Open-hearth furnace is a melting unit, which is designed for processing scrap and iron into steel of the required quality and chemical composition. The device is named for metallurgists and engineers from France. Emile and Pierre Martin have created a furnace in 1864. Next, let's consider its structure.
The General scheme of the open-hearth furnace
The unit is divided into lower and upper parts. The latter is located under the ground shop built to service the device at a height of 5-7 feet from the floor. In the upper part of the hearth furnace includes a working space and a head equipped with vertical channels extending down. The lower part is located under the working platform. It contains regenerative chambers with nozzles, sekovici and hogs with changeover devices.
Drawing the open-hearth furnace are presented in the article illustrates the device this part of the unit. In the workspace on top there is a bounding set, below (bottom). The front visible openings. They are referred to as the input Windows. Using them in open-hearth furnace is loaded with solid furnace charge and poured the liquid iron. Filling is carried out through a special side of the chute. Charging Windows, usually closed special lined covers with special holes “peepers”. They allow the steelmaker to observe the melting process and the status of the unit. The working space is in the most difficult conditions of all the elements, which includes open-hearth furnace. The temperature in this part of the unit is very high. In addition to sharp thermal effects, working space, and is subjected to mechanical shock. The materials used for this part of the device, under the action of chemical compounds that occur upon melting of the slag and metals. In resistance elements of the working space usually determine the stability of the whole furnace, as well as periods of major and intermediate repairs.
It is located above the molten metal. This part of the furnace needs to withstand the weight of the material, impacts during loading of the charge, the effect of the stresses which are formed with sharp and frequent temperature fluctuations, the influence of erosive processes in the course of interaction with the molten raw material. Front and back walls of the unit operate in virtually the same terms in which the bottom, since they are also in contact with the molten slag and metal. These elements spread from a special brick. Magnesite in part establishes the expansion joints. They are filled with wood strips, plywood, cardboard. In the process of heating they burn out, and when you extend the brick compresses the spaces.
This element is almost not in contact with the slag. In this regard, it is possible to produce basic and acidic refractory materials, regardless of the nature of the process. For the construction of the arch used magnesiochromite silica or heat-resistant brick.
They limit the ends of the working space. From design heads will depend on the quality of the functioning of the unit. Through these elements is fed fuel and air. Depending on the speed of their introduction into the workspace and level of interaction will depend on the shape and some other features of the torch. He, in turn, determines the quality with which are working the open-hearth furnace. Heads must ensure that:
- Optimum flatness of the torch along the length of the whole bath. It is necessary to transmit to it as much heat as possible, and walls and arches - as little as possible.
- Minimum resistance in the process of removing combustion products from the working space.
- Optimum mixing of air and fuel for complete combustion of the latter.
To meet the first and third conditions, the output section of the holes should be small. Thus will provide the maximum rate of fuel and air. To fulfill the second condition, it is necessary that the cross-section, on the contrary, was the maximum. This dual role of heads is to introduce air and fuel and to take waste products poses a rather difficult challenge to designers.
Flue gases, which depart from the workspace flow through the head. On the vertical channels, they fall into sekovici. They settle the order of 50-75% of dust. While accumulating the coarse fraction and the smaller in the larger scope are carried away in the pipe. The path of movement of gases dust which they contain, interacts with the materials of the masonry. This fact must be considered when selecting the last in the construction vertical channels, and slavikom.
These elements provide a constantly high temperature air and gas. In more severe conditions the work included the nozzles of the upper rows, as in this part of the deposition of dust and the heating maximum. These elements are made of foresteries or magnesiochromite brick. The work of lower bits is carried out at a temperature of 1000-2000 degrees. They are laid out of durable and cheaper refractory bricks.
Function changeover valve
Open-hearth furnace is a device reversible action. In the direction of gas flows on the system changed periodically. In hogs, air and gas lines are installed dampers, gate valves, chokes, and other elements that are United under the name “rocker”. The modern design of the unit operation “swap” is automated. Of hogs gases droop in the pipe. Its height is calculated so that the thrust which it is formed was sufficient for normal traffic flow all the way. The pipe is a fairly complex and relatively expensive construction. The height of this element in large aggregates more than one hundred meters. A pipe, usually made of red brick, the inner lining is formed by refractory bricks.
Marten furnaces during the war
Russia's first unit was launched at the Sormovo plant in 1870. At that time, the device was designed by A. Etnosov a young engineer. Of particular importance was the open-hearth furnace during the war. Of steel, received in them, cast details of tanks, missiles and rifles. Dangerous and very time consuming production was much needed in those years. Since that time, has also introduced the expression “open-hearth furnaces”. It is evidence of the power and steadfastness of the Soviet era. In 70-e years the production of units has been suspended because they were replaced by improved designs. However, the invention has acquired special symbolic significance for the Soviet state. Open-hearth furnace immortalized in movies and songs of that era.