Methods of obtaining metals. Types of alloys. Production of alkali metals

Modern man in his daily life is surrounded by various metals. In most of the objects that we use, these chemicals are present. This all happened because people found a variety of ways to get metals.

What are metals?

These inorganic chemicals are important for people. The acquisition of metals allows a person to create more and more perfect technique that improves our life. What are they? Before considering the general methods of obtaining metals, it is necessary to understand what they are. Metals are a group of chemical elements in the form of simple substances, which has the characteristic properties:

• heat and electrical conductivity;

• high plasticity;

• brilliance.

A person can easily distinguish them from other substances. A characteristic feature of all metals is the presence of a special luster. It is obtained by reflecting incident light rays on a surface that does not allow them to pass through. Glitter is a common property of all metals, but it is most clearly manifested in silver.

To date, scientists have discovered 96 such chemical elements, although not all of them are recognized as an official science. They are divided into groups, depending on their inherent characteristics. So the following metals are distinguished:

• Alkaline - 6;

• alkaline earth - 6;

• Transitional - 38;

• Lungs - 11;

• Semimetals - 7;

• lanthanides - 14;

• Actinides - 14.

Preparation of metals

In order to make an alloy, it is necessary first of all to obtain a metal from natural ore. Native elements are those substances that are in nature in a free state. These include platinum, gold, tin, mercury. They are separated from impurities mechanically or by chemical reagents.

The remaining metals are extracted by processing their compounds. They are contained in various fossils. Ore are minerals and rocks, which contain metal compounds in the form of oxides, carbonates or sulphides. For their production, chemical treatment is used.

METHODS OF METAL PRODUCTION:

• reduction of oxides by coal;

• obtaining tin from tin stone;

• smelting of iron from iron ore ;

• burning of 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, low-melting compounds are obtained, called slags.

In the presence of a significant amount of impurities, the ore is enriched before the metal is smelted by removing most of the unnecessary components. The most widely used methods of this treatment are flotation, magnetic and gravitational methods.

Alkali metals

Mass production of alkali metals is a more complicated 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 the melt of its chloride formed during the processing of spodumene.

• Sodium is extracted by calcination of soda with charcoal in tightly closed crucibles or by electrolysis of a chloride melt with the addition of calcium. The first way is the most time consuming.

• Potassium is obtained by electrolysis of the melt of its salts 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 extracted by the reduction of their chlorides with calcium at 700-800 ° C or zirconium at 650 ° C. The production of 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, because even the purest, simple substances have some proportion of impurities. So what is the difference between them? Virtually all metals used in industry and other branches of the national economy are used in the form of alloys, obtained purposefully by adding to the main chemical element other components.

Alloys

The technique needs a variety of metallic materials. At the same time, pure chemical elements are practically not used, since they do not possess the necessary properties for people. For our needs, we invented different ways of obtaining alloys. By this term we mean a macroscopically homogeneous material, which consists of 2 or more chemical elements. In this alloy in the alloy is dominated by metal components. This substance has its own structure. In alloys, the following components are distinguished:

• a base consisting of one or more metals;

• small additions of modifying and alloying elements;

• unsuccessful impurities (technological, natural, random).

It is metal alloys that are the main constructional material. In technology, they number more than 5000.

Types of alloys

Despite such a variety of alloys, the most important for people are those based on iron and aluminum. They are most often found in everyday life. Types of alloys are different. And they are divided by several criteria. So different methods of manufacturing alloys are used. By this criterion they are divided into:

• Cast, which are obtained by crystallization of a melt of mixed components.

• Powder, created by pressing a mixture of powders and subsequent sintering at high temperature. And often components of such alloys are not only simple chemical elements, but also their various compounds, such as carbides of titanium or tungsten in hard alloys. Their addition in varying amounts changes the properties of metallic materials.

The methods for obtaining alloys in the form of a finished product or billet are divided into:

• Foundry (silumin, cast iron);

• deformable (steel);

• powder (titanium, tungsten).

Types of alloys

The methods of obtaining metals are different, and the materials made by them have different properties. In a solid aggregate state, alloys are:

• Homogeneous (homogeneous), consisting of crystals of the same type. They are often called single-phase.

