Annealing, hardening and heat treatment of copper

Features of copper annealing

When heat treating copper and its alloys, two features of the material are taken into account: increased thermal conductivity and interaction with gases when heated. It is these factors that cause rapid and uniform heating of the metal along the perimeter of the section. Annealing copper is heating the metal followed by cooling, allowing you to change the properties of the material. Heat treatment makes the metal softer and more ductile. Copper is used in various fields where ductility is important.

Annealing of copper

Advantages and disadvantages of processing

An undeniable property of copper is its high electrical conductivity. It is used in construction and the manufacture of electrical equipment. The mechanical parameters of the metal are quite low, so it is not often used as a pure structural material.

• the treatment removes harmful substances from the metal and removes bacteria;
• the workpiece becomes soft and elastic, withstands pressure over 200 atmospheres;
• the material becomes resistant to corrosion;
• increase in hardness - the part can be bent several times without fear of cracks;
• reduction of residual stress during incomplete annealing.

There are significantly fewer disadvantages, but they still exist:

• the material requires slow cooling;
• copper is an expensive material;
• If handled incorrectly, soft metal can be damaged.

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.

What equipment is used

Copper undergoes two types of heat treatment:

• annealing to reduce remaining stress;
• recrystallization annealing.

The temperature regime for recrystallization of oxygen-free copper is 200–240°C, and that of electrolytic copper is 180–230°C. Metal containing oxygen is treated in a neutral environment to reduce losses after oxidation.

For annealing heat treatment, a shaft-type convection oven is used. In addition, the equipment is in demand for annealing wire, rope, rods, steels, and metal balls.

The oven has the following advantages:

• improved accuracy of temperature control;
• automation of heat treatment;
• the fan at the bottom of the device ensures stable heat transfer;
• processing error is +/-5C;
• heating is carried out from electricity;
• ammonia and pure nitrogen protect the metal from oxidation;
• capacity - 8–36 tons;
• ease of operation and installation.

The furnace lid is equipped with a special pneumatic device, which is responsible for opening and closing during the annealing process. The emergency valve operates automatically when the pressure rises to high or drops to low.

Annealing furnace

Processing principle

Annealing is a heat treatment procedure for copper that produces a stable, strong metal structure, free from residual stresses. Annealing technology goes through several stages:

1. Loading metal into equipment.
2. Installing the muffle and purging with protective gas to remove air.
3. Heating to 650–700 degrees.
4. Rapid cooling up to 100 degrees when immersing the product in water.
5. Giving the required shape.
6. Reheat to 350–400 degrees.
7. Air cooling and unloading.

The last stage of the technology is carried out twice as slow.

Required temperature for melting copper

Copper is not a fusible metal

People found the use of copper back in ancient times, when it was mined in the form of nuggets. Due to the low temperature required for the melting process, it began to be widely used for the manufacture of tools and hunting, nuggets can be melted over a fire. Nowadays, the technology for producing metal is not much different from that invented in ancient times; only furnaces are being improved, the firing speed and processing volumes are increased. A pertinent question here is what is the melting point of copper? The answer to this can be found in any textbook on physics and chemistry - copper begins to melt at a heating temperature of up to 1083 °C.

Boiling copper reduces its strength

In the process of thermal exposure of a metal, its crystal lattice is destroyed; this is achieved at a certain temperature, which remains constant for some time. At this moment, metal melting occurs. When the process of crystal destruction is completely completed, the temperature of the metal begins to rise again, and it turns into a liquid form and begins to boil. The melting point of copper is much lower than the one at which the metal boils. The boiling process begins with the appearance of bubbles, similar to water. At this stage, any metal, including copper, begins to lose its characteristics, which is mainly reflected in strength and elasticity. The boiling point of copper is 2560 °C. During cooling of the metal, a similar picture occurs as when heating - first the temperature drops to a certain degree, at this moment solidification occurs, which lasts for some time, then cooling continues to its normal state.

Why roast copper and how to do it

At collection points, non-ferrous metal is highly valued, especially copper, which has a higher price than other non-ferrous metals. Large volumes of copper can only be collected by collecting copper wires and wires, which are often sheathed. In this regard, many enterprising citizens have a question: how to burn copper at home. According to Russian legislation, it is possible to light fires for burning wires in order to remove the plastic sheathing only in specially designated areas. It is important to understand right away how to burn copper correctly, since this category of offenses entails a large fine.

How much does 1 kg of roasted copper cost?

The value of scrap after heat treatment is determined by the appraiser. It takes into account batch size, contamination and the presence of impurities. You can find out during the purchase how many criteria the appraiser is guided by.

Introduction: Punishment for lighting a fire and burning garbage

Russian legislation provides for several federal laws, articles of the Criminal Code and the Code of Administrative Offenses, as well as government regulations that prohibit the lighting of fires, burning of garbage and burning of wire. For different categories of offenses, different punishments are expected, from monetary fines to real terms. In order not to fall under the articles of the law, it is important to familiarize yourself in advance with the list of legislative acts that control the burning of waste, and in particular the burning of copper and aluminum. The main prohibiting and controlling articles are the following:

• Code of Administrative Offenses – Article 8.2.3;
• Article 51 of Federal Law No. 7 on environmental protection;
• Code of Administrative Offenses – Article 20.4;

What punishment these articles provide for and what they prohibit should be examined in detail so that there are no difficulties with the law when trying to dispose, process or transport scrap metal.

