Classification of stainless steel

Austenitic stainless steel: Austenitic stainless steel generally belongs to corrosion-resistant steel and is the most widely used type of steel. Among them, 18-8 stainless steel is the most representative. It has good mechanical properties and is convenient for machining, stamping, and welding. It has excellent corrosion resistance and good heat resistance in an oxidizing environment. However, it is particularly sensitive to the medium containing chloride ions (CL-) in the solution and is prone to stress corrosion.

304 Stainless Steel: The most commonly used stainless steel, it contains a small amount of chromium and nickel, has a very low carbon content, and is easy to heat treat. It is also better in high-temperature resistance, and the general use temperature limit is less than 650°C. 304 stainless steel has excellent stainless corrosion resistance and better resistance to intergranular corrosion. For oxidizing acids, it is concluded in experiments that 304 stainless steel has strong corrosion resistance in nitric acid below the boiling temperature with a concentration of ≤65%. It also has good corrosion resistance to alkaline solutions and most organic and inorganic acids.

304L stainless steel: the low-carbon version of 304, mainly for the carbon penetration of 304 steel. The lower carbon content minimizes the precipitation of carbides in the heat-affected zone near the weld, which can lead to intergranular corrosion (weld attack) in stainless steels in some environments.

321 stainless steel: Ni-Cr-Mo type austenitic stainless steel, its performance is very similar to 304, but due to the addition of metal titanium, it has better intergranular corrosion resistance and high-temperature strength. 321 stainless steel has excellent high-temperature stress-rupture performance and high-temperature creep resistance performance. It is used in field open-air machines in the chemical, coal, and petroleum industries that require high resistance to grain boundary corrosion, heat-resistant parts of building materials, and parts that are difficult to heat treat.

316 stainless steel: Mo is added, so its corrosion resistance, atmospheric corrosion resistance, and high-temperature strength are particularly good, and they can be used under harsh conditions. The corrosion resistance is better than 304 stainless steel, and it is resistant to the erosion of marine and aggressive industrial atmospheres. Due to the addition of Mo, it has certain corrosion resistance to dilute sulfuric acid and solutions containing chloride ions. 316 has better corrosion resistance and is more resistant to corrosion than 304 in high-temperature environments.

316L stainless steel: The carbon content of 316L is far lower than that of 316, and the high carbon content is the main factor causing the intergranular corrosion of metals. Therefore, 316L is widely used in important working conditions in the chemical industry, but the price of 316L is relatively high. It is better than 316 in terms of chloride ion corrosion resistance.

Stainless steel with high alloy content: the nickel content is 29%~30%, the chromium content is more than 20%, it has good corrosion resistance to acid and hydrochloric acid, and of course, it is more expensive.