What characterizes the plastic properties of metal

What properties do metals and alloys have?

Metal products and parts are used in various industries. There are many types of metals and each of them has strengths and weaknesses. When making parts for cars, airplanes or industrial equipment, craftsmen pay attention to the characteristics of the material. Therefore, it is required to know the properties of metals and alloys.

Properties of metals and alloys

Signs of metals

Metals have characteristics that characterize them:

1. High thermal conductivity. Metal materials conduct electricity well.
2. Shine on a break.
3. Ductility.
4. Crystal structure.

Not all materials are durable and have high wear resistance. The same applies to melting at high temperatures.

Metal classification

Metals are divided into two large groups - ferrous and non-ferrous. Representatives of both species differ not only in characteristics, but also in appearance.

Black

Representatives of this group are considered the most common and inexpensive. Most are gray or dark in color. They melt at high temperatures, have high hardness and high density. The main representative of this group is iron. This group is divided into subgroups:

1. Iron - representatives of this subgroup include iron, nickel and cobalt.
2. Refractory - this includes metals whose melting point starts at 1600 degrees. They are used to create bases for alloys.
3. Rare earths - these include cerium, praseodymium and neodymium. They have low strength.

There are uranium and alkaline earth metals, but they are less popular.

Colored

Representatives of this group are distinguished by their bright color, lower strength, hardness and melting point (not for everyone). This group is divided into the following subgroups:

1. Light - a subgroup that includes metals with a density of up to 5000 kg/m3. These are materials such as lithium, sodium, potassium, magnesium and others.
2. Heavy - this includes silver, copper, lead and others. Density exceeds 5000 kg/m3.
3. Noble - represented in this subgroup have a high cost and resistance to corrosion processes. These include gold, palladium, iridium, platinum, silver and others.

Refractory and low-melting metals are distinguished.
Tungsten, molybdenum and niobium are refractory, and all the rest are low-melting. Classification of substances. Metals | Chemistry 11th grade #20 | Info lesson

Main types of alloys

Humanity is familiar with various metal alloys. The most numerous of them are iron-based compounds. These include ferrites, steels and cast iron. Ferrites are magnetic, cast iron contains more than 2.4% carbon, and steel is a material with high strength and hardness.

Metal alloys made of non-ferrous metals require special attention.

Zinc alloys

Compounds of metals that melt at low temperatures. Zinc-based mixtures are resistant to corrosive processes. Easy to process.

Aluminum alloys

Aluminum and alloys based on it gained popularity in the second half of the 20th century. This material has the following advantages:

1. Low temperature resistance.
2. Electrical conductivity.
3. Light weight of workpieces compared to other metals.
4. Wear resistance.

However, we must not forget that aluminum melts at low temperatures. At temperatures around 200 degrees, performance deteriorates.

Aluminum is used in the manufacture of components for machines, the production of parts for aircraft, components of industrial equipment, utensils, and tools. Not many people know that aluminum is popular in the production of weapons. This is due to the fact that aluminum parts do not spark under strong friction.

To increase the strength of the part, aluminum is mixed with copper.
So that the workpiece can withstand pressure - with manganese. Silicon is added to make a regular casting. Aluminum. Aluminum alloys. Aluminum bicycle frames.

Copper alloys

Copper-based alloys are grades of brass. High precision parts are made from this material, as brass is easy to process. The alloy may contain up to 45% zinc.

Properties of alloys

To manufacture parts and structures, you need to know the basic properties of metals and alloys. If processed incorrectly, the finished part can quickly fail and destroy the equipment.

Internal combustion engine

Physical properties

These include visual parameters and material characteristics that change during processing:

1. Thermal conductivity. This determines how much the surface will transfer heat when heated.
2. Density. This parameter determines the amount of material contained in a unit of volume.
3. Electrical conductivity. The ability of a metal to conduct electric current. This parameter is called electrical resistance.
4. Color. This visual indicator changes under the influence of temperatures.
5. Strength. The ability of the material to maintain its structure during processing. This also includes hardness. These indicators also apply to mechanical properties.
6. Susceptibility to the action of magnets. This is the ability of a material to conduct magnetic rays through itself.

Physical foundations make it possible to determine in what area the material will be used.

Chemical properties

This includes the ability of the material to withstand the effects of chemicals:

1. Resistance to corrosive processes. This indicator determines how protected the material is from water.
2. Solubility. Resistance of the metal to solvents - acids or alkaline compounds.
3. Oxidability. The parameter indicates the release of oxides by the metal when it interacts with oxygen.

These characteristics are determined by the chemical composition of the material.

Mechanical properties

The mechanical properties of metals and alloys are responsible for the integrity of the material structure:

• strength;
• hardness;
• plastic;
• viscosity;
• fragility;
• resistance to mechanical loads.

Technological properties

Technological properties determine the ability of a metal or alloy to change during processing:

1. Ductility. Pressure processing of the workpiece. The material is not destroyed. The structure is changing.
2. Weldability. Susceptibility of the part to work with welding equipment.
3. Shrinkage. This process occurs when the workpiece is cooled after it has been heated.
4. Processing with cutting tools.
5. Liquation (solidification of liquid metal with decreasing temperature).

The main method of processing metal parts is heating.

The properties of metals and alloys are responsible for how the finished product will behave during operation.
When processing materials, it is also important to know its characteristics. Chemistry 48. Properties of metals and alloys. Combustion catalysts – Academy of Entertaining Sciences

What properties do metals and alloys have? Link to main publication

Source: https://metalloy.ru/splavy/i-metally-svojstva

Mechanical properties of metals

The main mechanical properties include strength, ductility, hardness, impact strength and elasticity. Most indicators of mechanical properties are determined experimentally by stretching standard samples on testing machines.

Strength is the ability of a metal to resist destruction when exposed to external forces.

Plasticity is the ability of a metal to irreversibly change its shape and size under the influence of external and internal forces without destruction.

Hardness is the ability of a metal to resist the penetration of a harder body into it.

Hardness is determined using hardness testers by introducing a hardened steel ball into the metal (on a Brinell device) or by introducing a diamond pyramid into a well-prepared sample surface (on a Rockwell device).

The smaller the indentation size, the greater the hardness of the metal being tested. For example, carbon steel has a hardness of 100 before hardening. . . 150 HB (Brinell), and after hardening - 500. . . 600 NV.

Impact strength is the ability of a metal to resist impact loads. This value, denoted by KS (J/cm2 or kgf • m/cm), is determined by the ratio of the mechanical work A spent on the destruction of the sample during impact bending to the cross-sectional area of ​​the sample.

Elasticity is the ability of a metal to restore its shape and volume after the cessation of external forces. This value is characterized by the elastic modulus E (MPa or kgf/mm2), which is equal to the ratio of stress a to the elastic deformation caused by it. Steels and alloys for the manufacture of springs and leaf springs must have high elasticity.

Mechanical properties are understood as characteristics that determine the behavior of a metal (or other material) under the influence of applied external mechanical forces. Mechanical properties usually include the resistance of a metal (alloy) to deformation (strength) and resistance to fracture (ductility, toughness, and the ability of the metal not to collapse in the presence of cracks).

As a result of mechanical tests, numerical values ​​of mechanical properties are obtained, i.e., values ​​of stress or deformation at which changes in the physical and mechanical states of the material occur.

Property evaluation

When assessing the mechanical properties of metallic materials, several groups of criteria are distinguished.