Article 8.2.3 of the Code of Administrative Offenses of the Russian Federation – Failure to comply with rules and requirements for waste management, improper processing of industrial waste, including illegal disposal, accumulation and transportation. The article provides for punishment in the form of a fine of 1,000 to 2,000 rubles (for legal entities up to 250 thousand, for officials up to 30 thousand rubles). According to Article 8.2.3 of the Code of Administrative Offenses, those actions with garbage that have resulted in epidemics, infections, or harm to the environment and the health of citizens are unlawful. This article does not include offenses that are criminal offenses.

Adopted in 2002, the 7th Federal Law “On Environmental Protection”, article 51 of which specifies the requirements for citizens who process and dispose of waste and garbage, has been revised several times. For 2022, the following prohibitions are relevant:

• It is prohibited to throw garbage and waste from a fire (for example, burnt plastic after burning copper), into water, bury it in the ground, or near urban and rural settlements.
• It is prohibited to place and store garbage (including metal waste) near urban and rural settlements, as well as near recreational areas, on animal migration routes, and fish spawning areas;
• It is prohibited to create a danger to humans and the environment by burning and disposing of waste.

The Code of Administrative Offenses of the Russian Federation also contains Article 20.4, which regulates the organization of fires, including for the purpose of roasting copper. According to this article, violation of fire safety requirements is punishable by a fine of 4 to 5 thousand, or arrest for up to 90 days. A place for making a fire must be equipped by insulating the fire pit. You should not light a fire in windy weather, and it is also important to properly dispose of waste - by burning or roasting it in barrels. The Criminal Code of the Russian Federation provides for punishment only for those actions that entailed the death of a person or caused serious harm to the health of citizens (Article 219).

How to burn copper (methods)

Copper is a unique metal that must be properly removed from its plastic casing. Unlike other non-ferrous metals, copper alloy can withstand extreme temperatures, so it can be fired in a fire. Aluminum, for example, can melt under the same conditions. Therefore, before starting firing, you need to sort the scrap. It is also important to organize the area and ensure the safety of others before starting a fire. Once this is done, you can begin to peel the wire from the sheath in the fire. How to burn copper and what factors should be taken into account can be seen in the video.

How to roast copper without smoke

What is roasted copper?

Buyers bring various types of cable scrap. Burnt copper (“F”) is a conductive wire core with a cross-section of 1 mm, which was obtained after heat treatment of illiquid goods. This category includes scrap contact cable.

Requirements for roasted copper:

• no traces of oil or paint;
• clogging content no more than 0.5%;
• absence of braid parts;
• normal background radiation;
• no traces of tinning.

The cost of baked copper is affected by the content of foreign impurities and total weight. Buyers work with retail and wholesale clients. They offer a high cost of copper per kg. Guaranteed immediate payment.

Conditions for obtaining burnt copper:

• burning of waste wire;
• manufacturing defect;
• burning of illicit cable.

Burnt copper is highly valued if the heat treatment is carried out in accordance with GOST. There should be no traces of melted plastic left on the metal. The quality of copper “Zh” is inferior to electrical color. But roasting reduces the preparation time for processing and increases the cost of purchase.

When is copper heat treatment used?

Heat treatment is the heating of raw materials or finished products

If it is necessary to increase the strength of products, elasticity, wear resistance, or, conversely, to obtain a softer metal that is amenable to further mechanical action, heat treatment of copper is used. This process can be carried out in various ways - hardening and annealing; they differ in heating temperature and cooling method. In order to impart hardness and strength to a copper product, it should be heated to a temperature of 600 o C and cooled in air, this is the so-called slow cooling. If you need soft metal, then the raw material should be heated to 600 o C and subjected to rapid cooling in water, then the product should be shaped, heated again, this time to 400 o C and left to cool slowly, resulting in a soft product. In order to bend a copper pipe, it is first filled with sand, this will avoid flattening during heat treatment, and then it is heated and given the desired shape. With the help of heat treatment of copper, the process of removing hardening and scale is carried out; for this, the metal is heated to 500 o C and cooled in water.

Composition, structure of brass alloy, its production: technology, forms

Often, by hardening, not only the hardness of the metal increases, but also its fragility, so it is necessary to perform one more stage - tempering, during which the strength and hardness are somewhat reduced, but the material becomes more ductile. Tempering is done at a temperature lower than in the previous process, and the metal is cooled gradually.

Hardening can be carried out without changing the structure of the metal (polymorphic transformation). In this case, there will be no problems with brittleness, but the required hardness will not be achieved.

And it can be increased through another heat treatment process called aging.

During aging, the supersaturated solid solution decomposes, as a result of which the strength and hardness of the material increases.

Steel tempering is a type of heat treatment used for parts hardened to a critical point at which a polymorphic change in the crystal lattice occurs.

It involves keeping the metal in a heated state for a certain period of time and slowly cooling it in the open air.

Tempering is done to reduce internal stress, as well as eliminate the fragility of the metal and increase its ductility.

Through aging, the required hardness of hardened steel is achieved. Aging can be:

• natural, in which the strength of the hardened metal spontaneously increases and its ductility decreases. This process occurs when kept in a natural environment;
• thermal. Aging is the process of increasing the hardness of a metal through exposure to high temperatures. Compared to the first type, in this case overaging may occur - this is when hardness, strength and fluidity limits, having reached their maximum value, begin to decrease;
• deformation. This aging is achieved through plastic deformation of a hardened alloy having the structure of a supersaturated solid solution.

What is metal hardening and its types?

Tempering is a popular way to improve the characteristics of a material. Heat treatment allows you to change the structure of the metal. The result of exposure to high temperature is an increase in hardness. After heating, the part quickly cools. To do this, it is immersed in a container filled with oil or water.

Most often, stainless steel, wire from different types of steel and knives are hardened at home. But after structural changes, the steel becomes brittle.

