Methods of melting metals and alloys. Features of melting copper alloys. Melting using homemade devices

Copper is considered one of the most common alloys today. A fairly common question is how to melt copper at home. High casting properties make it possible to obtain high-quality and precise products and to use the alloy as a coating. Copper casting can be carried out in the absence of special equipment. The process is characterized by a large number of different features, which will be discussed below.

Melting temperature

One of the most important parameters of each alloy is the melting point. It may depend on the concentration of alloying elements in the composition. Pure copper is cast at a temperature of 1080 °C, at which the crystal lattice is rearranged and the alloy becomes liquid. Copper can be melted even if there is an impurity in the form of tin, but it can vary from 930 to 1140 °C.

Zinc can be added to the composition, resulting in brass. Depending on the concentration of this alloying element, smelting can be carried out at 900 ⁰C.

When considering the features of copper smelting, the boiling point is taken into account. This figure is 2,560 °C. At home, it is almost impossible to achieve such a temperature. The boiling process is indicated by the appearance of gas bubbles.

Do not bring the alloy to a boil. This is due to the fact that after gases are released, the structure becomes porous. Due to this, not only decorative but also mechanical qualities are reduced.

Sequencing

If necessary, you can obtain products for decorative or practical purposes at home. Melting copper at home, step-by-step instructions are as follows:

1. The raw material is crushed and then placed in a crucible. It is worth considering that by reducing the size of pieces of metal, the melting process is significantly accelerated.
2. After filling the crucible, it is placed in an oven, which is preheated.
3. The molten alloy must be removed from the furnace using special pliers. Due to the active oxidation process, a homogeneous film may form on the surface. Before casting from copper, it must be removed.
4. The metal is carefully poured into the prepared container. It is worth considering that if the straightened alloy gets into exposed areas of the body, serious injuries may occur. In addition, some materials may ignite upon contact. Therefore, extreme caution must be taken.

When considering how to smelt copper at home, it is worth considering that you can use more than just furnaces. In some cases, a gas burner is used to heat the bottom of the crucible. The process is less productive, but it takes little time to prepare.

An ordinary blowtorch can be used as heating equipment. When using this technology, it is worth considering that contact of copper with air leads to the rapid appearance of oxide. In some cases, to reduce the intensity of oxidation, the surface is covered with crushed charcoal.

Copper smelting equipment

The preparatory stage involves the purchase of special equipment. You can melt copper at home if you have:

1. Muffle furnace. Modern design options make it possible to control the heating power with high precision, due to which the melting process is significantly simplified and a better result can be achieved.
2. A crucible designed to hold the charge and melt it.
3. Tongs with which the crucible is pulled out of the furnace. It is worth considering that the surface will heat up, so you need to use a special mechanism made of a heat-resistant alloy.
4. Hook and household vacuum cleaner.
5. Charcoal for surface coating.
6. A mold made of heat-resistant material into which casting will be carried out.
7. Gas burner or forge to increase the ductility of the alloy.

Purchase professional equipment only if copper casting is carried out periodically. It is characterized by high cost, as well as efficiency in use.

Muffle furnace

The easiest way to melt copper at home is to install a muffle furnace. Among its features we note:

1. The charge can be heated to higher temperatures, thereby increasing fluidity. This is due to high efficiency, since the walls of the structure reflect and accumulate heat.
2. The melting process is accelerated.
3. High performance. Uniform heat distribution allows large quantities of copper to be melted simultaneously.

In addition, the muffle furnace is quite easy to install if you follow all safety rules. Problems with installing such equipment at home often arise due to the large size of the structure.

Gas-burner

Copper casting at home using a gas burner is often carried out if copper products are made extremely rarely. Such a process is characterized by low financial costs. When choosing such a technology, the following are taken into account:

1. Low efficiency indicator.
2. At the time of melting, difficulties arise with uniform heat distribution.
3. Work should be carried out in an open space in compliance with fire safety rules.

A gas burner can heat the crucible within a few minutes. It is worth considering that copper will oxidize quickly.

Blowtorch

Melting when using blowtorches is extremely rare. This is due to the low efficiency of this method. As in the previous case, when using a blowtorch, active oxidation of the surface occurs.

