melting point of various metals. Melting point of metals

In the metallurgical industry, one of the main areas is the casting of metals and their alloys due to the cheapness and relative simplicity of the process. Molds with any outlines of various dimensions, from small to large, can be cast; it is suitable for both mass production and customized production.

Casting is one of the oldest areas of work with metals, and begins around the Bronze Age: 7-3 millennium BC. e. Since then, many materials have been discovered, leading to advances in technology and increased demands on the foundry industry.

Nowadays, there are many directions and types of casting, differing in technological process. One thing remains unchanged - the physical property of metals to go from solid to liquid, and it is important to know at what temperature melting begins different types metals and their alloys.

metal melting process

This process refers to the transition of a substance from a solid to a liquid state. When the melting point is reached, the metal can be in both a solid and a liquid state, a further increase will lead to a complete transition of the material into a liquid.

The same thing happens during solidification - when the melting limit is reached, the substance will begin to pass from a liquid state to a solid state, and the temperature will not change until complete crystallization.

At the same time, it should be remembered that this rule only applicable to bare metal. Alloys do not have a clear temperature boundary and make a transition of states in a certain range:

1. Solidus - the temperature line at which the most fusible component of the alloy begins to melt.
2. Liquidus is the final melting point of all components, below which the first crystals of the alloy begin to appear.

It is impossible to accurately measure the melting point of such substances; the transition point of the states indicates the numerical interval.

Depending on the temperature at which the melting of metals begins, they are usually divided into:

• Fusible, up to 600 °C. These include zinc, lead and others.
• Medium-melting, up to 1600 °C. Most common alloys, and metals such as gold, silver, copper, iron, aluminum.
• Refractory, over 1600 °C. Titanium, molybdenum, tungsten, chromium.

There is also a boiling point - the point at which the molten metal begins to transition into a gaseous state. This is a very high temperature, typically 2 times the melting point.

Pressure influence

The melting temperature and the solidification temperature equal to it depend on the pressure, increasing with its increase. This is due to the fact that as the pressure increases, the atoms approach each other, and in order to destroy the crystal lattice, they must be moved away. At increased pressure, more energy of thermal motion is required and the melting temperature corresponding to it increases.

There are exceptions when the temperature required to go into a liquid state decreases with increased pressure. Such substances include ice, bismuth, germanium and antimony.

Melting point table

It is important for anyone involved in the steel industry, whether a welder, foundry worker, smelter or jeweler, to know the temperatures at which the materials they work with melt. The table below lists the melting points of the most common substances.

Table of melting points of metals and alloys

Name	T pl, °C
Aluminum	660,4
Copper	1084,5
Tin	231,9
Zinc	419,5
Tungsten	3420
Nickel	1455
Silver	960
Gold	1064,4
Platinum	1768
Titanium	1668
Duralumin	650
Carbon steel	1100−1500
	1110−1400
Iron	1539
Mercury	-38,9
Melchior	1170
Zirconium	3530
Silicon	1414
Nichrome	1400
Bismuth	271,4
Germanium	938,2
tin	1300−1500
Bronze	930−1140
Cobalt	1494
Potassium	63
Sodium	93,8
Brass	1000
Magnesium	650
Manganese	1246
Chromium	2130
Molybdenum	2890
Lead	327,4
Beryllium	1287
will win	3150
Fechral	1460
Antimony	630,6
titanium carbide	3150
zirconium carbide	3530
Gallium	29,76

In addition to the melting table, there are many other auxiliary materials. For example, the answer to the question, what is the boiling point of iron lies in the table of boiling substances. In addition to boiling, metals have a number of other physical properties, such as strength.

In addition to the ability to transition from a solid to a liquid state, one of the important properties of a material is its strength - the ability of a solid body to resist destruction and irreversible changes in shape. The main indicator of strength is considered to be the resistance arising from the rupture of the workpiece, pre-annealed. The concept of strength does not apply to mercury, since it is in a liquid state. The designation of strength is accepted in MPa - Mega Pascals.

There are the following strength groups of metals:

• Fragile. Their resistance does not exceed 50MPa. These include tin, lead, soft alkali metals
• Durable, 50-500 MPa. Copper, aluminum, iron, titanium. The materials of this group are the basis of many structural alloys.
• High-strength, over 500 MPa. For example, molybdenum and.