1. Criteria determined regardless of the design features and nature of the service of products. These criteria are found by standard tests of smooth samples for tension, compression, bending, hardness (static tests) or impact bending of notched samples (dynamic tests).
2. Strength and plastic properties determined during static tests on smooth samples, although they are important (they are included in the calculation formulas), in many cases do not characterize the strength of these materials in real operating conditions of machine parts and structures. They can only be used for a limited number of simple-shaped products operating under static load conditions at temperatures close to normal.
3. Criteria for assessing the structural strength of a material, which are in the greatest correlation with the service properties of a given product and characterize the performance of the material under operating conditions.

Design strength of metals

Criteria for the structural strength of metallic materials can be divided into two groups:

• criteria that determine the reliability of metallic materials against sudden destruction (fracture toughness, work absorbed during crack propagation, survivability, etc.). These techniques, which use the basic principles of fracture mechanics, are based on static or dynamic tests of samples with sharp cracks that occur in real machine parts and structures under operating conditions (notches, through holes, non-metallic inclusions, microvoids, etc.). Cracks and micro-discontinuities greatly change the behavior of metal under load, since they are stress concentrators;
• criteria that determine the durability of products (fatigue resistance, wear resistance, corrosion resistance, etc.).

Criteria for evaluation

Criteria for assessing the strength of a structure as a whole (structural strength), determined during bench, full-scale and operational tests. These tests reveal the influence on the strength and durability of the structure of such factors as the distribution and magnitude of residual stresses, defects in the manufacturing technology and design of metal products, etc.

To solve practical problems in metallurgy, it is necessary to determine both standard mechanical properties and criteria for structural strength.

Similar materials

Source: https://www.metalcutting.ru/content/mehanicheskie-svoystva-metallov

Mechanical properties

Mechanical properties characterize the behavior of materials under load. In this article, we will consider 5 main mechanical properties of materials: strength, elasticity, ductility, brittleness and hardness.

What is Strength?

Strength is the ability of various materials to withstand stress under the external influence of various forces without destruction. Strength depends not only on the material, but also depends on the type of stress state - for example, it can be compression, tension or bending. Also, the strength is directly affected by the conditions under which the material is used - external influences, ambient temperature.

Strength tests

There is the concept of ultimate strength, which is the main quantitative characteristic of strength and is numerically equal to the breaking stress for a particular material. The tensile strength for each material is determined by the average result of a series of tests, since the main materials used in construction are characterized by heterogeneity.

If a static load occurs, to determine the strength, samples of a certain standard are tested (usually we are talking about samples with a cross-section of a circular shape, less often rectangular), the diagram thus reflects the dependence of the relative elongation on the magnitude of the stress acting on the sample. The strength of the material of various designs is justified by comparison those stresses that arise in a structure under external influence, also taking into account such indicators as strength and yield limits.

The so-called fatigue of a material (in particular, metal) is said if, under a large number of cyclically repeating external stresses, destruction occurs even at stresses less than the tensile strength. In this case, the cyclic strength is calculated, i.e. justification of the strength of the material, taking into account the load, which changes with a certain cycle.

Elasticity

If a material spontaneously restores its shape after the external force ceases to act, then this mechanical property is called the elasticity of the material. If, after removing the external load, the deformation completely disappears, then we should talk about reversible elastic deformation.

What does elasticity depend on?

The elasticity of a material is directly related to the interaction forces occurring between individual atoms. In solids, at a temperature equal to absolute zero and in the absence of any external influence, the atoms occupy positions called equilibrium. The potential energy of a body increases when exposed to external voltage, and the atoms are displaced from their equilibrium position.

Accordingly, when the external stress stops, the configuration of nonequilibrium atoms of the deformed material gradually becomes unstable and returns to an equilibrium state.

In addition to the forces of attraction and repulsion that act on each atom of the material from the others, there are also angular forces; they are directly related to the bond angles observed between the straight lines that connect the atoms to each other. Naturally, this is typical exclusively for macroscopic bodies and molecules containing many atoms. Angular forces are balanced at equilibrium values ​​of bond angles.

When talking about the quantitative characteristic of the elasticity of a material, the elastic modulus is used, which depends on the stress acting on the material and is determined by the derivative of the dependence of stress on deformation, which is applicable for the region of elastic deformation.

Plastic

Plasticity is the mechanical property of materials under the influence of an external load to change shape and size, and after the load ceases to act, to maintain it in a changed form.

Plasticity is an important property that is taken into account when choosing the material of the supporting structure, or when determining the technology (methodology) for manufacturing various products. For structures, a combination of high plasticity of the material and a high elasticity index is important. This combination of properties prevents sudden failure of the material.

In general, plasticity in the physics of materials is opposed to both elasticity and fragility - a plastic material retains the shape that external influences give it.

Plasticity is an important mechanical property

The study of plasticity is important when predicting the durability and strength of any structure, since plasticity often precedes destruction and it is important to consider the deformation processes occurring in the material. Measuring ductility, an important property of metals, is very important during pressure processing - forging and rolling.

This property of metals directly depends on the conditions under which deformation occurs - temperature, pressure, etc. The plasticity of metals affects such characteristics as elongation (absolute and relative) and contraction of the material.

When elongating, the length of the sample increases under the influence of the tension that occurs, and when narrowing, accordingly, due to the stretching of the sample, the cross-sectional area decreases.

Fragility

Brittleness refers to the mechanical properties of materials that are opposite to ductility. Those processes that increase ductility, respectively, reduce fragility, and vice versa. Materials that are brittle during static testing are destroyed without plastic deformation. This is typical, for example, for glass.

If during a static test a material is characterized by plasticity, but during a dynamic test it collapses, then we are talking about the so-called impact brittleness. Impact brittleness can be caused by yield limits (that is, the relationship between strain rate and resistance) and strength limits (changes in fracture resistance). Brittle fracture of a material occurs if the deformation resistance is equal to or greater than the tear resistance.

Accordingly, the plasticity of a material decreases if the increase in deformation resistance occurs faster than the increase in fracture resistance.

The factor on which the brittle state of a material directly depends is the uniformity of the stress state. A material goes from ductility to brittleness under a non-uniform stress state. Calculation of resistance to brittle fracture is an important justification for the strength of a structure.

Hardness

The mechanical property of a material not to undergo plastic deformation under external influence is called hardness. First of all, it depends on the mechanical characteristics of the material, in particular structure, elastic modulus, tensile strength, etc. The quantitative relationship between hardness and these characteristics is established by the general physical theory of elasticity.

The methods by which hardness is experimentally determined are both static (for example, a hard object is pressed into the surface or it is scratched) and dynamic.

Static methods also include hardness measurements according to Brinell (pressing a ball into a surface), Vickers (pressing a diamond tip) and Rockwell (for materials with high hardness a diamond cone is used, for materials with low hardness a steel ball is used).

Static methods also include sclerometry - scratching with a diamond structure in the form of a cone, pyramid, or with a pencil of varying hardness - the load that must be applied to create a scratch is assessed, as well as the size of the created scratch.

In dynamic methods for establishing the hardness of a material due to an impact load, an imprint is made with a ball (according to the principle of a pendulum) and the hardness value is characterized by how the material resists deformation from impact or by the parameters of the ball’s rebound from the surface, including the damping of pendulum oscillations.

Source: https://SoproMats.ru/materialyi/svoystva/

Technological properties of metals and alloys

One of the main properties of metals is their plasticity, i.e. the ability of a metal subjected to a load to deform under the influence of external forces without destruction and to produce residual (remaining after the load is removed) deformation.

