The microstructure of stainless steel after heat treatment can be divided into five categories

Update:27 Jul 2019
Summary:

The microstructure of stainless steel after heat treatm […]

The microstructure of stainless steel after heat treatment can be divided into five categories: ferritic stainless steel, martensitic stainless steel, austenitic stainless steel, austenitic-ferritic stainless steel and precipitation hardened stainless steel.

1. Ferritic stainless steel Contains chromium in 12%~30%. The corrosion resistance, toughness and weldability of these steels increase with the increase of chromium content, and they can resist corrosion of the atmosphere, nitric acid and brine solution, and have good resistance to high temperature and oxidation. Ideal for use in plant equipment for nitric acid and food.

2. Martensitic stainless steel The strength of this type of stainless steel body is relatively high, but the plasticity and weldability are relatively poor. Because it contains high carbon, it has high strength, hardness and wear resistance, but its corrosion resistance is worse than other steel bodies. It is usually used on some parts of mechanical properties, such as springs and turbine blades. And this type of steel body is used after quenching and tempering.

3. Austenitic stainless steel contains more than 18% chromium, and also contains about 8% nickel and a small amount of elements such as molybdenum, titanium and nitrogen. This type of steel has a good overall performance and can withstand the corrosion of a variety of media, mostly used to make some acid-resistant equipment, such as corrosion-resistant containers or equipment parts of the pipeline.

4. Austenitic-ferritic stainless steel is a stainless steel that accounts for about half of the austenite and ferrite structures. In the case of a lower C content, the Cr content is 18% to 28%, and the Ni content is 3% to 10%. Some steels also contain alloying elements such as Mo, Cu, Si, Nb, Ti, and N. This type of stainless steel combines the characteristics of austenitic and ferritic stainless steels. Compared with ferrite, it has higher plasticity, toughness, resistance to intergranular corrosion and weldability, and also maintains ferritic stainless steel. 475 °C brittleness and high thermal conductivity, with superplasticity. Compared with austenitic stainless steel, it has high strength and resistance to intergranular corrosion and chloride stress corrosion resistance. Duplex stainless steel has excellent pitting resistance and is also a nickel-saving stainless steel

5. Precipitation hardening stainless steel The matrix is ​​an austenitic or martensitic structure, which can be strengthened by age hardening. After proper heat treatment, such stainless steel can undergo martensite transformation and precipitate intermetallic chemicals on the martensite body to produce precipitation strengthening.