Stainless Steel is a big family and widely used metal material, there are various grades in this group, and these grades have special chemical compositions and properties to suit various applications, two of them are remarkable grades, namely, 304 stainless steel and 316 stainless steel, the most stainless steel grades are used all over the world.
304 stainless steel and 316 stainless steel are austenitic (a type of stainless steel) stainless steel, the difference between the two in the chemical composition is: that 316 stainless steel lowers the chromium (Cr) content to improve the nickel (Ni), and increases by 2%-3% of the molybdenum (Mo), the structural organization of the stainless steel greatly improves the corrosion resistance and abrasion resistance, so 316 stainless steel has better performance than 304 stainless steel. 304 stainless steel density is 7.93g/㎝, 316 stainless steel density is 7.98g/㎝, and 316 stainless steel is higher than 304 stainless steel. 316 stainless steel has better heat resistance than 304 stainless steel in addition to better abrasion resistance and corrosion resistance because the carbide formed by the molybdenum (Mo) element in 316 stainless steel is extremely stable, and it can prevent the austenite from melting when heated. Stop the austenite heating grain growth, and reduce the steel overheating sensitivity. 304 stainless steel acid, alkali, high density, polished without bubbles, high toughness, good processing performance, 316 stainless steel In addition to 304 stainless steel performance characteristics, but also resistant to corrosion of special media, you can enhance the chemical hydrochloric acid and the ocean’s corrosion resistance, to enhance the corrosion resistance of brine halogen solution. 316 stainless steel has added molybdenum and nickel, while 304 stainless steel is not, thus 316 stainless steel price will be a little higher than the price of 304.
304 Stainless Steel
304 stainless steel contains 18% chromium, 8% nickel, and other major alloying elements including small amounts of manganese, silicon and carbon, it is a typical 18/8 austenitic stainless steel grade, overall 304 presents excellent properties to meet many cases making it the most popular grade.
What makes 304 so popular?
- Resistant to oxidation, corrosion and durability
- Excellent formability, fabrication and welding characteristics
- Relatively less expensive
316 Stainless Steel
316 stainless steel contains 16% chromium, 10% nickel, and 2 to 3% molybdenum, and also contains silicon, manganese, and carbon content, it is second used grade.
316 is durable, easy-to-fabricate, clean, weld and finish grade, it is considerably more resistant to solutions of sulfuric acid, chlorides, bromides, iodides and fatty acids at high temperatures, especially in chloride environment.
Of course, 304 and 316 have some same points or similar points.
- They are both Austenitic stainless steels and possess similar structures.
- They are non-magnetic and will have a slight magnetic property after cold working.
- Similar mechanical properties, like Tensile strength, Yield point, Elongation and Hardness.
- Both 304 and 316 can be used for general corrosion service.
What Is The Difference Between 304 And 316 Stainless Steel?
The key difference between 304 and 316 stainless steel is that 316 grade has better corrosion resistance thanks to the addition of molybdenum of 2.0-3.0% than 304, especially for chloride applications, and longer service life. 304 grade is a cost-effective choice and performs well for general service, selecting which grade depends on your application and environment.
Chemical Composition
There are different chemical compositions and alloy proportions between 304 and 316, these differences make them have different functions and characteristics.
304 and 316 Chemical Composition Comparison, max %.
| Grade | C | Si | Mn | P | S | N | Cr | Ni | Mo | Iron |
|---|---|---|---|---|---|---|---|---|---|---|
| 304 | 0.08 | 1.00 | 2.00 | 0.045 | 0.030 | 0.10 | 18 – 20 | 8.0 – 10.5 | – | Bal. |
| 316 | 0.08 | 1.00 | 2.00 | 0.045 | 0.030 | 0.10 | 16 – 18 | 10.0 – 14.0 | 2.0 – 3.0 | Bal. |
The key difference between 304 and 316 stainless steel in chemical composition is molybdenum element, 316 has 2 – 3% of it, however, 304 does not have, this is the most important factor in deciding their use range, both grades have a similar proportion of other alloys.
Corrosion Resistance
Standard 304 grade can against corrosion attack due to high Chromium content with low carbon content, it is excellent in many corrosive media.
However, 304 has one weakness, it is subject to pitting and crevice corrosion in warm chloride environments, and to stress corrosion cracking above 60 °C (approximate).
316 has superior corrosion resistance because of the addition of molybdenum, this gives 316 the ability to withstand harsh environments, especially in chloride environments, 316 possesses an obvious advantage compared to 304.
Cost
The cost of stainless steel depends on the alloys that are present in their composition, 304 and 316 have similar alloy content except 316 has molybdenum added, molybdenum is a more expensive alloy, making 316 more expensive than 304, in many cases, grade 304 is typically more affordable than grade 316.
Use Range
When selecting which type is the best option for your intended use, cost and corrosion resistance requirements must be considered as presented above, it is hard to say which one is better, depending on your application.
304 stainless steel has excellent comprehensive properties suitable for most applications, considering cost concerns, 304 is the better option for many industries, the typical applications have:
- Household products
- Auto parts
- Medical equipment
- Building materials
- Chemicals
- Food process
- Agriculture
- Ship parts
- Heat exchanger
316 is known as marine stainless steel, often considered one of the most suitable choices when selecting austenitic stainless steel for seawater environments and marine applications. Still, we should note it is not resistant to warm seawater.
- Food preparation equipment particularly in chloride environments
- Laboratory benches & equipment
- Coastal architectural paneling, railings & trim
- Boat fittings
- Chemical containers, including for transport
- Heat Exchangers
- Woven or welded screens for mining, quarrying & water filtration
- Threaded fasteners
- Springs
Dual certification: when stainless steel is required for use in a high-temperature environment, like 425-860 °C range, 304 and 316 may not be resistant to carbide precipitation to reduce corrosion resistance, as derivative and alternative grades, 304L and 316L with lower carbon perform well in the above temperature range, 304H and 316H are heat resisting grades which can be used in elevated temperatures above about 500 °C.