When using a blowtorch, take into account the fact that it takes quite a lot of time to heat up the metal. In this case, heating must take place without interruption, since the metal cools quickly, after which it begins to crystallize.

Horn

At home, casting copper blanks can be done in a forge. This oven is characterized by the following features:

1. It is often used in blacksmithing.
2. It is worth taking into account the low efficiency indicator, due to which it takes much longer to melt copper.
3. There are two designs: open and closed.

The melting temperature when using a forge is relatively low. Therefore, not all copper can be melted using this method.

Melting using homemade devices

Melting can be carried out using homemade structures. They are often a combination of a heat source and a housing made of heat-reflecting material. You can melt copper at home using such devices.

As a rule, by creating a special reflective structure, efficiency is increased and the process of heating the charge is accelerated. You can make a reflective body for the crucible using heat-resistant bricks.

2014-05-30

Copper products look very beautiful and stylish, thereby making you want to create a copper product yourself. For these purposes, the metal must first be melted. In the casting process, most people use several main types of copper - pure red and alloys such as bronze and brass.

The process of smelting copper products in a muffle furnace

First, you need to put the prepared pieces of metal into the crucible, then place the crucible in the muffle furnace. Adjust heat to desired position. When the metal begins to melt, an oxide film appears on its surface.

When a certain melting temperature is reached, you need to open the door and grab the crucible using tongs. Use a steel hook to remove the formed oxide film, and then pour the molten metal into molds prepared in advance. If the muffle furnace has the necessary power, it can melt a variety of copper alloys or red copper.

How to melt copper using other methods

If it is not possible to use a muffle furnace, there is an alternative - to melt the metal using an autogen, in which case the flame should be directed from the bottom of the crucible in an upward direction. This process is accompanied by good air access. In order to avoid strong oxidation of copper, you can sprinkle crushed charcoal on top.

Yellow copper, the so-called brass, and some types of bronze, which are fusible, can be melted using a blowtorch. This process is somewhat similar to using an autogen, it is worth considering that the crucible should be as engulfed in flame as possible.

If it is not possible to use an autogen or a blowtorch, use an ordinary forge. You need to place the crucible on top of the charcoal layer. To increase the combustion temperature, you can use the technology of blowing air into the combustion zones. For these purposes, you can use a blow-out household vacuum cleaner. Its hose should be equipped with a metal tip that can be narrowed, which will make it possible to obtain a much thinner stream of air.

Red copper is viscous and fusible, so it is practically unsuitable for figured casting. Brass is better suited for this procedure. It melts easier and its color is much brighter.

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Copper is a fairly ductile material with a golden-pink color or pure pink if there is no oxide film. He is extremely popular. Quite often you can find copper products, various souvenirs, many decorative elements, beautiful and unusual objects. There are also some useful household details. This material is held in high regard by many craftsmen. The most common uses of pure red copper, bronze and brass (its alloys).

But what if you are not a professional craftsman and at the same time decide to make something from this metal? A reasonable question arises: “How to melt copper at home?”

What will you need for work?

Before you start processing copper and its alloys, you need to acquire all the necessary tools:

• crucible;
• forceps;
• muffle furnace;
• charcoal;
• bugle;
• household vacuum cleaner;
• a hook made of iron wire;
• a mold for a product to be manufactured.

Make sure that before melting copper at home, all the tools are at hand and neatly laid out, not piled up.

How to smelt copper yourself?

To ensure that all work is completed successfully, without any problems, simply follow the algorithm given below:

• All copper fragments are placed in a crucible, which is placed in a muffle furnace.
• It is necessary to set the desired position for the heating regulator. You can monitor the condition of the contents through a window in the oven door.
• Next, in order to melt copper, you need to wait for the required temperature so that the metal begins to melt. As soon as this happens, you need to open the furnace and use special tongs to grab the crucible.
• When melting, an oxide film will appear on the surface of the metal. It will need to be removed to the side using a hook made of iron wire.
• After this, you can begin making various copper products by simply pouring it into pre-prepared molds.

