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

What it is?

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.

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.

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.

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.

Tompak - Steel - Tompak

Description

Multilayer bimetallic tape of the L90StL90 brand is made of low-carbon steel, clad on both sides with L90 tombac.

Compound

• The base is low-carbon high-quality steel grade 08Yu with a chemical composition in accordance with GOST 9045.
• The coating is L90 brass with a chemical composition in accordance with GOST 15527.

The thickness of the cladding layer h1 and h2 is the same for both sides and ranges from 4 to 6% of the thickness of the finished strip. At the Customer's request, the thickness of the cladding layer can be up to 10% per side.

Specifications

Variety

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.

This is interesting: Brass - composition, grades, characteristics of the alloy

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.

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.

This is interesting: Inch threads - dimensions, table, GOST with diameters and pitch, designations in mm

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.

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.

Where is Tompak most often 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.

Chemical composition and main characteristics

The alloy of zinc and copper, known to many, has been used for a long period. An example is that it was used in the manufacture of the first tools and some jewelry, as well as household utensils. Tompak was also obtained several centuries ago and was actively used by humans. In common parlance it also has names: similor, oreid, chrysochalk, chryzoin, princetal.

A certain chemical composition makes the alloy widespread. An example is the active use of tombak in the manufacture of various counterfeits and decorative elements, since it resembles gold.

As previously noted, the alloy in question is a combination of zinc and copper, and therefore belongs to the brass group.

At the same time, the composition of the alloy is significantly different, copper from 88 to 97%, zinc no more than 10%.

Do not forget that strength and other properties largely depend on the concentration of zinc. This element also largely determines the color of the material. Due to a significant increase in zinc in the composition, the color changes from red to light yellow, which is characteristic of gold. In addition, the following qualities change:

1. Antifriction properties are significantly increased.
2. Chemical and technological characteristics are improved.
3. The cost is significantly reduced compared to the price of pure copper.

The tombac used is characterized by quite a large number of advantages, which include the following:

1. The material is characterized by increased resistance to corrosion.
2. The wear resistance of the surface layer is significantly increased.
3. The alloy has increased weldability.
4. High ductility largely determines the possibility of application when using products on which engraving is applied.
5. It is possible to expose the surface to enamel and gold powder.
6. The absence of magnetic properties can also be called an important material property that must be taken into account.

The conducted research allows us to determine the basic properties of tombak. They are as follows:

1. Hardness reaches 145 MPa.
2. The melting point is 1040 degrees Celsius.
3. Relatively low coefficient of friction.
4. The tensile strength of the created product is about 520 MPa.
5. The relative elongation is 3%.

In general, we can say that tombak has exceptional performance characteristics. They determine the scope of application.

Types of copper-nickel alloys

A copper alloy alloyed with nickel forms a large number of solid solutions, which are divided into several groups:

• structural;
• electrical;
• jewelry.

The main characteristics of structural copper-nickel alloys: high hardness, abrasion resistance, corrosion resistance. Manganese, chromium, aluminum, zinc and other components are used together with nickel.

In electrical alloys, the manganese content may exceed nickel. The alloys have stable resistance and high conductivity.

Decorative compounds include copper and nickel compounds that lend themselves well to various types of processing: cutting, deformation. They have high fluidity.

Constantan

The alloy is marked - MNMts 40-1.5. This designation indicates that it contains about 40% nickel. Constantan belongs to electrical materials. It has high ohmic resistance and low linear expansion when heated.

Plastic material can be easily processed by rolling. Wire and sheets for thermoelectrodes and converters are made from constantan.

Kopel

A copper-nickel alloy with high thermal stability, marked MNMts 43-0.5. An additional alloying component is manganese. Available in the form of wire of various diameters. Used for the manufacture of compensation wires and low-temperature converters. Resistant to acidic environments, works in inert gases.

The main property is high stability of resistance when changing temperatures. Refers to heat-resistant materials. Stably retains its characteristics at temperatures up to 600⁰.

