Stainless steel, as well -known as difficult, is the most used material in all types of industry: automotive, astronautics, pharmaceuticals, medicine, energy, metalworking – this is only a small share of the spheres of activity that uses a “stainless steel” at present. However, the most famous for ordinary inhabitants is the use of household. Almost all objects used by people daily, starting from cutlery and door handles, ending with elements of complex electrical appliances consist of it.
The father of stainless steel is called the English scientist Harry Brearli. Having received an order from the weapons company for the development of technology to increase the operating time of trunks, which were too quickly destroyed under the influence of temperature, it began to experiment with the compositions of steel. His main task was to create a metal resistant to erosion. By adding chrome to the alloy to increase the melting temperature of the material, Brearli as a result of experiments with nitric acid found that the resulting metal was resistant to chemical effects. Subsequently, it was he who in 1913 patented the first doped steel.
It gained its popularity due to resistance to aggressive environments such as the atmosphere, sea and river water, acids, salts solutions and the like. Although this type of steel is commonly called corrosion-resistant, it is still prone to all metals. The level of resistance to corrosion depends on the measure of alloying elements in the alloy. The main admixture is chrome. The amount of the content of this element determines the protective properties of steel from corrosive destruction. Corrosion is called the spontaneous process of metal destruction under the influence of the external environment.
Stainless steels are divided into groups according to their properties, which are distributed according to GOST 5632 – 72:
• corrosion -resistant – the most common, protected from external chemical and electrochemical deformation, caused primarily by natural, natural effects. Especially in demand in the market, corrosion -resistant steel channel.
• heat -resistant (water -resistant) have a high level of resistance to the chemical erosion of the metal surface in gas media at a temperature of 550 ° C.
• heat -resistant – this is the most resistant type of steel type, which for a long time withstands work at high temperatures in loaded systems.
Due to the different structures of steels, they were divided into four classes. Martensitic steels differ in high carbon content and are used mainly after heat treatment with a polished or polished surface. Used in the production of cutlery, various blades and blades.
Austenitic-ferrite (duplex) type is characterized by the most concentrated value of chromium and low nickel content. This class has a number of advantages compared to others, as it differs in double strength with the average indicators of plasticity and resistance to deformation from shock loads. Used in shipbuilding, construction and manufacturing industry.
Ferrita stainless steel alloys are similar to low -carbon in properties, but they have higher corrosion resistance. On average they contain from 11% to 17% chromium. Used for the production of household appliances and in the automotive industry.
Austenitic steel contains 18% chromium and 8% of nickel. Is the most popular and common class. Nicknamed “0” by the brand according to the American Institute of Chugun and Steel. Its main advantages are high strength, corrosion resistance from a large number of aggressive media, excellent formability, plasticity and welding.
Such a distribution according to structural characteristics acquired due to cooling steel under normal atmospheric conditions after high -temperature heating is considered conditional.
To label steels and their alloys, a system of numbers and letters developed in the USSR is used, which also operates in the territories of the CIS and Russia. The amount of carbon is located at the beginning of the code. Next, there are letter designations with numerical quantitative indicators of the presence in the alloy of alloying substances. For example, the letter “x” in the name of the “21x18N08” brand denotes chromium, and the subsequent number suggests that this alloy contains 18% of this impurities. Using these simple knowledge, you can easily determine the exact composition of the alloy, knowing the letters that indicate the chemical elements. In addition to Russian GOST, there are several more standards for stainless steels in the world, the most popular of which are American AISI and European EN.
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