We all know that 304 and 316 are the most popular and widely used investment casting types in a stainless steel foundry. From the naked eye, it can be extremely difficult to tell the difference between them. But when selecting 304 or 316 stainless steel for casting, we have to understand the differences between these two stainless steel types.
Grade 304 stainless steel is generally regarded as the most common austenitic stainless steel casting type. It contains high nickel content that is typically between 8 and 10.5 percent by weight and a high amount of chromium at approximately 18 to 20 percent by weight. Other major alloying elements include manganese, silicon, and carbon. The remainder of the chemical composition is primarily iron.
For the high amounts of chromium and nickel, 304 stainless steel castings have excellent corrosion resistance. Common applications of 304 stainless steel castings include:
Same as 304 stainless steel, Grade 316 stainless steel has high amounts of chromium and nickel. Besides, silicon, manganese, and carbon, with the majority of the composition being iron, are also included in 316 stainless steel. The major difference between 304 and 316 stainless steel is that 316 containing a significant amount of molybdenum, which is lacked in 304. The added molybdenum content in 316 stainless steel results in an increased corrosion resistance, that is why 316 stainless steel castings are more corrosion resistant than 304 stainless steel castings.
316 stainless steel is often considered one of the most suitable choices when selecting a suitable stainless steel casting grade for marine applications. Typical applications of 316 stainless steel castings include:
- Chemical processing equipment components
- Medical device components
- Marine hardwares
- And so on
Difference Between 304 and 316 Stainless Steel Casting
The most basic difference between 304 stainless steel casting and 316 stainless steel casting is that 316 stainless steel casting contains more nickel and a bit of molybdenum element. The general mechanical properties of the two metals are mostly comparable.
The increased nickel content and the inclusion of molybdenum in 316 stainless steel shows better chemical resistance than 304 stainless steel. This difference makes 316 stainless steel resist acids and chlorides, including salt, thus 316 stainless steel castings are ideal for chemical processing and marine applications.
However, the increased nickel and added molybdenum also makes 316 stainless steel castings more expensive than 304 stainless steel castings
Additionally, when casting 304 stainless steel, the melting point is a bit higher than that of casting 316 stainless steel. The melting range of 316 stainless steel casting is 2,500 °F – 2,550 °F (1,371 °C – 1,399 °C), roughly 50 to 100 degrees Fahrenheit lower than the melting point of 304 stainless steel casting.
Though the 304 stainless steel casting has a higher melting point, 316 stainless stee casting has a better resistance to chemicals and chlorides (like salt) than 304 stainless steel casting. When it comes to applications with chlorinated solutions or exposure to salt, 316 stainless steel castings are considered superior.
Tips on Selecting 304 or 316 Stainless Steel Casting
Even if understanding the difference between 304 and 316 stainles steel casting, buyer or designer may still doubt whether to select 304 or 316 stainless steel as the casting material. If the stainless steel casting part works with a very powerful corrosives or relies on chlorides, then 316 stainless steel casting is definitely worth it. In such woking environment, 316 stainless steel castings will last longer than 304 stainless steel castings.
However, for applications using milder acids or where salt exposure isn’t a concern, selecting 304 stainless steel castings is also workable.
Just be sure you are familar with the application, working environment and other related factors when choosing a stainless steel casting material for your industrial parts. For example, if you have limited budget, and the part is only for decorative purpose, then 304 stainless steel casting is enough. But if the part will work in salty sea environment, then 316 stainless steel casting is suggested. Overall, 316 can be worth the expense if you need to have superior corrosion resistance. For many other applications, grade 304 stainless steel will serve perfectly fine.
CFS Foundry has rich experience in both 304 stainless steel casting and 316 stainless steel casting. Our advanced investment casting process can guarantee better size accuracy and surface finish than other companies. Looking for a good stainless steel casting company for your project? Pls send us your drawings or samples for a free quoting!