If we are talking about non-ferrous metals, then the structure does not change. For example, after hardening copper it is impossible to achieve a good hardness index.

However, in the absence of structural changes, the material does not become excessively brittle

To reduce the brittleness of steel after heat treatment, the workpiece is tempered. This is an additional heat treatment. The product is first heated and then slowly cooled.

Features of steel hardening

The main material that is subjected to heating and rapid cooling is stainless steel and alloys based on it. To improve the performance of the product, it is necessary to perform additional heating and then slow cooling. This will relieve internal tension. Processing features for different types of steel:

1. Hardening of steel 45. After heating and rapid cooling, the strength increases 3 times.
2. Carrying out the procedure with 40X steel. Heats up to a temperature of 860 degrees Celsius.

There are special reference books that contain information about the correct temperature conditions for processing various types of steel.

Hardening methods

The essence of any hardening is the transformation of austenite into martensite (iron-carbon diagram). Depending on the temperature regime, hardening can be complete or incomplete. The first method is to harden tool steel, and the second is to harden non-ferrous steel.

During hardening, one or more coolants can be used. The method of heat treatment also depends on this. Depending on the cooling medium, heat treatment of the metal can be:

• using one cooler;
• with cooling;
• intermittent;
• stepped;
• isothermal.

Quenching in one cooler

This method is used for heat treatment of simple parts made of alloy and carbon steel. The part is heated to the required temperature and then cooled in liquid. Carbon steel with a diameter of 2 to 5 mm is cooled in water, parts of smaller diameter and all alloy steel are cooled in oil.

Hardening with cooling

When heat treating with a single coolant, thermal and structural internal stress conditions often occur. They develop when the temperature difference reaches a minimum.

Tensile stress is formed on the surface of the metal, and compressive stress is formed in the center. To reduce these stresses, before lowering the heated part into the liquid, it is kept in the open air for a short time.

The temperature of the part in this case should not be below the 0.8 K line on the iron-carbon diagram.

Intermittent

This hardening is carried out in two environments - water and oil or water and air. A part heated to a critical point is first quickly cooled in water, and then slowly in oil or in the open air.

This heat treatment method is used for high-carbon steel.

This method is complex, since the cooling time in the first environment is very short and only a highly qualified specialist can determine it.

Stepped

With intermittent heat treatment, the part cools unevenly—thinner surfaces cool faster than others. In addition, it is very difficult to adjust the time the part is in the first medium (water). Therefore, it is better to use step hardening.

This method allows the part to be cooled in an environment at a temperature above the martensitic point. The first stage is cooling and holding the part in a given environment until all sections of the part reach the same temperature.

The second stage is the final slow cooling (transformation of austenite into martensite).

Isothermal

In isothermal heat treatment, the part is heated to a critical point and then lowered into an oil or salt bath at a temperature of 250 degrees. Leave for half an hour and then cool in the open air.

This hardening provides high structural strength and is used for alloy and structural steels in which the decomposition of austenite in the intermediate region does not completely occur.

Subsequently, it turns not into martensite, but into bainite + 20% retained austenite, enriched in carbon. With this hardening, high strength and good toughness can be achieved.

Temperature conditions during metal hardening

High-quality heat treatment of metals requires compliance with the correct temperature conditions. They depend on the composition of the steel alloy.

There are color charts that tell you how to properly heat or cool a steel part, depending on the brand.

Most steels achieve the desired characteristics by uniform heating to 780–850 °C and rapid cooling to a temperature of 300–450 °C. After this there is a slow cooling to normal temperature.

How is machining carried out?

After the annealing process, the metal must be given shape, shine, and pattern; for this purpose, mechanical processing methods are used. To begin, the product must be cleaned of oil, oxides, heat and other contaminants; processes can only be carried out on a dry surface. Cold or mechanical processing of copper is performed in several ways:

For presentation, copper products are subjected to mechanical processing

• rolling;
• broach;
• grinding;
• polishing

The metal rolling process is carried out using a mechanical or automatic installation equipped with rollers, between which a sheet of copper billet is passed. The thickness of the finished product is adjusted depending on the need. The rollers are lubricated with oil or a special emulsion, which leaves a thin layer of film on the finished product.

Copper drawing is carried out in the manufacture of wire, cores for wires and cables. Performed using an extruder mechanism, the diameter is adjusted automatically according to preset parameters.

Copper grinding

Grinding of copper products occurs using discs and belts coated with an abrasive coating. For grinding, abrasive materials with a grain size of about 180–200 microns are usually used; for products that have been forged, 80–100 microns will be sufficient.

Polishing is carried out using fabric or felt discs, pumice, tripoli, as well as using iron oxide and Vienna lime. This process is performed on polishing machines; for copper, a speed of 20–40 m/s is sufficient; an increase leads to a deeper removal of the top layer. To prevent discoloration, use a weak solution of organic acid, for example, oxalic or tartaric. It is effective to treat the polished surface with solutions containing a corrosion inhibitor; they prevent oxidation and retain color longer.

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Hardening a metal allows you to make some changes in its structure, making it softer or, conversely, harder.
When hardening, a lot depends not only on the heating itself, but also on the cooling process and time. Manufacturers mainly harden steel, making the product more durable, however, copper can also be hardened if the need arises. Copper is hardened using the annealing method.

During heat treatment, copper can be made softer or harder, depending on what it will be used for in the future. However, it is important to remember that the method of hardening copper is significantly different from the way steel is hardened.

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WATCH THE VIDEO ON THE TOPIC: Experiments in chemistry. Hardening and tempering of steel

Principles of metal hardening at home

Bleaching and bleaching solutions. Bleaching is placing the product in acid. Industrially produced bleach solutions "Sparex" Sparex 2. They work slower than acids, but are less corrosive and less dangerous to work with.