Metal strength table

The most common alloys in everyday life

As can be seen from the table, the melting points of the elements vary greatly even for materials often found in everyday life.

Thus, the minimum melting point of mercury is -38.9 ° C, therefore, at room temperature, it is already in a liquid state. This explains the fact that household thermometers have a lower mark of -39 degrees Celsius: below this indicator, mercury turns into a solid state.

Solders most commonly used in domestic use, have in their composition a significant percentage of the content of tin, which has a melting point of 231.9 ° C, so most of the solders melt at the operating temperature of the soldering iron 250−400 ° C.

In addition, there are low-melting solders with a lower melt boundary, up to 30 ° C, and are used when overheating of the soldered materials is dangerous. For these purposes, there are solders with bismuth, and the melting of these materials lies in the range from 29.7 - 120 ° C.

The melting of high-carbon materials, depending on the alloying components, lies in the range from 1100 to 1500 °C.

The melting points of metals and their alloys are in a very wide temperature range, from very low temperatures (mercury) to a limit of several thousand degrees. Knowledge of these indicators, as well as other physical properties, is very important for people who work in the metallurgical field. For example, knowing at what temperature gold and other metals melt will be useful to jewelers, casters, and smelters.

Metals have a number of original properties that are unique to these materials. There is a melting point of metals at which the crystal lattice is destroyed. The substance retains volume, but it is no longer possible to speak of the constancy of form.

In its pure form, individual metals are extremely rare. In practice, alloys are used. They have certain differences from pure substances. When complex compounds are formed, crystal lattices are combined with each other. Therefore, the properties of alloys can differ markedly from the constituent elements. The melting temperature no longer remains a constant value, it depends on the concentration of the ingredients included in the alloy.

The concept of the temperature scale

Some non-metal objects also have similar properties. The most common is water. Regarding the properties of the liquid that occupies a dominant position on Earth, a temperature scale has been developed. The reference points are the temperature of change in the aggregate states of water:

1. The transformations from liquid to solid and vice versa are taken as zero degrees.
2. Boiling (vaporization inside the liquid) at normal atmospheric pressure (760 mm Hg) is taken as 100 ⁰С.

Attention! In addition to the Celsius scale, in practice, temperature is measured in degrees Fahrenheit and on the absolute Kelvin scale. But when studying the properties of metal objects, other scales are used quite rarely.

Crystal lattices of metal

A solid is characterized by constancy:

• shape, the object retains linear dimensions in different conditions;
• volume, the object does not change the amount of substance occupied;
• masses, the amount of a substance expressed in grams (kilograms, tons);
• density, there is a constant mass per unit volume.

Upon transition to a liquid state, having reached a certain temperature, the crystal lattices are destroyed. Now you can not talk about the constancy of form. The liquid will take the form in which it is poured.

When evaporation occurs, only the mass of the substance remains constant. Gas will take up the entire volume that will be provided to it. Here it cannot be argued that the density is a constant value.

When liquids are combined, options are possible:

1. Liquids completely dissolve one into another, this is how water and alcohol behave. Throughout the volume, the concentration of substances will be the same.
2. Liquids are stratified in density, the connection occurs only at the interface. Only temporarily can you get a mechanical mixture. By mixing liquids of different properties. An example is oil and water.

Metals form alloys in the liquid state. To obtain an alloy, each of the components must be in a liquid state. In alloys, phenomena of complete dissolution of one into another are possible. Options are not excluded when the alloy will be obtained only as a result of intensive mixing. The quality of the alloy in this case is not guaranteed, therefore, they try not to mix components that do not allow obtaining stable alloys.

The resulting substances soluble in each other, when solidified, form crystal lattices of a new type. Determine:

• Heliocentered crystal lattices, they are also called body-centered. In the middle is a molecule of one substance, and around are four more molecules of another. It is customary to call such lattices loose, since in them the bond between metal molecules is weaker.
• Face-centered crystal lattices form compounds in which the component molecules are located on the faces. Metal scientists call such crystalline alloys dense. In reality, the density of the alloy may be higher than that of each of the components included in the composition (alchemists of the Middle Ages were looking for alloys in which the density would correspond to the density of gold).

