Stainless steel of ferritic structure has good mechanical properties. They are materials of high yield strength, easier to cut and machine, they have good heat conductivity, show better resistance to stress corrosion caused by chlorides comparing to austenitic steels. The basic property of this steel is also its magnetism. Ferritic steel can be distinguished by missing nickel in its chemical composition. However, it contains at least 10.5% of chromium. Other elements composing the alloy are molybdenum, aluminium and titanium. Ferritic steels when stabilized with niobium show high strength to deformation.
Missing expensive nickel in the ferritic steel makes it inexpensive. Therefore it is commonly used within industry. It is mostly used in automotive and food industries as well as petroleum and coke sector. Moreover, it is used for construction of some devices in chemical industry, kitchen and household equipment.
Ferritic steels can be divided to five groups.
Group I includes up to 14% of chromium, which protects it against corrosion. According to AISI, the group includes the following steel grades: 409, 410, 410L, 420. Low content of chromium translates to low price of these grades. They find application within an environment deprived of contact with water. They can be used for interior decoration, for production of vehicle exhaust systems and other elements of vehicles and stereo equipment.
Group II and steel grade 430 is the most popular among ferritic steels. Share of this grade in the global production is 48%. It includes 18% of chromium, shows good resistance to corrosion, thus can be used in an environment requiring higher degree of corrosion resistance – e.g. in applications in contact with water. It is used for production of household equipment such as dishwashers or drums in washing machines.
Group III covers steels that include alloying additives such as titanium and niobium, which provide better weldability and plasticity. The following types are distinguished: 430Ti, 439, 441. The steel is used within similar fields as Group II: e.g. production of exhaust systems in vehicles, welded parts of washing machines and dishwashers, in food industry for production of tanks and tank truck.
Grades of steel composing Group IV and Group V characterize with chromium content from 18% to 30%. They also include addition of molybdenum, which provides the highest corrosion resistance. The steel can be used for sea-coast applications, for production of household equipment, elements in the automotive industry or civil engineering.
The most popular grade of ferritic steel is steel EN 1.4016 (AISI 430).