Jewelry alloys: cupronickel, nickel silver, alpaca, Tibetan silver, tombac, brass

What is brass

The main components of brass alloy are copper and zinc. The proportional components of these metals may be different. The amount of zinc varies. Its minimum value is 20%. The maximum reaches 50%. At the same time, the alloy changes its color: it can be golden, yellow or green.

The percentage of zinc is so important that it can change the characteristics of the material. This refers to its ductility and hardness.

Properties and composition of pseudo-precious brass

Brass has been known for a very long time, since the times of the ancient Romans, and this despite the fact that zinc was discovered only 5 centuries ago. In those distant times of antiquity, galmei (zinc ore) was added to the mentioned alloy instead of pure Zn. But the tombac that we know today was invented by Christopher Pinchbecker in the 17th century. The alloy became widespread not only in England; within a few decades people learned about it all over the world. And by the way, many scammers got rich by passing off coins, various jewelry and products made from this type of brass as gold. Today in everyday life you can find other names for this alloy - similor, princetal, chrysochalk, oreid and chrysorin.

As you may have guessed, it is an alloy of copper and zinc. The content of the first element ranges from 88 to 97%, and the second - no more than 10%. If you increase the share of Zn to 10–20%, then you get a semi-tompak. The content of the last element affects the properties of brass and its color. As it increases, the color changes from red to yellow. Sometimes tombac bars can be confused with precious gold in the photo. Such a change leads to improved antifriction, technological and mechanical properties, and the cost, on the contrary, decreases. This is due to the relative cheapness of zinc compared to copper.

The material has excellent anti-corrosion properties and wear resistance. It welds perfectly with various steels and precious metals. It is distinguished by increased plasticity. Easily amenable to enameling and gilding, forging, drawing and engraving.

Another feature is the complete absence of magnetic properties.

Product made from tombak

The hardness of the material reaches 145 MPa. The temperature at which the melting process begins is 1045 °C. Without the use of lubricant, the friction coefficient is 0.44. If you use special lubricants, this figure can be reduced to 0.074. Tensile strength ranges from 440 to 520 MPa, and elongation after break is about 3%. Brass L90 has a density of 8780 kg/m3. To obtain the specified characteristics, additional elements are introduced into the composition of the tombac alloy. Their content is only a few tenths of a percent. The result is a material with an ideal ratio of ductility and strength, excellent appearance and reasonable price.

The alloy, depending on the further fate, can be sheet or in bars. The marking indicates the letter “L” first, followed by the percentage of copper. For example, L96 consists of 95–97% Cu, no more than 0.2% impurities and the rest is Zn. But if you see the designation L90 on a product, it means that the main element is contained within 88–91%, impurities are less than 0.2%. Brands L85 and L80 belong to semi-tompak. The share of additional components in them can reach 0.3%.

Characteristics

The main quality in the characteristics of brass is its corrosion resistance. But it also has other properties:

1. The ability of the alloy to withstand aggressive environments, especially after coating the surface with varnish.
2. Strength of brass.
3. Plasticity of the alloy.
4. The ability of the material to be processed by pressure. The process is carried out both hot at high temperatures and cold.
5. The alloy can be subjected to resistance welding and soldering.
6. Thermal conductivity, which increases with increasing percentage of copper.
7. Melting point, which is 880–950 degrees. With less zinc added, the melting point decreases.
8. The material has non-magnetic properties.

The main factor in the hardness and ductility of the joint is zinc. An increase in its quantitative content is directly related to an increase in strength characteristics. Plasticity increases only up to a quantitative zinc content of 36%. With a subsequent increase to 45%, this indicator decreases.

In order to increase the hardness of the alloy, a heat treatment called cold hardening is carried out. It helps not only to increase the strength index, but also relieves internal, structural stresses.

Alloying additives affect the performance characteristics. Their influence is indicated in the table:

Marking

There are 2 types of alloys:

1. Two-component. The main components are copper and zinc. They are marked with the letter L. Next are numbers indicating the amount of copper in percent. L60: contains 60% copper, and the remaining 40% zinc.
2. Multicomponent. In addition to the main components, alloying elements are added. Also in front is the letter L. Then follows a list of additives. At the end, numbers are written through a dash indicating the percentage of each component. The amount of zinc is not indicated, but calculated. For example: Brand LAZhMts66-6-3-2 has 66% Cu, 6% Al, 3% Fe and 2% Mn. By calculation, the amount of zinc is determined to be 23%.