Important Note

It is worth noting that there are many stories on the Internet about how people melted this metal not with special equipment, but over a fire, in a tin can. As a rule, such authors have no idea what the melting point of copper actually is - 1083 degrees. The essence of what has been said is that you should be prepared for quite large financial expenses. Many tools are not very cheap. Plus, before you melt copper, you should take care of safety equipment.

How to melt brass?

This material is a multicomponent copper alloy. Parts made from it are often used to create various structures.

What is needed for melting? To melt brass, you need to have all the tools listed in the following list:

• muffle furnace;
• blowtorch;
• gas-burner;
• crucible;
• metal tongs;
• charcoal;
• iron wire;
• the shape of the product that will be made from this metal.

Instructions for melting material

To avoid various injuries, as well as damage to materials, you must act strictly according to the instructions provided. Another important point is to ensure ventilation in the work area. The second thing to do is to grind the material itself, which will allow it to melt faster. Once this is done, you can get to work:

• put all the material in a crucible and place it in the oven;
• using an element that regulates the temperature, set the desired degree of melting (from 880 to 950 degrees); turn on the oven;
• While the metal is melting, watch it through the window in the furnace door;
• once the required brass condition has been achieved, the door can be opened;
• using an iron wire hook, remove the oxide film from the surface;
• using tongs and taking all precautions, grab the crucible with them;
• carefully remove it from the oven and begin pouring the contents into the forms prepared in advance.

The following tips can make the work process a little easier if you suddenly don’t have some of the necessary tools at hand:

• If there is no muffle furnace, you can use a blast furnace, if available. It is worth noting that it can also be rented. But before you melt copper, make sure the device is capable of heating up to 1083 degrees. And also make sure that it can withstand operation at a given temperature.
• If you still had to use a blast furnace, find out more about how to properly work with temperature changes. Otherwise, the metal may begin to boil.
• The mold for making a copper product must have a higher melting point than the metal itself.

Also, instead of furnaces for processing brass, you can use other available tools. You can use a torch or blowtorch for heating. To process metal with it, you need to place the device in a stable position with the flame facing up. Place a stand made of iron wire above it. Place a crucible on top of everything with brass folded into it. Next, you need to turn on the heating tool, setting the fire power so that it can completely cover the bottom of the vessel. Due to the fact that melting will occur in the open air, the brass will begin to oxidize. To reduce this effect, cover the surface of the vessel with a dense layer of charcoal.

Copper is extremely popular and common metal, used in the production of electronics, power transmission, and the manufacture of a variety of alloys.

What is the melting point of copper, how is it mined and why it is interesting? Let's talk about all this.

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How is copper obtained?

The reserves of this metal on Earth are relatively small (compared to other elements). Moreover, it is found both in the form of nuggets and in composition of complex compounds. Most often these are copper pyrite, chalcopyrite, bornite and chalcocite. They are found in sedimentary rocks, but most often in hydrothermal veins. Total copper deposits in the world quite large, but there are only a few really large ones of strategic importance .

On Russian territory This is Udokan, located in the Trans-Baikal Territory. If we consider Europe, the largest deposit is the German Mansfeld. Kazakhstan can boast of such reserves in its neighboring countries – they are in the city of Zhezkazgan.

A serious honey belt is located in Central Africa. The USA also has a large deposit - Morenci. Finally, Chile can boast of two serious production points at once - Colhausi and Escondida.

Copper ore is mined open method. Only a relatively small part of the deposits, where the raw materials lie at great depths, use the mining method.

After mining, the ore undergoes complex processing to separate the pure metal from the slag. Different methods are used for this: electrolysis, hydrometallurgy, as well as pyrometallurgy.

How did our ancestors smelt copper?

This is the oldest metal which people have mastered. Amazing plasticity has become its main advantage. It is thanks to him that even with primitive tools one can process metal, making household items and various tools.

Our ancestors learned to process the first metal around 4th millennium BC. Finding cobblestones of unusual color, people tried to process them, hitting them with heavy stones as usual. However, the nuggets did not split, but were only deformed. Thus, the primitive masters were able to make the first tools.

