline solutions to +750°F (+400°C).
    Hastelloy BASTM A743 Grade N-12MWell suited for handling hydrofluoric acid at all concentrations and temperatures. Good resistance to sulphuric and phosphoric acids to +1200°F (+649°C).
    Hastelloy CASTM A743 Grade CW-12MGood resistance to span oxidation conditions. Good properties at high temperatures. Good resistance to sulphuric and phosphoric acids to +1200°F (+649°C).
    InconelASTM A743 Grade CY-40Very good for high-temperature service. Good resistance to spangly corrosive media and atmosphere to +800°F (+425°C).
    BronzeASTM B62Water, oil&gas: up to 400°F. Excellent for brine and seawater service.

    Why Austenitic Stainless Steels Used for Industrial Valves

    Austenitic stainless steel is commonly used in the manufacturing of a variety of industrial valves due to its excellent mechanical properties, corrosion resistance, and versatility. Here are some types of industrial valves typically made of austenitic stainless steel and their common applications:

    Ball Valves

    Made from austenitic stainless steel for its durability and corrosion resistance. They are often used in applications where a tight shut-off is required, such as in oil and gas production, petrochemicals, and certain high-pressure industrial applications.

    Austenitic Stainless Steel Gate Valves

    These are often made from austenitic stainless steel when they need to be resistant to corrosive environments. Gate valves are primarily used in wastewater and other abrasive fluid applications.

    Globe Valves

    Made from austenitic stainless steel when high resistance to flow is needed and corrosive conditions are present. These valves are often used in throttling applications, particularly in the food and beverage industry, the chemical industry, and steam systems.

    Check Valves

    Austenitic stainless steel is used to check valves in systems where backflow prevention is needed in a corrosive environment. They are commonly used in water systems, chemical processing, and marine applications.

    Butterfly Valves

    Often made from austenitic stainless steel for systems requiring the regulation of large flow rates in a limited space, and where high corrosion resistance is needed. They’re frequently found in water supply systems, food and beverage, and chemical processing industries.

    Plug Valves

    Made from austenitic stainless steel when there is a need for minimal fluid trapping in corrosive applications. They’re often used in the oil and gas industry.

    Diaphragm Valves

    These are often made of austenitic stainless steel and are used in applications requiring a sterile environment, such as pharmaceuticals, food and beverage, and biotechnological industries.

    The main reason to use austenitic stainless steel in these valves is the material’s excellent corrosion resistance, good formability, and high-temperature performance. These properties make austenitic stainless steel a good choice for valves used in demanding environments like chemical processing plants, oil and gas refineries, power generation facilities, and numerous other industries.

    THINKTANK is a professional manufacturer of austenitic stainless steel valves and alloy stainless steel valves. If you have any questions, feel free to inquire at any time.

    Picture of Will Don

    Will Don

    After earning my bachelor's degree in mechanical engineering from Zhejiang Normal University in 2008, l was fortunate enough to begin my career with Siemens, Fisher, and YTC, focusing on control valve accessories. Over the past dozen years, l've poured my heart and energy into understanding technology and fluid solutions for control valves.
    Now, as the marketing director for THINKTANK, a trusted branch of the Taiwan STONE valve group, I can't help butf eel proud of how far we've come. Our knowledge isn't just reaching professionals like engineer and valve distributors; it's also inspiring the next generation of automation college students.
    l genuinely hope you're enjoying our articles and finding them helpful.Your thoughts, questions, and feedback mean the world to me, so please don't hesitate to reach out to marketing[at] Whether you're a seasoned expert or just curious about the field, I'm here to connect, share, and learn together.

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    I am the author of this article, and also the CEO and marketing director of THINKTANK, with 15 years of experience in the industrial valve industry. If you have any questions, you can contact me at any time.

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