How to distinguish gold from brass

Even though gold and brass look similar, there are ways to tell one from the other. This is checked as follows:

1. Gold has a more saturated color. In addition, over time, brass darkens because it oxidizes in air, but gold does not.
2. If you put a magnet near it, brass will be attracted, but gold will not.
3. Brass has a higher density, which means it is heavier. This is noticeable when throwing pieces of metal in your palms.
4. Availability of sample.
5. If you test with acid, the gold will not react and the brass will discolor.

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Advantages and disadvantages

Brass alloy has characteristics that are positive in one case and negative in another. They consist of the following:

1. Light weight. This quality, together with high strength, is used in certain industries.
2. The alloy has good ductility.
3. Low cost.
4. Corrosion resistance decreases with increasing amount of copper.
5. Thermal conductivity indicators are lower than those of pure copper and bronze.

Properties

The density of the copper alloy is 8300 - 8800 kilograms per cubic meter. The difference in values ​​is due to the ratio of metals in the alloy and the amount (presence or absence) of additional materials. Tombak begins to melt at 890 - 940 degrees; with an increase in the percentage of zinc in the alloy, the melting point decreases. Tompak is well processed by pressure, both hot and cold, has high mechanical and casting properties, excellent corrosion resistance and wear resistance. The alloy has increased weldability and bonds well with steel, non-ferrous and precious metals. A valuable feature is the complete absence of magnetic properties.

The amount of zinc in an alloy determines its characteristics and affects its color. The more zinc, the lighter the alloy will be; you can achieve a color change from copper-red to light yellow, absolutely identical to the color of gold. This “golden” tombac contains zinc - 15% and an aluminum additive in the amount of 5%. It is precisely because of the gold coloring that products and counterfeit coins made from tombac were used by various swindlers. In addition to color, with an increase in the percentage of zinc in the composition, the following qualities of the alloy change compared to copper:

• antifriction properties increase;
• technological and mechanical characteristics are increased;
• the cost is reduced compared to the price of pure copper

The alloy has a high degree of ductility, which allows it to be processed by deformation methods, forged, turned and engraved, gilded and used for products with enamel, such as awards. In the latter case, the zinc content in tombac should not exceed 3–5%. This is the so-called enameling tombak.

What is tompak?

Tompak is one of the many varieties of brass, which combines zinc and copper in a certain proportion. The comparison of this metal with gold is based only on external similarity, since in terms of chemical composition, characteristics and other features, these two metals are completely different. Although brass has been known to mankind for a long time, they first started talking about tombac only in the eighteenth century - after the discovery made by Christopher Pinchbecker. At that time, a similar alloy was actively used in England. And only a few decades later its popularity spread to other countries.

On the similarity of tombac to a jewelry mineral, many dishonest people were able to make good money by passing off coins and jewelry made of brass alloy as real ones made of gold.

The metal in question can be called similore, princetal, chrysorine, chrysochalk, ororeid. When you hear these names, don’t be surprised - they’re all the same metal.

Tombak has many advantages:

• good resistance to corrosion damage;
• excellent wear resistance;
• good weldability with other metals;
• plasticity is sufficient for the use of deformation and engraving methods;
• possibility of enameling and gilding;
• immunity to magnets.

One type of metal, called semi-tompak, deserves special attention. Its difference from tombak lies in the percentage of zinc, which can range from 10–20%. This feature explains the change in the basic properties of the metal:

• rich yellow color;
• decreased plasticity;
• increased refractoriness.

Such characteristics make it possible to use semi-tombak for the production of some technical parts. This type of metal is less common compared to tombac. This is due to the presence of a large number of deficiencies due to the high zinc content in it.

