Durability and reliability of mechanisms depend on the material from which they were made, that is, on the totality of all its properties and features, which determine the performance characteristics. To date, most of the units and machine parts are made from different grades of steel. Consider this material in more detail.
What is Steel?
Steel is an alloy of two chemical elements: iron (Fe) and carbon (C), the content of the latter should not exceed 2%. If there is more carbon, then this alloy belongs to cast iron.
But steel is not only a chemically pure compound of two elements, it contains both harmful impurities, for example sulfur and phosphorus, and special additives that give the desired properties to the material-increase strength, improve workability, plasticity, etc.
If the carbon alloy is less than 0.025% and contains a small amount of impurities, then it is considered a technical iron. This material differs from steels in all respects, it has high magnetic characteristics, and it is used as a material for the manufacture of electrical components. There is no pure iron in nature, it is very difficult to obtain it even in laboratory conditions.
Despite the fact that there is very little carbon in the percentage, it has a significant influence on the mechanical and technical properties of the material. The increase in this substance leads to an increase in hardness, strength increases, but plasticity is sharply reduced. And, as a consequence, the technological characteristics change: with increasing carbon casting properties decrease, machinability of cutting deteriorates. In this case, low-carbon steel is also poorly processed by cutting.
Getting the steel. Metallurgy
Steel is the most common alloy on the planet. It is produced in an industrial way from cast iron, from which, under the influence of high temperatures, excess carbon and other impurities are burnt out. Steels are mainly produced in two ways: melting in open-hearth furnaces and melting of electric furnaces. Material made in an electric furnace is called electrostatic. It turns out to be cleaner in composition. In addition, there are many special processes for the production of alloys with special properties, for example, electric arc melting in vacuum or electron beam melting.
More details about steels and other alloys can be learned by studying such a science as metallurgy. It is considered one of the sections of physics and covers not only information about steel grades and their composition, but also contains information about the structure and property of materials at the atomic and structural level.
The students of specialized universities pass a special course "Industrial steels", where they thoroughly disassemble alloys of special purpose: construction, improved, cemented, for cutting and measuring tools, magnetic, spring-spring, heat-resistant, steel for structures in cold climates, etc.
Classification of steels in quality
All steel quality is divided into:
- steel of ordinary quality;
- high quality steel;
The quality of steel directly depends on the percentage of harmful impurities (composition) and compliance with the declared mechanical and technological characteristics. All kinds of industry are used in industry, but in different directions: they become of ordinary quality for non-essential parts, they become of high quality and high-quality ones are used in constructions to which special requirements are imposed.
Steel according to GOST: classification
- GOST 380-88. Carbon of ordinary quality - Article 1, Article 2, Ст3пс, etc. Numbers from 0 to 6 designate the brand, as the number increases, the carbon content increases. Letters ps, kn; cn - indices of the degree of deoxidation of the material: half-serene, boiling, calm, respectively.
- GOST1050-74. Carbon steel quality - 05; 08; 10; 20ps; 08 kop. The figures to 60 are the average content of C in hundredths of a percent, the letters ps, kn; cn is analogous to Clause 1.
- GOST 5632-72. High-alloy steels and alloys, corrosion-resistant, heat-resistant and heat-resistant - 30ХГСА, ГН2; 50X; 20HN3A. The first figures are the carbon content: 30 - 0.3%; 40 - 0.4%; 45 - 0.45%, letters - the corresponding alloying element (X-chromium, D-manganese, T-titanium, A-nitrogen, etc.), figure by letter - percentage of alloying element. If there is no figure, then the proportion of the substance is 1.5%, the letter A at the end means that it is high-grade steel. This applies to both tooling and alloy steels.
- GOST1435-74. Carbon tool - У7, У8, У10А. Explanation: У7 - 0,7% С; V8 - 0.8% C; Y - carbon; A - high-quality.
- GOST5950-73. Alloyed instrumental - 5ХГН; X12; 8X3, etc. The decoding of the brand is similar to item 3, but the content of C is indicated in tenths of a percent. If the carbon is less than 0.1%, then the figures are not indicated - ХВ4; HCG; HVG, etc.
- GOST801-78. Bearing - ШХ4; SHX15; SHX15SG. ShH - bearing, the figure - the chromium content: ШХ4 - 0,4% chromium, ШХ15 - 1,5% chromium, other letters and numbers - the content of additional alloying elements.
- GOST 1414-75. Structural high and high machinability cutting - A12, A20, A30, A40G. Decoding of the carbon content: А20 - 0,2% С, А12 - 0,12% С, А30- 0,3% С.