The solution should not be boiled as dangerous fumes are released. The active substance in these bleaches is sodium bisulfate. These solutions are effective for silver and gold alloys, brass, bronze and copper.

It should not be used to bleach sterling silver. Can be used cold or warmed up. Nickel bleach releases hazardous substances when boiling.

If you leave metal in it for a long time, significant etching of products is possible.

The active ingredients of this bleach are sodium bisulfate and potassium bichromate. Some people prefer to prepare their own bleaches. These chills are dilute acids and require care when handling them. Remember to add acid to water little by little and never vice versa.

Otherwise, splashing and intense fumes may occur, which is very dangerous. Bleaching solutions become saturated with copper ions during operation.

If an iron or steel object is placed in such a solution, copper will settle on all gold or silver items currently in the solution.

When such an object is removed, the release of copper stops. Poultry solutions for self-preparation. Bleaching solutions remove CuO -copper II oxide, which is black or gray in color. Red cuprous oxide, Cu.

Its formation is typical of sterling silver and low-grade gold alloys. This phenomenon can be reduced to: The consequences of burnout can be eliminated or reduced by chemical means. Since the oxide lies beneath the surface of the metal, the use of abrasives alone is usually ineffective. Immerse the product for a few seconds, the surface will darken, rinse, and brush.

Repeat until completely eliminated. Caution: These chemicals are extremely toxic, handle with care and avoid inhaling fumes. Heat until a thin film of oxide forms, immerse in fresh bleach, rinse, and gently brush.

Repeat 35 times. Gilding by etching. N2 solution 3. Electroflaking process. Apply current at voltage B for 5 seconds. Repeat if necessary. Rinse thoroughly.

3 ways to harden metal yourself

Copper is also subjected to heat treatment. In this case, copper can be made either softer or harder. However, unlike steel, copper is hardened by slow cooling in air, and copper becomes soft by rapid cooling in water. The wire or tube will then become solid.

with copper. This is permissible because they are doped with other elements (Mg, a solution of copper and aluminum (hardening without polymorphic transformation).

How to harden tin?

A similar topic on copper, bronze and brass is here. Hardening of beryllium bronze. Aging at degrees, if memory serves, hours. However, if the part is not very critical and thin-walled, then 1 hour is possible. We make tape up to 0.5 without hardening, aging immediately. After aging, elastic properties will appear. Question about BrB2.

Annealing, hardening and heat treatment of copper

Every craftsman who works with metalworking or carpentry tools probably knows how to harden metal at home. It is believed that to do this, it is enough to heat the product red-hot and then cool it in a container of water.

However, in a home workshop, this method can only produce hard and brittle metal, which is quite suitable for chisels and knives, but unsuitable for hammers, punches or chisels.

Heat treatment modes depend on the steel grade and the required parameters of the product after hardening, and these include not only hardness, but also strength, wear resistance, ductility and toughness.

During manufacturing, metal products are subjected to additional heat treatment.

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The process of hardening steel allows you to increase the hardness of the product by approximately two times.

Many manufacturers carry out a similar process at the time of production, but in some cases it must be repeated because the hardness of the steel or other alloy is low.

This is why many people wonder how to harden metal at home? Hardening metal at home. In order to carry out the work of hardening steel, you need to take into account how such a process is carried out correctly.

Question about hardening copper

Are you interested in heat treatment: annealing, hardening of rolled copper? The price is optimal. To obtain an equilibrium structure without internal stresses, semi-finished products are subjected to two-stage annealing.

Are you interested in heat treatment: annealing, hardening of copper? Site search. Contact number. Directory Copper, brass, bronze Copper information Processing, rolling and deformation of copper.

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However, unlike steel, copper is hardened by slow cooling in air, and copper becomes soft by rapid cooling.

Copper, its properties, applications. Copper alloys. Examples

View full version: Copper washers in hydraulic systems. Velomania forum. There are Hope Mono mini brakes. Changed the hydraulic line.

Melting copper at home: step-by-step instructions, video

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Bleaching and bleaching solutions.

Annealing of copper and brass metals

FCC crystal lattice with period a 0, r.

Technical and technological properties of copper: high electrical and thermal conductivity, sufficient corrosion resistance, good workability under pressure, weldability by all types of welding, easy to solder, easy to polish.

Pure copper has low strength and high ductility. The disadvantages of copper include:. There are two main groups of copper alloys: brass - alloys of copper and zinc; bronzes are alloys of copper with other elements.

Turning processing method

A common method of processing copper workpieces is turning, using special machines equipped with cutters. Thanks to this processing method, it is possible to produce a wide variety of shapes and parts of cylindrical, spherical, conical shapes. The mechanism of operation of lathes is the action of the cutting mechanism on the part, it cuts into the workpiece and removes the excess layer, which turns into chips. The speed of movement of the cutting mechanism is of great importance in processing various types of metal. Since copper is a soft material, 40 - 50 m/s will be sufficient. Using copper turning, you can obtain the following types of products:

Turning allows you to get a part of any shape

• washers;
• bushings;
• flanges;
• hairpins;
• fittings.

Enterprises engaged in metal turning can produce a wide variety of types of products for individual orders. The machines are adjusted to the parameters of each detail. Using turning equipment, threads are applied to copper workpieces, chamfers are turned, holes are drilled, and geometric cutting is carried out. The use of automated machines makes it possible to perform the most complex finishing of workpieces with maximum precision, while reducing the percentage of defects and minimizing waste.

