A person uses a variety of materials to provide for his needs. And they undoubtedly include metals. Indeed, it is now practically impossible to find such an area of human activity in which they were absent. And metals are divided into several main groups: non-ferrous, noble and black.
The group of ferrous metals includes chromium, manganese and, of course, iron with its many alloys. And iron alloys are the basis of modern technology. And although new ceramic and polymeric materials are now appearing, they will not be able to soon replace the good old steel and cast iron.
Steel is an alloy of iron with carbon, and the carbon content in this alloy should not exceed 2.14%. If its content is higher than this figure, then this alloy is already cast iron. Steel is obtained from cast iron or from scrap metal in various steel furnaces at metallurgical enterprises. And one of the oldest and already outdated processes is the production of steel in open-hearth furnaces. Its principle is that cast iron and scrap metal are processed in a reflective furnace. In order to melt solid charge materials and heat steel to the required temperature, as well as to compensate for significant heat losses, additional heat is required. It is obtained by burning fuel in a stream of very hot air.
In order for the process of fuel combustion to give the maximum effect and less energy is spent on the production of steel, it is necessary that this fuel burns in the workspace. For this, air is supplied to the furnace in a larger than necessary amount. This accordingly creates an excess of oxygen in her atmosphere. Also in this atmosphere there is oxygen, which was formed as a result of the decomposition of water and carbon dioxide at high temperatures. Thus, an excess of oxygen is formed in the working space of the furnace, which contributes to the oxidation of iron and other elements of the charge. As a result of this oxidation, many oxides of various metals are formed. Together with impurities and particles of the collapsing lining, they form slag. This slag is lighter than steel, and it covers it during smelting. Therefore, steel production by the open-hearth method is gradually being replaced by new technologies.
This is especially true for those grades of steel that contain many components. Their percentage must be maintained very strictly. The well-known stainless steel belongs to such steels. And the production of stainless steel is a rather complicated task, which is very difficult to solve with the open-hearth method. At the same time, carbon is very low in stainless steel, and this further complicates the task. And for smelting stainless steel and other similar brands often use electric arc furnaces. They can have different power and capacity. The source of heat in such a furnace is an electric arc. It occurs between the electrodes and the charge or liquid metal, after they are supplied with a current of the required strength.
This arc is a stream of electrons, metal vapor, slag and ionized gases. Its temperature exceeds the mark of 3000 degrees. It can arise from both direct and alternating current applications. But in electric arc furnaces, only alternating current is used. At first, while the metal in the furnace has not warmed up well, the arc in it goes out when the polarity is changed at the electrodes. But then, when the charge is completely melted and the bath is covered with an even layer of slag, this arc stabilizes and starts to burn evenly. Further, the production of steel in such a furnace proceeds without complications.
Induction furnaces are also used for melting metals. The principle of their action is this: an alternating magnetic field excites an electric current in the metal, and heat is released, which is used to melt this metal. And the source of the magnetic field in such a furnace is an inductor. The production of steel in an induction furnace has several advantages over an electric arc furnace. Firstly, it has the ability to more accurately adjust the melting temperature, and it gives a higher efficiency. And secondly, the absence of electric arcs and electrodes in such a furnace makes it possible to obtain low carbon steels in it. Melting in an induction furnace also gives low fumes of alloying elements, which is very important in the smelting of complex alloy steel.