Modern man in his everyday life is surrounded by a variety of metals.Most items that we use, these chemicals are present.It all happened because people have found various ways of obtaining metals.
What metals
these valuable substances for people engaged in inorganic chemistry.Production of metals allows a person to create a more perfect technique, improve our lives.What are they?Before we consider the common methods of producing metals, it is necessary to understand what they are.Metals are a group of chemical elements in the form of simple substances have characteristic properties:
• thermal and electrical conductivity;
• high plasticity;
• shine.
person can easily distinguish them from other substances.A characteristic feature of all metals is the presence of a special shine.It is obtained by reflection of incident light rays on impermeable surface thereof.Luster - is the common property of all metals, but it is most clearly manifested in silver.
To date, scientists discovered 96 of these chemical elements, although not all of them are recognized by official science.They were divided into groups depending on their inherent characteristic properties.So there are the following metals:
• Alkaline - 6;
• alkaline - 6;
• transient - 38;
• Lightweight - 11;
• semimetals - 7;
• lanthanides - 14;
• actinides - 14.
Obtaining metals
In order to produce an alloy, it is necessary first of all to get metals from natural ores.Native elements - are those substances that are naturally in the free state.These include platinum, gold, tin and mercury.They are separated from impurities by mechanical or chemical agents.
Other metals mined by the processing of their compounds.They are contained in a variety of minerals.Ore - a minerals and rocks, which contain metal compounds as the oxides, carbonates or sulfides.For their production using chemical treatment.
Methods for producing metal:
• reduction of oxides with coal;
• obtain tin from tin stone;
• pig iron from iron ore;
• burning of sulfur compounds in special furnaces.
To facilitate obtaining metals from gangue added thereto various substances called fluxes.They help remove unwanted impurities such as clay, limestone, sand.As a result of this process produced fusible compounds called slag.
the presence of significant amounts of impurities ore before smelting metal enriched by removing much of the unnecessary components.The most widely used methods for this treatment - flotation, magnetic and gravitational method.
Alkali metals
mass production of alkali metal - a more complicated process.This is due to the fact that they occur in nature in the form of chemical compounds.Because they are reducing their receipt accompanied by high energy costs.There are several ways of obtaining the alkali metal:
• Lithium can be obtained from its oxide in vacuo or by electrolysis of a melt of its chloride formed during processing spodumene.
• Sodium is produced by calcination of coal ash in sealed crucibles or by electrolysis of molten chloride with added calcium.The first method is the most time consuming.
• Potassium is produced by electrolysis of molten salts thereof, or by passing it through a pair of sodium chloride.Also, it is formed by reacting a molten potassium hydroxide and liquid sodium at a temperature of 440 ° C.
• Cesium and rubidium extracted by restoring their calcium chloride at 700-800 ° C or zirconium at 650 ° C.Preparation of the alkali metal in this way is very energy intensive and costly.
differences between metals and alloys
fundamentally clear boundary between metals and their alloys virtually non-existent, since even the clean, simple materials have a fraction of impurities.So what's the difference between them?Almost all metals used in industry and other sectors of the economy, are used as alloys produced specifically by adding basic chemical elements of other components.
alloys
technique needs a variety of metal materials.Thus pure chemical elements are not practically used because they do not possess the necessary properties for humans.For their needs we have invented various ways to produce alloys.This term refers to a macroscopically homogenous material, which consists of two or more chemical elements.In this case the alloy metal components predominate.This material has the structure.The alloys are following components:
• base, consisting of one or more of the metals;
• small additions of modifying and alloying elements;
• undeleted impurities (technological, natural, casual).It
metal alloys are the main structural material.In technology, there are more than 5000.
Types alloys
Despite such a variety of alloys, the most important for people to play those, which are based on iron and aluminum.They are more common in everyday life.Types of alloys are different.And they are separated by several criteria.Since there are different methods for producing alloys.According to this criterion, they are divided into:
• Cast, which are obtained by crystallization of the melt blended components.
• Powder by using a mixture of powders, pressing and subsequent sintering at high temperature.And often components of such alloys are not only simple chemical elements and their various compounds such as titanium carbide or tungsten hard alloys.Their addition in various quantities changes the properties of metallic materials.
Methods for producing alloys in the form of the finished product or the workpiece is divided into:
• foundries (silumin, cast iron);
• deformable (steel);
• powder (titanium, tungsten).
types of alloys
Methods for producing metals are different, and both made it through the materials have different properties.In the solid state the alloys are:
• homogeneity (homogeneous), consisting of crystals of the same type.They are often referred to as single-phase.