Recommended files

The purpose of annealing is to bring the system closer to an equilibrium state by eliminating, to one degree or another, its physical and chemical heterogeneity, which are a consequence of technological operations in the production of the alloy and products from it. Depending on the type of annealing, its consequences may be a decrease in the degree of chemical heterogeneity (liquation), elimination of a nonequilibrium structure, a decrease in the level of internal stresses, a decrease in strength and hardness, an increase in ductility and machinability by cutting, pressure, etc.

The most common types of annealing for non-ferrous metals and their alloys are:

— homogenizing annealing, the purpose of which is to eliminate the chemical heterogeneity of alloys; it is carried out mainly for semi-finished products, primarily ingots;

- recrystallization annealing of deformable semi-finished products - blanks, forgings, sheets, sectional profiles in order to eliminate the effects of cold hardening (hardening) and increase technological properties as a result of the development of recrystallization processes;

— annealing to relieve residual stresses, mainly in ingots, castings and deformed semi-finished products, in order to improve their technological properties;

— complete annealing, as a result of which not only softening processes can occur as a result of the development of recrystallization, but also phase transformations that ensure complete decomposition of solid solutions and the release of excess phases;

— stabilizing annealing, which ensures a more complete release of excess phases (aging) in semi-finished and finished products.

Annealing temperature

The choice of heating temperature is chosen depending on what properties of the part they want to obtain. To make it plastic, it is necessary to heat it to a temperature of 500-700 degrees, and then cool it sharply in water. In this case, the heating rate does not significantly affect the properties of copper. Cooling in water is preferable, since after this it is much easier to remove scale.

To reduce hardness, complete annealing is used. The workpiece is heated to 900 degrees Celsius and then slowly cooled, most often together with the furnace. The internal stress that arises during machining disappears.

After cutting the copper and obtaining the finished product, the part can be heated to a temperature of 400-450 degrees and cooled in air at room temperature (within 1.5 hours). This will return the hardness of the processed part.

Heat treatment of metals. Annealing

Annealing of copper

Copper is also subjected to heat treatment . In this case, copper can be made either softer or harder. However, unlike steel, copper is hardened by slow cooling in air, and copper becomes soft by rapid cooling in water. If a copper wire or tube is heated red hot (600° C) over a fire and then quickly immersed in water, the copper will become very soft. After giving the desired shape, the product can again be heated over a fire to 400 ° C and allowed to cool in air. The wire or tube will then become solid. If it is necessary to bend the tube, it is tightly filled with sand to avoid flattening and cracking.

Annealing brass increases its ductility. After annealing, brass becomes soft, easily bends, knocks out and stretches well. For annealing, it is heated to 600 ° C and allowed to cool in air at room temperature.

Annealing and hardening of duralumin

Annealing of duralumin is carried out to reduce its hardness. The part or workpiece is heated to approximately 360°C, as during hardening, held for some time, and then cooled in air. The hardness of annealed duralumin is almost half that of hardened duralumin.

Approximately the heating temperature of a duralumin part can be determined as follows: At a temperature of 350-360 ° C, a wooden splinter, which is passed along the hot surface of the part, becomes charred and leaves a dark mark. The temperature of the part can be determined quite accurately using a small (about the size of a match head) piece of copper foil, which is placed on its surface. At a temperature of 400°C, a small greenish flame appears above the foil.

Annealed duralumin has low hardness; it can be stamped and bent twice without fear of cracks.

Hardening. Duralumin can be hardened. When hardening, parts made of this metal are heated to 360-400°C, held for some time, then immersed in water at room temperature and left there until completely cooled. Immediately after this, duralumin becomes soft and flexible, easily bent and forged. It acquires increased hardness after three to four days. Its hardness (and at the same time fragility) increases so much that it cannot withstand bending at a small angle.

Duralumin acquires its highest strength after aging. Aging at room temperatures is called natural, and at elevated temperatures - artificial. The strength and hardness of freshly hardened duralumin, left at room temperature, increases over time, reaching its highest level after five to seven days. This process is called duralumin aging.

Annealing of steel parts

To facilitate mechanical or plastic processing of a steel part, its hardness is reduced by annealing. The so-called full annealing consists in the fact that the part or workpiece is heated to a temperature of 900 ° C, maintained at this temperature for some time necessary to warm it throughout its entire volume, and then slowly (usually together with the furnace) cooled to room temperature.

Internal stresses that arise in the part during machining are removed by low-temperature annealing, in which the part is heated to a temperature of 500-600°C and then cooled along with the furnace. To relieve internal stresses and slightly reduce the hardness of steel, incomplete annealing is used - heating to 750-760 ° C and subsequent slow (also together with the furnace) cooling.

Annealing is also used when hardening is unsuccessful or when it is necessary to overheat a tool for processing another metal (for example, if a copper drill needs to be overheated to drill cast iron). During annealing, the part is heated to a temperature slightly below the temperature required for hardening, and then gradually cooled in air. As a result, the hardened part again becomes soft and amenable to machining.

How to harden copper

Technologies for imparting greater hardness to metals and alloys have been improved over many centuries.

Modern equipment makes it possible to carry out heat treatment in such a way as to significantly improve the properties of products even from inexpensive materials.

Hardening of steel and alloys

Hardening (martensitic transformation) is the main method of imparting greater hardness to steels.

In this process, the product is heated to such a temperature that the iron changes its crystal lattice and can be additionally saturated with carbon.

After holding for a certain time, the steel is cooled.

This must be done at high speed to prevent the formation of intermediate forms of iron.

As a result of rapid transformation, a solid solution supersaturated with carbon with a distorted crystal structure is obtained.

Both of these factors are responsible for its high hardness (up to HRC 65) and brittleness.

