At the dawn of mankind, people tried to master the creation of various elements from metals. Such things were more elegant, thin and durable. Copper was one of the first to be “conquered.” The presence of ore required the material to be melted and separated from the slag. This was performed in hot coals on the ground. The temperature was increased by bellows that created heat. The process was hot and labor-intensive, but it made it possible to obtain unusual jewelry, dishes and tools. A separate area was the production of weapons for hunting, which could serve for a long time. The melting point of copper is relatively low, which makes it possible today to melt it in a domestic setting and produce items necessary for repairing mechanisms or electrical equipment. What is the melting temperature of copper and its alloys? How can you perform this procedure at home?

In the periodic table this material is called Cuprum. It is assigned atomic number 29. It is a plastic material that can be easily processed in hard form by grinding and carving equipment. Good voltage conductivity allows copper to be actively used in electrical and industrial equipment.

In the earth's crust, the material occurs in the form of sulfide ore. Frequently encountered deposits are found in South America, Kazakhstan, and Russia. This is copper pyrite and copper luster. They form at average temperatures, like thin geothermal layers. Pure nuggets are also found that do not require slag separation, but require melting to add other metals, since copper is usually not used in its pure form.

The metal has a reddish-yellow tint due to the oxide film that immediately covers the surface upon interaction with oxygen. The oxide not only gives a beautiful color, but also promotes higher anti-corrosion properties. The material without an oxide film has a light yellow color.

Pure copper melts when it reaches 1080 degrees. This relatively low figure allows you to work with metal both in production conditions and at home. Other physical properties of the material are as follows:

• The density of copper in its pure form is 8.94 x 103 kg/m2.
• The metal is distinguished by good electrical conductivity, which at an average temperature of 20 degrees is 55.5 S.
• Copper transfers heat well, and this figure is 390 J/kg.
• The release of carbon when a liquid material boils starts at 2595 degrees.
• Electrical resistance (specific) in the temperature range from 20 to 100 degrees - 1.78 x 10 Ohm/m.

Melting of metal and its alloys

The copper melting schedule has five process steps:

1. At a temperature of 20-100 degrees, the metal is in a solid state. Subsequent heating promotes a color change that occurs as the top oxide is removed.
2. When the temperature reaches 1083 degrees, the material turns into a liquid state, and its color becomes completely white. At this moment, the crystal lattice of the metal is destroyed. For a short period, the temperature increase stops, and after reaching a completely liquid stage, it resumes.
3. The material boils at 2595 degrees. This is similar to the boiling of a thick liquid, where carbon is also released.
4. When the heat source is turned off, the peak temperature begins to decrease. During crystallization, the temperature decrease slows down.
5. After reaching the solid stage, the metal cools down completely.

The melting point of bronze is slightly lower due to the presence of tin. The destruction of the crystal lattice of this alloy occurs when it reaches 950-1100 degrees. An alloy of copper and zinc, known as brass, can melt from 900°C. This allows you to work with materials using simple equipment.

Melting at home

Melting copper at home is possible in several ways. To do this you will need a number of devices. The complexity of the process depends on the specific type of equipment used.

The easiest way to melt copper at home is a muffle furnace. Metal craftsmen will have such a device that they can use. The pieces of metal are placed in a special container - a crucible. It is installed in the oven, on which the required temperature is set. Through the viewing window, you can notice the process of transition to a liquid state, and by opening the door, remove the oxide film. This must be done with a steel hook and wearing a protective glove. The heat from the stove is quite intense, so you need to act carefully.

Another way to smelt copper at home is with a propane-oxygen flame. It is also well suited for metal alloys with zinc or tin. The working tool in the hands of the master can be a torch or cutter. An acetylene-oxygen flame will also work, but it will take a little longer to heat the material. Pieces of the alloy are placed in a crucible mounted on a heat-resistant base. The burner performs random movements throughout the entire body of the container. A quick effect can be obtained if you make sure that the flame torch touches the surface of the crucible with its blue tip. The temperature is highest there.

Another way is a powerful microwave. But in order to increase the heat-saving properties and protect the internal parts of the equipment from overheating, it is necessary to place the crucible in a heat-resistant material and cover it on top. These can be special types of bricks.

The simplest economic method is a layer of charcoal on which a forge with copper is installed. You can increase the heat using a blow-out vacuum cleaner. The tip of the hose aimed at the coals should be metal, and the nozzle should be flat to enhance air flow.

The production of parts and other elements from copper by melting it at home is possible due to the relatively low temperature of destruction of the crystal lattice in the material. Using the devices described above and watching the video, most will be able to achieve this goal.