Plasticity is sometimes characterized by the amount of elongation of a sample under tension.
The ratio of the increment in the length of a sample during stretching to its original length, expressed as a percentage, is called relative elongation and is denoted δ,%.

Elongation is determined after rupture of the sample and indicates the ability of the metal to elongate under the influence of tensile forces.

Ductility

The ability of a metal to be subject to pressure treatment (forging, rolling, pressing, etc.) without destruction is called its malleability. The malleability of a metal depends on its ductility. Ductile metals usually also have good malleability.

Shrinkage

Metal shrinkage is the reduction in volume of molten metal when it solidifies and cools to room temperature.
The corresponding change in linear dimensions, expressed as a percentage, is called linear shrinkage.

Fluidity

The ability of molten metal to fill a mold and produce good castings that accurately reproduce the shape is called fluidity. In addition to good filling of the mold, better fluidity contributes to the production of a healthy, dense casting due to a more complete release of gases and non-metallic inclusions from the liquid metal. The fluidity of a metal is determined by its viscosity in the molten state.

Wear resistance

The ability of a metal to resist abrasion, surface destruction, or dimensional change due to friction is called wear resistance.

Corrosion resistance

The ability of a metal to resist chemical or electrochemical destruction in an external humid environment under the influence of chemical reagents and at elevated temperatures is called corrosion resistance.

Machinability

The ability of a metal to be processed using various cutting tools is called machinability.

Source: http://www.paxildefects.net/svoiystva-metallov/tehnologicheskie-svoiystva.html

Properties of metals and alloys

Metals, as well as alloys based on them, are characterized by physical, mechanical, chemical and technological properties. The most important physical properties are: density, melting and boiling points, thermal conductivity, thermal expansion, heat capacity, electrical properties. Metals and alloys also differ in color, some of them have a specific smell.

The density of widely used technical metals and alloys, depending on the method of production and the amount of impurities, is kg/m3;

aluminum – 2500-2700,

cast iron – 7000-7800,

steel – 7800 – 7900,

copper – 8300 – 8900,

lead – 11300-11400,

mercury (liquid) – 13600.

Melting temperature

Each metal has its own specific melting point, °C:

tin – 232,

lead – 327,

zinc – 419.5,

aluminum – 660,

copper – 1083,

steel – 1300 – 1400.

Molten (liquid) metals boil at the following temperatures, °C: 1740 (lead), 2270 (tin), 2600 (copper), 3200 (pure iron).

Heat capacity

Metals conduct heat well and have low heat capacity. For example, thermal conductivity coefficient, W/ (m °C). copper is 403; steel – 58; for comparison, the thermal conductivity coefficient of granite is 2.92; concrete - up to 1.55, water - 0.599; air - 0.023. The specific heat capacity, kJ / (kg -°C), of aluminum alloys is 0.9; cast iron – 0.5: steel – 0.46–0.48; copper and bronze - 0.38: for comparison, the specific heat capacity of pine is 2.51; concrete – 0.8–0.92.

Indicators of thermal expansion are the coefficients of volumetric and linear expansion, the value of which can be used to judge the change in the volume or linear dimensions of the part, respectively, when its temperature fluctuates. Thus, the coefficient of linear expansion of steel is 1.14 • 10-6, for aluminum it is approximately twice as much.

Read also: Determining the true density of crushed stone (gravel) grains

The electrical properties of metals are characterized by electrical conductivity and its inverse property – electrical resistance.
Silver, copper, and aluminum have good electrical conductivity and correspondingly low electrical resistance. Copper has the lowest electrical resistance among technical metals (1.67 IO-4 Ohm • m). For aluminum it is 1.6 times, and for iron it is 5.8 times greater.

Mechanical properties include strength, ductility, hardness, impact strength, and abrasion.

Metals are characterized by high strength in both compression and tension. For example, the tensile strength of gray cast iron is 1004-200 MPa, for ordinary steels - 3504-400 MPa, for high-quality steels - 1.25 times higher than for ordinary ones.

The plasticity of metals is taken into account when determining mechanical properties and processing workpieces to obtain finished products from them. Of the heavy metals, the most ductile are copper and lead, the relative elongation of which reaches 60 and 55%, respectively. After mechanical treatment (hardening), the relative elongation of copper is reduced to several percent.

Hardness depends on the composition and structure of the metal. The harder the metal, the wider the possibilities for its use in the manufacture of machine parts and tools; the softer it is, the easier it is to process.

Lead has the lowest hardness - 254 - 4-40 MPa (Brinell), the hardness of gray cast iron - 1000 4-1200 MPa, high-quality steel - 2-2.5 times more.

The greatest hardness, close to the hardness of diamond, is found in vanadium, tungsten, titanium, and zirconium carbides, which are used for the manufacture of cutters, cutters, and drill bits.

Impact strength (impact resistance) is checked for machine parts and tools operating under short-term heavy loads. The test is carried out on pendulum pile drivers (a pendulum with a load rises to a certain height and then falls, hitting the sample in the place of a previously made mark). For gray cast iron, the impact strength, J/m2, is in the range of 0.5-1, for other castings it is 2-7.

Read also: Aluminum sheet: properties and types of material

Bearings, machine cylinders, piston rings, brake pads and other parts operating under high friction conditions are tested for abrasion. Abrasion is assessed by the amount of mass loss of the rubbing surfaces or the time of abrasion of the imprint extruded on the surface of the sample with a diamond tool.

Basic mechanical properties of metals. Technological properties of metals:

Nowadays, materials used mainly for the manufacture of machines and devices include metals and alloys of metals with other metals and non-metals. Therefore, the determination of the mechanical properties of metals becomes very important. No less important is knowledge of such general patterns as the periodicity of changes in the capabilities of their elements and their compounds, the dependence of properties on the types and characteristics of chemical bonds in alloys based on them.

Basic mechanical properties of metals

Metals are substances that are characterized by thermal conductivity, electrical conductivity, and plasticity. All of them, with the exception of mercury, are solids at room temperature. The melting point ranges from -38.78 to +3380°C. The mechanical and technological properties of metals have a high ability to absorb light, and therefore even in very thin layers they are opaque.

However, a smooth and clean surface layer reflects light well and gives a characteristic shine. Most surfaces are white and gray. Only copper and gold have a yellow tint. Some metals have a gray color with a faint bluish, yellowish or reddish tint. In the solid state, they all have a crystalline form. In the vapor state, metals are monatomic. Based on their specific gravity, they are divided into light and heavy.

There is another division - into ferrous and non-ferrous metals.

Metals in nature and methods of their extraction

In nature, metals are found both in a free state (Cu, Au, Ag, Hg, Pt) and in the form of various compounds - oxides, sulfides, carbonates, sulfates, phosphates, chlorides, nitrates and other compounds. When extracting them from ores and minerals, various reduction methods are used. In practice, those compounds and minerals have value from which industry can easily and inexpensively obtain pure metal.

Carbon is used to obtain iron from iron ore. Reducing agents can be hydrogen, aluminum, calcium, sodium, which have a greater ability to add oxygen. The production of iron from sulfides takes place in two stages: first, sulfate is obtained, and then burned and converted into oxides, then the resulting oxide is reduced using the technology of production from oxides. From carbonates, carbonate is first decomposed by heating.

By similar actions, different types of iron can be obtained from different natural compounds. The method of electrolysis produces active metals, alkali, alkaline earth, aluminum, magnesium, etc. The latter are produced by electrolysis of melts (molten salts). When a direct electric current is passed, ions are released at the cathode.

