Since the time stainless steel was invented, it has been used widely everywhere – home, offices, and industries. Due to its durability, weldability, appearance, and performance, it is commonly used everywhere. Stainless steel is constructed using various composition or carbon and metal, which categorizes it into the following types –
•Austenitic stainless steel
•Duplex stainless steel
•Ferritic stainless steel
•Martensitic stainless steel
•Precipitation-hardening stainless steel
To a normal consumer, the grades of stainless steel would not matter that much. But to a manufacturer, differences between different grades of steel, such as 304 and 316 can be huge. Stainless steel is a member of the iron-based alloys family that contains at least 11% chromium, which prevents iron from rusting and gives heat-resistant properties.
316 Stainless Steel
316 stainless steel is a commonly used alloy with the melting range of 1371-1399C. It is austenitic stainless steel so it has qualities like corrosion resistance, high strength, and high concentrations of nickel and chromium. The tensile strength of 316 stainless steel of 579 MPa and the maximum use temperature of almost 800C. This alloy has added molybdenum in the formulation, which enhances its resistance to alkalis, chloride pitting, and acids.
Out of 304 and 316 Stainless Steel Pipe Tube and other equipment, it is difficult to pick out which one is used the most. Additionally, due to their mechanical and physical properties, you cannot distinguish the two with naked eyes. The main point of difference is in the material composition of 316 stainless steel –
•10% nickel
•2% molybdenum
•16% chromium
The inclusion of molybdenum and increased nickel content makes 316 stainless steel alloy comparatively pricier than 304 one. But 316 grade is better in the sense that it provides better corrosion resistance specifically against chlorinated solutions and chlorides. So, in applications where exposure to powerful corrosives and salt is an issue, 316 stainless steel is desirable.
Applications of 316 stainless steel are –
•Medical-surgical instruments
•Chemical equipment
•Pharmaceutical equipment
•Marine parts
•Stainless steel baskets
•Outdoor electrical closures
304 Stainless Steel
304 stainless steel is known for its durability in terms of strength, corrosion and oxidation resistance, and high melting point (1399C-1454C). However, as 304 stainless steel reaches the melting point, its tensile strength decreases. Grade 304 is specifically exceptional for its robust tensile strength of almost 621 MPa. The maximum operating temperature of 304 stainless steel alloy is almost approximately 870C.
304 stainless steel is amongst the most common stainless steel grades used due to its excellent corrosion resistance as it has a high amount of chromium. Its chemical composition contains –
•8% nickel
•18% chromium
•At times, a small percentage of manganese and carbon
These elements made 304 stainless steel resistant to oxidation. So, it is easy to clean and sanitize. Some of the common applications of 304 stainless steel are –
•Wheel covers
•Auto moldings and trim
•Electrical enclosures
•Kitchen appliances and equipment
•Storage tanks
However, it is susceptible to pitting, areas of corrosion because of exposure to saline environments, or high chloride solutions.
Difference Between 316, 304 Stainless Steel
The primary difference between the two is that the 316 stainless steel category has more nickel and a small percentage of molybdenum in the mix. The usual mechanical properties of 316 and 304 stain steel metals are similar.
Due to the inclusion of molybdenum and increased nickel content, 316 grade has better chemical resistance as compared to 304 stainless steel. It can resist chlorides, acids, and salts, which makes 316 stainless steel ideal for marine and chemical processing applications.
However, due to the addition of molybdenum and nickel, 316 stainless steel tends to be more expensive. Additionally, the 304 grade’s melting point is higher than 316 grade by up to 100 degrees Celsius. Although 304 grade has a higher melting point, 316 grade has better resistance to chlorides and chemicals than 304 stainless steel.
Moreover, due to the molybdenum’s addition, pitting from chemical environments is reduced and allows 316 grade to be used in caustic and highly acidic environments that would otherwise eat the metal. So, 316 can withstand corrosive applications and caustic solutions like vapor degreasing and other cleaning processes. This is why this grade is more suitable for medical and pharmaceutical applications. Since sterilization processes combine both high temperatures and strong disinfectants to prevent contamination, 316 stainless steel is ideal.
Apart from that, salt eats away the protective oxide covering in 304 stainless steel. Salt air and seawater can damage most of the metals. So, for marine applications, 316 stainless steel is more suitable as it is more resistant to chloride pitting and salt.
Conclusion
All of these factors make 316 stainless steel more versatile and tough, specifically for pipes and tubes. The overall bill could cost you more but you will save immensely on replacing them or repairing them. However, if the application of stainless steel does not require resistance against salt, acids, and harsh chemicals, you can go for 304 stainless steel.