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

Casting is one of the oldest areas of working with metals, and begins around the Bronze Age: 7-3 millennium BC. e. Since then, many materials have been discovered, leading to advancements 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 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 either a solid or liquid state; further increase will lead to the complete transition of the material into a liquid.

The same thing happens when solidifying - when the melting limit is reached, the substance will begin to transition from a liquid 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 undergo state transitions in a certain range:

1. Solidus is 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 alloy crystals begin to appear.

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

Depending on the temperature at which metals begin to melt, they are usually divided into:

• Low-melting, 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.

Effect of pressure

The melting temperature and the equal solidification temperature depend on pressure, increasing with its increase. This is due to the fact that with increasing pressure the atoms come closer to each other, and in order to destroy the crystal lattice they need to be moved away. At increased pressure, greater thermal energy is required and the corresponding melting temperature increases.

There are exceptions when the temperature required to transform 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 metallurgical industry, whether a welder, foundry worker, smelter or jeweler, to know the temperatures at which the materials they work with melt. The table below shows the melting points of the most common substances.

Table of melting temperatures of metals and alloys

In addition to the melting table, there are many other supporting 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 the resistance that occurs when a pre-annealed workpiece breaks. The concept of strength does not apply to mercury because 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-alkaline metals
• Durable, 50−500 MPa. Copper, aluminum, iron, titanium. 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 elements vary greatly even among materials commonly found in everyday life.

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

The most common solders in household use contain a significant percentage of tin, which has a melting point of 231.9 °C, so most solders melt at the operating temperature of the soldering iron 250−400 °C.

In addition, there are low-melting solders with a lower melt limit, up to 30 °C, and are used when overheating of the materials being soldered 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.

Melting of high-carbon materials, depending on alloying components, ranges 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 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, knowledge of the temperature at which gold and other metals melt will be useful to jewelers, foundries and smelters.

Physical properties of metals.

Density. This is one of the most important characteristics of metals and alloys. According to their density, metals are divided into the following groups:

lungs(density not more than 5 g/cm 3) - magnesium, aluminum, titanium, etc.:

heavy- (density from 5 to 10 g/cm 3) - iron, nickel, copper, zinc, tin, etc. (this is the most extensive group);

very heavy(density more than 10 g/cm3) - molybdenum, tungsten, gold, lead, etc.

Table 2 shows the density values ​​of metals. (This and the following tables characterize the properties of those metals that form the basis of alloys for artistic casting).

Table 2. Metal density.

Melting temperature. Depending on the melting point, the metal is divided into the following groups:

fusible(melting point does not exceed 600 o C) - zinc, tin, lead, bismuth, etc.;

medium-melting(from 600 o C to 1600 o C) - these include almost half of the metals, including magnesium, aluminum, iron, nickel, copper, gold;

refractory(more than 1600 o C) - tungsten, molybdenum, titanium, chromium, etc.

Mercury is a liquid.

When making artistic castings, the melting point of the metal or alloy determines the choice of melting unit and refractory molding material. When additives are introduced into a metal, the melting point, as a rule, decreases.

Table 3. Melting and boiling points of metals.

Specific heat. This is the amount of energy required to raise the temperature of a unit mass by one degree. Specific heat capacity decreases with increasing atomic number of an element in the periodic table. The dependence of the specific heat capacity of an element in the solid state on atomic mass is described approximately by the Dulong and Petit law:

m a c m = 6.

Where, m a- atomic mass; c m- specific heat capacity (J/kg * o C).

Table 4 shows the specific heat capacity of some metals.

Table 4. Specific heat capacity of metals.

Latent heat of fusion of metals. This characteristic (Table 5), along with the specific heat capacity of the metals, largely determines the required power of the melting unit. Melting a low-melting metal sometimes requires more thermal energy than a refractory metal. For example, heating copper from 20 to 1133 o C will require one and a half times less thermal energy than heating the same amount of aluminum from 20 to 710 o C.

Table 5. Latent heat of metal

Heat capacity. Heat capacity characterizes the transfer of thermal energy from one part of the body to another, or more precisely, the molecular transfer of heat in a continuous medium due to the presence of a temperature gradient. (Table 6)

Table 6. Thermal conductivity coefficient of metals at 20 o C

The quality of artistic casting is closely related to the thermal conductivity of the metal. During the smelting process, it is important not only to ensure a sufficiently high temperature of the metal, but also to achieve a uniform temperature distribution throughout the entire volume of the liquid bath. The higher the thermal conductivity, the more uniformly the temperature is distributed. During electric arc melting, despite the high thermal conductivity of most metals, the temperature difference across the cross section of the bath reaches 70-80 o C, and for a metal with low thermal conductivity this difference can reach 200 o C or more.

