Modern man is surrounded by various metals in his daily life. Most of the items we use contain these chemicals. This all happened because people found a variety of ways to obtain metals.
What are metals
Inorganic chemistry deals with these valuable substances for people. Obtaining metals allows a person to create more and more perfect technology that improves our lives. What are they? Before considering the general methods for obtaining metals, it is necessary to understand what they are. Metals are a group of chemical elements in the form of simple substances with characteristic properties:
• thermal and electrical conductivity;
• high ductility;
• glitter.
A person can easily distinguish them from other substances. A characteristic feature of all metals is the presence of a special brilliance. It is obtained by reflecting incident light rays onto a surface that does not transmit them. Shine is a common property of all metals, but it is most pronounced in silver.
OnTo date, scientists have discovered 96 such chemical elements, although not all of them are recognized by official science. They are divided into groups depending on their characteristic properties. The following metals are isolated in this way:
• alkaline – 6;
• alkaline earth – 6;
• transitional – 38;
• light – 11;
• semimetals – 7;
• Lanthanides – 14;
• actinides – 14.
Obtaining metals
In order to make an alloy, you must first obtain metal from natural ore. Native elements are those substances that are found in nature in a free state. These include platinum, gold, tin, mercury. They are separated from impurities mechanically or with the help of chemical reagents.
Other metals are mined by processing their compounds. They are found in various fossils. Ores are minerals and rocks, which include metal compounds in the form of oxides, carbonates or sulfides. To obtain them, chemical processing is used.
Methods for obtaining metals:
• reduction of oxides with coal;
• getting tin from tin stone;
• iron ore smelting;
• burning sulfur compounds in special furnaces.
To facilitate the extraction of metals from ore rocks, various substances called fluxes are added to them. They help remove unwanted impurities such as clay, limestone, sand. As a result of this process, fusible compounds are obtained,called dross.
In the presence of a significant amount of impurities, the ore is enriched before smelting the metal by removing a large part of the unnecessary components. The most widely used methods for this treatment are flotation, magnetic and gravity.
Alkali metals
Mass production of alkali metals is a more complex process. This is due to the fact that they are found in nature only in the form of chemical compounds. Since they are reducing agents, their production is accompanied by high energy costs. There are several ways to extract alkali metals:
• Lithium can be obtained from its oxide in a vacuum or by electrolysis of a melt of its chloride, formed during the processing of spodumene.
• Sodium is extracted by calcining soda with coal in tightly closed crucibles or by electrolysis of a chloride melt with the addition of calcium. The first method is the most time-consuming.
• Potassium is obtained by electrolysis of a melt of its s alts or by passing sodium vapor through its chloride. It is also formed by the interaction of molten potassium hydroxide and liquid sodium at a temperature of 440 ° C.
• Cesium and rubidium are mined by reducing their chlorides with calcium at 700–800 °C or zirconium at 650 °C. Obtaining alkali metals in this way is extremely energy intensive and expensive.
Differences between metals and alloys
A fundamentally clear boundary between metals and their alloys practically does not exist, since even the purest, simplest substances havesome amount of impurities. So what is the difference between them? Almost all metals used in industry and in other sectors of the national economy are used in the form of alloys obtained purposefully by adding other components to the main chemical element.
Alloys
Technology needs a variety of metal materials. At the same time, pure chemical elements are practically not used, since they do not have the properties necessary for people. For our needs, we have invented different ways to obtain alloys. This term refers to a macroscopically homogeneous material that consists of 2 or more chemical elements. In this case, metal components predominate in the alloy. This substance has its own structure. In alloys, the following components are distinguished:
• base consisting of one or more metals;
• small additions of modifying and alloying elements;
• non-removed impurities (technological, natural, random).
Metal alloys are the main structural material. In technology, there are more than 5000 of them.
Types of alloys
Despite such a variety of alloys, those based on iron and aluminum are of the greatest importance for people. They are the most common in everyday life. The types of alloys are different. Moreover, they are divided according to several criteria. So various methods of manufacturing alloys are used. According to this criterion, they are divided into:
• Cast, whichobtained by melt crystallization of mixed components.
• Powder, created by pressing a mixture of powders and then sintering at high temperature. Moreover, often the components of such alloys are not only simple chemical elements, but also their various compounds, such as titanium or tungsten carbides in hard alloys. Their addition in certain quantities changes the properties of metallic materials.
Methods for obtaining alloys in the form of a finished product or blank are divided into:
• foundry (silumin, cast iron);
• wrought (steels);
• powder (titanium, tungsten).
Types of alloys
Methods for obtaining metals are different, while the materials made thanks to them have different properties. In the solid state of aggregation, alloys are:
• Homogeneous (uniform), consisting of crystals of the same type. They are often referred to as single-phase.