A little history

This alloy has been known since the times of ancient South American pre-Columbian civilizations; brass jewelry, dishes, and tools were found during archaeological excavations. Instead of zinc, the production secret of which was lost in Europe in the 10th-11th centuries and rediscovered only a few centuries ago, the alloy was made at that time using rich zinc-containing ore - galmey (a mixture of zinc spar ZnCO3 and zinc silicate).

The tombac was reinvented in England by the London watchmaker Christopher Pinchbecker (1670 - 1732). It is he who is considered the author of the chemical composition of this alloy. Initially, the alloy was used to make chains and watch parts. But soon tombak became widespread not only in England, it became known all over the world. Many fortunes were made by various scammers based on the similarity of tombac to gold; they became rich by passing off coins and items made from it as gold.

Marking

Tombak, cast in bars or made in the form of rolled sheets, is marked with the designation “L90”, where “L” is brass, and the number “90” means the percentage of copper content. Impurities in such an alloy are less than 0.2%. “L96” means that the alloy is 95-97% copper, no more than 0.2% impurities, the rest is zinc. If the number on the marking is “85” or less, then it is not a tombac, but a semi-tompak. And this means that the amount of zinc in the alloy is more than 10%, its ratio can reach up to 22%. The amount of additional components can reach 0.3%. By increasing the volume of zinc, the basic properties of the alloy change:

• the color changes, it becomes more yellow;
• the degree of plasticity decreases;
• refractoriness increases.

This material is more often used for the manufacture of technical parts; bellows, flexible hoses, condensation tubes, and wire mesh used in filter-driers for refrigeration machines are made from it.

Jewelry alloys: cupronickel, nickel silver, alpaca, Tibetan silver, tombac, brass

Previously, the article “Varieties of jewelry alloys and their properties” was written

Now, as promised, I am writing about jewelry alloys.

What is jewelry alloy? This is any alloy from which jewelry is made (simply costume jewelry), but does not contain precious metals. For the most part, jewelry sellers do not write what kind of alloy this or that piece of jewelry is made from, indicating the composition simply as a jewelry alloy.

There are a great variety of jewelry alloys, so in this article I will describe only a few of them.

Cupronickel is an alloy that, as a rule, consists of 70-80% copper and 30-20% nickel. May contain impurities of silver, iron, zinc, manganese. It has a silvery color with a barely noticeable yellowish tint. If the alloy contains silver, it is very difficult to distinguish it from silver jewelry. Cupronickel has been known since the 3rd century BC; in those distant times, the alloy of copper and nickel was called “white copper”. In fact, this alloy is called cupronickel only in Russia and the countries of the former USSR. In other countries, this alloy is called “German silver” (in English German silver), since the Germans made a lot of jewelry, household items, and even minted coins from this alloy. This alloy was also called “poor man’s silver.”

Who doesn’t know the good old classics of Soviet jewelry - turquoise or amber in cupronickel? Or enamel in cupronickel, made using filigree or filigree techniques. Cupronickel alloy was widely and successfully used in the USSR.

Unlike silver, cupronickel is a cheaper, but at the same time durable alloy, does not darken, does not corrode and is easy to clean.

Set of the Soviet period. Cupronickel with Ural malachite.

Set of the Soviet period. Cupronickel with Ural charoite.

Filigree products made from cupronickel are often silvered and plated with gold. On costume jewelry of the Soviet period you can find the mark MNTs, which means copper-nickel-zinc alloy. This is only the composition of the alloy, but not its ratio. The MNC mark could be found on both cupronickel and nickel silver.

Nickel silver (translated as new silver) is very similar in appearance and composition to cupronickel, but this alloy is cheaper than cupronickel, it contains about 40% copper, up to 15% nickel and up to 45% zinc. Often, when making it, exact proportions are not followed and various other metals are added to the composition of nickel silver. Nickel silver is a durable and elastic alloy. May have a blue or greenish tint. Nickel silver, as well as cupronickel, is widely used in the manufacture of jewelry with filigree and enamel. As a rule, many sellers of vintage jewelry do not distinguish between nickel silver and nickel silver, choosing to describe the jewelry at random, because... Visually it is very difficult to distinguish these two alloys.

Icon pendants were and are often made from nickel silver.

Fruit plate made of nickel silver from the early Soviet period with hand-painted ceramics.

