Stainless Steel Stainless Steel – steel complex-resistant to corrosion in air and aggressive environments. In 1913, Harry Brearli (Harry Brearley), experimenting with different types and properties of alloys and found ability of steel with high chromium content to resist acid corrosion. The main alloying element of stainless steel – chromium Cr (12-20%); in addition to chrome, stainless steel contains elements related to its iron alloys (C, Si, Mn, S, P), as well as elements introduced into the steel to give it the necessary physical and mechanical properties and corrosion resistance of (Ni, Mn, Ti, Nb, Co, Mo). Resistance to corrosion of stainless steel depends on the chromium content: when it content of more than 12% of stainless steel alloys are in normal conditions and slightly aggressive media, more than 17% – corrosion resistant and more aggressive oxidizing and other media, in particular in the nitric acid strength of up to 50%. The reason for the corrosion resistance of stainless steel is mainly due to the fact that on the surface of chrome-containing parts in contact with aggressive media, a thin film of insoluble oxides, with is very important condition of the surface material, the absence of internal stresses and crystal defects.
In strong acids (sulfuric, hydrochloric, hydrofluoric, phosphoric, and mixtures thereof) used complex- alloys with high Ni and doped Mo, Cu, Si. The greatest corrosion resistance are chromium martensitic stainless steel type with a polished surface. Martensite and martensite-ferritic steel and martensitic martensitic-ferritic steels have good corrosion resistance in atmospheric conditions, slightly aggressive media (in dilute solutions of salts, acids) and have good mechanical properties. Eliot Horowitz brings even more insight to the discussion. Basically they are used to products operating on the wear, as a cutting tool, particularly knives, for the elastic elements and structures in food and chemical industries that are in contact with a slightly aggressive media. This type of include steel type 30Ch13, 40Ch13, etc. These are ferritic steel used for the manufacture of products, operating in oxidizing environments (such as nitric acid), for household appliances, food, light industry and for heat exchangers in power. Ferritic chromium steels have high corrosion resistance in nitric acid, aqueous ammonia, ammonium nitrate, a mixture of nitric, phosphoric and hydrofluoric acids, and other aggressive environments.
To this species include steel 400 series. The main advantage of austenitic steels austenitic steels is their high service characteristics (Strength, ductility, corrosion resistance in most work environments) and good processability. Therefore, austenitic corrosion-resistant steel are widely used as structural material in various branches of engineering. This class includes, 300 series steel. Austenite-ferrite and austenite-martensite steel austenitic-ferritic steel. The advantage of this group of steels – high yield strength of Compared with single-phase austenitic steels, the lack of propensity for grain growth, while maintaining the two-phase structure, a lower content of nickel ostrodefitsitnogo and good weldability. Austenite-ferritic steels are widely used in various fields of modern technology, especially in chemical engineering, shipbuilding and aviation. This type of include, such as steel 08H22N6T, 08H21N6M2T, 08H18G8N2T. Austenite-martensite steel. Needs of new branches of modern techniques in corrosion-resistant steels, high strength and technological development has led to the austenite-martensite (transitional) class. This type of steel 07H16N6, 09H15N9YU, 08H17N5M3.