This was the reason for the transition from the Stone Age to the Copper Age. Making metal weapons took no more effort than making stone ones. But it served much longer, and if damaged copper ax or the knife could be repaired - stone analogues had to be made anew.

At how many degrees does copper melt? Today, this temperature does not seem high to experts - only 1083 degrees Celsius.

However for ancient metallurgists it was unattainable, so they learned to melt the material for full processing much later - only in the 3rd millennium BC, when the necessary technologies appeared. However, even before this, in many settlements craftsmen heated copper nuggets over fires, noticing that hot metal was much easier to process.

What has changed over time

Of course, modern copper products cannot be compared with those that were made five thousand years ago. Instead of rough copper knives, axes and arrowheads and spears, today the most complex parts for electronics are produced. But all the properties of the metal remained unchanged. At what temperature copper melts today, it melted at the same temperature thousands of years ago. But significantly technology has improved.

For example, previously clean (relatively clean, of course) metal from ore mined in the most primitive ways. For example, ore and coal were placed in a clay jug. The vessel was placed in the pit, the mixture was set on fire, and the pit was filled up. When coal burned, carbon monoxide was released. By contacting the ore, it triggered a reaction, which resulted in the release of metal and a small amount of water.

Today, as mentioned above, different methods are used to remove impurities from ore. Using a special copper melting chart and various processing methods, specialists can obtain almost absolutely pure metal. Let's consider hydrometallurgical as an example as the easiest to understand.

Copper ore is poured sulfuric acid. Copper, as a relatively active metal, reacts to form copper sulfate. Iron, when in contact with it, displaces copper. The reaction produces ferrous sulfate and copper.

Physical properties

Has a rare color– golden-pink, which is very unusual for metals. It reacts relatively easily and also combines with other metals, significantly changing their properties. A demonstration of this is the combustion process - enough mix pure metal with sulfur and heat the mixture.

What makes it in demand is its excellent electrical conductivity - the best performance only silver has.

In addition, it boasts good thermal conductivity, which makes it an indispensable material in the production of thermal cooling tubes and radiators. The boiling point of copper is quite high - 2567 degrees Celsius.

Fuse metal at home or industrial goes the same way. The temperature rises gradually and constantly. However, when sufficient heat is received, the crystal lattice is destroyed. At this point, the temperature stops rising, even though the heating does not stop. Melting point of copper, as mentioned above, is 1085 degrees Celsius . Only after the metal has completely melted will the temperature continue to rise. It boils at 2567 degrees Celsius.

When cooled, the crystal lattice is restored and the metal hardens. The crystallization temperature is 1085 degrees, and when lowered it becomes even more dense.

Alloys can have a strong excellent melting point. For example, the melting point of aluminum and copper is 1040 degrees Celsius.

How to melt at home

Some people have hobbies related to metal casting. Those who are just embarking on this fascinating path are often interested in how to melt copper at home. For this you will need:

• melting mold;
• forceps;
• raw materials for smelting;
• a high-pressure gas burner is the best solution, since not every household has a forge;
• protective equipment (glasses, thick gloves).

Once you have everything you need, you're ready to start melting at home. The step-by-step instructions are quite simple:

1. If possible, crush the metal– can be turned into sawdust using a file. This will allow it to melt faster.
2. Place in a mold to melt– it must be made of a material with a high melting point.
3. Wear protective equipment light the burner and direct the flame to the raw materials.
4. When the copper melts, Grab the melting mold with tongs and pour the liquid metal into the prepared mold.

As you can see, everything is quite simple. However, this method Not suitable for all alloys. For example, the melting point of steel is too high - a conventional burner will not work here. This also applies to the alloy of copper and iron.

The scope of application is very wide. Here are just a few examples:

• transmission of electricity– low resistance makes this metal extremely popular;
• instrumentation– resistance to water, including sea water, is very important in many areas;
• when soldering– also due to good electrical conductivity;
• water pipes– it conducts heat well;
• cooling radiators– the thermal conductivity of metal allows not only to warm rooms, but also to cool equipment.

Useful video

Now you know everything about copper, how to obtain it, history, use, and how to process it at home. Surely this knowledge will be useful for you.

