Modern man in his daily life is surrounded by various metals. Most of the items we use contain these chemicals. This all happened because people have found a variety of methods for producing metals.
What are metals
Inorganic chemistry deals with these substances that are valuable to humans. Obtaining metals allows a person to create an increasingly advanced technique that improves our lives. What are they? Before you consider the general methods for producing metals, you need to understand what they are. Metals are a group of chemical elements in the form of simple substances with characteristic properties:
• heat and electrical conductivity;
• high ductility;
• brilliance.
A person can easily distinguish them from other substances. A characteristic feature of all metals is the presence of a special shine. It is obtained due to the reflection of the incident rays of light on a surface that does not transmit them. Gloss is a common property of all metals, but it is most pronounced in silver.
To date, 96 such chemical elements have been discovered by scientists, although not all of them are recognized as official science. They are divided into groups depending on their inherent characteristic properties. So the following metals are distinguished:
• alkaline - 6;
• alkaline earth - 6;
• transitional - 38;
• lungs - 11;
• semimetals - 7;
• lanthanides - 14;
• actinides - 14.
Metal production
In order to make an alloy, it is first necessary to obtain 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 using chemicals.
The remaining metals are mined by treating their compounds. They are found in various minerals. Ore is minerals and rocks, which include metal compounds in the form of oxides, carbonates or sulfides. To obtain them, chemical treatment is used.
Methods for producing metals:
• reduction of coal oxides;
• 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 to remove unwanted impurities such as clay, limestone, sand. As a result of this process, fusible compounds called slags are obtained.
In the presence of a significant amount of impurities, the ore before smelting is enriched by removing a large part of 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 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 receipt is accompanied by high energy costs. There are several ways to extract alkali metals:
• Lithium can be obtained from its oxide in vacuum or by electrolysis of the melt of its chloride formed during the processing of spodumene.
• Sodium is obtained 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 laborious.
• 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 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 have some fraction of impurities. So what is the difference between the two? 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
Technique needs a variety of metallic materials. At the same time, pure chemical elements are practically not used, since they do not possess the properties necessary for people. For our needs, we have invented different methods for producing alloys. This term refers to a macroscopically homogeneous material, which 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:
• a base consisting of one or more metals;
• small additives of modifying and alloying elements;
• non-removed impurities (technological, natural, random).
Metal alloys are the main structural material. In technology, they number more than 5000.
Types of Alloys
Despite such a variety of alloys, those most important for people are those based on iron and aluminum. They are most often found in everyday life. Types of alloys are different. Moreover, they are divided according to several criteria. Thus, various alloy manufacturing methods are used. According to this criterion they are divided into:
• Cast, which are obtained by crystallization of the melt of mixed components.
• Powder, created by pressing a mixture of powders and subsequent 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 varying amounts changes the properties of metallic materials.
Methods for producing alloys in the form of a finished product or workpiece are divided into:
• foundries (silumin, cast iron);
• deformable (steel);
• powder (titanium, tungsten).
Types of Alloys
The methods for producing metals are different, while the materials made thanks to them have different properties. In the solid state of aggregation, alloys are:
• Homogeneous (homogeneous), consisting of crystals of the same type. They are often called single-phase.
• Heterogeneous (heterogeneous), referred to as multiphase. Upon receipt, 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 interstitial and substitution, chemical compounds (carbides, intermetallic compounds, nitrides), crystallites of simple substances.
Alloy Properties
Regardless of what 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. In any case, they differ from the characteristics of their phases, which depend solely on the crystalline structure of the material. The macroscopic homogeneity of heterogeneous (multiphase) alloys is obtained as a result of the 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 (gloss).
Varieties of alloys
Various methods for producing alloys have allowed a person to invent a large number of metallic materials with various 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 are characterized by intrinsic safety or antifriction 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).
In production, people use other types of metal materials, such as fusible, heat-resistant, corrosion-resistant and amorphous alloys. Also widely used are magnets and thermoelectrics (telurides and selenides of bismuth, lead, antimony and others).
Iron alloys
Almost all iron smelted on Earth goes to the production of simple and alloy steels. It is also used in the production of cast iron. Iron alloys have gained their popularity due to the fact that they have properties that are useful to humans. They were obtained by adding various components to a simple chemical element. So, despite the fact that various alloys of iron are made on the basis of one substance, steel and cast irons have different properties. Thanks to this, they find different areas of application. Most steels are harder than cast iron. Various methods for the preparation of these metals make it possible to obtain different grades (brands) of these iron alloys.
Improving the properties of alloys
Due to the fusion of certain metals and other chemical elements, materials with improved characteristics can be obtained. So, for example, the yield strength of pure aluminum is 35 MPa. Upon receipt of the 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 ordinary steels are divided into types:
• low-carbon (0.25% carbon) is used for the manufacture of various designs;
• high carbon (more than 0.55%) is intended for the production of cutting tools.
Various grades of alloy steels are used in mechanical engineering and other products.
An alloy of iron with carbon, the percentage of which is 2-4%, is called cast iron. The composition of this material also includes silicon. Various products with good mechanical properties are cast from cast iron.
Non-ferrous metals
In addition to iron, other chemical elements are used to make various metallic materials. As a result of their compounds, non-ferrous alloys are obtained. In people's lives, materials based on:
• 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, and aluminum. They are called bronzes. There are several types of such alloys.
• Lead, which is a regular solder (tertiary). In this alloy, 2 parts of tin are added to 1 part of this chemical. In the manufacture of bearings, babbitt is used, 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 mechanical properties.
Production methods
The main methods for producing metals and alloys:
• Foundry, in which solidification of a homogeneous mixture of different molten components occurs. To obtain alloys, pyrometallurgical and electrometallurgical methods for producing metals are used. In the first embodiment, for the heating of raw materials using thermal energy obtained in the process of fuel combustion. The pyrometallurgical method produces steel in open-hearth furnaces and cast irons in blast furnaces. In the electrometallurgical method, the raw materials are heated in induction or electric arc furnaces. In this case, the raw materials melt 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 furnaces.