Vintage nickel silver belt buckle with natural stones, South America.

Unlike cupronickel, they often try to plate nickel silver in cutlery so that there is no metallic taste in jewelry, because... Nickel is considered an allergenic metal, and silver plating makes nickel silver jewelry hypoallergenic.

Chemical composition and main characteristics

An alloy of copper and zinc, which is well known to everyone under the name “brass,” has been used by people since ancient times, making weapons, tools, dishes and many other products from it. Initially, instead of zinc, which was discovered by scientists only 5 centuries ago, zinc-containing ore – galmey – was used to produce such an alloy. The tombak itself was invented in the 17th century. It is believed that the author of the chemical composition of this alloy was the Englishman Christopher Pinchbecker.

Thanks to its characteristics (first of all, its very beautiful color), tombac became known throughout the world in just a few decades. By the way, this alloy gained enormous popularity among scammers who passed off products made from it as gold, deceiving gullible citizens and earning a lot of money from it. Both before and now in everyday life and among specialists you can hear different names for tombak:

• princetal;
• chrysochalk;
• similor;
• oreid;
• Chrysorin.

Cold-rolled brass strip L90 - the material from which tombak products are subsequently made

Tompak, as is already clear from all of the above, is an alloy of copper and zinc, with the first element contained in tombak 88–97%, and the second (zinc) – no more than 10%. There is also such a material as semi-tompak. This is an alloy whose chemical composition is 10–20% zinc.

The amount of zinc in the composition of any brass, including tombac, affects not only the characteristics of the alloy, but also its color. Thus, with an increase in the content of this element in the composition of brass, the color of its surface changes from red to light yellow. Increasing the quantitative content of zinc in the chemical composition of tombac makes it possible to achieve:

• obtaining a noble golden color;
• improving anti-friction characteristics;
• good mechanical and technological characteristics;
• significant reduction in cost (when compared with the price of pure copper).

Chemical composition of copper alloys used to imitate gold

Tompak has a whole list of advantages, which include:

• exceptionally high corrosion resistance;
• increased wear resistance;
• good weldability with various materials (steel, non-ferrous and precious metals);
• high ductility (which makes it possible to use plastic deformation methods for processing tombak and engraving on the surface of products made from it);
• subject to enameling and gilding;
• non-magnetic.

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Tompak also has the following characteristics:

• hardness – up to 145 MPa;
• the temperature at which the alloy begins to melt is 10450 Celsius;
• friction coefficient: without the use of lubricant – 0.44; when using special type lubricants – 0.074;
• tensile strength - 440–520 MPa;
• the relative elongation that the material receives after breaking is 3%;
• material density – 8780 kg/m3.

The characteristics of L90 brass, which is called “tompak,” can be improved if various components are added to its chemical composition in small quantities. This minor modification allows us to obtain a material that optimally combines characteristics such as ductility, strength, good workability, attractive appearance and affordable price.

Modern manufacturers produce tombak in the form of rolled sheets or bars, which determines the options for further use of such material. You can find out exactly what elements and in what quantities are included in the chemical composition of the alloy by its marking. Thus, the letter “L”, which is necessarily present in the designation of tombak, means that this is brass. The numbers after this letter indicate how much base metal – copper – is contained in the alloy. In such brass, in addition to copper and zinc, there are necessarily impurities, the exact amount of which can be found out from special tables. It should be borne in mind that alloys in which copper is less than 90% (L85, L80, etc.) belong to the semi-tombac category.

Comparison by technical and user characteristics

Life time. The smooth inner surface of steel pipes, coated on the outside with an aluminum jacket, does not contribute to the deposits of lime and salt deposits.

The typical service life of bimetallic radiators is more than 20 years, and here their only rival is cast iron.

It is believed that due to unreliable paint and varnish coating and insufficient corrosion resistance of steel, the service life of steel appliances is lower and ranges from 15-20 years.

Heat transfer from radiators is a relative concept. Aluminum has a high heat transfer coefficient. The bimetallic section has a heat output of about 200 W. For steel sections of the same area, this figure is almost two times lower.

