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What is the difference between 316 and 904 grade flue liner??

Both 316L and 904L are grades of stainless steel that offer different properties and characteristics. Here's a comparison between 316L and 904L grade stainless steel:

316L Stainless Steel:

  1. Composition: 316L is an austenitic stainless steel that contains around 16-18% chromium, 10-14% nickel, and 2-3% molybdenum. The addition of molybdenum enhances its corrosion resistance, especially in chloride-rich environments.

  2. Corrosion Resistance: 316L stainless steel is known for its excellent corrosion resistance, making it suitable for a wide range of applications, including marine environments and exposure to various chemicals. It performs well in most non-extreme conditions.

  3. Common Applications: 316L is commonly used in industries like marine, chemical processing, food and beverage, pharmaceuticals, and medical devices. It's also widely used for architectural purposes due to its aesthetic appearance.

  4. Machinability and Formability: 316L offers good machinability and formability, making it relatively easy to work with for various fabrication processes.

904L Stainless Steel:

  1. Composition: 904L is a high-alloy austenitic stainless steel with higher levels of chromium, nickel, and molybdenum compared to 316L. It typically contains around 19-23% chromium, 23-28% nickel, 4-5% molybdenum, and small amounts of copper.

  2. Corrosion Resistance: 904L stainless steel is known for its exceptional corrosion resistance, especially in harsh environments containing sulfuric acid and other aggressive acids. It's used in applications where corrosion resistance is critical.

  3. Common Applications: 904L is often used in industries like chemical processing, petrochemical, pharmaceuticals, and oil and gas. It's particularly valued in applications involving sulfuric acid, such as in equipment for acid production and handling.

  4. Machinability and Formability: 904L is more difficult to machine and form compared to standard austenitic stainless steels like 316L. Its higher alloy content can lead to reduced machinability and increased tool wear.

Key Differences:

  1. Corrosion Resistance: While both grades offer good corrosion resistance, 904L stands out for its exceptional resistance to specific aggressive environments, particularly containing sulfuric acid.

  2. Alloy Composition: 904L contains higher levels of chromium, nickel, molybdenum, and additional elements like copper, contributing to its enhanced corrosion resistance.

  3. Applications: 316L is more commonly used in a wide range of applications, while 904L is chosen for specialized applications requiring extreme corrosion resistance, especially in aggressive chemical environments.

  4. Machinability and Formability: 316L is generally easier to machine and form compared to 904L.

In summary, the choice between 316L and 904L stainless steel depends on the specific requirements of your application, with 904L being chosen for its superior corrosion resistance in highly aggressive environments.

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