Difference Between Grade 304 SS vs 304l SS

 Introduction:

In the modern world, stainless steel is ubiquitous, being used in everything from kitchen appliances to industrial machinery. One of the most common grades of Stainless steel 304, as well as its low-carbon variant, 304L. These two grades are similar, but they differ in subtle but crucial ways that make them suitable for varying applications. To understand the disparities and respective strengths of Grades 304 SS vs 304L SS, let’s examine their specifications.

The Foundation: Grade 304 Stainless Steel:

A stainless steel alloy containing chromium and nickel, 304 Stainless steel is an austenitic stainless steel. Due to its composition, it is highly corrosion and oxidation-resistant in various environments because it consists of 18% chromium and 8% nickel. Despite its versatility, this alloy is widely used in a range of industries, including architecture and food processing.

Properties of 304 Stainless Steel Grade:

Corrosion Resistance: Grade 304 stainless steel exhibits excellent corrosion resistance, particularly in mildly corrosive environments such as air and freshwater.

Strength and Durability: With its robust composition, Grade 304 exhibits commendable strength and durability, so it can be used in structural applications.

Ease of Fabrication: Manufacturers prefer SS 304 for its malleability and ease of fabrication, which allows for diverse shaping and forming processes.

Temperature Resistance: Grade 304 is a good corrosion-resistant stainless steel that is resistant to high temperatures. However, prolonged exposure to high temperatures can cause it to become sensitized, which reduces its resistance to corrosion.

The Evolution: Grade 304L Stainless Steel:

The
stainless steel 304L, often called Grade “L” because of its low carbon content, is a variation of Grade 304. The ‘L’ signifies a maximum carbon content of 0.03%, which minimizes the risk of sensitization and subsequent corrosion problems. With this variant, corrosion resistance is similar to Grade 304, but some limitations have been addressed, particularly in welding applications.

Grade 304L Stainless Steel Properties:

Reduced Sensitization: Grade 304L has a low carbon content that mitigates sensitization, the precipitation of chromium carbide at grain boundaries, which compromises corrosion resistance.

Weldability: Grade 304L has improved weldability over Grade 304 since it is less prone to carbide precipitation during welding.

Corrosion Resistance: Even though Grade 304L SS offers comparable corrosion resistance to Grade 304, it offers an advantage in environments with frequent welding and high temperatures.

Choosing Between Grades 304 and 304L:

When choosing between SS 304 vs 304L, attention should be paid to the specific requirements of the application. To assist in the decision-making process, consider the following:

Welding Requirements: Due to its reduced sensitization and improved weldability, Grade 304L is preferred for applications requiring welding. By ensuring structural integrity, it minimizes the risk of weld decay.

Corrosive Environment: The corrosion resistance of SS 304 vs 304L is commendable in environments where corrosion is a significant concern. The SS 304L may, however, provide additional assurance against sensitization-related issues if the application exposes it to corrosive agents or elevated temperatures frequently.

Cost Considerations: Since Grade 304L stainless steel has a specialized composition, it may cost a little more than Grade 304 stainless steel. It is essential to evaluate budgetary constraints along with performance requirements.

304 Stainless Steel Chemical Compositions:

Element % Present

Carbon (C) 0.07

Chromium (Cr) 17.50 – 19.50

Manganese (Mn) 2.00

Silicon (Si) 1.00

Phosphorous (P) 0.045

Sulphur (S) 0.015b)

Nickel (Ni) 8.00 – 10.50

Nitrogen (N) 0.10

Iron (Fe) Balance

304 Stainless Steel Mechanical properties:

Property Value

Comprehensive Strength 210 MPa

Proof Stress 210 Min MPa

Tensile Strength 520 – 720 MPa

Elongation 45 Min%

304 Stainless Steel Physical Properties:

Property Value

Density 8,000 Kg/m3

Melting Point 1450 °C

Thermal Expansion 17.2 x 10-6 /K

Modulus of Elasticity 193 GPa

Thermal Conductivity 16.2W/m.K

Electrical Resistivity 0.072 x 10-6 Ω .m

 

Conclusion:

There are many difference between 304 and Grade 304L stainless steel, but their subtle differences determine their suitability for various applications. Because of its low carbon content, Grade 304L is a preferred choice for welding and high-temperature environments. However, Grade 304 remains a versatile and widely used stainless steel grade, particularly where welding is not a primary concern. Having a clear understanding of these disparities allows engineers, designers, and manufacturers to make informed decisions, ensuring that their applications will perform optimally and last for a long time.