Steel: steel production, process and methods. Technology of steel production

Steel products, even with the active distribution of high-strength plastics, retain their positions in the market. Carbon alloys with different characteristics are used in instrumentation and automotive, construction and manufacturing. A unique combination of elasticity and strength makes the material profitable in terms of long-term operation. Accordingly, the products serve longer and cheaper maintenance. But this is not all the virtues that steel has. The acquisition of steel with the use of modern technologies allows to allocate the structure of the metal and additional properties.

General information about production technologies

The main task of the technologist is to provide a process in which the content of carbon and all kinds of impurities, such as sulfur and phosphorus, decreases in the workpiece. The basis for the preparation is cast iron. It is worth noting that furnaces for the manufacture of cast iron appeared in the Middle Ages, while the first production of steel was realized only in 1885, and to this day the methods of production of the alloy are developing and improving. Differences in the approaches to the process are mainly due to the way of carbon oxidation.

As a raw material, cast iron is used. It can be applied in solid or molten form. Iron-containing products can also be used, the production of which was carried out by direct reduction. Practically all methods of obtaining steel in one form or another also provide for the process of refining from impurities. For example, converter technology provides their blowing with oxygen.

Converter method

With this method, molten iron, as well as impurities and wastes in the form of ore, scrap metal and flux can be used as a base. Compressed air is fed through the technological holes to the prepared substrate, facilitating the performance of chemical reactions. Also in the process, thermal action takes place, in which oxygen and impurities are oxidized. Of particular importance are the characteristics of the stove structure, in which steel is processed. The production of steel can occur in aggregates with different lining - the most common ways to protect structures with refractory bricks and dolomite. By the type of lining, the converter method is also divided into two other methods: Thomas and Bessemer.

The Thomas method

A special feature of this method is the careful processing of cast iron containing up to 2% phosphorus impurities. With regard to the technology of lining, it is realized with the use of calcium and magnesium oxides . Due to this solution, the slag forming elements are provided with an excessive amount of oxides. The process of phosphorous combustion is one of the key sources of thermal energy in this case. By the way, the combustion of 1% phosphoric content increases the furnace temperature by 150 ° C. Thomas's alloys have a low carbon content and are most often used as technical iron. In the future, wire, roofing iron , etc. are produced from it. In addition, the production of steel (cast iron) can be used to produce phosphorous slag for further use as fertilizer in soils with high acidity.

The Bessemer method

This method involves processing the bases, which contain a small amount of sulfur and phosphorus. But at the same time there is a high content of silicon - about 2%. During purging, oxidation of silicon occurs primarily, which contributes to intensive heat release. As a result, the temperature in the furnace rises to 1600 ° C. Oxidation of iron is also intense as the combustion of carbon and silicon. With the Bessemer method, the process of obtaining steel provides for a complete transition of phosphorus to steel. All reactions in the furnace go quickly - an average of 15 minutes. This is due to the fact that oxygen, blown through the cast iron base, reacts with the appropriate substances throughout the volume. The finished steel may contain a high concentration of iron monoxide in a dissolved form. This feature refers to the minuses of the process, as the overall quality of the metal is reduced. For this reason, it is advisable for technologists to deoxidize alloys before casting using special components in the form of ferromanganese, ferrosilicon or aluminum.

Obtaining in open-hearth furnaces

If, in the case of the converter metal production method, provision is made for the combustion with air oxygen, the open-hearth method requires the inclusion of iron ores and rust scrap into the process. Of these materials, oxygen forms iron oxide, which also contributes to the burnout of carbon. The furnace itself includes a melting bath in the base of the structure, which is closed by a heat-resistant brick wall. Also, several chambers of regenerators are provided, providing preliminary heating of the air mass and gas. Regenerating blocks are equipped with special nozzles made of fire-resistant brick.

Like converters, open-hearth melting furnaces function periodically. As the new batches of charge are laid, that is, the cast iron base, steel is gradually produced. The steel production takes place slowly, since the processing of pig iron takes about 7 hours. But the open-hearth furnaces allow to regulate the chemical properties of the alloy by adding iron additives in different proportions-ore and scrap are used for this. At the final stage of the formation of the metal, the operation of the furnace stops, the slag is poured off, followed by the addition of a deoxidizer. By the way, in such a furnace, it is also possible to produce alloy steels.

Electrothermal method

To date, electrothermal production of steels is considered to be the most effective. So, in comparison with open-hearth furnaces and converter this method provides the possibility of more precise control of the quality of steel - including due to the regulation of the chemical composition. The interaction of furnace chambers with the air environment deserves special attention. The electrothermal technology of steel production provides for minimal access to air, causing other advantages. For example, this minimizes the accumulation of iron monoxide and foreign particles in the alloy, and also allows more efficient burning of phosphorus and sulfur.

A high temperature regime at 1650 ° C makes it possible to perform melting of problem slags, which require thermal treatment at elevated capacities. Also in electric furnaces, it is possible to alloy steel with refractory metals, among which tungsten and molybdenum. However, there is a serious drawback in this method of obtaining steels. Used furnaces require large amounts of energy, which makes this process the most expensive.

Dependence of the properties of the metal on the element base

The performance qualities of steel are determined by the set of chemical elements that the alloy was endowed with during the manufacturing process. One of the key components through which this metal acquires its basic properties in the form of hardness and strength, is carbon. The higher it is, the more reliable the steel. Manganese with silicon has little effect on the quality of the material, but their use is necessary in the manufacture of certain steel grades to perform the deoxidation process. Sulfur and phosphorus have a negative effect on the formation of the product. Depending on the technique used, the steel composition may have different concentrations of these elements. In any case, sulfur increases the brittleness of the metal, and also reduces the properties of strength and plasticity. Phosphorus, in turn, gives the steel a cold-brittle, which in the process of exploitation can be expressed by fragility.

Steel processing techniques

Not always the process of final formation of the structure of the metal is completed after the main receipt. Further, in order to improve product characteristics, additional processing means may be employed. These include deformation methods in the form of forging, stamping and rolling. This helps already at the production stage to form a complex of necessary technical properties, which will have ready-made steel. The production of steel at the outlet gives a plastic structure, and therefore the technologies of primary processing are quite diverse. So, in addition to deformation, methods of hardening, annealing and normalization can be applied.

Conclusion

Steel is associated with reliability and durability. In the case of high-quality products of this kind, such characteristics are justified. For example, individual grades provide rather high qualities of strength and elasticity. Depending on the technology used for the production, the use of steel can be oriented to maintain a hardness, the ability to withstand dynamic loads, etc. The metal most advantageous from the viewpoint of technical and operational properties makes it possible to obtain an electrothermal method. But at the same time it is also the most expensive, therefore this technique is used only in special cases - for creating special steels.