Copper and copper alloys can be prepared in all furnaces that provide temperatures of 1000-1300°C. However, it is preferable to use units in which overheating to these temperatures is carried out in a shorter time. In this regard, the furnaces used in modern practice for melting copper and copper alloys can be arranged in the following sequence: electric induction (high-frequency, low-frequency and industrial frequency) furnaces, electric arc furnaces with indirect arc (IA), crucible and reverberatory (flame) furnaces, heated fuel oil or gas. The choice of furnace is determined by the type of alloy, the need for metal, the requirements for castings, territorial production conditions, economic considerations, etc. In copper foundries, therefore, you can find both antediluvian coke-heated furnaces and modern electric furnaces. The best quality metal is obtained by melting in induction furnaces, but with proper melting, good results can be achieved using any of the listed furnace units.

Melting of copper, bronze and brass in various furnaces is basically similar, but there are specific features depending on the design of the furnaces, melting time, the possibility of using fluxes, variety of charge, etc. The general requirement is that the metal melting time be minimal, the metal should be pure oxides, gases and harmful impurities, irretrievable losses of metal were small; the technology was simple and reliable, and the costs of materials and maintenance were minimal.

Pure copper is used in technology mainly in the form of rolled products (wire, sheets, rods, etc.). Shaped cast products from copper are difficult to obtain due to its low casting properties. Ingots for rolling are produced by casting into water-cooled molds or by a continuous method.

Copper smelting, if a large amount of metal is needed at once, is carried out in flame reverberatory furnaces with a capacity of up to 50 tons and above. In small-scale production, copper can be smelted in electric as well as crucible furnaces. Particularly pure oxygen-free copper is smelted in vacuum induction furnaces or in furnaces with a controlled atmosphere that excludes contact with oxygen.

Copper smelting consists of either simply melting and overheating it to the required temperatures, followed by deoxidation, or simultaneously during the smelting process it is refined (cleaned) from impurities if the charge used contains a significant amount of impurities (5-10%).

Refining smelting is carried out in reverberatory flame furnaces, where the atmosphere can be easily varied. The process of oxidative-refining smelting consists sequentially of the oxidation of impurities, the removal of the resulting impurity oxides and the reduction of dissolved cuprous oxide.

Oxidation occurs from the beginning of smelting and throughout the entire period of melting of the charge; for this purpose, a strongly oxidizing atmosphere is maintained in the furnace. Zinc, iron and other impurities are oxidized. Naturally, copper is also oxidized at the same time. To more completely remove harmful impurities, the molten copper bath is purged with compressed air or oxygen. The oxidation of impurities occurs in a sequence corresponding to the elasticity of dissociation of their oxides, both as a result of a direct reaction between oxygen and the impurity, and due to the interaction of copper oxide Cu 2 O with impurities that have a greater chemical affinity for oxygen than copper:

Cu 2 O + Me = MeО + 2Cu.

According to the law of mass action, the majority of impurities are oxidized through Cu 2 O; in addition, Cu 2 O dissolves well in copper and provides convenient conditions for the oxidation of impurities throughout the entire volume of the metal. The sequence of oxidation of impurities present in copper is as follows: zinc, iron, sulfur, tin, lead, arsenic, antimony, etc. If there are impurities of aluminum, magnesium, silicon, then they are oxidized first, as they have a higher affinity for oxygen.

The resulting oxides, which are basic in nature, float up and become slagged with slag silica:

ZnO + SiO 2 → (ZnO SiO 2),

FeO + SiO 2 → (FeO SiO 2)

Along with impurities, Cu 2 O also passes into the slag in quantities determined by the chemical equilibrium between the metal and the slag:

+ (SiO 2) → (Cu 2 O SiO 2).

This reaction is undesirable: it increases copper losses. Therefore, the slag is selected in such a way that its composition includes oxides whose basicity is higher than that of cuprous oxide, and they would displace Cu 2 O from the slag into the metal according to the reaction

(Cu 2 O SiO 2) + (Me`O) → (Me`O SiO 2) +.

