Steel resistant to weak corrosive media such as air, steam, and water, and chemical corrosive media such as acids, alkalis, and salts. Also known as stainless acid-resistant steel. In practical applications, steel that is resistant to corrosion by weak corrosive media is often called stainless steel, and steel that is resistant to chemical media is called acid-resistant steel. Due to the difference in chemical composition between the two, the former is not necessarily resistant to chemical media corrosion, while the latter is generally non-corrosive. The corrosion resistance of stainless steel depends on the alloying elements contained in the steel. Chromium is the basic element for the corrosion resistance of stainless steel. When the chromium content in the steel reaches about 1.2%, the chromium interacts with the oxygen in the corrosive medium to form a very thin oxide film (self-passivation film) on the surface of the steel. , Can prevent further corrosion of the steel matrix. In addition to chromium, commonly used alloying elements include nickel, molybdenum, titanium, niobium, copper, nitrogen, etc., to meet the requirements of various uses for the structure and performance of stainless steel Conduit Elbows Manufacturers.
Stainless steel is usually divided into:
1. Ferritic stainless steel. Containing 12% to 30% chromium. Its corrosion resistance, toughness and weldability increase with the increase of chromium content, and its resistance to chloride stress corrosion is better than other types of stainless steel.
2. Austenitic stainless steel. The chromium content is more than 18%, and it also contains about 8% nickel and a small amount of molybdenum, titanium, nitrogen and other elements. Good overall performance, resistant to corrosion by various media.
3. Austenitic-ferritic duplex stainless steel. It has the advantages of austenitic and ferritic stainless steel, and has superplasticity.
4. Martensitic stainless steel. High strength, but poor plasticity and weldability.
5. Precipitation hardening stainless steel. It has good forming properties and good weldability, and can be used as an ultra-high-strength material in the nuclear industry, aviation and aerospace industries.
According to the composition, it can be divided into Cr series (SUS400), Cr-Ni series (SUS300), Cr-Mn-Ni (SUS200) and precipitation hardening series (SUS600).