Notes

1. ↑
   A dictionary of arts, manufactures and mines: containing a clear exposition of their principles and practice Robert Hunt (ed.), D. Appleton & Co.: 1856: pp243
2. Bank of Russia. A variety of Bank of Russia coins in denominations of 10 and 50 kopecks, model 1997. — (coins of the 1997 sample, coated with tombac, have been issued since 2006, previously they were made of brass). Retrieved January 29, 2009. Archived from the original on June 2, 2012.

Where is Tompak used?

Tombak is used for cladding steel, i.e. coating the surface of steel products with a thin layer of an alloy, which is used in the manufacture of charges and bullets for firearms and producing a steel-brass bimetal. The use of such bimetallic sheets saves stainless steel and non-ferrous metals, protecting the steel core from corrosion and destruction and giving the surface the desired properties. This technology can dramatically reduce the cost of the product. Bimetal is used for various elements of chemical equipment, where other coatings cannot cope with corrosion. Bimetallic wire is used for communication lines. Tombak is used for the manufacture of high-precision measuring and other equipment.

Due to its good resonator properties, the bells of brass wind musical instruments are made from the alloy. It is used to make:

• artistic products (paintings made using metal chasing technique);
• radiator tubes and drawn pipes with a diameter of up to 30 mm;
• insignia;
• accessories;
• cigarette cases and cigarette holders;
• some types of medals and coins.

For example, Russian coins in denominations of 10 and 50 kopecks. School Gold medals are made from tombac and then gilded. The bronze medals of the 1980 Summer Olympics in Moscow were made of tombac. In 1942-1943, Canada issued tombac coins in denominations of 5 cents.

Due to its beautiful color and ease of processing, tombak is widely used by jewelers in the manufacture of costume jewelry. The alloy is used to make dishes, figurines, candlesticks, and in interior decoration and furniture. In Eastern countries, elegant thin-walled waterware, jugs, bowls, and trays are made from tombac, which is decorated with unique patterns, thereby creating works of art. The dishes are protected from the destructive effects of water on the alloy by tinning with tin, which allows the artistic beauty of the products to be preserved for a long time.

Areas of application

Tompak, the products from which have a very beautiful color, is actively used in jewelry due to its good workability. Individual jewelry is made from it, and products made of gold, silver and other metals are decorated with it. Due to the exceptional decorative characteristics of tombak, it is used to make furniture elements, dishes, figurines, and other interior items.

Tombac bowl and jug

The production of jewelry and decorative items is not the only area of ​​application for this type of brass. Tompak is also used in various branches of modern industry. In particular, wire is produced from such an alloy, which can be used for various purposes. Dishes made from tombac are very popular (especially in the countries of Central Asia) (water jugs, trays on which it is quite easy to apply any pattern, as well as colanders and other household items). Since brass reacts quite critically to contact with water, dishes made from tombak must be tinning using tin.

Production methods

Methods for obtaining tombak have expanded significantly since its discovery, but the essence of each of them comes down to a single scheme.

1. The composition is heated in an electric oven to 1300–1400 degrees. With such heating, silicate is released, floating to the surface of the alloy, which makes it possible to remove it from there without unnecessary difficulties.
2. The resulting metal is poured into a container and purged with oxygen. This stage requires the use of special equipment. This treatment provokes the release of thermal energy in large quantities and triggers a chemical reaction.
3. At this stage, copper is formed, which contains many impurities, which reduces its properties.
4. The composition is subjected to electrical cleaning using acidified copper sulfate.
5. Zinc is added to molten copper to produce a strong alloy with high corrosion resistance.

The process of obtaining tombak is complex, labor-intensive and energy-consuming. This explains the high cost of the metal, which is still much lower than the price of gold.

Alloys in orthopedic dentistry

Metal occupies a central place among materials in dentistry. Most fixed dentures and removable denture frames are cast (or stamped) from dental alloys. Alloys in dentistry are used as auxiliary materials for soldering and stamping. Dental instruments are made from them.