Melting point of metals

Different substances have different melting points. It is customary to divide metals into:

1. Fusible - it is enough to heat them up to 600 ⁰С in order to obtain a substance in liquid form.
2. Medium-melting metals are melted in the temperature range of 600…1600 ⁰С.
3. Refractory are metals that can melt at temperatures above 1600 ⁰С.

The table shows low-melting metals in ascending order. Here you can see that the most unusual metal is mercury (Hg). Under normal conditions, it is in a liquid state. This metal has the lowest melting point.

Table 1, melting and boiling points of low-melting metals:

Table 2, melting and boiling points of medium melting metals:

Table 3, melting and boiling points of refractory metals:

To conduct the melting process, different devices are used. For example, blast furnaces are used to smelt pig iron. For melting non-ferrous metals, internal heating is carried out using currents high frequency.

In molds made of non-metallic materials, there are non-ferrous metals in the solid state. An alternating microwave magnetic field is created around them. As a result, the crystal lattices begin to loosen. The molecules of the substance begin to move, which causes heating inside the entire mass.

If it is necessary to melt a small amount of low-melting metals, muffle furnaces are used. In them, the temperature rises to 1000 ... 1200 ⁰С, which is sufficient for melting non-ferrous metals.

Ferrous metals are melted in convectors, open-hearth furnaces and induction furnaces. The process comes with the addition of alloying components that improve the quality of the metal.

The most difficult thing is to work with refractory metals. The problem is that you need to use materials that have a temperature higher than the melting point of the metal itself. Currently aviation industry considers the use of titanium (Ti) as a structural material. At high speed flight in the atmosphere, the skin is heated. Therefore, a replacement for aluminum and its alloys (AL) is needed.

The maximum melting point of this contented light metal attracts designers. Therefore, technologists are developing technological processes and equipment to produce parts from titanium and its alloys.

metal alloys

To design products from alloys, their properties are first studied. To study in small containers, the studied metals are melted in different ratios to each other. As a result, graphs are built.

The lower axis represents the concentration of component A with component B. Temperature is considered vertically. Here, the values ​​\u200b\u200bof the maximum temperature are noted when all the metal is in a molten state.

When cooled, one of the components begins to form crystals. The eutectic is in the liquid state - an ideal combination of metals in an alloy.

Metal scientists distinguish a special ratio of components at which the melting point is minimal. When alloys are made, they try to select the amount of substances used in order to obtain a eutectoid alloy. His mechanical properties the best possible. Crystal lattices form ideal face-centered positions of atoms.

The crystallization process is studied by studying the hardening of samples upon cooling. They build special graphs where they observe how the cooling rate changes. There are ready-made diagrams for different alloys. Marking the beginning and end points of crystallization, determine the composition of the alloy.

Wood's fusion

In 1860, the American dental technician Barnabas Wood was looking for the optimal ratio of ingredients to make teeth for clients at the lowest melting temperatures. He found an alloy that has a melting point of only 60.2 ... 68.5 ⁰С. Even in hot water, the metal melts easily. It includes:

• tin - 12.5 ... 12.7%;
• lead - 24.5 ... 25.0%;
• bismuth - 49.5 ... 50.3%;
• cadmium - 12.5 ... 12.7%.

The alloy is interesting for its low temperature, but has not found practical application. Attention! Cadmium and lead are heavy metals, contact with them is not recommended. Many people can become poisoned by contact with cadmium.

Alloys for soldering

In practice, many are faced with melting when soldering parts. If the surfaces of the materials to be joined are cleaned of impurities and oxides, then it is not difficult to solder them with solders. It is customary to divide solders into hard and soft solders. Soft are the most common:

• POS-15 - 278…282 °C;
• POS-25 - 258…262 °C;
• POS-33 - 245…249 °C;
• POS-40 - 236…241 °C;
• POS-61 - 181…185 °C;
• POS-90 - 217…222 °C.

They are produced for enterprises manufacturing various radio engineering devices.

Hard solders based on zinc, copper, silver and bismuth have a higher melting point:

• PSr-10 - 825…835 °С;
• PSr-12 - 780…790 °С;
• PSr-25 - 760…770 °С;
• PSr-45 - 715…721 °С;
• PSr-65 - 738…743 °С;
• PSr-70 - 778…783 °С;
• PMC-36 - 823…828 °С;
• PMTs-42 - 830…837 °С;
• ПМЦ-51 - 867…884 °С.