• Heterogeneous (heterogeneous), called multiphase. When they are obtained, a solid solution (matrix phase) is taken as the base of the alloy. The composition of heterogeneous substances of this type depends on the composition of its chemical elements. Such alloys may contain the following components: solid solutions of interstitial and substitution, chemical compounds (carbides, intermetallides, nitrides), crystallites of simple substances.
Alloy properties
Regardless of what methods of obtaining metals and alloys are used, their properties are completely determined by the crystallinephase structure and microstructure of these materials. Each of them are different. The macroscopic properties of alloys depend on their microstructure. In any case, they differ from the characteristics of their phases, which depend solely on the crystal structure of the material. The macroscopic homogeneity of heterogeneous (multiphase) alloys is obtained as a result of a uniform distribution of phases in the metal matrix.
The most important property of alloys is weldability. Otherwise, they are identical to metals. So, alloys have thermal and electrical conductivity, ductility and reflectivity (luster).
Varieties of alloys
Different methods of obtaining alloys have allowed man to invent a large number of metallic materials with different properties and characteristics. According to their purpose, they are divided into the following groups:
• Structural (steel, duralumin, cast iron). This group also includes alloys with special properties. So they are distinguished by intrinsic safety or anti-friction properties. These include brass and bronze.
• For pouring bearings (babbit).
• For electric heating and measuring equipment (nichrome, manganin).
• For the production of cutting tools (win).
People also use other types of metal materials in production, such as fusible, heat-resistant, corrosion-resistant and amorphous alloys. Magnets and thermoelectrics (telurides and selenides of bismuth, lead, antimony and others) are also widely used.
Iron alloys
Practically all the iron smelted on Earth is directed to the production of simple and alloyed steels. It is also used in the production of iron. Iron alloys have gained their popularity due to the fact that they have properties that are beneficial to humans. They were obtained by adding various components to a simple chemical element. So, despite the fact that various iron alloys are made on the basis of one substance, steels and cast irons have different properties. As a result, they find a variety of applications. Most steels are harder than cast iron. Various methods for obtaining these metals allow you to obtain different grades (brands) of these iron alloys.
Improve alloy properties
By fusing certain metals and other chemical elements, materials with improved characteristics can be obtained. For example, the yield strength of pure aluminum is 35 MPa. When obtaining an alloy of this metal with copper (1.6%), zinc (5.6%), magnesium (2.5%), this figure exceeds 500 MPa.
By combining different proportions of different chemicals, metal materials with improved magnetic, thermal or electrical properties can be obtained. The main role in this process is played by the structure of the alloy, which is the distribution of its crystals and the type of bonds between atoms.
Steels and irons
These alloys are obtained by combining iron and carbon (2%). In the production of alloyed materials, they are addednickel, chrome, vanadium. All ordinary steels are divided into types:
• low carbon (0.25% carbon) used for various structures;
• High carbon (more than 0.55%) designed for cutting tools.
Different grades of alloy steels are used in mechanical engineering and other products.
The alloy of iron with carbon, the percentage of which is 2-4%, is called cast iron. This material also contains silicon. Various products with good mechanical properties are cast from cast iron.
Non-ferrous metals
Besides iron, other chemical elements are also used to make various metallic materials. As a result of their combination, non-ferrous alloys are obtained. In people's lives, materials based on:have found the greatest use
• Copper, called brass. They contain 5-45% zinc. If its content is 5-20%, then brass is called red, and if 20-36% - yellow. There are alloys of copper with silicon, tin, beryllium, aluminum. They are called bronzes. There are several types of these alloys.
• Lead, which is a common solder (tretnik). In this alloy, 2 parts of tin fall on 1 part of this chemical. Bearings are produced using babbitt, which is an alloy of lead, tin, arsenic and antimony.
• Aluminum, titanium, magnesium and beryllium, which are light non-ferrous alloys with high strength and excellent mechanicalproperties.
Methods of obtaining
Main methods for obtaining metals and alloys:
• Foundry, in which a homogeneous mixture of different molten components solidifies. To obtain alloys, pyrometallurgical and electrometallurgical methods of obtaining metals are used. In the first variant, thermal energy obtained in the process of fuel combustion is used to heat the raw material. The pyrometallurgical method produces steel in open-hearth furnaces and cast iron in blast furnaces. With the electrometallurgical method, the raw materials are heated in induction or electric arc furnaces. At the same time, the raw material is softened very quickly.
• Powder, in which powders of its components are used to make the alloy. Thanks to pressing, they are given a certain shape, and then sintered in special ovens.