Article outline:

• Classification of metals and alloys in dentistry
• Structural metal alloys in orthopedic dentistry
• Noble metal alloys in dentistry
• Base alloys in orthopedic dentistry
• Auxiliary metal alloys in dentistry

Reanimation of the surface from oxide

Due to their wear resistance, brass and all its types are called “eternal metal”. But this does not mean that products made from these alloys do not need to be looked after. They, like silver, darken, especially due to contact with water. It’s easy to fix the situation; let’s look at several ways to clean brass.

For the simplest case, you will need acetone, soap, water and a cotton pad. Prepare a weak soap solution and soak the cotton wool in acetone. Wipe the product thoroughly with a disc and then wash it in the solution. All that remains is to dry it and enjoy the magnificent view. The second method is also available to any housewife. You will need a metal container with a minimum capacity of 3 liters, water, 250 ml of simple vinegar and 25 g of salt. Mix all the ingredients, place the brass product in the solution and place the pan or bowl on the fire. Bring to a boil and add clean water if necessary. We continue until the brass item is clean.

The following method can be dangerous to the skin and eyes, so it requires caution. To clean tombac using this method, mix 10 liters of water and 200 g of oxalic acid in a plastic container. This method is used for processing large products. Be sure to follow safety precautions. Wear rubber gloves and a respirator. Carefully place the product in a container with the solution and leave it there for several hours. Then very carefully remove it and rub it with a dry cloth.

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You can also clean tarnish with lemon. Cut the fruit and immerse it in table salt, and then rub the surface to be treated. If you also need to polish, then a simple toothpaste will come in handy. Rub it in with a cotton cloth, and then rinse the element in clean running water.

Before cleaning, make sure that the product is actually made of brass and not covered with it. To do this, just bring a magnet. Tompak will not react at all. If the item is just coated with a thin layer of alloy, do not use abrasive substances, as this can easily damage the surface layer.

First way

Prepare a solution consisting of 3 liters of water, a small tablespoon of salt (25 g) and a glass of ordinary vinegar. The product should be placed in this solution and boiled until the surface is completely clean. As necessary, add water to the original volume. After cleaning, the item is washed with running water and dried.

Second way

The item that needs to be cleaned is carefully placed for several hours in a solution consisting of 10 liters of water and 200 ml of oxalic acid. To make it, you must use plastic containers. Use this volume of solution to clean large products. When cleaning small items and the need to use less solution, you can proportionally reduce the volume of components. This method is potentially dangerous to the skin and eyes, therefore, if used, it is necessary to use rubber gloves and a respirator as personal protective measures. After cleaning, the product must be thoroughly rinsed under running water and rubbed with a dry cloth.

Products with enamel, glass inserts, other metals, paintings and other artistic elements are not recommended to be cleaned using these methods.

Third

A solution containing water and soap is required. You also need acetone. A cotton swab or disk is moistened in acetone and the product is thoroughly wiped with it. After such treatment, it is washed with soapy water until the original shine of the surface is completely restored and be sure to wipe dry.

Fourth method

The simplest one is to wipe the surface of the product to be cleaned with half a lemon or lime, which is first dipped in table salt. After such cleaning, the surface can be polished with regular toothpaste and a cotton cloth as a gentle abrasive polishing compound. Then you need to rinse the item in running water and wipe dry.

Fifth method

You need to buy a cleaning agent for non-ferrous metals in retail chains. Most often it is sold in the form of tubes with cream or paste, and apply it strictly according to the instructions.

Sixth method

Polish the product using GOI paste. This product is called the paste of the State Optical Institute and was developed about 80 years ago. To clean and polish the product, apply the paste to a soft cloth. A few drops of spindle oil are applied to better dissolve the paste, and then the product is polished with slow movements. After polishing, the item is washed to degrease and wiped dry.

What is a semi-tompak?

Semi-tompak should be included in a separate category. The differences lie in the concentration of zinc, which increases to 10-20%. Due to this, the basic properties of tombak change. The key features are the following:

1. The product takes on a more yellow tint.
2. The degree of ductility decreases and refractoriness increases.
3. The material is often used to make technical parts.

This alloy is found much less frequently in comparison with tombac. This is due to the fact that an increase in the amount of zinc causes a large number of deficiencies to appear.