The refractory technological properties of metals are used to obtain them in powder or sponge form, followed by pressing at high temperatures.

The structure of metals and their physical properties

The mechanical properties of metals are influenced by the features of their internal structure in the solid state. The metal lattice has such a feature that its nodes contain molecular particles, that is, equilibrium exists. Valence electrons are in a relatively free state and are not strictly attached to each atom, forming the so-called electron gas. That is, the crystal lattice consists of positive ions, and the spaces between the ions are filled with electrons.

In the presence of a temperature difference or under the influence of an external potential difference, these electrons easily move and conduct heat and electric current without displacing material particles. In the vapor state, the mechanical properties of metals facilitate the conduction of electric current only in ionized form. It is characteristic that as the temperature increases, the electrical conductivity decreases due to the fact that their volume resistance increases.

When heated or (even when exposed to photons), the energy of electrons increases, as a result of which they can even be easily emitted (the appearance of cathode rays and photoelectron emission, used in radio engineering, in electron tubes and measuring light intensity using photocells).

Thus, a metal lattice is actually an ionic lattice, at the vertices of which there are positive ions of the same name, the mutual repulsion of which is compensated not by opposite charged anions, but by the joint efforts of free electrons.

Testing the mechanical properties of metals

Dissolution can only occur when they are converted into water-soluble compounds, that is, chemically. Some can liquefy in liquid mercury (silver, gold), forming so-called amalgams. Iron is capable of forming both mixtures and intermetallic compounds (intermetallic phases) with each other, which have a certain composition.

To obtain a picture of changes in properties with temperature, cooling curves obtained by studying the cooling rate are used. The preheated substance is allowed to cool and the temperature is measured every hour. The results are plotted on a diagram on which time is plotted on the abscissa axis and temperature on the ordinate axis.

If the technological properties of metals in the system, accompanied by the release of heat, do not change during cooling, then the temperature decreases gradually. If some changes occur in the system, then there is a temporary delay in the cooling of the system caused by phase transitions.

Using thermal analysis based on cooling curves, it is possible to study the composition of compounds that can form between the constituent parts of alloys.

Changes in alloy characteristics depending on composition

In general, when a substance passes from a liquid to a solid state, the substance is released in the form of more or less large particles - crystals, or a shapeless amorphous mass (glues, rubber, etc.). The smallest possible volume of a crystal lattice, which reproduces the features of its structure, is characterized by a unit cell.

The form of a solid depends on the nature of the substance and on the conditions under which the transition to the solid state takes place. If there are identical atoms at the vertices, then the distance between them in the crystal is equal to the sum of their radii, that is, the radius of the atom is equal to half of this distance.

Filling of crystal lattices with molecules and ions occurs with the most dense packing, that is, ions and molecules fill the space with a minimum volume. The symmetry elements of crystals of a solid are its center, planes and axes. Their most characteristic feature is anisotropy, that is, the dissimilarity of their characteristics (strength, thermal conductivity, dissolution rate, etc.

) in different directions. The absence of strictly directed bonds between atoms, the mechanical properties of metals make it possible to place two or more elements in a metal lattice, which are arranged in a certain order, forming intermetallic structures.

Alloys

When mixing different metals in a molten state, particles of the main component can be replaced by particles of another or several elements without changing the crystal lattice, forming solid solutions. Materials containing two or more types of atoms and having characteristic properties (brilliance, thermal conductivity, electrical conductivity) are called alloys.

In the molten state, metals dissolve well in each other and, as a rule, without restrictions. Often, a number of heterogeneous zones can form in these solutions, indicating their limited solubility. The mechanical properties of the metals on which the alloy is formed differ from the physical and mechanical properties of alloys. When dissolved in mercury, so-called amalgams are formed.

In practice, three types of alloys are distinguished: solid solutions, those that have the character of chemical compounds of metals, and a mixture of crystals.

Formation of the elementary crystal lattice of alloys

A variety of methods for producing alloys makes it possible to produce them with desired properties. In practice, compounds based on iron, copper, nickel, etc. are widely used. The physical and mechanical properties of the metals from which the alloy is obtained differ significantly from the properties of the alloys.

The added atoms can form “tighter” localized bonds, and the sliding of layers of atoms is reduced. This leads to a decrease in ductility and an increase in the hardness of the alloys. Thus, the strength of iron increases 10 times with the addition of 1% carbon, nickel or manganese.

In brass, which contains 65-70% chromium and 30-5% zinc, the strength is 2 times greater than pure copper and 4 times greater than pure zinc. The industry produces many varieties of alloys of various metals with specified properties.

Structure of metals

By studying the structure of atoms, one can observe that they all have a small number of electrons at the outer energy level, and they are characterized by the ability to only give up electrons when forming compounds. In compounds, metals always have a positive oxidation state. When compounds are formed, the particles donate electrons, exhibiting the properties of a reducing agent.

The ability to donate electrons varies and depends on the structure of the atom. The more easily it gives up electrons, the more active it is. A quantitative characteristic of the mechanical properties of metals to give up an electron is the ionization potential. It is understood as the minimum electric field voltage (in volts) at which the electron receives such acceleration that it is capable of causing ionization of the atom.

Activity in aqueous solutions is characterized by a standard electrode potential and can be quantified using a standard hydrogen electrode, the potential of which is taken to be ± 0. Noble metals have a positive standard potential.

According to their chemical properties, they are able to interact with water, acids, alkalis, salts, oxides, and organic substances.

Interaction with non-metals

In all cases of the formation of compounds with nonmetals, electrons transfer from metal atoms to nonmetal atoms. Hydrides are compounds with hydrogen. Alkaline and alkaline earth compounds are formed by direct interaction with hydrogen.

Halides are salts of hydrohalic acids, polar molecules that, for metals of groups 1 and 2, are highly soluble in water. They are formed by the direct interaction of iron with halogens and hydrohalic acids with iron. In their environment, metals interact with it very actively.

The oxides are predominantly fundamental in nature, these include oxides of aluminum, zinc, lead (II), chromium (III). They can be obtained from elements by decomposing salts with hydroxide and roasting sulfides. The basic mechanical properties of metals in air contribute to their coating with an oxide film.

If it does not tightly cover the surface, it does not protect against destruction, and the process of chemical corrosion occurs. Some metals form a very dense oxide film, which prevents oxygen from the air and other oxidizing agents from penetrating through it and protects the metal from corrosion.

Source: https://www.syl.ru/article/198796/new_osnovnyie-mehanicheskie-svoystva-metallov-tehnologicheskie-svoystva-metallov

General characteristics of metals

   If in D.I. Mendeleev’s periodic table of elements we draw a diagonal from beryllium to astatine, then on the lower left along the diagonal there will be metal elements (these also include elements of side subgroups, highlighted in blue), and on the upper right - non-metal elements (highlighted yellow). Elements located near the diagonal - semimetals or metalloids (B, Si, Ge, Sb, etc.) have a dual character (highlighted in pink).

 As can be seen from the figure, the vast majority of elements are metals.

By their chemical nature, metals are chemical elements whose atoms give up electrons from external or pre-external energy levels, forming positively charged ions.

Almost all metals have relatively large radii and a small number of electrons (from 1 to 3) at the outer energy level. Metals are characterized by low electronegativity values ​​and reducing properties.

