Stainless Steel-304L

Stainless Steel Material Properties
Though there are numerous grades and varieties of stainless steel out there on the market, they share similar properties of corrosion resistance and high strength. Each grade has varying degrees of these properties. When compared to standard steel, stainless steel material properties generally translate into higher corrosion resistance, higher ductility, higher tensile strength, and both higher cryogenic and heat toughness.

These admirable properties of stainless steel make it well suited for multiple applications across a variety of different industries. However, each stainless steel grade has its own unique degree of these properties which makes them suited for different applications.

The 300 series of stainless steel is classified as austenitic steel and is especially recognized for its hardiness, easy maintenance, and strong corrosion resistant abilities. With these advantageous material properties, the 300 series is used for a wide variety of applications. Predominantly, the 300 series is used in the automotive, construction, and aerospace industries. Grade 304 is the most widely used alloy of this series.

Stainless Steel Mechanical Properties and Differences
The other key differences between grade 304 and its variant, grade 304L, are between their mechanical properties. Grade 304L has a slight, but noticeable, reduction in key mechanical performance characteristics compared to the “standard” grade 304 stainless steel alloy.

For example, the ultimate tensile strength (UTS) of 304L is roughly 85 ksi (~586 MPa), less than the UTS of standard grade 304 stainless, which is 90 ksi (~620 MPa). The difference in yield strength is slightly greater, with 304 SS having a 0.2% yield strength of 42 ksi (~289 MPa) and 304L having a 0.2% yield strength of 35 ksi (~241 MPa).

This means that if you had two steel wire baskets and both baskets had the exact same design, wire thickness, and construction, the basket made from 304L would be structurally weaker than the standard 304 basket.

However, the density of 304 stainless steel is the same as 304L.

Why Would You Want to Use 304L, Then?
So, if 304L is weaker than standard 304 stainless steel, why would anyone want to use it?

The answer is that the 304L alloy’s lower carbon content helps minimize/eliminate carbide precipitation during the welding process. This allows 304L stainless steel to be used in the “as-welded” state, even in severely corrosive environments.

If you were to use standard 304 stainless in the same way, it would degrade much faster at the weld joints.

Basically, using 304L eliminates the need to anneal weld joints prior to using the completed metal form—saving time and effort.

In practice, both 304 and 304L can be used for many of the same applications. The differences are often minor enough that one isn’t considered massively more useful over the other. When stronger corrosion resistance is needed, other alloys, such as grade 316 stainless steel, are usually considered as an alternative.