Man began to own iron (forge, melt) several millennia after mastering work with copper. The first native iron in the form of lumps was found in the Middle East in 3000 BC. And metallurgy of iron, according to experts, arose in several places on the planet, different peoples mastered this process at different times. Thanks to this, iron, as a material for the manufacture of tools for labor, hunting and war, replaced stone and bronze.
The first processes for making iron were called raw-cheese. The bottom line was that iron ore with charcoal was poured into the pit, which was ignited and tightly corked, leaving a blast hole through which fresh air was blown. In the process of such heating, the melting temperature of iron, of course, could not be achieved, a softened mass (crice) was obtained, in which there was slag (ash from fuel, ore oxides and rocks).
Further, the obtained criterion was forged several times, removing slag and other unnecessary inclusions, this laborious process was carried out several times, as a result of which one fifth reached the final operation from the total mass. With the invention of the water wheel, it became possible to supply a significant amount of air. Thanks to such blasting, the melting point of iron became attainable, and metal appeared in liquid form.
This metal was cast iron, which was not forged, but it was noticed that it fills the mold well. These were the first experiments on cast iron, which, with some improvements and changes, have survived to the present day. Over time, a method was found for processing cast iron into wrought iron. Pieces of cast iron were loaded with charcoal, during this process the cast iron softened, impurities, including carbon, were oxidized. As a result, the metal became thick, the melting point of iron increased, i.e. it turned out wrought iron.
Thus, metallurgists of that time were able to divide the single process into two stages. This two-stage process in the idea itself has survived to the present time, the changes are more related to the appearance of processes occurring in the second stage. Pure iron or metal, having a minimum of impurities, has almost no practical use. The melting point of iron in the iron - carbon diagram is at point A, which corresponds to 1535 degrees.
The boiling point of iron occurs when it reaches 3200 degrees.
In the open air, iron eventually becomes coated with an oxide film; in a humid environment, a loose layer of rust appears. Iron from its inception to the present day is one of the main metals. Iron is used mainly in the form of alloys, which vary in properties and composition.
At what temperature iron melts depends on the content of carbon and other components that make up the alloy. The most widely used carbon alloys are cast iron and steel. Alloys containing carbon more than 2% are called cast iron, less than 2% relate to steel. Cast iron is obtained in blast furnaces, by remelting ores from the sinter plant.
Steel is smelted in open-hearth, electric and induction furnaces, in converters.
As a charge metal scrap and cast iron are used. By oxidizing processes, excess carbon and harmful impurities are removed from the charge, and additives of alloying materials make it possible to obtain the desired grade of steel. To obtain steel and other alloys, modern metallurgy uses electroslag remelting technologies, vacuum, electron beam and plasma melts.
New methods of steel melting are under development, providing for automation of the process and providing high-quality metal.
Scientific developments have reached such a level when it is possible to obtain materials that withstand vacuum and high pressure, large temperature differences, aggressive media, radiation, etc.