Stainless steel is a kind of high alloy steel that can resist corrosion. Have beautiful surface, need not pass the surface treatment such as plating color or paint, so a lot of machinery factory to show oneself is stainless steel, often do not make any paint treatment, and black material (so-called black material is the name of general iron and steel) is must undertake rust prevention treatment.

Division by chemical composition of steel

According to the characteristic elements in the steel is divided into chromium stainless steel and nickel stainless steel two categories:

Chrome

Apart from iron, the main alloying element in steel is chromium, which is chromium series stainless steel, equivalent to AISI 400 series in the United States.

Chromium nickel

In addition to iron, the main alloying elements in steel are chromium and nickel, namely chromium nickel series stainless steel, equivalent to AISI 300 series in the United States.

Classification according to the structure of steel

The microstructure of steel refers to the characteristics of crystal structure and microstructure of steel. Crystal structure refers to the microscopic structure of crystal. The common crystal structure of iron and steel materials mainly includes body centered cube and face centered cube. The crystal structure of steel is one of the most basic factors that determine the mechanical, chemical and physical properties of steel.

Microstructure refers to the microstructure of steel observed under a microscope.

Stainless steel according to its different organization structure classification, mainly can be divided into five categories. That is, martensitic stainless steel, ferritic stainless steel, austenitic stainless steel, duplex stainless steel and precipitate hardened stainless steel.

Ferritic stainless steel

Ferritic stainless steel is one of the most common stainless steel materials, is a ferritic structure in the use of stainless steel. The chromium content of this stainless steel is between 11% and 30%, in addition, it also contains a small amount of molybdenum, titanium, niobium and other elements.

In addition to having good corrosion resistance, the biggest characteristic of ferritic stainless steel is good oxidation resistance, excellent stress resistance, and it also has good thermal conductivity and minimal expansion coefficient. However, the plasticity of ferritic stainless steel is poor, so this kind of stainless steel material is mainly used to make corrosion-resistant parts.

Austenitic stainless steel

Austenitic stainless steel is a kind of stainless steel material with stable internal austenitic structure. In addition to 18% chromium and 8% nickel, it also contains a small amount of molybdenum, titanium, nitrogen and other elements.

This stainless steel material belongs to the comprehensive performance of the product, can withstand the corrosion of a variety of media. Moreover, the toughness and plasticity of austenitic stainless steel are better, and its free cutting performance is also very good. At present, austenitic stainless steel materials are widely used in various industries.

Duplex stainless steel

Austenite - ferrite duplex stainless steel is a kind of stainless steel product with half austenite and half ferrite structure. It has the characteristics of austenitic stainless steel material and ferritic stainless steel material, and compared with ferritic stainless steel, its plasticity is better, higher toughness, compared with austenitic stainless steel, its thermal conductivity is better, the expansion coefficient is smaller.

The representative grades of duplex stainless steel are 1CR25Ni5MO1.5 (AISI 329), 1Cr21Ni5Ti (1X21H5T), 00Cr22Ni5Mo3N (SAF 2205) and 00Cr26Ni7Mo3N (SAF 2507), etc.

Martensitic stainless steel

Martensitic stainless steel is a hardening stainless steel material, the biggest characteristic of this stainless steel material is that the mechanical properties of this stainless steel material can be changed by heat treatment. At present, the stainless steel material is mainly used in the processing of steam turbine blades, surgical instruments and other products.