304 Vs 304L Stainless Steel - What Is The Difference
Despite the wide range of grades and types of stainless steel available on the market, they all share two common properties: great strength and corrosion resistance. These qualities come in varying degrees in each stainless steel grade.
Stainless steel generally has superior corrosion resistance, ductility, tensile strength, and both higher cryogenic and heat toughness material qualities as compared to normal steel. The 3xx group of stainless steel, also known as the chromium-nickel group, is known for its toughness, ease of maintenance, corrosion resistance, and non-magnetic properties.
The most popular alloy in this series is grade SAE 304 stainless steel. In this article, we’ll cover the differences between the 304 stainless steel type and its low-carbon variant, stainless steel type 304L.
What is SAE 304 Stainless Steel?
As previously stated, the SAE 304 stainless steel is the most versatile and widely used stainless steel alloy across various industries due to its fantastic mechanical and physical properties, good formability, and excellent weldability among steels.
It’s mostly comprised of 0.08% carbon, 18-20% chromium, and 8-10% nickel, which is why it’s also known as 18/8 stainless steel. This low-carbon austenitic stainless steel also contains traces of manganese, silicon, phosphorous, and sulfur, but those are typically smaller than 1%. The rest of the alloy is balanced out by weight with iron.
What is SAE 304L Stainless Steel?
The SAE 304 stainless steel is a low-carbon version of SAE 304 stainless steel, which offers some advantages over the base alloy in terms of weldability. It contains chromium and nickel in the same proportions as the base SAE 304 alloy. However, the carbon content is significantly lower, topping out at 0.03% by weight. The rest of the alloy is balanced out with iron.
SAE 304 vs SAE 304L: What are the Differences?
As we already know, even the subtlest of differences in the chemical makeup of an alloy can significantly alter the material's properties. For example, the added 2% molybdenum in SAE 316L makes the steel more resistant to corrosion in acidic environments. Here are the basic differences between SAE 304 and SAE 304L.
Chemical Composition
As previously said, the only difference between the two alloys is the lower carbon content associated with SAE 304L (in which L actually denotes low carbon). Both alloys still contain the same amounts of chromium, nickel, and other trace elements.
The decreased carbon concentration of 304L reduces damaging or dangerous chromium carbide precipitation during welding. Therefore, grade 304L does not require annealing or any other heat treatment and can be used "as welded" in corrosive environments that would otherwise cause intergranular corrosion.
Similar to Type 304 stainless steel, it is frequently employed in the production of beer brewing and wine-making, as well as for non-food applications such as chemical storage, mining, and construction.
Corrosion Resistance
Both 304 and 304L alloys have exhibited uniform corrosion resistance in most corrosive environments, though 304L showed a lower corrosion resistance in severely corrosive environments.
Mechanical Properties
Due to lower carbon content, SAE 304L has a lower tensile strength of 85 KSI compared to SAE 304, which is approx 90 KSI. Additionally, the yield strength of SAE 304L is approx. 35 KSI, while SAE 304 offers 42 KSI.
From this, we can conclude that the 304L offers less in terms of tensile and yield strength, despite their comparable densities.
Welding Properties
Due to its lower carbon content, alloy 304L is marginally easier to weld, but its primary advantage is lesser carbide precipitation, which results in lower corrosion at grain boundaries.
Choosing Between SAE 304 and 304L
In summary, the differences between SAE 304 and SAE 304L are subtle, as they only differ in carbon content. In practice, both 304 and 304L can be used for many of the same applications. If you want to learn more about various grades of stainless steel, visit our Engineer Resource Guides or find specific stainless steel products by browsing our online catalogs.