The use of hard solders allows you to get strong connections.

Attention! Cp means that silver is used in the composition of the solder. Such alloys have a minimum electrical resistance.

Melting point of non-metals

Non-metallic materials can be presented in solid and liquid form. Inorganic substances are presented in table. four.

Table 4, melting point of inorganic non-metals:

In practice, users are most interested in organic materials: polyethylene, polypropylene, wax, paraffin, and others. The melting point of some substances is shown in table. 5.

Table 5, melting point of polymeric materials:

Attention! The glass transition temperature is understood as the state when the material becomes brittle.

Video: melting point of known metals.

Conclusion

1. The melting point depends on the nature of the substance itself. Most often it is a constant value.
2. In practice, not pure metals are used, but their alloys. They usually have properties much better than pure metal.

- the first in importance and prevalence of structural material. It has been known since ancient times, and its properties are such that when iron was learned to be smelted in significant quantities, the metal replaced all other alloys. The age of iron has come and, judging by, this time will not end soon. This article will tell you what is the specific gravity of iron, what is its melting point in its pure form.

Iron is a typical metal, and chemically active. The substance reacts at normal temperature, and heating or increasing humidity greatly increases its reactivity. Iron corrodes in air, burns in an atmosphere of pure oxygen, and in the form of fine dust it can also ignite in air.

Pure iron is malleable, but in this form the metal is very rare. In fact, iron is an alloy with small proportions of impurities - up to 0.8%, which is characterized by the softness and malleability of a pure substance. Importance for the national economy has alloys with carbon - steel, cast iron, stainless steel.

Polymorphism is inherent in iron: there are as many as 4 modifications that differ in structure and lattice parameters:

• α-Fe - exists from zero to +769 C. It has a body-centered cubic lattice and is a ferromagnet, that is, it retains magnetization in the absence of an external magnetic field. +769 С – Curie points for metal;
• from +769 to +917 C, β-Fe appears. It differs from the α-phase only in the lattice parameters. Almost all physical properties at the same time, they are preserved with the exception of magnetic ones: iron becomes a paramagnet, that is, it loses its ability to magnetize and is drawn into a magnetic field. Metal science does not consider the β-phase as a separate modification. Since the transition does not affect significant physical characteristics;
• in the range from 917 to 1394 C, there is a γ-modification, which is characterized by a face-centered cubic lattice;
• at temperatures above +1394 C, a δ-phase appears, which is characterized by a body-centered cubic lattice.

At high pressure, as well as when the metal is alloyed with some additives, an ε-phase is formed with a hexagonal close-packed lattice.

Temperature phase transitions changes noticeably when doped with the same carbon. Actually, the very ability of iron to form so many modifications serves as the basis for processing steel in different temperature conditions. Without such transitions, the metal would not have become so widespread.

Now it is the turn of the properties of iron metal.

This video tells about the structure of iron:

Metal properties and characteristics

Iron is a fairly light, moderately refractory metal, silver-gray in color. It reacts readily with dilute acids and is therefore considered an element of medium activity. In dry air, the metal is gradually covered with an oxide film, which prevents further reaction.

But at the slightest humidity, instead of a film, rust appears - loose and heterogeneous in composition. Rust does not prevent further corrosion of iron. However, the physical properties of the metal, and, most importantly, its alloys with carbon are such that, despite the low corrosion resistance, the use of iron is more than justified.

Mass and Density

The molecular weight of iron is 55.8, which indicates the relative lightness of the substance. What is the density of iron? This indicator is determined by the phase modification:

• α-Fe - 7.87 g / cu. cm at 20 C, and 7.67 g / cu. cm at 600 C;
• the γ-phase is distinguished by an even lower density - 7.59 g / cc at 1000C;
• the density of the δ-phase is 7.409 g/cm3.

As the temperature rises, the density of iron naturally decreases.

And now let's find out what is the melting point of iron in Celsius, comparing it, for example, with or cast iron.

Temperature Range

The metal is classified as moderately refractory, which means a relatively low temperature of the change in the state of aggregation:

• melting point - 1539 C;
• boiling point - 2862 C;
• Curie temperature, that is, the loss of the ability to magnetize - 719 C.