When hardening, most carbon and tool steels are heated to a temperature of 800 to 900C, but high-speed steels P9 and P18 are heated at 1200-1300C.

Microstructure of high-speed steel R6M5: a) cast state; b) after forging and annealing; c) after hardening; d) after vacation. ×500.

Quenching modes

The heated product is lowered into a cooling medium, where it remains until it cools completely. This is the simplest hardening method, but it can only be used for steels with a low carbon content (up to 0.8%) or for parts of simple shape. These limitations are associated with thermal stresses that arise during rapid cooling - parts of complex shapes can warp or even crack.

With this method of hardening, the product is cooled to 250-300C in a saline solution for 2-3 minutes to relieve thermal stress, and then cooling is completed in air. This helps prevent cracks or warping of parts.

The disadvantage of this method is the relatively low cooling rate, so it is used for small (up to 10 mm in diameter) parts made of carbon or larger ones made of alloy steels, for which the hardening rate is not so critical.

It begins with rapid cooling in water and ends with slow cooling in oil. Typically, such hardening is used for products made of tool steels. The main difficulty lies in calculating the cooling time in the first environment.

• Surface hardening (laser, high frequency currents)

Used for parts that must be hard on the surface, but have a viscous core, for example, gear teeth.

During surface hardening, the outer layer of the metal is heated to supercritical values, and then cooled either during the heat removal process (with laser hardening) or by liquid circulating in a special inductor circuit (with high-frequency current hardening)

Vacation

Hardened steel becomes excessively brittle, which is the main disadvantage of this hardening method.

To normalize the structural properties, tempering is carried out - heating to a temperature below the phase transformation, holding and slow cooling.

During tempering, a partial “cancellation” of hardening occurs, the steel becomes slightly less hard, but more ductile.

There are low (150-200C, for tools and parts with increased wear resistance), medium (300-400C, for springs) and high (550-650, for highly loaded parts) tempering.

Temperature table for quenching and tempering steels

Hardening metal at home: hardening steel correctly

If you know how to harden metal correctly, then even at home you can increase the hardness of products made from it two to three times.

The reasons why there is a need for this can be very different.

Such a technological operation is required, in particular, if the metal needs to be given hardness sufficient to enable it to cut glass.

Hardening metal at home

Most often, a cutting tool needs to be hardened, and heat treatment is performed not only when its hardness needs to be increased, but also when this characteristic needs to be reduced. When the hardness of the tool is too low, its cutting part will jam during operation, but if it is high, the metal will crumble under the influence of mechanical loads.

Few people know that there is a simple way to check how well a steel tool is hardened, not only in production or at home, but also in a store when purchasing. In order to perform this test, you will need a regular file.

It is passed along the cutting part of the purchased tool.

If it is poorly hardened, then the file will seem to stick to its working part, and in the opposite case, it will easily move away from the tool being tested, while the hand in which the file is located will not feel any irregularities on the surface of the product.

Dependence of steel hardness on heat treatment mode

This problem can be solved quite easily: you can harden metal even at home, without using complex equipment and special devices. However, you should know that low-carbon steels cannot be hardened.

At the same time, the hardness of carbon and tool steel alloys can be easily increased even at home.

Technological nuances of hardening

Hardening, which is a type of heat treatment of metals, is performed in two stages. First, the metal is heated to a high temperature and then cooled.

Different metals and even steels belonging to different categories differ from each other in their structure, therefore their heat treatment modes do not coincide.

Heat treatment modes for some non-ferrous alloys

Heat treatment of metal (hardening, tempering, etc.) may be required for:

• its strengthening and increasing hardness;
• improving its ductility, which is necessary when processing by plastic deformation.

Many specialized companies harden steel, but the cost of these services is quite high and depends on the weight of the part that needs to be heat treated. That is why it is advisable to do this yourself, especially since you can do it even at home.

If you decide to harden the metal on your own, it is very important to correctly carry out such a procedure as heating. This process should not be accompanied by the appearance of black or blue spots on the surface of the product.

The bright red color of the metal indicates that heating is occurring correctly.

This video demonstrates this process well, which will help you get an idea of ​​the degree to which to heat the metal subjected to heat treatment.

As a heat source for heating the metal product that needs to be hardened to the required temperature, you can use:

• a special oven powered by electricity;
• blowtorch;
• an open fire that you can make in the yard of your house or in your country house.

Melting copper at home: step-by-step instructions, video

Copper products are actively used not only in various industries, but also in everyday life. In this regard, it is quite natural that many craftsmen have a question about how to melt copper and make various products from it at home using the casting method. Knowledge of this technology, which has been known to mankind since ancient times, allows us to create various objects not only from copper, but also from its alloys - brass and bronze.

Melting copper in a homemade stove

How to harden copper - Metals, equipment, instructions

Technologies for imparting greater hardness to metals and alloys have been improved over many centuries. Modern equipment makes it possible to carry out heat treatment in such a way as to significantly improve the properties of products even from inexpensive materials.

How to harden steel over an open fire

As mentioned above, you can harden steel at home, using an open fire for heating. Naturally, such a process should begin by starting a fire, in which a lot of hot coals should form. You will also need two containers. You need to pour mineral or synthetic oil into one of them, and ordinary cold water into the other.

Characteristics of copper

Copper is one of the first metals that man learned to mine and process. Products made of copper and its alloys were used as early as the 3rd century BC, as evidenced by historical data and the results of archaeological excavations. The widespread use of copper has largely been facilitated by the fact that it can be quite easily processed by various mechanical methods. In addition, it can be easily melted.

Copper, the surface of which has a distinct yellowish-red color, due to its softness, can easily be processed by plastic deformation. When the surface of copper interacts with the surrounding air, it becomes covered with an oxide film, which gives it such a beautiful color.