The most typical metals are located at the beginning of the periods (starting from the second), then from left to right the metallic properties weaken. In the group from top to bottom, the metallic properties increase as the radius of the atoms increases (due to an increase in the number of energy levels). This leads to a decrease in electronegativity (the ability to attract electrons) of elements and an increase in reducing properties (the ability to donate electrons to other atoms in chemical reactions).

Typical metals are s-elements (IA-group elements from Li to Fr. PA-group elements from Mg to Ra). The general electronic formula of their atoms is ns1-2. They are characterized by oxidation states + I and + II, respectively.

The small number of electrons (1-2) in the outer energy level of typical metal atoms means that these electrons are easily lost and exhibit strong reducing properties, as reflected by low electronegativity values. This implies the limited chemical properties and methods of obtaining typical metals.

A characteristic feature of typical metals is the tendency of their atoms to form cations and ionic chemical bonds with non-metal atoms. Compounds of typical metals with nonmetals are ionic crystals of “metalanion of a nonmetal,” for example, K+ Br—, Ca2+ O2-. Cations of typical metals are also included in compounds with complex anions - hydroxides and salts, for example Mg2+(OH-)2, (Li+)2CO32-.

The A-group metals that form the amphoteric diagonal in the Periodic Table Be-Al-Ge-Sb-Po, as well as the metals adjacent to them (Ga, In, Tl, Sn, Pb, Bi) do not exhibit typical metallic properties.

The general electronic formula of their atoms ns 2 np 0-4 suggests a greater variety of oxidation states, a greater ability to retain their own electrons, a gradual decrease in their reducing ability and the appearance of oxidizing ability, especially in high oxidation states (typical examples are compounds Tl III, PbIV, Biv) .

Similar chemical behavior is characteristic of most (d-elements, i.e. elements of the B-groups of the Periodic Table (typical examples are the amphoteric elements Cr and Zn).

This manifestation of duality (amphoteric) properties, both metallic (basic) and non-metallic, is due to the nature of the chemical bond. In the solid state, compounds of atypical metals with nonmetals contain predominantly covalent bonds (but less strong than bonds between nonmetals).

In solution, these bonds are easily broken, and the compounds dissociate into ions (in whole or in part).

For example, the metal gallium consists of Ga2 molecules; in the solid state, the chlorides of aluminum and mercury (II) AlCl3 and HgCl2 contain strongly covalent bonds, but in solution AlCl3 dissociates almost completely, and HgCl2 - to a very small extent (and even then into HgCl+ and Cl—).

General physical properties of metals

Due to the presence of free electrons ("electron gas") in the crystal lattice, all metals exhibit the following characteristic general properties:

1) Plasticity - the ability to easily change shape, stretch into wire, roll into thin sheets.

2) Metallic luster and opacity. This is due to the interaction of free electrons with light incident on the metal.

3) Electrical conductivity. It is explained by the directional movement of free electrons from the negative pole to the positive one under the influence of a small potential difference. When heated, electrical conductivity decreases, because As the temperature increases, vibrations of atoms and ions in the nodes of the crystal lattice intensify, which complicates the directional movement of the “electron gas”.

4) Thermal conductivity. It is caused by the high mobility of free electrons, due to which the temperature quickly equalizes over the mass of the metal. The highest thermal conductivity is found in bismuth and mercury.

5) Hardness. The hardest is chrome (cuts glass); the softest alkali metals - potassium, sodium, rubidium and cesium - are cut with a knife.

6) Density. The smaller the atomic mass of the metal and the larger the radius of the atom, the smaller it is. The lightest is lithium (ρ=0.53 g/cm3); the heaviest is osmium (ρ=22.6 g/cm3). Metals with a density of less than 5 g/cm3 are considered “light metals”.

7) Melting and boiling points. The most fusible metal is mercury (mp = -39°C), the most refractory metal is tungsten (mp = 3390°C). Metals with melting temperature above 1000°C are considered refractory, below – low-melting.

General chemical properties of metals

Strong reducing agents: Me0 – nē → Men+

A number of voltages characterize the comparative activity of metals in redox reactions in aqueous solutions.

I. Reactions of metals with non-metals

1) With oxygen:
2Mg + O2 → 2MgO

2) With sulfur:
Hg + S → HgS

3) With halogens:
Ni + Cl2 –t°→ NiCl2

4) With nitrogen:
3Ca + N2 –t°→ Ca3N2

5) With phosphorus:
3Ca + 2P –t°→ Ca3P2

6) With hydrogen (only alkali and alkaline earth metals react):
2Li + H2 → 2LiH

Ca + H2 → CaH2

II. Reactions of metals with acids

1) Metals in the electrochemical voltage series up to H reduce non-oxidizing acids to hydrogen:

Mg + 2HCl → MgCl2 + H2

2Al+ 6HCl → 2AlCl3 + 3H2

6Na + 2H3PO4 → 2Na3PO4 + 3H2

2) With oxidizing acids:

When nitric acid of any concentration interacts with concentrated sulfuric acid with metals, hydrogen is never released!

Zn + 2H2SO4(K) → ZnSO4 + SO2 + 2H2O

4Zn + 5H2SO4(K) → 4ZnSO4 + H2S + 4H2O

3Zn + 4H2SO4(K) → 3ZnSO4 + S + 4H2O

2H2SO4(k) + Cu → Cu SO4 + SO2 + 2H2O

10HNO3 + 4Mg → 4Mg(NO3)2 + NH4NO3 + 3H2O

4HNO3(k) + Cu → Cu (NO3)2 + 2NO2 + 2H2O

III. Interaction of metals with water

1) Active (alkali and alkaline earth metals) form a soluble base (alkali) and hydrogen:

2Na + 2H2O → 2NaOH + H2

Ca+ 2H2O → Ca(OH)2 + H2

2) Metals of medium activity are oxidized by water when heated to an oxide:

Zn + H2O –t°→ ZnO + H2

3) Inactive (Au, Ag, Pt) - do not react.

IV. Displacement of less active metals by more active metals from solutions of their salts:

Cu + HgCl2 → Hg+ CuCl2

Fe+ CuSO4 → Cu+ FeSO4

In industry, they often use not pure metals, but their mixtures - alloys , in which the beneficial properties of one metal are complemented by the beneficial properties of another. Thus, copper has low hardness and is unsuitable for the manufacture of machine parts, while alloys of copper and zinc ( brass ) are already quite hard and are widely used in mechanical engineering.

Aluminum has high ductility and sufficient lightness (low density), but is too soft. Based on it, an alloy with magnesium, copper and manganese is prepared - duralumin (duralumin), which, without losing the beneficial properties of aluminum, acquires high hardness and becomes suitable for aircraft construction.

Alloys of iron with carbon (and additions of other metals) are the well-known cast iron and steel.

Metals in their free form are reducing agents. However, the reactivity of some metals is low due to the fact that they are covered with a surface oxide film , which is resistant to varying degrees to the action of chemical reagents such as water, solutions of acids and alkalis.

For example, lead is always covered with an oxide film; its transition into solution requires not only exposure to a reagent (for example, dilute nitric acid), but also heating. The oxide film on aluminum prevents its reaction with water, but is destroyed by acids and alkalis. A loose oxide film (rust ) that forms on the surface of iron in humid air does not interfere with further oxidation of iron.

Under the influence of concentrated stable is formed on metals . This phenomenon is called passivation . Thus, in concentrated sulfuric acid, metals such as Be, Bi, Co, Fe, Mg and Nb are passivated (and then do not react with the acid), and in concentrated nitric acid - metals A1, Be, Bi, Co, Cr, Fe , Nb, Ni, Pb, Th and U.