It should be borne in mind that when talking about the melting or boiling point, they are dealing with the δ-phase of a substance.

This video will tell you about the physical and chemical properties gland:

Mechanical characteristics

Iron and its alloys are so common that although they began to be used later than, for example, and, they became a kind of standard. When metals are compared, they point to iron: stronger than steel, 2 times softer than iron, and so on.

Characteristics are given for a metal containing small proportions of impurities:

• hardness on the Mohs scale - 4–5;
• Brinell hardness - 350-450 Mn / sq. m. Moreover, chemically pure iron has a higher hardness - 588–686;

Strength indicators are extremely dependent on the amount and nature of impurities. This value is regulated by GOST for each brand of alloy or pure metal. Thus, the ultimate compressive strength for unalloyed steel is 400–550 MPa. When hardening this grade, the tensile strength increases to 700 MPa.

• the impact strength of the metal is 300 MN/sq m;
• yield strength –100 MN/sq. m.

We will learn further about what is needed to determine the specific heat capacity of iron.

Heat capacity and thermal conductivity

Like any metal, iron conducts heat, although its performance in this area is low: in terms of thermal conductivity, the metal is inferior to aluminum - 2 times less, and - 5 times.

The thermal conductivity at 25°C is 74.04 W/(m·K). The value depends on the temperature;

• at 100 K the thermal conductivity is 132 [W/(m.K)];
• at 300 K - 80.3 [W / (m.K)];
• at 400 - 69.4 [W / (m.K)];
• and at 1500 - 31.8 [W / (m.K)].

• The coefficient of thermal expansion at 20 C is 11.7 10-6.
• The heat capacity of a metal is determined by its phase structure and depends rather intricately on temperature. With an increase to 250 C, the heat capacity slowly increases, then increases sharply until the Curie point is reached, and then begins to decrease.
• The specific heat capacity in the temperature range from 0 to 1000C is 640.57 J/(kg K).

Electrical conductivity

Iron conducts current, but not nearly as well as copper and silver. The specific electrical resistance of the metal under normal conditions is 9.7 10-8 ohm m.

Since iron is a ferromagnet, its performance in this area is more significant:

• saturation magnetic induction is 2.18 T;
• magnetic permeability - 1.45.106.

Toxicity

Metal does not pose a danger to the human body. steel and the manufacture of iron products can be dangerous, but only due to high temperatures and those additives that are used in the production of various alloys. Iron waste - scrap metal, pose a danger to environment, but quite moderate, since the metal rusts in air.

Iron does not have biological inertness, therefore it is not used as a material for prosthetics. However, in the human body, this element plays one of the critical roles: a violation in the absorption of iron or an insufficient amount of the latter in the diet guarantees anemia at best.

Iron is absorbed with great difficulty - 5-10% of the total amount supplied to the body, or 10-20% if there is a lack of it.

• The usual daily iron requirement is 10 mg for men and 20 mg for women.
• The toxic dose is 200 mg/day.
• Lethal - 7–35 g. It is almost impossible to get such an amount of iron, so iron poisoning is extremely rare.

Iron is a metal whose physical characteristics, in particular strength, can be significantly changed by recourse to machining or the addition of a very small amount of alloying elements. This feature, combined with the availability and ease of extraction of metal, makes iron the most demanded structural material.

A specialist will tell you more about the properties of iron in the video below:

In the metallurgical industry, one of the main areas is the casting of metals and their alloys due to the cheapness and relative simplicity of the process. Molds with any outlines of various dimensions, from small to large, can be cast; it is suitable for both mass production and customized production.

Casting is one of the oldest areas of work with metals, and begins around the Bronze Age: 7-3 millennium BC. e. Since then, many materials have been discovered, leading to advances in technology and increased demands on the foundry industry.

Nowadays, there are many directions and types of casting, which differ in the technological process. One thing remains unchanged - the physical property of metals to pass from a solid to a liquid state, and it is important to know at what temperature the melting of different types of metals and their alloys begins.

metal melting process

This process refers to the transition of a substance from a solid to a liquid state. When the melting point is reached, the metal can be in both a solid and a liquid state, a further increase will lead to a complete transition of the material into a liquid.

