Classification of stainless steel pipes

Austenitic stainless steel pipe: Austenitic stainless steel pipe generally belongs to corrosion-resistant steel and is the most widely used type of steel. Among them, 18-8 stainless steel pipe is the most representative. It has good mechanical properties and is easy to use. Perform 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 pipe: the most commonly used stainless steel pipe, 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 pipe has excellent stainless corrosion resistance and better resistance to intergranular corrosion. For oxidizing acids, it is concluded in the experiment that in nitric acid below the boiling temperature with a concentration of ≤65%, 304 stainless steel pipes have strong corrosion resistance. It also has good corrosion resistance to alkaline solutions and most organic and inorganic acids.

304L stainless steel pipe: The low-carbon version of 304 is 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 may lead to intergranular corrosion (weld erosion) of stainless steel pipes in certain environments.

321 stainless steel pipe: It is a Ni-Cr-Mo type austenitic stainless steel pipe, its performance is very similar to 304, but due to the addition of metal titanium, it has better grain boundary corrosion resistance and high-temperature strength. 321 stainless steel pipe has excellent high-temperature stress rupture performance and high-temperature creep resistance performance, and 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 pipe: Mo is added, so its corrosion resistance, atmospheric corrosion resistance, and high-temperature strength are particularly good, and it can be used under harsh conditions. The corrosion resistance is better than that of 304 stainless steel pipe, 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 pipe: the carbon content of 316L is much lower than that of 316, and the high carbon content is the main factor causing intergranular corrosion of metals. Therefore, under the important working conditions of the chemical industry, 316L is widely used, but the price of 316L is high. 316L is better than 316 in chloride ion corrosion resistance.

Stainless steel pipe 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.