Stainless steel is widely employed in various applications due to its remarkable corrosion resistance. Among the different types of stainless steel, 304L and AISI 321 are two particularly popular alloys, each characterized by distinct specifications. Stainless steel 304L is also referred to 1.4307 and AISI 321 is an equivalent 1.4541 (even though technically they are not exactly the same materials due to minor differences in European and respectively American norms).

Below, we will explore the key differences between this two stainless steel grades.

General Differences:

Alloys_Macro

The differences between these two stainless steel grades are based on the precipitation of carbides, closely related to the carbon concentration in the alloy. A higher carbon concentration increases the tendency of carbides to precipitate, especially at specific temperatures, making the material more susceptible to intergranular corrosion. Starting with AISI 304, which has a carbon concentration of 0.07%, to mitigate this issue, the initial strategy is to lower the carbon concentration, as in the case of 304L (maximum 0.03% carbon), which has shown significant benefits in this context. However, reducing the carbon content may not always be sufficient and could lead to a decrease in mechanical properties, especially at elevated temperatures. In some cases, it is preferable to keep the original carbon concentration unchanged, as in the case of 321, which has a maximum of 0.08% carbon, and introduce other elements, such as titanium. These elements form carbides with carbon instead of chromium, thus preserving the material’s corrosion resistance.

Chemical Composition of 304L Stainless Steel:

Stainless steel 304L is an austenitic alloy with the following chemical composition according to ASTM A 240:

  • Carbon: 0.030
  • Manganese: 2.00
  • Phosphorus: 0.045
  • Sulfur: 0.030
  • Silicon: 1.00
  • Chromium: 18.0–20.0
  • Nickel: 8.0–12.0

The component percentages may vary slightly depending on production standards and manufacturer specifications. The “L” in 304L indicates a low carbon content, reducing susceptibility to intergranular corrosion and making this alloy suitable for a wide range of applications, especially in corrosive environments.

Chemical Composition of AISI 321 Stainless Steel:

AISI 321 stainless steel is an austenitic alloy with the following chemical composition according to ASTM A 240:

  • Carbon: 0.08
  • Manganese: 2.00
  • Phosphorus: 0.045
  • Sulfur: 0.030
  • Silicon: 1.00
  • Chromium: 17.0–19.0
  • Nickel: 9.0–12.0
  • Titanium: 5×(C+N)-0.70

Titanium is a key element in 321 stainless steel, contributing to increase resistance to intergranular corrosion at high temperatures. This alloy is commonly used in applications requiring resistance to high temperatures and corrosion, such as automotive exhaust systems and boiler components. Specifications may vary slightly based on production standards and manufacturer specifications.

Applications of 304L Stainless Steel:

Stainless steel 304L is widely utilized across various industries due to its excellent anti-corrosive properties and corrosion resistance. It plays a crucial role in the manufacturing of equipment for the food industry, chemical storage tanks, and medical devices. Its ability to withstand the corrosive environments of chemical and food industries makes it an ideal choice for pipelines, heat exchangers, and containers for liquid processing. Moreover, stainless steel 304L is frequently employed in architectural applications due to its durability and aesthetic appeal.

Applications of AISI 321 Stainless Steel:

coke-ovens-profile

The most requested profiles in this grade of steel are primarily angular or U-shaped, while structural beams are required for external structures. This type of steel finds use in high-temperature environments, where ensuring high resistance to thermal corrosion is essential.

coke-oven

One of the various applications fields in which Montanstahl specializes with AISI 321 alloy, producing customized profiles, is in the construction of doors used, for example, in coke ovens. These profiles, subjected to careful cutting and welding processes, are key components in the construction of the strong support structures needed for the doors. These profiles, subjected to careful cutting and welding processes, constitute fundamental components in the construction of robust support structures required for doors. Their strength is crucial, as they must withstand significant thermal stresses resulting from prolonged exposure to high temperatures, considering the thermal expansion of the furnace body.
In another context, in the medical sector Montanstahl produces profiles in W1.4541 (AISI 321 with controlled sulfur content) for manufacturing machinery. These profiles are used as components for machines dedicated to the sterilization of medical instruments, mainly configured as “L” profiles and subject to high pressure. In compliance with the European Pressure Equipment Directive (PED), clearly indicate which types of steel are acceptable, with 321 standing out as one of the most suitable.

Montanstahl and fast shipping:

While both stainless steels 304L and 321 are austenitic and offer corrosion resistance, 321 is particularly suitable for high-temperature and pressure applications. Montanstahl offers the possibility of fast delivery on even thicknesses, as we have the raw material ready to be processed using any production technology. Contact us for more information!

stainless-steel-coils