The same thing happens during solidification - when the melting limit is reached, the substance will begin to pass from a liquid state to a solid state, and the temperature will not change until complete crystallization.

It should be remembered that this rule applies only to pure metal. Alloys do not have a clear temperature boundary and make a transition of states to some range:

1. Solidus - the temperature line at which the most fusible component of the alloy begins to melt.
2. Liquidus is the final melting point of all components, below which the first crystals of the alloy begin to appear.

It is impossible to accurately measure the melting point of such substances; the transition point of the states indicates the numerical interval.

Depending on the temperature at which the melting of metals begins, they are divided into:

• Fusible, up to 600 °C. These include tin, zinc, lead and others.
• Medium-melting, up to 1600 °C. Most common alloys, and metals such as gold, silver, copper, iron, aluminum.
• Refractory, over 1600 °C. Titanium, molybdenum, tungsten, chromium.

There is also a boiling point - the point at which the molten metal begins to transition into a gaseous state. This is a very high temperature, typically 2 times the melting point.

Pressure influence

The melting temperature and the solidification temperature equal to it depend on the pressure, increasing with its increase. This is due to the fact that as the pressure increases, the atoms approach each other, and in order to destroy the crystal lattice, they must be moved away. At increased pressure, more energy of thermal motion is required and the melting temperature corresponding to it increases.

There are exceptions when the temperature required to go into a liquid state decreases with increased pressure. Such substances include ice, bismuth, germanium and antimony.

Melting point table

It is important for anyone involved in the steel industry, whether a welder, foundry worker, smelter or jeweler, to know the temperatures at which the materials they work with melt. The table below lists the melting points of the most common substances.

Melting point table metals and alloys

Name	T pl, °C
Aluminum	660,4
Copper	1084,5
Tin	231,9
Zinc	419,5
Tungsten	3420
Nickel	1455
Silver	960
Gold	1064,4
Platinum	1768
Titanium	1668
Duralumin	650
Carbon steel	1100−1500
Cast iron	1110−1400
Iron	1539
Mercury	-38,9
Melchior	1170
Zirconium	3530
Silicon	1414
Nichrome	1400
Bismuth	271,4
Germanium	938,2
tin	1300−1500
Bronze	930−1140
Cobalt	1494
Potassium	63
Sodium	93,8
Brass	1000
Magnesium	650
Manganese	1246
Chromium	2130
Molybdenum	2890
Lead	327,4
Beryllium	1287
will win	3150
Fechral	1460
Antimony	630,6
titanium carbide	3150
zirconium carbide	3530
Gallium	29,76

In addition to the melting table, there are many other auxiliary materials. For example, the answer to the question, what is the boiling point of iron lies in the table of boiling substances. In addition to boiling, metals have a number of other physical properties, such as strength.

Metal strength

In addition to the ability to transition from a solid to a liquid state, one of the important properties of a material is its strength - the ability of a solid body to resist destruction and irreversible changes in shape. The main indicator of strength is considered to be the resistance arising from the rupture of the workpiece, pre-annealed. The concept of strength does not apply to mercury, since it is in a liquid state. The designation of strength is accepted in MPa - Mega Pascals.

There are the following groups strength of metals:

• Fragile. Their resistance does not exceed 50MPa. These include tin, lead, soft alkali metals
• Durable, 50-500 MPa. Copper, aluminum, iron, titanium. The materials of this group are the basis of many structural alloys.
• High-strength, over 500 MPa. For example, molybdenum and tungsten.

Metal strength table

The most common alloys in everyday life

As can be seen from the table, the melting points of the elements vary greatly even for materials often found in everyday life.

Thus, the minimum melting point of mercury is -38.9 ° C, therefore, at room temperature, it is already in a liquid state. This explains the fact that household thermometers have a lower mark of -39 degrees Celsius: below this indicator, mercury turns into a solid state.

Solders, the most common in domestic use, contain a significant percentage of tin, which has a melting point of 231.9 ° C, so most solder melts at a soldering iron operating temperature of 250-400 ° C.

In addition, there are low-melting solders with a lower melt boundary, up to 30 ° C, and are used when overheating of the soldered materials is dangerous. For these purposes, there are solders with bismuth, and the melting of these materials lies in the range from 29.7 - 120 ° C.