Grades of technical copper and their chemical composition

The characteristics of copper, such as electrical and thermal conductivity, are also of great importance, for which it ranks second among all metals, second only to silver. Due to these properties, products made from it are actively used in the electrical industry, as well as in cases where it is necessary to ensure rapid heat removal from a heated object.

Another important parameter of copper, which directly affects the amount of energy and labor consumed in the production of products from it, is the melting point. For pure copper, the temperature at which the metal changes from solid to liquid is 1083°. If you mix copper with tin and get bronze, then the melting point of such an alloy will already be 930–1140°, depending on the content of the main alloying additive in it. A copper alloy such as brass, which is obtained by adding zinc to the base metal, has an even lower melting point, which is in the range of 900–1050°.

Nickel plating of metal, aluminum, copper and brass, technology review

Often, by hardening, not only the hardness of the metal increases, but also its fragility, so it is necessary to perform one more stage - tempering, during which the strength and hardness are somewhat reduced, but the material becomes more ductile. Tempering is done at a temperature lower than in the previous process, and the metal is cooled gradually.

Hardening can be carried out without changing the structure of the metal (polymorphic transformation). In this case, there will be no problems with brittleness, but the required hardness will not be achieved.

And it can be increased through another heat treatment process called aging.

During aging, the supersaturated solid solution decomposes, as a result of which the strength and hardness of the material increases.

Steel tempering is a type of heat treatment used for parts hardened to a critical point at which a polymorphic change in the crystal lattice occurs.

It involves keeping the metal in a heated state for a certain period of time and slowly cooling it in the open air.

Tempering is done to reduce internal stress, as well as eliminate the fragility of the metal and increase its ductility.

Through aging, the required hardness of hardened steel is achieved. Aging can be:

• natural, in which the strength of the hardened metal spontaneously increases and its ductility decreases. This process occurs when kept in a natural environment;
• thermal. Aging is the process of increasing the hardness of a metal through exposure to high temperatures. Compared to the first type, in this case overaging may occur - this is when hardness, strength and fluidity limits, having reached their maximum value, begin to decrease;
• deformation. This aging is achieved through plastic deformation of a hardened alloy having the structure of a supersaturated solid solution.

What quenching media are suitable for self-hardening?

The choice of the environment where the self-hardening process will be carried out is as important a stage as the heating itself, since crystallization and polymorphic transformation reactions occur differently in different environments.

In everyday life, water, oil, solutions of salts and polymers, and air are suitable for quenching cooling.

• Water can quickly cool a hot material, which, with an increased carbon content, can lead to some disadvantages - deformation, brittleness, cracking. Therefore, low-carbon materials, or products with partial hardening, are hardened in water.
• Mineral oil cools hot steel much more slowly, and therefore more evenly, which minimizes the appearance of unevenness in the structure and its stress, and, accordingly, defects due to hardening. Typically, alloy steel or material with a high percentage of carbon is cooled with oil.
• Aqueous solutions of sodium chloride or hydroxide, with a concentration of around 10%, will cool a heated product much more evenly than just water. This will allow achieving the same structural transformation throughout the entire cross-section of the metal. More suitable for hardening processing of products made of low-alloy and high-carbon steels.
• Polymer solutions (silicate, detergents) reduce the cooling rate of the material, and therefore defects and deformation of the product are reduced.

For cooling, water is taken at a temperature from 20º to 80ºС, oil - at a temperature from 20º to 200ºС, salt solutions - at a temperature from 20ºС to a maximum.

Hardening methods

The essence of any hardening is the transformation of austenite into martensite (iron-carbon diagram). Depending on the temperature regime, hardening can be complete or incomplete. The first method is to harden tool steel, and the second is to harden non-ferrous steel.

During hardening, one or more coolants can be used. The method of heat treatment also depends on this. Depending on the cooling medium, heat treatment of the metal can be:

• using one cooler;
• with cooling;
• intermittent;
• stepped;
• isothermal.

Quenching in one cooler

This method is used for heat treatment of simple parts made of alloy and carbon steel. The part is heated to the required temperature and then cooled in liquid. Carbon steel with a diameter of 2 to 5 mm is cooled in water, parts of smaller diameter and all alloy steel are cooled in oil.

Hardening with cooling

When heat treating with a single coolant, thermal and structural internal stress conditions often occur. They develop when the temperature difference reaches a minimum.

Tensile stress is formed on the surface of the metal, and compressive stress is formed in the center. To reduce these stresses, before lowering the heated part into the liquid, it is kept in the open air for a short time.

The temperature of the part in this case should not be below the 0.8 K line on the iron-carbon diagram.

Intermittent

This hardening is carried out in two environments - water and oil or water and air. A part heated to a critical point is first quickly cooled in water, and then slowly in oil or in the open air.

This heat treatment method is used for high-carbon steel.

This method is complex, since the cooling time in the first environment is very short and only a highly qualified specialist can determine it.

Stepped

With intermittent heat treatment, the part cools unevenly—thinner surfaces cool faster than others. In addition, it is very difficult to adjust the time the part is in the first medium (water). Therefore, it is better to use step hardening.

This method allows the part to be cooled in an environment at a temperature above the martensitic point. The first stage is cooling and holding the part in a given environment until all sections of the part reach the same temperature.

The second stage is the final slow cooling (transformation of austenite into martensite).

Isothermal

In isothermal heat treatment, the part is heated to a critical point and then lowered into an oil or salt bath at a temperature of 250 degrees. Leave for half an hour and then cool in the open air.

This hardening provides high structural strength and is used for alloy and structural steels in which the decomposition of austenite in the intermediate region does not completely occur.

