A comprehensive introduction to stainless steel

Stainless acid-resistant steel is referred to as stainless steel. It is composed of two parts: stainless steel and acid-resistant steel. In short, steel that can resist atmoSPHEric corrosion is called stainless steel, and steel that can resist chemical media corrosion is called acid-resistant steel. Stainless steel is a high-alloy steel with more than 60% iron as the matrix and adding alloying elements such as chromium, nickel, and molybdenum.

When the chromium content in the steel exceeds 12%, the steel is not easy to corrode and rust in the air and dilute nitric acid. The reason is that chromium can form a very tight chromium oxide film on the steel surface, which effectively protects the steel from corrosion. The chromium content in stainless steel generally exceeds 14%, but stainless steel is not absolutely rust-free. In coastal areas or some places with serious air pollution, when the chlorine ion content in the air is high, the stainless steel surface exposed to the atmosphere may have some rust spots, but these rust spots are limited to the surface and will not erode the internal matrix of the stainless steel.　

Generally speaking, steel with a content of Wcr greater than 12% has the characteristics of stainless steel. According to the microstructure after heat treatment, stainless steel can be divided into five categories: ferritic stainless steel, martensitic stainless steel, and austenitic stainless steel, austenitic-ferritic stainless steel and precipitation carbide stainless steel.

Stainless steel is usually divided into:

1. Ferritic stainless steel. Ferritic stainless steel contains 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. Austenitic stainless steel has 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. Martensitic stainless steel has high strength, but poor plasticity and weldability.

Pre: What are the advantages of NM400 abrasion resistant steel plate

Next: Application and characteristic analysis of S355J0WP weather resistant steel plate