The melting of high-carbon materials, depending on the alloying components, lies in the range from 1100 to 1500 °C.

The melting points of metals and their alloys are in a very wide temperature range, from very low temperatures (mercury) to a limit of several thousand degrees. Knowledge of these indicators, as well as other physical properties, is very important for people who work in the metallurgical field. For example, knowing at what temperature gold and other metals melt will be useful to jewelers, casters, and smelters.

Each metal or alloy has unique properties, including its melting point. In this case, the object passes from one state to another, in a particular case, it becomes from a solid to a liquid. To melt it, it is necessary to bring heat to it and heat it until the desired temperature is reached. At the moment when the desired temperature point of a given alloy is reached, it can still remain in a solid state. With continued exposure, it begins to melt.

Mercury has the lowest melting point - it melts even at -39 ° C, tungsten has the highest - 3422 ° C. For alloys (steel and others), determine exact number extremely difficult. It all depends on the ratio of the components in them. For alloys, it is written as a numerical interval.

How is the process

Elements, whatever they are: gold, iron, cast iron, steel, or any other - melt about the same. This happens with external or internal heating. External heating is carried out in a thermal furnace. For internal, resistive heating is used, passing an electric current or induction heating in high frequency electromagnetic field. The impact is about the same.

When heating occurs, the amplitude of thermal vibrations of molecules increases. Appear lattice structural defects accompanied by the breaking of interatomic bonds. The period of lattice destruction and accumulation of defects is called melting.

Depending on the degree at which metals are melted, they are divided into:

1. fusible - up to 600 ° C: lead, zinc, tin;
2. medium-melting - from 600 ° C to 1600 ° C: gold, copper, aluminum, cast iron, iron and most of all elements and compounds;
3. refractory - from 1600 ° C: chromium, tungsten, molybdenum, titanium.

Depending on what the maximum degree is, the melting apparatus is also selected. It should be the stronger, the stronger the heating.

The second important value is the degree of boiling. This is the parameter at which liquids begin to boil. As a rule, it is twice the degree of melting. These values ​​are directly proportional to each other and are usually given at normal pressure.

If the pressure increases, the amount of melting also increases. If the pressure decreases, then it decreases.

Characteristic table

Metals and alloys - indispensable basis for forging, foundry, jewelry and many other areas of production. Whatever the master does ( gold jewelry, cast iron fences, knives made of steel or copper bracelets), for correct operation he needs to know the temperatures at which this or that element melts.

To find out this parameter, you need to refer to the table. In the table you can also find the degree of boiling.

Among the most commonly used elements in everyday life, the melting point indicators are as follows:

1. aluminum - 660 °C;
2. melting point of copper - 1083 °C;
3. melting point of gold - 1063 ° C;
4. silver - 960 °C;
5. tin - 232 °C. Tin is often used for soldering, since the temperature of a working soldering iron is just 250–400 degrees;
6. lead - 327 °C;
7. melting point of iron - 1539 ° C;
8. melting temperature of steel (an alloy of iron and carbon) - from 1300 °C to 1500 °C. It fluctuates depending on the saturation of steel components;
9. melting point of cast iron (also an alloy of iron and carbon) - from 1100 ° C to 1300 ° C;
10. mercury - -38.9 ° C.

As is clear from this part of the table, the most fusible metal is mercury, which is already in a liquid state at positive temperatures.

The degree of boiling of all these elements is almost twice, and sometimes even higher than the degree of melting. For example, for gold it is 2660 ° C, for aluminum - 2519°C, for iron - 2900 ° C, for copper - 2580 ° C, for mercury - 356.73 ° C.

For alloys such as steel, cast iron and other metals, the calculation is approximately the same and depends on the ratio of components in the alloy.

The maximum boiling point for metals is rhenium - 5596°C. The highest boiling point is in the most refractory materials.

There are tables that also indicate density of metals. The lightest metal is lithium, the heaviest is osmium. Osmium has a higher density than uranium and plutonium when viewed at room temperature. Light metals include: magnesium, aluminum, titanium. Heavy metals include most common metals: iron, copper, zinc, tin and many others. Last group- very heavy metals, these include: tungsten, gold, lead and others.

