The role of iron in the history of human civilization is very difficult to overestimate. It was it that made it possible for people to resist the world around them, served as the basis for everything that was created in the future. Of course, bronze was the first, but due to its rather narrow distribution, it became, as it were, a material for the elite, who have access to the source of raw materials. While iron, due to its presence in almost any place, was used by everyone, while surpassing bronze in its capabilities. The metal is sourced from widespread minerals. But the path from them to finished products is very long, so it is reasonable to ask how and what is made of iron ore.
A few words about the ore
Without touching on specific rocks of minerals, it is worth noting the division into:
- high-grade ores (iron content more than 50%);
- privates (25-50%);
- poor (iron less than 25%).
Another approach to ore classification is by composition. Usually it is:
- hydrates of oxides;
- iron oxides;
- carbonate salts of iron oxide.
For completeness of information about ores, it is worth mentioning the main ones:
- magnetic iron ore;
- red iron ore;
- brown iron ore;
- spar iron ore.
Iron deposits are widespread throughout the world. For the needs of the industry, first of all, rich ores are used, but the rest are used quite successfully. True, for this they go through a cycle of enrichment, which includes a number of operations (grinding, washing, blowing, roasting), as a result of which the concentration of iron in the feedstock increases and the content of waste rock and impurities decreases.
What is obtained from iron ore?
The simplest answer - iron - although correct, is not complete. This took place at the first stage, when people were just beginning to understand the essence of metal.
About the varieties of iron
First of all, it must be said that iron is a malleable silver-colored metal that easily reacts with other elements, in particular with oxygen. Its designation is Fe. In fact, iron in the industry in its pure form is not used, but is mainly used as an alloy, primarily with carbon (C). According to its content, they speak of:
- pure iron, C
Cheese-fired method of obtaining iron
In this case, very often the raw material was bog ore, which is widespread throughout Europe. This made it possible to obtain metal weapons, tools of production and household utensils almost everywhere, which significantly accelerated the development of society, and also opened the way for the development of new, previously inaccessible territories.
The essence of the process itself is quite simple - ore and charcoal were poured in layers into an earthen kiln resembling a small cylinder about a meter in diameter. Holes (lances) were provided on the side for air supply with bellows. The furnace was fired up and the ore began to be smelted, constantly blowing air into the furnace.
Features of the technology were:
- supply of cold, "raw" air, which is why the name of the process went;
- rather low melting temperature, about 950 ° C.
The result was a sintered piece of a mixture of iron and slag, called a crust. It was hammered to remove all the debris, and in the end, pure iron remained. Later, household utensils were made from it, or the metal was used as a blank for steel. The technologies were different. Many people are familiar with words such as haralug or structure (objects made from a certain material): they meant steel weapons, only the methods of its production were different in each case.
Pig iron and its processing
Cheese-blowing production was distinguished by a low yield of the finished product and a large amount of raw materials that went to waste (slag). In the end, another technology began to be widely used in metallurgy, which consists in the fact that iron ore was first produced into pig iron, and then from it - steel. For this, it was necessary to build special furnaces, the so-called blast furnaces, in which the raw materials were melted.
With this approach, a temperature of about 1500 ° C developed, as a result of which the ore was completely melted, the Fe oxides included in its composition were reduced to pure metal, and it was saturated with carbon. It turned out cast iron, an alloy of Fe with C. Usually 90% of liquid cast iron is sent for processing, that is, after processing it using a special technology, the carbon content in it decreases, which will result in the formation of steel.
Its quality is regulated by the content of C in the composition, as well as special alloying additives, chromium, vanadium and others, which give the finished metal the necessary properties.
Mastering the smelting of iron gave man those tools, weapons, which made it possible to significantly expand his capabilities. However, the initial method turned out to be not entirely convenient and required too much raw material consumption. Therefore, over time, a different technology was adopted, when cast iron is obtained from iron ore, and only steel with the necessary characteristics is obtained from it.
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