Favorable conditions for temperature equalization are created during induction melting.

Thermal expansion coefficient. This value, which characterizes the change in the dimensions of a 1 m long sample when heated by 1 o C, is important for enamel work (Table 7)

The thermal expansion coefficients of the metal base and enamel should be as close as possible so that the enamel does not crack after firing. Most enamels representing a solid coefficient of silicon oxides and other elements have a low coefficient of thermal expansion. As practice has shown, enamels adhere very well to iron and gold, and less firmly to copper and silver. It can be assumed that titanium is a very suitable material for enameling.

Table 7. Thermal expansion coefficient of metals.

Reflectivity. This is the ability of a metal to reflect light waves of a certain length, which is perceived by the human eye as color (Table 8). Metal colors are shown in Table 9.

Table 8. Correspondence between color and wavelength.

Table 9. Metal colors.

Pure metals are practically not used in decorative and applied arts. For the manufacture of various products, alloys are used, the color characteristics of which differ significantly from the color of the base metal.

Over the course of a long time, vast experience has been accumulated in the use of various casting alloys for the manufacture of jewelry, household items, sculptures and many other types of artistic casting. However, the relationship between the structure of the alloy and its reflectivity has not yet been revealed.

Steel is an alloy of iron to which carbon is mixed. Its main benefit in construction is strength, because this substance retains its volume and shape for a long time. The whole point is that the particles of the body are in a position of equilibrium. In this case, the attractive and repulsive forces between the particles are equal. The particles are in a clearly defined order.

There are four types of this material: regular, alloy, low-alloy, high-alloy steel. They differ in the number of additives in their composition. The usual one contains a small amount, and then increases. The following additives are used:

• Manganese.
• Nickel.
• Chromium.
• Vanadium.
• Molybdenum.

Melting temperatures of steel

Under certain conditions, solids melt, that is, they turn into a liquid state. Each substance does this at a certain temperature.

• Melting is the process of transition of a substance from a solid to a liquid state.
• Melting point is the temperature at which a crystalline solid melts and turns into a liquid state. Denoted by t.

Physicists use a specific table of melting and crystallization, which is given below:

Based on the table, we can safely say that the melting point of steel is 1400 °C.

Stainless steel is one of the many iron alloys found in steel. It contains Chromium from 15 to 30%, which makes it rust-resistant, creating a protective layer of oxide on the surface, and carbon. The most popular brands of this type are foreign. These are the 300th and 400th series. They are distinguished by their strength, resistance to adverse conditions and ductility. The 200 series is of lower quality, but cheaper. This is a beneficial factor for the manufacturer. Its composition was first noticed in 1913 by Harry Brearley, who conducted many different experiments on steel.

At the moment, stainless steel is divided into three groups:

• Heat resistant- at high temperatures it has high mechanical strength and stability. The parts that are made from it are used in the pharmaceutical, rocketry, and textile industries.
• Rust-resistant- has great resistance to rusting processes. It is used in household and medical devices, as well as in mechanical engineering for the manufacture of parts.
• Heat resistant- is resistant to corrosion at high temperatures, suitable for use in chemical plants.

The melting point of stainless steel varies depending on its grade and the number of alloys from approximately 1300 °C to 1400 °C.

Cast iron is an alloy of carbon and iron, it contains impurities of manganese, silicon, sulfur and phosphorus. Withstands low voltages and loads. One of its many advantages is its low cost for consumers. There are four types of cast iron:

The melting points of steel and cast iron are different, as stated in the table above. Steel has higher strength and resistance to high temperatures than cast iron, temperatures differ by as much as 200 degrees. For cast iron, this number ranges from approximately 1100 to 1200 degrees, depending on the impurities it contains.

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

Low-melting metals

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

Medium melting metals

Medium-melting metals begin to transform from solid to liquid at temperatures from 600°C to 1600°C. They are used to make slabs, reinforcements, blocks and other metal structures suitable for construction. This group of metals includes iron, copper, aluminum, and they are also part of many alloys. Copper is added to alloys of precious metals such as gold, silver, and platinum. 750 gold consists of 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. This is a lightweight, ductile and inexpensive metal that does not oxidize or rust, therefore it is widely used in the manufacture of tableware. The temperature is 1539 degrees. This 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 additionally processed and covered with a protective layer of paint, drying oil, or prevent moisture from entering.

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 transition from solid to liquid at a temperature of 1769 degrees, and tungsten at a temperature of 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 vapors are poisonous, so it is used only in closed containers or in laboratories. A common use of mercury is as a thermometer to measure body temperature.