Stainless steel is a type of steel, and steel means that the amount of carbon (C) is less than 2%, and iron is more than 2% . The addition of chromium (Cr), nickel (Ni), manganese (Mn), silicon (Si), titanium (Ti), molybdenum (Mo) and other alloying elements in the smelting process improves the properties of the steel and makes the steel corrosion resistant. This is what we call stainless steel.
What are the characteristics of "steel" and "iron", and how do 304, 304L, 316, and 316L come from, and what is the difference between them?
Steel: A material containing iron as the main element and having a carbon content of generally less than 2% and containing other elements.
Iron: a metal element, atomic number 26. Iron materials have strong ferromagnetism and good plasticity and thermal conductivity.
Stainless steel: resistant to weak corrosive media such as air, steam, water or stainless steel. The commonly used steel grades are 304, 304L, 316, 316L
304 stainless steel
304 stainless steel is the most common steel grade. As a widely used steel, it has good corrosion resistance, heat resistance, low temperature strength and mechanical properties. It has good hot workability such as stamping and bending, and no heat treatment hardening.
304L stainless steel
(L is low carbon)
As a low-carbon 304 steel, its corrosion resistance is similar to that of 304 under normal conditions, but it is excellent in resistance to intergranular corrosion after welding or after stress relief; it can be maintained well without heat treatment, corrosion resistance.
316 stainless steel
Due to the addition of molybdenum, 316 stainless steel is particularly resistant to corrosion, atmospheric corrosion and high temperature strength. It can be used under harsh conditions; it has excellent work hardening properties.
316L stainless steel
As a low carbon series of 316 steel, it has excellent resistance to intergranular corrosion in addition to the same characteristics as 316 steel.
Performance comparison
316 and 316L stainless steel are molybdenum-containing stainless steels. The molybdenum content of 316L stainless steel is slightly higher than that of 316 stainless steel. Due to the molybdenum in steel, the total performance of this steel is better than that of 304 stainless steel. Under high temperature conditions, when the concentration of sulfuric acid is lower than 15% and higher than 85%, 316 stainless steel has a wide range of applications. 316 stainless steel also has good resistance to chloride attack and is therefore commonly used in marine environments. 316L stainless steel has a maximum carbon content of 0.03 and can be used in applications with maximum corrosion resistance.
Corrosion resistance
316 stainless steel has better corrosion resistance than 304 stainless steel and has good corrosion resistance in the production of pulp and paper. Moreover, 316 stainless steel is also resistant to erosion by marine and aggressive industrial atmospheres.
In general, 304 stainless steel and 316 stainless steel have little difference in chemical resistance, but they differ in some specific media.
The stainless steel originally developed was 304, which is sensitive to pitting corrosion under certain conditions. An additional 2-3% increase in molybdenum reduces this sensitivity, which gives birth to 316. In addition, these additional molybdenum can also reduce the corrosion of certain hot organic acids.
316 stainless steel has almost become the standard material for the food and beverage industry. Due to the shortage of molybdenum in the world and the higher nickel content in 316 stainless steel, the price of 316 stainless steel is more expensive than 304 stainless steel.
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