• Heterogeneous (heterogeneous), referred to as multiphase.When they are received as a base alloy taken a solid solution (matrix phase).Composition of heterogeneous substances of this type depends on the composition of its chemical elements.Such alloys may include the following components: solid solutions and substitution, chemical compounds (carbides, intermetallic compounds, nitrides) crystallites simple substances.
Properties alloys
Regardless of what methods of producing metals and alloys are used, their properties are completely determined by the crystal structure of the phases and microstructure of these materials.Each of them are different.Macroscopic properties of the alloys are dependent on their microstructure.They are in any case different from the characteristics of the phase solely dependent on the crystal structure of the material.Macroscopically uniform heterogeneous (multi-phase) of the alloys obtained by the uniform distribution of phases in the matrix metal.
most important properties of the alloy considered weldability.Otherwise, they are identical metals.Thus, the alloys have thermal and electrical conductivity, ductility and reflectivity (gloss).
Species alloys
Various methods of producing alloys allowed the man to invent a large number of metallic materials with different properties and characteristics.According to the purpose they are divided into the following groups:
• Construction (steel, anodized aluminum, cast iron).This group includes alloys with special properties.So they differ intrinsically safe or anti-friction properties.These include brass and bronze.
• To fill the bearings (babbitt).
• for electric and measuring equipment (nichrome, manganin).
• For the production of cutting tools (win).
people use in the production of other kinds of metal materials such as low-melting, heat-resistant, corrosion-resistant and amorphous alloys.Also, it is widely used magnets and thermoelectrics (teluridy and selenides of bismuth, lead, antimony and others).
iron alloy
Almost all of the iron is smelted in the world is directed to the production of simple and alloy steels.It is also used in the production of pig iron.Alloys of iron got its popularity due to the fact that they have beneficial properties for humans.They were obtained by adding to the simple chemical element of the various components.Thus, despite the fact that the various iron alloys manufactured on the basis of a single substance, steels and cast irons have different properties.Because of this, they are different fields of application.Most steels harder iron.Various methods of producing these metals allow to get different varieties (brand) of iron alloys.
Improved properties of alloys
Through fusion of certain metals and other chemical elements can obtain materials with improved characteristics.For example, the yield strength of pure aluminum is 35 MPa.In the preparation of the metal alloy with copper (1.6%), Zn (5.6%), magnesium (2.5%) the index exceeds 500 MPa.Due
compound in various ratios of different chemical substances can be prepared metallic materials are superior in magnetic, thermal, or electrical properties.The main role in this process is the structure of the alloy, which is the distribution of its crystals and the type of bonds between the atoms.
steel and iron
These alloys are obtained by combining iron and carbon (2%).In the production of alloyed materials added to them nickel, chromium, vanadium.All the usual types of steel divided into:
• Mild (0.25% carbon) used for the manufacture of different designs;
• high carbon (greater than 0.55%) is intended for the manufacture of cutting tools.
Different brands of alloy steels are used in mechanical engineering, and other products.
alloy of iron with carbon, which is the percentage of 2-4% is called pig iron.The composition of this material includes silicon.Of the various cast iron products having good mechanical properties.
ferrous metals
addition to iron, for the manufacture of a variety of metal materials used and other chemical elements.As a result of their compounds are non-ferrous alloys.In life, people have found the greatest use of materials based on:
• Copper, called brass.They contain 5-45% zinc.If its content is 5-20%, it is called red brass, and if 20-36% - yellow.There are alloys of copper and silicon, tin, beryllium, aluminum.They are called bronzes.There are several types of these alloys.
• Lead is a conventional solder (tretnik).In this alloy, per 1 part of the chemical crouches 2 pieces of tin.In the manufacture of bearings used babbitt, which is an alloy of lead, tin, arsenic and antimony.
• aluminum, titanium, magnesium, and beryllium is a light non-ferrous alloys, high strength and excellent mechanical properties.
Methods for producing
main methods of obtaining metals and alloys:
• Foundry, at which the solidification of the molten homogeneous mixture of various components.For alloys used pyrometallurgical and Elektrometallurgical methods for metals.The first option is used to heat the raw heat energy generated during the combustion process.Pyrometallurgical method provides steel in open-hearth furnaces and pig iron in blast furnaces.When electrometallurgical process material is heated in the electric arc or induction furnaces.At the same time raw material rasslavlyaetsya very quickly.
• Powder, wherein the alloy used for the manufacture of powders of its components.Through pressing them they give a definite shape and then sintered in special furnaces.