Subsequently, it turns not into martensite, but into bainite + 20% retained austenite, enriched in carbon. With this hardening, high strength and good toughness can be achieved.

Ways to increase the hardness of metal yourself using hardening

To harden or temper, the metal should be heated very much - at least to a crimson color. For these purposes, a thermal oven is optimally suited, and in its absence, an open flame of a fire, a gas burner, a blowtorch, or a high-voltage current. When preparing to carry out hardening, you need to first take into account many points.

• The higher the initial hardness of the material, the more it needs to be heated.
• The more carbon a material has in its composition, the slower the cooling should occur.
• If the task is to harden the entire object, then it will require uniform heating over the entire surface.
• There is no need to overheat the product; it is better to avoid the appearance of blue or black spots on the hot surface.
• Prepare tongs and containers with a cooler (coolers, if there are several of them) in advance.

It is better to carry out complete, total hardening on the flame of a fire made of coals - they hold high heat for a long time, and the fire will allow you to place the entire dimensional part there and heat it evenly.

Partial hardening, for example, of a cutting edge, can be done using a blowtorch; it can also easily harden small parts - bolts, drills, nails.

Methodology

In order to carry out the work of hardening steel, you need to take into account how such a process is carried out correctly.

Hardening is a process of increasing the hardness of the surface of an iron or alloy, which involves heating a sample to a high temperature and then cooling it.

Despite the fact that at first glance the process in question is simple, different groups of metals differ in their unique structure and characteristics.

Heat treatment at home is justified in the following cases:

1. If necessary, strengthen the material, for example, at the cutting edge. An example is the hardening of chisels and chisels.
2. If it is necessary to increase the plasticity of an object. This is often necessary in the case of hot forging.

Professional hardening of steel is an expensive process. The cost of 1 kg of increasing surface hardness costs approximately 200 rubles. It is possible to organize hardening of steel at home only taking into account all the features of increasing surface hardness.

Process Features

Steel can be hardened taking into account the following points:

1. Heating should occur evenly. Only in this case the structure of the material is homogeneous.
2. The steel should be heated without the formation of black or blue spots, which indicates severe overheating of the surface.
3. The sample cannot be heated to an extreme state, since changes in the structure will be irreversible.
4. The bright red color of the metal indicates that the steel has been heated correctly.
5. Cooling must also be carried out evenly, for which a water bath is used.

Temperature of the workpiece depending on the color when heated

It is recommended to take these points into account when considering how to harden at home.

Modes of hardening and tempering of steels

Equipment and features of the process

Special equipment is often used to heat the surface. This is due to the fact that heating steel to the melting point is quite difficult. The following equipment is often used at home:

1. electric oven;
2. blowtorch;
3. thermal oven;
4. a large fire that is surrounded to redirect the heat.

Mobile forge for heating parts

When choosing a heat source, you should take into account the fact that the part must be completely placed in the oven or fire on which the heating is carried out. It will also be correct to select equipment based on the type of metal that will be processed. The higher the strength of the structure, the more the alloy is heated to impart plasticity.

In cases where only part of the part needs to be hardened, jet hardening is used. It provides for a jet of cold water to hit only a certain part of the part.

A water bath or barrel or bucket is often used to cool steel. It is important to take into account the fact that in some cases gradual cooling is carried out, in others it is rapid and abrupt.

In everyday life, hardening is often carried out over an open fire. This method is only suitable for a one-time process of increasing surface hardness.

All work can be divided into several stages:

1. First you need to make a fire;
2. at the time of lighting the fire, two large containers are prepared that will correspond to the size of the part;
3. In order for the fire to produce more heat, you need to provide a large amount of coals. they give a lot of heat for a long time;
4. one container should contain water, the other should contain motor oil;
5. special tools should be used to hold the hot part being processed. In the video you can often see blacksmith pliers, which are the most effective;
6. After preparing the necessary tools, you should place the object in the very center of the flame. in this case, the part can be buried in the very depths of the coals, which will ensure heating of the metal to a fusible state;
7. coals that are bright white are hotter than others. The metal smelting process must be closely monitored. the flame should be crimson, but not white. if the fire is white, then there is a possibility of overheating of the metal. in this case, performance deteriorates significantly and service life is reduced;
8. the correct color, uniform over the entire surface, determines the uniform heating of the metal;
9. if darkening to a blue color occurs, this indicates a strong softening of the metal, that is, it becomes excessively plastic. this should not be allowed, since the structure is significantly disrupted;
10. when the metal is completely heated, it should be removed from the source of high temperature;
11. after this, the hot metal should be placed in a container with oil with a frequency of 3 seconds;
12. The final stage can be called immersing the part in water. In this case, the water is periodically shaken. This is due to the fact that the water quickly heats up around the product.

When performing work, care should be taken as hot oil can cause damage to the skin. In the video you can pay attention to what color the surface should be when the desired degree of plasticity is achieved.

But to harden non-ferrous metals, it is often necessary to be exposed to temperatures in the range of 700 to 900 degrees Celsius. It is practically impossible to heat non-ferrous alloys over an open fire, since it is impossible to achieve such a temperature without special equipment.

An example is the use of an electric furnace, which is capable of heating the surface up to 800 degrees Celsius.

How to mine copper at home?

Those who will build their own home will certainly make their own small, but not simple, choice. What materials should be used for electrical wiring, as well as plumbing and heating, gas supply, what practice exists here, what materials are justified, and why? The choice of materials here is quite wide, but there is often no clear answer.

Steel, metal-plastic, PVC and copper pipes, aluminum and copper wires - this is the set of materials that is most often used in heating and water supply systems and electrical wiring.