When interacting with oxidizing agents in acidic solutions, most metals transform into cations, the charge of which is determined by the stable oxidation state of a given element in compounds (Na+, Ca2+, A13+, Fe2+ and Fe3+)

The reducing activity of metals in an acidic solution is transmitted by a series of stresses. Most metals are transferred into solution with hydrochloric and dilute sulfuric acids, but Cu, Ag and Hg - only with sulfuric (concentrated) and nitric acids, and Pt and Au - with “regia vodka”.

Metal corrosion

An undesirable chemical property of metals is their corrosion, i.e. active destruction (oxidation) upon contact with water and under the influence of oxygen dissolved in it (oxygen corrosion). For example, the corrosion of iron products in water is widely known, as a result of which rust forms and the products crumble into powder.

Corrosion of metals also occurs in water due to the presence of dissolved gases CO2 and SO2; an acidic environment is created, and H+ cations are displaced by active metals in the form of hydrogen H2 ( hydrogen corrosion ).

contact corrosion) can be especially corrosive A galvanic couple occurs between one metal, for example Fe, and another metal, for example Sn or Cu, placed in water. The flow of electrons goes from the more active metal, which is to the left in the voltage series (Re), to the less active metal (Sn, Cu), and the more active metal is destroyed (corroded).

It is because of this that the tinned surface of cans (iron coated with tin) rusts when stored in a humid atmosphere and handled carelessly (iron quickly collapses after even a small scratch appears, allowing the iron to come into contact with moisture). On the contrary, the galvanized surface of an iron bucket does not rust for a long time, since even if there are scratches, it is not the iron that corrodes, but the zinc (a more active metal than iron).

Corrosion resistance for a given metal increases when it is coated with a more active metal or when they are fused ; Thus, coating iron with chromium or making an alloy of iron and chromium eliminates corrosion of iron. Chromed iron and steel containing chromium ( stainless steel ) are highly resistant to corrosion.

  General methods of obtaining metals in industry:

• electrometallurgy , i.e., the production of metals by electrolysis of melts (for the most active metals) or salt solutions;

• pyrometallurgy , i.e. the recovery of metals from ores at high temperatures (for example, the production of iron in the blast furnace process);

• hydrometallurgy , i.e., the separation of metals from solutions of their salts by more active metals (for example, the production of copper from a CuSO4 solution by the action of zinc, iron or aluminum).

Native metals are sometimes found in nature (typical examples are Ag, Au, Pt, Hg), but more often metals are found in the form of compounds ( metal ores ). Metals vary in abundance in the earth's crust: from the most common - Al, Na, Ca, Fe, Mg, K, Ti) to the rarest - Bi, In, Ag, Au, Pt, Re.

Source: http://himege.ru/obshhaya-xarakteristika-metallov/

Mechanical properties of metals: elasticity, ductility, hardness, viscosity

original article

The properties of metals are often judged only by their hardness, tensile strength and elongation. Based only on these parameters, conclusions are drawn about the capabilities of the metal or different alloys are compared.

In fact, this information is absolutely insufficient to decide the suitability of a material for a specific task.

In addition to the mentioned parameters, the applicability of metals and alloys is determined by a) structural strength, b) the degree of manifestation of inelastic phenomena, c) wear resistance, d) corrosion resistance and many others.

On this page we will find out what exactly determines the most common parameters of mechanical properties and consider the main indicators of structural strength. Wear and corrosion resistance are discussed on other pages.  

1. ELASTIC AND PLASTIC DEFORMATIONS

The mechanical properties of metals and alloys are determined by how they perceive external loads, i.e. resist deformation and destruction. When they are deformed, two different types of deformations are observed - elastic and plastic - which differ in both external manifestations and internal mechanisms. It is clear that the properties that determine the elastic and plastic state of metals must be described by different characteristics.

Elastic deformations occur due to changes in interatomic distances; they do not change the structure of the metal, its properties and are reversible. Reversibility means that after removing the load the body takes on its previous shape and size, i.e. There is no residual deformation.

Plastic deformations occur due to the formation and movement of dislocations; they change the structure and properties of the metal. After the load is removed, the deformations remain, i.e. plastic deformations are irreversible.

2.1. LIMITS OF PROPORTIONALITY, ELASTICITY and FLUIDITY.

The region of stresses at which only elastic deformation occurs is limited by the proportionality limit ?pt. In this region, only elastic deformations take place in each grain, and for the sample as a whole, Hooke’s law is satisfied - the deformation is proportional to the stress (hence the name of the limit).

With increasing stress, microplastic deformations occur in individual grains. At such loads, residual stresses are insignificant (0.001% - 0.01%).

The stress at which residual deformations appear within the specified limits is called the conditional elastic limit. In its designation, the index indicates the amount of residual deformation (in percent) for which the elastic limit was determined, for example ?0.01.

The stress at which plastic deformation already occurs in all grains is called the conditional yield strength. Most often, it is determined at a residual deformation value of 0.2% and is designated ?0.2.

Formally, the difference between the limits of elasticity and yield is associated with the accuracy of determining the “boundary” between the elastic and plastic states, which is what the word “conditional” reflects. It is obvious that ?pts

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Properties of metals

Metals are a group of elements in the form of simple substances that have characteristic metallic properties, such as high thermal and electrical conductivity, positive temperature coefficient of resistance, high ductility, malleability and metallic luster. In this article, all properties of metals will be presented in the form of separate tables.

The properties of metals are divided into physical, chemical, mechanical and technological.

Physical properties of metals

Physical properties include: color, specific gravity, fusibility, electrical conductivity, magnetic properties, thermal conductivity, heat capacity, expansion when heated.

The specific gravity of a metal is the ratio of the weight of a homogeneous metal body to the volume of the metal, i.e. this is the density in kg/m3 or g/cm3.

The fusibility of a metal is the ability of a metal to melt at a certain temperature, called the melting point.

Electrical conductivity of metals is the ability of metals to conduct electric current; it is a property of a body or environment that determines the occurrence of electric current in them under the influence of an electric field.

 Electrical conductivity refers to the ability to conduct primarily direct current (under the influence of a constant field), in contrast to the ability of dielectrics to respond to an alternating electric field by oscillating bound charges (alternating polarization), creating an alternating current.

The magnetic properties of metals are characterized by: remanent induction, coercive force and magnetic permeability.

The thermal conductivity of metals is their ability to transfer heat from more heated particles to less heated ones. The thermal conductivity of a metal is determined by the amount of heat that passes through a metal rod with a cross section of 1 cm2 and a length of 1 cm for 1 second. at a temperature difference of 1°C.

The heat capacity of metals is the amount of heat absorbed by a body when heated by 1 degree. The ratio of the amount of heat absorbed by a body with an infinitesimal change in its temperature to this change in a unit mass of a substance (g, kg) is called specific heat capacity, 1 mole of a substance is molar (molar).

Expansion of metals when heated . All metals expand when heated and contract when cooled. The degree of increase or decrease in the original size of the metal with a change in temperature of one degree is characterized by the coefficient of linear expansion.

Chemical properties of metals

Chemical properties include oxidation, solubility and corrosion resistance.

