The chemical composition of AISI304 and AISI304L
AISI304 and AISI304L are two stainless steel grades that are commonly used in the manufacturing of metallic products. As grades of stainless steel, they are both relatively low-cost and highly sturdy when fabricated correctly. AISI304 is a standard, low carb stainless steel and AISI304L is an ultra-low carb version of the same grade of steel.
The two steel grades differ primarily in their carbon content. AISI304 contains up to 0.08% carbon and AISI304L contains a maximum of 0.03% carbon. Although containing less carbon, AISI304L does contain higher levels of some other elements in comparison to AISI304. These elevated levels of elements such as manganese and nickel increase the ductility and sensitivity of the material. This means that AISI304L is suitable for use where higher stress levels are expected.
In terms of corrosion resistance, both grades are martensitic stainless steels with good corrosion resistance, however AISI304L has higher corrosion resistance due to its lower carbon content. Both steels can be utilised in environments where they can expect to be exposed to a range of organic and inorganic acids and are both approved for use in food processing.
The melting range of AISI304 and AISI304L have similar melting points, with AISI304 melting at a range of 1454 to 1516°C and AISI304L melting at 1453 to 1474°C. Both grades of steel can be manipulated using a range of processes due to their relatively low melting points, including weldability and machinability.
The table below summarises the chemical composition and mechanical properties of AISI304 and AISI304L grades of stainless steel.
Chemical Composition (wt %)
AISI304 AISI304L
Carbon (C) 0.08 max 0.03 max
Manganese (Mn) 2.00 2.0
Phosphorus (P) 0.045 0.045
Sulphur (S) 0.03
Silicon (Si) 1.0
Chromium (Cr) 18.00 19.00
Nickel (Ni) 10.0
Mechanical Properties
AISI304 AISI304L
Tensile strength 515 MPa 485 MPa
Yield strength 205 MPa 170 MPa
Elongation 40 % 40 %
Both AISI304 and AISI304L are cost-effective materials that can be used in a variety of applications. Due to their low carbon content, both steels have very low carbon levels which eliminate the risk of carbide precipitation and provides an excellent resistance to intergranular corrosion. Additionally, both grades are readily weldable and have good cold formability. AISI304’s superior tensile and yield strengths make it more suitable for use in applications subject to higher stress levels, whereas AISI 304L offers the same mechanical properties but with higher corrosion resistance. Ultimately, the choice of steel grade will be dictated by the properties of the application.
