304 and 316 are mainly used in different environments. 304 is mainly used in indoor and outdoor environments, while 316 is used in marine, chemical, food and medical industries.

The mechanical properties of the two materials are similar. The following is a list of the differences between the two materials

I. 304 Stainless Steel

It is a kind of universal stainless steel material. It has a wide range of functions, such as food equipment, general chemical equipment, atomic energy industrial equipment and so on. It has excellent corrosion resistance and moulding performance.

II. 316 Stainless Steel

It is a kind of hollow long circular wire, which is widely used in petroleum, chemical, medical, food, light industry, mechanical instruments and other industrial transportation pipelines and mechanical structural components. In addition, when bending and torsion strength are the same, the weight is lighter, so it is also widely used in manufacturing mechanical parts and engineering structures. It is also commonly used in the production of various conventional weapons, barrels, artillery shells and so on.

(1) Component differentiation.

Composition Table of 304 Stainless Steel and 316 Stainless Steel

Composition Table of 304 Stainless Steel and 316 Stainless Steel

Note: There are different requirements for phosphorus content in national standard and American standard.

(2) Brand differentiation

304:06Cr19Ni10, 304L:00Cr19Ni10;

316:0Cr17Ni12Mo2, 316L:00Cr17Ni14Mo2.
(3) The difference of corrosion resistance

Generally, 304 stainless steel and 316 stainless steel have little difference in chemical corrosion resistance, but they are different in some specific media. The relationship between 304 and other stainless steel materials can be clearly seen in the picture shared before. When 304 stainless steel was originally developed, it was more sensitive to pitting corrosion under specific conditions. In order to reduce these sensitivities, an additional 2-3% molybdenum was added to produce 316 stainless steel. These extra molybdenum can also reduce the corrosion of some thermoorganic acids. Among all kinds of water quality (distilled water, drinking water, River water, boiler water, etc.), 304 stainless steel and 316 stainless steel have almost the same corrosion resistance, but 316 stainless steel is more suitable when the content of chloride ion in the medium is very high.

(4) Price difference

Because of the worldwide shortage of molybdenum and higher nickel content in 316 stainless steel, 316 stainless steel is more expensive than 304 stainless steel.

(5) Low Carbon Types

The corrosion resistance of austenitic stainless steel comes from the chromium oxide protective layer formed on the metal surface. When the material is heated to 450 - 900 degrees, the structure will change, and chromium carbide will form along the crystal edge instead of chromium oxide protective layer, which will reduce the corrosion resistance, also known as "intergranular corrosion". As a result, 304L and 316L reduce intergranular corrosion due to their low carbon content. In particular, higher intergranular corrosion sensitivity does not mean that non-low carbon content is more susceptible to corrosion, and it is also higher in high chlorine environment.

In addition, 316 mainly reduced the content of Cr, increased the content of Ni and increased the content of Mo2%~3%. Therefore, its corrosion resistance is better than 304, which is suitable for use in chemical industry, seawater and other environments. Similarly, 316 cost is higher than 304. Generally 316 is used in places with higher requirements to replace 304.