Stainless steel is a common name of a large family of quality steel grades, which due to the chromium content is 10.5%, are resistant to destruction under the influence of a chemical or electrochemical reaction with the surrounding environment. In the Toolbox, this property is called the resistance to corrosion.
Included in chrome steel, react with oxygen in the air, invisible to the naked eye, surface creates a layer of chromium oxide, which protects the steel against corrosive agents. Protective layer, damaged mechanically or by chemical compounds, after contact with oxygen, is intrinsic rebuild. This occurs even in so poor in oxygen-free environments as ordinary water.
Higher chromium content of the steel gives better resistance to corrosion. This resistance is further increased after the addition of molybdenum. Addition of nickel has to obtain the structure of austenitic stainless steel, which facilitates its processing of the plastic welding and cold.
The most widespread are austenitic chromium-nickel stainless type 18/8, containing about 18% chromium and 8% nickel. They represent more than 50% of the world production of stainless steel. Constantly 18/8 are used for example for the production of household goods (m.in. pots), for the production of pet food equipment and mass caterers and construction, both elements inside and outside the building.
Austenitic stainless steels are the most commonly used in this group of materials. Appendix 8% nickel in stainless steel with 18% chromium provides a durable corrosion-resistant austenitic structure stalom. Austenitic stainless have the best corrosion resistance and mechanical properties are in the range of 450 to 950 MPa.
As alloying additives, mainly chromium and molybdenum may further improve corrosion resistance.
Ferritic steel is called so because it contains in its rate of ferrite. Steel ferrytyczną are divided into three groups according to the chromium Supplement 13, 17 and 25% carbon content between 0 and 1% of ferritic steel is characterized by good mechanical properties and forming higher than austenitic steel and high resistance to corrosion.
the main addition of alloying is chrome + small admixtures of molybdenum, titanium, niobium and other ingredients
steel is called ferrytyczną, because of their structural construction has a Ferrite-permanent solution of carbon in iron containing small quantities, less than 0.025%, and sometimes other add-ons alloys
- less thermal expansion as compared with austenitic steel,
- excellent corrosion resistance at elevated temperatures
- better thermal conductivity compared to austenitic steel,
- by niobem stability better resistance to creep,
- easier cutting and treatment of austenitic, greater susceptibility to deep,
- less susceptibility to deformation in the rear-view, gięciu
- higher yield than the popular 304 austenitic steel or carbon steel,
- greater resistance to stress corrosion of austenitic steel.
Ferritic steels are divided into genres: 1.4000, 1.4003, coat 1.4016, 1.4510.
Pearlitic steel-duplex austenitic
Pearlitic steels-austenitic stainless steels are corrosion-resistant steels wysokostopowymi, which thanks to the relevant chemical composition and heat treatment have a structure consisting of two basic phases: ferrite and austenite.
Pearlitic steels-austenitic stainless steels in terms of strength in excess and it significantly, austenitic, for example. their yield is at least twice.
A mixture of high content of chromium, nickel and molybdenum allows for good corrosion resistance against high environmental acidification. However, chromium, molybdenum and nitrogen to avoid pitting corrosion and the formation of various cracks in the structure.
Duplex steels offer good resistance to corrosion in the average acidity (solutions containing up to 15% of the acid). Are often used to construct with chlorides containing acids, nitric acid or other strong organic acids.
Pearlitic steel-austenitic is divided into genres: 1.4362, 1.4410, 1.4460, 1.4462.
Martensitic steels (Martensitic stainless steel) are characterized by a similar concentration of chromium as ferritic steels, but increased the concentration of carbon. 1%.
Martensite structure odpuszczonego provides the stalom high strength properties to 1100 MPa tensile strength. Martensitic stainless steels are magnetic. Their corrosion resistance is low. Can be used in contact with the nitric acid, acetic, bornym, benzoesowym, oil, pikrynowym, carbonates, nitrates and ługami. Their corrosion resistance decreases with increasing temperature. Resistance to atmospheric corrosion is sufficient only in very clean air. Mechanical properties of these steels can be better using the hardening and tempering treatment.
Selection of martenzytycznych steel is quite large, with their chemical composition, and, in particular, the content of carbon, chromium and other components of the alloying elements (eg. MO) is such that you can get the optimal steel band, i.e. properties. the strength, ductility (especially when dynamic loads) and sufficient corrosion resistance. The most legating hardness Martensitic stainless steels, carbon-containing get chromium, molybdenum and vanadium.
Martensitic steels are divided into genres: 1.4006, 1.4021, 1.4028 1.4031 1.4034 1.4057,,,, 1.4122.