Metal oxidation is the reaction of a metal combining with oxygen, accompanied by the formation of oxides (oxides). If we consider oxidation more broadly, then these are reactions in which atoms lose electrons and various compounds are formed, for example, chlorides, sulfides. In nature, metals are found mainly in an oxidized state, in the form of ores, so their production is based on the reduction processes of various compounds. The solubility of metals is their ability to form homogeneous systems with other substances - solutions in which the metal is in the form of individual atoms, ions, molecules or particles. Metals dissolve in solvents, which are strong acids and caustic alkalis. The most commonly used in industry are: sulfuric, nitric and hydrochloric acids, a mixture of nitric and hydrochloric acids (aqua regia), as well as alkalis - caustic soda and caustic potassium. The corrosion resistance of metals is their ability to resist corrosion.

Mechanical properties of metals

Mechanical - strength, hardness, elasticity, viscosity, plasticity.

The strength of a metal is its ability to resist external forces without breaking.

The hardness of metals is the ability of a body to resist the penetration of another, harder body into it.

The elasticity of metals is the property of a metal to restore its shape after the cessation of the action of external forces that caused a change in shape (deformation).

The toughness of metals is the ability of a metal to resist rapidly increasing (impact) external forces. Viscosity is the opposite property of brittleness.

Plasticity of metals is the property of a metal to deform without destruction under the influence of external forces and retain a new shape after the force ceases. Plasticity is the inverse property of elasticity.

Technological properties of metals

Technological ones include hardenability, fluidity, malleability, weldability, and machinability.

The hardenability of metals is their ability to obtain a hardened layer of a certain depth.

The fluidity of metals is the property of a metal in a liquid state to fill a casting mold and reproduce its outlines in a casting.

The malleability of metals is a technological property that characterizes their ability to be processed by deformation, for example, forging, rolling, stamping without destruction.

The weldability of metals is their ability to form a permanent joint during the welding process that meets the requirements determined by the design and operation of the product being manufactured.

The machinability of metals by cutting is their ability to change the geometric shape, dimensions, and surface quality due to mechanical cutting of the workpiece material with a cutting tool. The machinability of metals depends on their mechanical properties, primarily strength and hardness.

Modern methods of testing metals are mechanical tests, chemical analysis, spectral analysis, metallographic and radiographic analyses, technological tests, flaw detection. These tests provide an opportunity to gain insight into the nature of metals, their structure, composition and properties, as well as determine the quality of finished products.

Table “Properties of metals: Cast iron, Cast steel, Steel”

1. Ultimate tensile strength
2. Yield strength (or Rp 0.2);
3. Relative elongation of the sample at break;
4. Bending strength;
5. The bending strength is given for a cast steel sample;
6. The fatigue limit of all types of cast iron depends on the mass and cross-section of the sample;
7. Elastic modulus;
8. For gray cast iron, the modulus of elasticity decreases with increasing tensile stress and remains almost constant with increasing compressive stress.

Table "Properties of spring steel"

1. Ultimate tensile strength,
2. Relative reduction in the cross-section of the sample at rupture,
3. Bending strength;
4. Ultimate strength under alternating cyclic loading at N ⩾ 107,
5. Maximum stress at a temperature of 30°C and a relative elongation of 1 2% for 10 hours; for higher temperatures, see section “Methods of joining parts”,
6. see section “Methods of connecting parts”;
7. 480 N/mm2 for cold-worked springs;
8. Approximately 40% more for cold-worked springs

Table "Properties of non-ferrous metals"

1. Elastic modulus, reference data;
2. Ultimate tensile strength;
3. Yield strength corresponding to plastic deformation of 0.2%;
4. Bending strength;
5. Largest value;
6. For individual samples

Table "Properties of light alloys"

1. Ultimate tensile strength;
2. Yield strength corresponding to plastic deformation of 0.2%;
3. Bending strength;
4. Largest value;
5. Strength indicators are given for samples and for castings;
6. Indicators of ultimate bending strength are given for the case of plane loading

Table "Metal-ceramic materials (PM)1) for plain bearings"

1. In accordance with DIN 30 910, 1990 edition;
2. In relation to the bearing 10/16 g 10;
3. Carbon is contained mainly in the form of free graphite;
4. Carbon is contained only in the form of free graphite

Table “Properties of metal-ceramic materials (PM)1 for structural parts”

1. In accordance with DIN 30 910, 1990 edition;

Table “Properties of soft magnetic materials”

1. Data applies to magnetic rings only.

Table “Properties of soft magnetic ferrites”

1. Standardized values;
2. Loss of magnetic properties by the material depending on frequency at low magnetic flux density (B < 0.1 mT);
3. Loss of magnetic properties at high magnetic flux density; measured preferably at f = 25 kHz, V = 200 mT, Θ = 100°C;
4. Magnetic permeability in a strictly sinusoidal magnetic field; measured at f

Source: http://press.ocenin.ru/svojstva-metallov/

Steel 

Steel belongs to ferrous metals. Carbon steel, which is an alloy of iron with carbon and other elements, is best suited for artistic processing. Steel has high quality characteristics, including the following:

• Elasticity
• Strength
• Hardening ability - a piece of steel is heated at a high temperature until red-hot and then dipped in water. Thanks to this, the metal acquires varying degrees of hardness and elasticity.
• Possibility of “releasing” by heating to red heat and then slowly cooling.
• Ability to be processed with a forging hammer in a heated state, since the steel is perfectly forged.
• Possibility of cutting metal into thin strips.

The softness of steel is directly proportional to the amount of carbon in its composition. The less carbon there is in a metal, the softer and easier it is to process. The softness of steel increases during annealing, that is, “releasing” the metal. To do this, the steel is heated red-hot and then subjected to a slow cooling procedure.

Steel for the manufacture of various products and artistic processing is produced in the form of graded material. For engraving and minting, U8 and U10 steels are most often used, where the letter “U” indicates the amount of carbon in the alloy.

The blade of the knives is made of stainless carbon steel

Non-ferrous metals

Non-ferrous metals are much more expensive than ferrous metals because they have many unique properties. The main one is the lack of reaction with a magnet, that is, non-ferrous metals are not attracted and are not magnetized. In addition, most of them are practically resistant to oxidation, so the products are characterized by a long service life.

https://www.youtube.com/watch?v=ZXK7JVDM-90

The production of non-ferrous metals for artistic processing is carried out in various forms:

• Ribbons
• Stripes
• Chushki
• Tubes
• Wire
• Rods
• Sheets

Let's look at the characteristic features of the most popular non-ferrous metals among craftsmen:

• Copper is a fairly soft metal of a beautiful red-orange hue, characterized by increased ability to forge and has high electrical conductivity and the ability to conduct heat. Processing copper is not particularly difficult, but the craftsman must keep in mind the high viscosity of this metal.

Copper can be soldered using tin and braze. Copper sheet is the main material for chasing and engraving work. Copper wire is used to make decorative items and openwork sculptures.

Copper sink

• Bronze is an alloy of copper and tin. The quantitative tin content affects the color of the alloy, which can take on pink, red, yellow or gray shades. If a bronze product is covered with a layer of patina (a decorative coating of copper oxide), then it acquires a noble smoky-greenish tint and looks ancient and truly expensive. Bronze is most often used for inlay and foundry work.

Sheet bronze

• Brass is an alloy of copper and zinc. The shade of the metal depends on the amount of zinc. According to its qualitative characteristics, brass is a harder alloy than pure red copper, therefore its degree of malleability is much lower. Compared to copper, brass has some brittleness, but at the same time it is more elastic.

Brass can easily be processed in various ways; in particular, it can be used for the manufacture of thin parts in inlays, as well as jewelry of various configurations. For embossing work it is used in sheet form.

