One of the most important decisions any manufacturer must make is determining the best material for a given application. Many years ago, choosing between steel and aluminum, for example, might have been relatively simple. However, with the increasing diversity of metal alloys, modern-day materials have an ever-expanding list of very specific properties available. It makes selecting the right stainless steel more difficult than ever.
304 and 316 stainless steel alloys are two of the most popular and versatile stainless steel alloys. Anyone who works with stainless steel must understand the differences between these two industry workhorses to know which applications they are best suited for.
What are the main characteristics of 304 stainless steel?
SAE 304 stainless steel is the most commonly used stainless steel alloy today. It, too, is an austenitic stainless steel, which means it is a metallic, iron allotrope. It is not as conductive as carbon steel, both electrically and thermally, and it is not magnetic.
The most important property of stainless steel is its corrosion-resistant stainless steel alloys, 304 alloys provide excellent resistance in a wide range of atmospheric environments. However, in chloride environments, it is prone to pitting and crevice corrosion. At temperatures above 60 °C, there is also a problem with stress corrosion cracking. The main difference between it and 316 stainless steel is that seawater, in particular, can hurt the metal’s longevity.
304 stainless steel is also well-known for its machinability and formability. This alloy is suitable for stamping applications such as sinks and saucepans. Due to its low yield strength and high elongation, 304 can be easily formed into a variety of complex shapes.
Making it even more cost-effective, the metal hardens quickly after shaping and can be air-cooled. Another advantage is that after forming, stress relief annealing can be performed for additional improvements.
304L stainless steel is also very weldable, making it an excellent choice for commercial welding applications. Fusion and resistance welding are examples of this. It is important to note that uniform temperatures are required when forming 304 stainless steel, which is typically between 2300 °F and 1700 °F.
Aside from corrosion resistance, the property most responsible for 304’s popularity is its versatility. 304 stainless steel is currently used in a wide variety of applications. There is almost no industry that does not have numerous examples of 304. When dealing with stress relieving or welding, most comparable materials experience intergranular corrosion, but this is not the case with 304L. Although this alloy cannot be heat treated, it can be hardened and strengthened through a cold working process.
What are the main characteristics of 316 stainless steel?
SAE 316 grade stainless steel is the second most common in commercial use today, after SAE 304. The addition of approximately 2 to 3 percent molybdenum to austenitic stainless steel, which, like 304, contains significant amounts of chromium and nickel, is the key difference in its molecular makeup.
Because of the addition of molybdenum, it is more corrosion resistant than 304. It is much more resistant to the negative effects of chloride exposure and can even withstand general corrosion from sulfuric acid and the like. As a result, 316 has become a preferred material in the chemical and petrochemical industries, as well as pharmaceuticals and food processing. It’s also popular for wastewater treatment plants and any marine application or architectural structure that’s close to the water.
When comparing the two materials visually, it is nearly impossible to discern any differences. The only way to know for sure is to conduct a material test report that analyses the chemical composition of the alloy. That is how comparable these two grades are.
There is one more significant difference between the two materials: price. Because of the higher nickel and molybdenum content, 316 is significantly more expensive. For most applications, the cost difference is insignificant because 304 performs equally well. However, for applications that will be exposed to chloride, such as marine structures, the price difference is fully justified because the increased longevity will more than pay for itself.
What are the best applications for 316 and 304 stainless steel alloys?
As previously stated, the two most common stainless steel alloys on the market today are 304 and 316. 304 can be found in a wide range of applications across many industries. Refrigerators and dishwashers, food processing equipment, pipes, heat exchangers, machinery parts, automobile headers, architecture, and vaporizers are all examples of this.
Because of its higher cost, 316 is almost exclusively used in applications that require increased corrosion resistance. Chemical processing and storage equipment, petrochemical refinery equipment, medical devices, and structures and buildings found in or near marine environments are all examples.
Whatever material you choose; you can be confident that you will benefit from stainless steel’s many appealing properties in addition to its corrosion resistance. There is a stainless steel alloy that is ideal for your job, whether it is for its aesthetic appearance, durability, strength, or ease of fabrication.
