Types of stainless steel
Types of stainless steel
Stainless steel is available in a variety of grades and finishes, depending on the environment the metal is expected to withstand. According to the microstructure, they can be divided into four major categories.
Austenitic stainless steelAustenitic stainless steel has austenite as the main microstructure. Austenite is a solid solution of iron and carbon that forms above a critical temperature of 723°C. This stainless steel series exhibits high toughness and impressive high temperature resistance.
70% of all stainless steels are austenitic. It contains at least 16% chromium and 6% nickel.
Austenite stabilizers are elements added to promote the formation of the austenite microstructure. This stainless steel grade is a non-magnetic metal and cannot be hardened by heat treatment. Corrosion resistance can be modified according to the usage environment.
ferritic stainless steel
Ferritic steels usually contain only chromium as an alloying element. Chromium content ranges from 10.5 to 18%. They have general corrosion resistance and poor manufacturing characteristics. Heat treatment methods also do not help harden the metal.
They generally have better engineering capabilities than austenitic steels. Unlike austenitic stainless steels, they are magnetic. They also have good resistance to stress corrosion, which reduces wear on corrosive materials.
Duplex stainless steel
Duplex stainless steels are a mixture of austenitic and ferritic stainless steels. Therefore, it has the properties of its two components. It has a high chromium and low nickel concentration. Duplex stainless steels have unique advantages due to their high tensile strength and good weldability.
It shows good stress corrosion resistance, but not as good as ferritic grades. It is tougher than ferritic grades, but less than austenitic grades.
Martensitic stainless steel
This type of stainless steel consists of high carbon and low chromium content. Like ferritic grades, it is magnetic. It does exhibit poor weldability compared to other grades, but it has higher hardenability and can be heat treated to improve performance.
Martensitic stainless steels have lower corrosion resistance than austenitic and ferritic stainless steels with the same chromium and alloy content.
Precipitation Hardened Stainless Steel
This subgroup provides a combination of austenitic and martensitic properties. Hardening is achieved by adding one or more elements such as aluminum, molybdenum, niobium, titanium and copper.
It is capable of developing high tensile strength through heat treatment. It contains chromium and nickel as alloying elements. These grades are used in high speed applications such as turbine blades.