Embossing on brass

• Zinc is perfect for casting both in its pure form and in alloys with other metals. Pure zinc is difficult to forge, but it is easy to solder, engrave, and machine with a variety of tools. The melting point is 419* C.

Sheet zinc

• Tin is a non- ferrous metal, known for a long time for its softness and ductility. Its melting point is only 252* C. As a component, tin is included in various types of bronze. When broken, tin produces a characteristic, recognizable crunch. Pure tin and its alloys are ideal for making inlays. Tin is also used for tinning and soldering dishes, both in its pure form and in alloys with lead. At the same time, its oxidation products are harmless.

Set of tin soldiers

• Aluminum is a silvery-white non-ferrous metal that melts at a temperature of about 658* C. A characteristic feature of aluminum is its lightness and ease of metal processing. Cast aluminum is quite brittle, but when rolled (annealed) it acquires the desired ductility.

Aluminum crafts from Madagascar

• Lead is a soft non-ferrous metal with a bluish-gray tint. It melts at a temperature of 327* C and resists corrosion well. However, it should be noted that lead oxides are poisonous. Lead is suitable for foundry work and the manufacture of molded products.

Lead (standard)

• Silver is also a non-ferrous metal, but it is also a precious metal. Pure silver is too soft and therefore difficult to work with. For the manufacture of products it is used in the form of alloys with copper. Silver inserts are used in inlays, engraving, embossing and niello.

Antique silver items

Let's consider some properties of metals that affect the quality of artistic products:

• Malleability of the metal - Malleable ductile metals require greater cutting force, but their toughness must be taken into account. A piece of copper or lead needs to be chopped to the end, but brass, zinc or steel can be chipped with a chisel and then simply broken. Harder brass gives a smooth surface when turned, while aluminum or copper seems to drag on the cutter.
• Brittleness is the ability of solid materials to fracture due to mechanical stress without noticeable plastic deformation. This property is the opposite of plasticity. Heavily hardened steel, as well as many types of brass and bronze, are very brittle and will break into pieces under strong impacts. The brittleness of a metal is not always a sign of its hardness; for example, a zinc casting is brittle but not hard. A hardened steel knife is both hard and brittle.
• Elasticity is the property of metals to restore their shape and volume after the cessation of external forces or heating that caused the deformation. To a large extent, special grades of steel have this property.
• Melting when heated - the ability of a metal to melt when heated is an important quality, since melting is considered one of the most accessible and cheapest ways to produce metal products. Parts of huge machines and small metal sculptures are made in the same way.

If there is a need to harden a part while maintaining the viscosity of the metal, craftsmen use high-frequency currents. In this case, the part is hardened to a depth of several millimeters. However, the rest of the metal mass inside the product remains unchanged. And finally, metal parts can be processed without heating - for example, by engraving and metal carving.

Silver products

Source: http://design-fly.ru/materiali/svojstva-metallov.html

Properties of metals: chemical, physical, technological

Chemical properties of metals

Physical properties of metals

Mechanical properties of metals

Technological properties of metals

Interesting facts about metals

Metals, video

It is no secret that all substances in nature are divided into three states: solid, liquid and gaseous. And solid substances, in turn, are divided into metals and non-metals; this division is also reflected in the table of chemical elements of the great chemist D.I. Mendeleev. Our article today is about metals, which occupy an important place both in chemistry and in many other areas of our lives.

Chemical properties of metals

We all, one way or another, encounter chemistry in our daily lives. For example, during cooking, dissolving table salt in water is the simplest chemical reaction. Metals also enter into various chemical reactions, and their ability to react with other substances is their chemical properties.

Among the basic chemical properties or qualities of metals, one can distinguish their oxidability and corrosion resistance. When metals react with oxygen, they form a film, that is, they exhibit oxidizability.

Corrosion of metals occurs in a similar way - their slow destruction due to chemical or electrochemical interaction. The ability of metals to resist corrosion is called their corrosion resistance.

Physical properties of metals

Among the main general physical properties of metals are:

• Melting.
• Density.
• Thermal conductivity.
• Thermal expansion.
• Electrical conductivity.

An important physical parameter of a metal is its density or specific gravity. What it is? The density of a metal is the amount of substance contained in a unit volume of the material. The lower the density, the lighter the metal. Light metals are: aluminum, magnesium, titanium, tin. Heavy metals include such metals as chromium, manganese, iron, cobalt, tin, tungsten, etc. (in total there are more than 40 types).

The ability of a metal to change from a solid to a liquid state is called melting. Different metals have different melting points.

The rate at which heat is conducted in a metal when heated is called the thermal conductivity of the metal. And compared to other materials, all metals have high thermal conductivity; to put it simply, they heat up quickly.

In addition to thermal conductivity, all metals conduct electric current, although some do it better and some worse (this depends on the structure of the crystal lattice of a particular metal). The ability of a metal to conduct electric current is called electrical conductivity. Metals with excellent electrical conductivity are gold, aluminum and iron, which is why they are often used in the electrical industry and instrument making.

Mechanical properties of metals

The main mechanical properties of metals are their hardness, elasticity, strength, toughness and ductility.

When two metals come into contact, microdents can form, but a harder metal can withstand impacts more effectively. This resistance of the metal surface to external impacts is its hardness.

How does the hardness of a metal differ from its strength? Strength is the ability of a metal to resist destruction under the influence of any other external forces.

The elasticity of a metal refers to its ability to return to its original shape and size after the load that caused the deformation of the metal is removed.

The ability of a metal to change shape under external influence is called plasticity.

Technological properties of metals

The technological properties of metals and alloys are important primarily in their production, since the ability to undergo various types of processing in order to create a variety of products depends on them.

Among the main technological properties are:

• Ductility.
• Fluidity.
• Weldability.
• Hardenability.
• Cutting processing.

Malleability refers to the ability of a metal to change shape in hot and cold states. The malleability of metal was discovered in ancient times, so blacksmiths engaged in processing metal products, turning them into swords or plowshares (depending on need) for many centuries and historical eras were one of the most respected and sought-after professions.

The ability of two metal alloys to join together when heated is called weldability.

The fluidity of the metal is also very important; it determines the ability of the molten metal to flow over the prepared form.

The ability of a metal to harden is called hardenability.

Interesting facts about metals

• The hardest metal on Earth is chromium. This bluish-white metal was discovered in 1766 near Yekaterinburg.
• Conversely, the softest metals are aluminum, silver and copper. Due to their softness, they are widely used in various fields, for example, in electrical equipment manufacturing.
• Gold - which for centuries has been the most precious metal itself - has another interesting property - it is the most ductile metal on Earth, which also has excellent ductility and malleability. Also, gold does not oxidize at normal temperatures (to do this it needs to be heated to 100C), has high thermal conductivity and moisture resistance. Surely all these physical characteristics make real gold so valuable.
• Mercury is a unique metal, primarily in that it is the only metal that has a liquid form. Moreover, under natural conditions, mercury does not exist in solid form, since its melting point is -38C, that is, in a solid state it can exist in places where it is simply very cold. And at room temperature 18C, mercury begins to evaporate.
• Tungsten is interesting because it is the most refractory metal in the world; in order for it to start melting, a temperature of 3420C is needed. It is for this reason that in light bulbs the filaments that take the main heat shock are made of tungsten.

Metals, video

And finally, an educational video on the topic of our article.

Source: https://www.poznavayka.org/fizika/svoystva-metallov/