Another indicator found in the tables is thermal conductivity of metals. Worst of all, neptunium conducts heat, and silver is the best thermal conductor. Gold, steel, iron, cast iron and other elements are in the middle between these two extremes. Clear characteristics for each can be found in the desired table.

Melting temperature, along with density, refers to physical characteristics metals. Metal melting point- the temperature at which the metal passes from the solid state, in which it is in the normal state (except mercury), to the liquid state when heated. During melting, the volume of the metal practically does not change, therefore, the normal temperature for the melting point is atmospheric pressure does not affect.

Melting point of metals is in the range from -39 degrees Celsius to +3410 degrees. For most metals, the melting point is high, however, some metals can be melted at home by heating on a conventional burner (tin, lead).

Classification of metals by melting point

1. fusible metals, whose melting point fluctuates up to 600 degrees Celsius, for example zinc, tin, bismuth.
2. Medium melting metals, which melt at a temperature from 600 to 1600 degrees Celsius: such as aluminum, copper, tin, iron.
3. Refractory metals, whose melting point reaches over 1600 degrees Celsius - tungsten, titanium, chrome and etc.
4. - the only metal that is under normal conditions (normal atmospheric pressure, average ambient temperature) in a liquid state. The melting point of mercury is about -39 degrees Celsius.

Table of melting points of metals and alloys

Metal	Melting temperature, degrees Celsius
Aluminum	660,4
Tungsten	3420
Duralumin	~650
Iron	1539
Gold	1063
Iridium	2447
Potassium	63,6
Silicon	1415
Brass	~1000
fusible alloy	60,5
Magnesium	650
Copper	1084,5
Sodium	97,8
Nickel	1455
Tin	231,9
Platinum	1769,3
Mercury	–38,9
Lead	327,4
Silver	961,9
Steel	1300-1500
Zinc	419,5
Cast iron	1100-1300

When melting metal for the manufacture of metal products-castings, the choice of equipment, material for metal molding, etc. depends on the melting temperature. It should also be remembered that when alloying a metal with other elements, the melting point most often decreases.

Interesting fact

Do not confuse the concepts of "metal melting point" and "metal boiling point" - for many metals, these characteristics are significantly different: for example, silver melts at a temperature of 961 degrees Celsius, and boils only when heating reaches 2180 degrees.

The melting point of a metal is the minimum temperature at which it changes from solid to liquid. During melting, its volume practically does not change. Metals are classified by melting point depending on the degree of heating.

fusible metals

Fusible metals have a melting point below 600°C. These are zinc, tin, bismuth. Such metals can be melted at home by heating them on the stove, or using a soldering iron. Fusible metals are used in electronics and engineering to connect metal elements and wires for the movement of electric current. The melting point of tin is 232 degrees, and zinc is 419.

Medium melting metals

Medium-melting metals begin to change from a solid to a liquid state at temperatures from 600°C to 1600°C. They are used to make slabs, rebars, blocks and other metal structures suitable for construction. This group of metals includes iron, copper, aluminum, they are also part of many alloys. Copper is added to precious metal alloys such as gold, silver, and platinum. 750 gold contains 25% alloy metals, including copper, which gives it a reddish tint. The melting point of this material is 1084 °C. And aluminum begins to melt at a relatively low temperature of 660 degrees Celsius. It is a light, ductile and inexpensive metal that does not oxidize or rust, so it is widely used in the manufacture of utensils. The melting point of iron is 1539 degrees. It is one of the most popular and affordable metals, its use is widespread in the construction and automotive industries. But due to the fact that iron is subject to corrosion, it must be further processed and covered with a protective layer of paint, drying oil, or moisture should not be allowed to enter.

Refractory metals

The temperature of refractory metals is above 1600°C. These are tungsten, titanium, platinum, chromium and others. They are used as light sources, machine parts, lubricants, and in the nuclear industry. They are used to make wires, high-voltage wires and are used to melt other metals with a lower melting point. Platinum begins to change from solid to liquid at 1769 degrees, and tungsten at 3420°C.

Mercury is the only metal that is in a liquid state under normal conditions, namely, normal atmospheric pressure and average ambient temperature. The melting point of mercury is minus 39°C. This metal and its fumes are poisonous, so it is only used in closed containers or in laboratories. A common use of mercury is as a thermometer to measure body temperature.