Manufacturing

In the brass production process, special cards are used indicating the melting technology; it is developed in industrial bureaus. Often the raw materials for the alloy are copper blanks, as well as zinc scrap. The melting operation of this material is a complex process for which furnaces of various modifications are used. Induction units operating in a low-frequency network with a magnetic core are more often used.

When melting, substances may evaporate from the composition. Since zinc is considered a metal harmful to health, it is recommended to install high-power ventilation in production areas. During the entire cycle, temperature indicators are monitored, which prevents the alloy from igniting.

It is recommended to first clean the furnace cavities from previous casting products. Next, the copper blanks are heated to a bright red hue, then zinc scrap is added. This sequence prevents the formation of oxidative reactions. Casting-type brass is poured into round, flat molds for ease of subsequent processing.

To improve the quality of the alloy, use:

• tin and manganese, which increases strength and resistance to destruction in an aggressive environment;
• lead, as a result, the brass workpiece can be processed with cutters on a machine;
• high resistance to acidic and alkaline environments is achieved by adding nickel;
• aluminum protects the alloy from zinc evaporation during casting;
• silicon improves welding properties with metals, but reduces strength.

Corrosion resistance

In many ways, the material in question is popular due to its high corrosion resistance. Thereby:

1. Tompak alloy is used in the manufacture of various decorative products that do not lose their properties over a long period. An example is tableware or inexpensive jewelry.
2. The service life of products is significantly extended. Corrosion not only spoils the decorative qualities, but reduces the basic properties.
3. High corrosion resistance can be achieved by using copper as the basis of the composition. This material does not react to moisture and some chemicals.

In general, we can say that the scope of application of tombac largely depends on the corrosion resistance indicator.

However, over time, due to exposure to high humidity, an oxide film appears. It significantly reduces the decorative qualities of the resulting product.

Definition

What are bimetals? One of the layers of such materials is most often inexpensive steel. The second layer is made of expensive non-ferrous or even noble metals. Composites of this type are usually used when it is necessary to impart special properties to the product. Also, the use of such materials in various fields helps to save on aluminum, copper, bronze, silver, etc.

Thus, what a bimetal is is clear. This is a composite, most often consisting of two layers. Such materials differ from ordinary ones in special properties. The layer of cheap steel in bimetals is always called the base layer. A layer of expensive material is cladding.

The page provides examples of photos of different types of bimetals and products made from them. Materials of this type are actually used very widely in the national economy.

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Production methods

Today, tombak can be produced using a variety of technologies. The most widely used option is the use of an electric oven, which heats the composition to 1400 degrees Celsius. When exposed to such a temperature, silicate is released, which floats to the surface and is removed.

Among other features, we note the following:

1. The result is base metal, which is poured into a special container. There are quite a large number of different devices whose purpose is to release tombak. The base composition must be heated to a temperature of 1400 degrees Celsius. In this case, certain safety rules must be observed.
2. The next step is to flush the resulting composition with oxygen. Special equipment is also used for this. The purging procedure leads to the active release of thermal energy and a chemical reaction.
3. As a result of a chemical reaction when exposed to oxygen, copper is formed. It is characterized by the fact that it has a large number of various impurities, due to which the properties are significantly reduced.
4. Next, the composition is electrically cleaned using special acidified copper sulfate.
5. Zinc is introduced into the resulting straightened copper. This material increases strength and corrosion resistance.

The above information indicates that the process of obtaining such a composition is quite complex and time-consuming. That is why the cost of tombak is quite high, but much less than the cost of the precious metal.

Do not forget that tombac is an alloy of copper and zinc. This composition has very attractive characteristics and is used in the creation of various high-precision measuring and other equipment. In addition, decorative characteristics are highly valued. At a certain ratio of the main components, the alloy resembles gold, but the properties are significantly different.

Rental products

The production of parts can be carried out in a variety of ways; the most widely used method is mechanical removal of material from the surface. Processing can be carried out using turning or milling equipment. The fairly wide spread of this technology was determined by the appearance of a large number of blanks.

The production activities of many organizations are aimed at producing rolled products. It is processed on turning equipment and can be characterized by different diameters. The length and basic properties are standardized, which allows you to select the appropriate blank for the production of the required product.