Such oxides can be CaO, MnO, FeO, etc. In practice, basic open-hearth slag of the following composition is used for this purpose: 24-40% CaO, 10-15% FeO, 10-15% Al 2 O 3, 8-12% MnO and 25-30% SiO 2. Slag is placed on the copper surface during melting in an amount of 1.5-2% by weight of the charge. To liquefy the slag, fluorspar CaF 2, cryolite Na 3 AlF 6, soda ash Na 2 CO 3, etc. are additionally added to it.

The slagging of impurities is accelerated by mixing the metal with the slag. Stirring the metal also makes it easier to remove lead from copper, since it settles at the bottom due to its greater density. Sulfur is removed during the oxidation period in the form of a gaseous product SO 2 by the reaction:

Cu 2 S + 2Cu 2 O ↔ 6Cu + SO 2.

During the removal of sulfur, “boiling” of the metal is observed.

The completeness of melt oxidation is determined by taking fracture samples. A dense, immature, brown, coarse-crystalline fracture indicates the end of the oxidative period of smelting. The slag is removed from the surface of the liquid metal and the reduction of cuprous oxide, which is contained in the solution after removing the slag to 10%, begins. Such copper in the solid state is brittle and, without deoxidation, is unsuitable for casting ingots. The atmosphere of the furnace is made reducing, i.e.

The torch burns with an excess of fuel and a lack of air (smoking flame). The recovery of copper from nitrous oxide is enhanced by an operation commonly called “teasing” the metal. Teasing is done by immersing raw aspen or birch logs in the melt. When wood burns, water vapor and wood distillation products (hydrogen and hydrocarbons) are released, as a result of which the metal boils vigorously, mixes well and interacts more actively with the reducing atmosphere of the furnace.

During this period, the surface of the bath is covered with charcoal to enhance the restorative atmosphere. Cuprous oxide dissolved in the metal, in contact with such an atmosphere, is reduced: Cu 2 O + CO = 2Cu + CO 2.

Since copper at this moment contains a large amount of oxygen, immersing raw logs is relatively harmless with regard to the possibility of saturating the metal with hydrogen, since its solubility in copper with a significant amount of oxygen is very low.

The fracture test of well-deoxidized copper has a dense, fine-grained fracture of a light pink color. The metal is considered ready for casting when the copper oxide content is brought to approximately 0.4%; a further reduction in the Cu 2 O content is not considered desirable, since from this moment the danger of copper saturation with hydrogen increases, which, during subsequent crystallization of the cast copper, is able to interact with oxygen with the formation of water vapor bubbles, reducing the density and properties of copper.

Smelting copper from a pure charge consists of melting, overheating, deoxidation and casting. For this purpose, electric induction furnaces are used in procurement shops. Smelting is usually carried out under a protective cover of calcined charcoal, which protects the metal from oxidation. After melting the charge, a deoxidizing agent is introduced into the bath - phosphorous copper in an amount of 0.1-0.3% by weight of the charge. Then the melt is thoroughly mixed, controlled by fracture, kept for 3-5 minutes, and then, upon reaching a temperature of 1150-1200°C, poured.

Lithium, which is a good copper deoxidizer, is also used to remove oxygen. Sometimes a complex deoxidizer of lithium and phosphorus is used (when it is necessary to obtain a particularly pure metal), as well as magnesium.

However, almost all deoxidizers, remaining in copper, reduce its most important property - electrical conductivity, therefore they strive to keep their amount in copper to a minimum, and the highest quality oxygen-free copper is melted in furnaces with a special protective atmosphere in the form of generator gas or in a vacuum, in which no deoxidation required.

Oxygen-free copper contains at least 99.97% Cu - it is more ductile than conventional copper, more corrosion-resistant and has high electrical conductivity.

Despite the poor casting properties of copper, in particular low fluidity, quite complex hollow castings can be obtained from it by casting into sand or metal molds. In this case, the copper must be very well deoxidized and cleaned of hydrogen (by blowing with nitrogen). To improve its casting properties, up to 1.0% Sn + Zn + Pb is added. The smaller quantities of these elements it is possible to obtain a shaped casting, the higher its properties (electrical and thermal conductivity). Blast furnace tuyeres, valves, rings and other parts are cast from such copper.