• Heterogeneous (heterogeneous), called multiphase. When they are produced, a solid solution (matrix phase) is taken as the basis of the alloy. The composition of heterogeneous substances of this type depends on the composition of its chemical elements. Such alloys can contain the following components: solid solutions of introduction and substitution, chemical compounds (carbides, intermetallides, nitrides), crystallites of simple substances.

Properties of alloys

Regardless of which methods of producing metals and alloys are used, their properties are completely determined by the crystal structure of the phases and the microstructure of these materials. Each of them is different. The macroscopic properties of alloys depend on their microstructure. They differ in any cases from the characteristics of their phases, which depend solely on the crystal structure of the material. Macroscopic homogeneity of heterogeneous (multiphase) alloys is obtained as a result of a uniform distribution of phases in the matrix of the metal.

The most important property of alloys is weldability. In the rest they are identical to metals. Thus, alloys have a thermal and electrical conductivity, plasticity and reflectivity (shine).

Varieties of alloys

Various methods of obtaining alloys allowed a person 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 includes alloys with special properties. So they differ intrinsically safe or antifrictional properties. These include brass and bronze.

• For casting of bearings (babbitt).

• For electric heating and measuring equipment (nichrome, manganin).

• For the production of cutting tools (wins).

In production, people use other types of metallic materials, such as low-melting, 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

Virtually all the iron produced on Earth is sent to the production of simple and alloyed steels. It is also used in the production of cast iron. Alloys of iron have gained their popularity due to the fact that they possess useful properties for a person. They were obtained by adding various components to a simple chemical element. So, despite the fact that different iron alloys are made on the basis of a single substance, steel and cast iron have different properties. Due to this they find different applications. Most steels are harder than cast iron. Different methods of obtaining these metals allow obtaining different grades (brands) of these iron alloys.

Improved properties of alloys

Due to the fusion of certain metals and other chemical elements, it is possible to obtain materials with improved characteristics. For example, the yield strength of pure aluminum is 35 MPa. In the production of an alloy of this metal with copper (1.6%), zinc (5.6%), magnesium (2.5%), this figure exceeds 500 MPa.

Due to the combination in different ratios of various chemicals, it is possible to obtain metallic materials with improved magnetic, thermal or electrical properties. 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.

Steel and cast iron

These alloys are obtained by combining iron and carbon (2%). In the production of alloyed materials, nickel, chromium, and vanadium are added to them. All conventional steels are divided into types:

• Low-carbon (0.25% carbon) is used for the manufacture of various structures;

• High-carbon (more than 0.55%) is intended for the production of cutting tools.

Various grades of alloyed steels are used in engineering and other products.

The alloy of iron with carbon, the percentage of which is 2-4%, is called cast iron. The composition of this material includes silicon. Cast iron is cast by various products with good mechanical properties.

Non-ferrous metals

In addition to iron, other chemical elements are also used for manufacturing various metallic materials. As a result of their connection, non-ferrous alloys are produced. In people's lives, materials based on:

• Copper, called brass. They contain 5-45% zinc. If its content is 5-20%, then the 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 such alloys.

• Lead, which is a conventional solder (tractor). In this alloy, 1 part of this chemical is covered by 2 parts of tin. In the production of bearings, babbitt is used, which is an alloy of lead, tin, arsenic and antimony.

• Aluminum, titanium, magnesium and beryllium, which are light colored alloys with high strength and excellent mechanical properties.

Methods of obtaining

The main methods of obtaining metals and alloys:

• Foundry, under which solidification of a homogeneous mixture of different molten components occurs. Pyrometallurgical and electrometallurgical methods for obtaining metals are used to produce alloys. At the first variant for heating up of raw materials use the thermal energy received during combustion of fuel. The pyrometallurgical method produces steels in open-hearth furnaces and cast iron in blast furnaces. In the electrometallurgical method, the raw material is heated in induction or electric arc furnaces. At the same time, the raw material is very quickly relaxed.

• Powder, in which powder of its components is used to make the alloy. Thanks to pressing, they are given a certain shape, and then sintered in special furnaces.