This article will talk about iron, its chemical and physical properties. They are of great importance for determining the method of transportation of iron, its storage conditions, production, smelting, etc.
Iron is one of the most popular metals. But it is often the name given to its alloy with some admixture, for example, with carbon. This helps to preserve the ductility and softness of the metal itself. The indicator in this composition will be the amount of pure metal, carbon and impurities.
For steelmaking, the metallization method is used, which helps the product to become more resistant to external influences, such as erosion, corrosion, wear. The content of additional impurities may be different.
The percentage of carbon in the alloy can range from 0.2% to 10%. It depends on how the iron is reduced. Moreover, the number and degree of metallization can vary widely. In gaseous reduction processes, filamentous carbon is deposited from the gas phase onto the surface of iron. But the reaction is not fully completed, and the product that has undergone the metallization has soot formed of carbon on its surface and in the pores.
High carbon content, up to 10%, is possible in the dust generated during transportation and handling of materials with metallization, for example, metallized pellets, in which carbon decreases and dust starts, which is unacceptable because of the increased risk of fire.
In the process of direct reduction of iron, the amount of phosphorus does not decrease, and the percentage of its content during metallization is equal to its amount in the feedstock. This may be reduced by the complete enrichment of the ore used for the reduction process. Moreover, the ratio of phosphorus and iron depends on the increase in the percentage of iron, which leads to a decrease in the percentage of phosphorus. In most compositions, it is equal 0,010-0,020%, rarely 0,030%.
Raw materials for direct reduction of iron are often pellets that are not subjected to fluxing, since most of the sulfur in them is removed by oxidizing roasting, and then the main source of sulfur will be the reducing agent.
With the initial solid reducing agent, the amount of sulfur in the composition of the metallized material may be high. Then its reduction can be achieved by adding limestone and dolomite.
In the case of a gaseous reducing agent, a product with a low percentage of sulfur, up to 0.003, is obtained at the outlet.
Nitrogen and hydrogen
Nitrogen is contained in small quantities in the ore, which determines its small percentage in metallized materials, up to 0.003%. The amount of hydrogen reaches 150 cubic meters. see 100 gr., and in the steel its percentage is the same as in the smelting of scrap.
The amount of non-ferrous metals, namely nickel, chromium, lead, copper, has the composition of direct reduced iron, and is often low due to the purity of the raw materials. Such an indicator of sponge iron can be compared with iron. The difference will only be that in the cast iron there is chromium in a reduced form.
Titanium, chromium, vanadium are in the metallized pellets in the composition of the oxides. In the smelting process, it is rather simple to organize the possibility that prevents them from being recovered from the slag. This gives the ability to get the metal, which will include a low percentage of titanium, chromium and, possibly, manganese.
Iron, the composition of which includes tin, lead, zinc and other non-ferrous metals, and in a small and stable percentage, is formed during the oxidative process of burning pellets,direct reduction of iron and smelting. All this is due to the small amount of impurities of the named metals in the ore, as well as their partial removal.
It has been determined that zinc removal is possible during metallization and smelting. Lead evaporates during firing and recovery, but to a small extent, and the main thing will be the smelting process. Tin, like antimony, is difficult to remove from the composition due to their low content, or even goes into the metal. Laboratory studies have shown that what constitutes iron is determined by the amount of non-ferrous metals as impurities. Their percentage ranges from less than 0.01, both in steel with nickel, chromium and copper, and to less than 0.001 - in compositions with tin, lead, arsenic, antimony and zinc.
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