Wire

Nickel silver

Jewelry copper alloy with a nickel content of 15% and zinc within 20%. Nickel gives the alloy a white color with a greenish or blue tint.

German chemists invented the alloy as a cheap substitute for white gold, no different in appearance. Nickel silver turned out to be harder, resistant to moisture and steam. Does not darken and does not lose its decorative properties. In Europe it was used to make awards and jewelry. Currently, medals, orders, guitar frets and surgical instruments are made from it.

Kunial

The alloy is available in 2 versions and has the letters A and B at the end of the marking. Both types of alloy are corrosion resistant. At elevated temperatures it is prone to cracking.

Kunial-A is additionally alloyed with aluminum, cobalt and iron. Produced in the form of rods.

Kuniali-B - only nickel is dissolved in copper, the content of other substances in total is no more than 1%. The material is used to make strips for springs and springs.

Manganin

In addition to copper and nickel, this alloy contains 13% manganese. It has a beautiful golden-red color. Manganin may contain iron. It belongs to the initially aged alloys - it acquires its mechanical properties after heat treatment. Possesses electrical stability under temperature changes.

Manganin is used in high-precision electrical measuring instruments to create standards.

There is another alloy composition in which copper is replaced by silver. The technical characteristics are practically the same. White Manganin is much more expensive.

Monel

In addition to copper and nickel, manganese and iron are added to the alloy. Monel is named after the head of the American chemical laboratory where the alloy was developed. The material is corrosion resistant, ductile and durable. It is highly resistant to acids and alkalis. Marked - NMZHMts28-2.5-1.5.

Monel is used in the manufacture of instruments and equipment for the chemical and oil industries. Used in apparatus manufacturing, medicine and the shipbuilding industry for the manufacture of anti-corrosion parts.

The alloy is highly plastic, easily processed in cold and hot conditions. Mechanical processing is only possible at low speeds.

Cupronickel

White carbide contains copper in the range of 70–90%. Refers to jewelry compositions. In addition to nickel, it has alloying substances:

• 0.8% iron;
• 1% manganese.

It has high corrosion resistance in sea soda and gas environments. The melting point is in the range of 1150–1230⁰, does not depend on the ratio of the components.

The most common brands of cupronickel are MNZhMts30-1-1 and MN16. It receives its technical characteristics after annealing. Belongs to the group of initially aged alloys.

Cupronickel is used to make spoons, forks, tableware, and various decorations. It lends itself well to processing, carving, and embossing. Surgical instruments, coins, and medals are made from it.

Structure and composition

As in other alloys, the properties of the material are determined by the composition and phase state. Moreover, the differences are so great that they make brass of different brands non-interchangeable.

There are 2 types of alloys: two-component and multi-component.

• Two-component, that is, consisting of 2 metals. In this case, impurities may be present, but in such a volume that does not affect the quality. The main thing is copper, therefore, in the labeling, for example, only the share of copper is indicated, and the share of zinc is simply calculated. The properties of such an alloy are largely determined by the phase composition. Thus, brass with a zinc content of up to 39% includes only one phase - the α phase. This alloy is characterized by high ductility, but its strength is relatively low.
• As the proportion of zinc increases, the metal cannot completely dissolve in copper, and the β phase eventually appears. In this case, ductility decreases, and strength increases sharply up to a zinc content of 45%, and then falls again.

• Multi-component brasses include other metals and non-metals along with copper and zinc. They have a very noticeable effect on the properties of the alloy. They are determined by the nature of the component. Thus, the addition of tin significantly increases resistance to seawater. And the addition of nickel, for example, increases the mechanical strength of a product made from such brass.

Another classification is related to the processing methods of the alloy.

• Deformable, that is, brass that can be deformed in a cold state. Such brass alloys are produced in the form of sheets, rods, wires, from which, for example, all kinds of pipes are then made.
• Foundry - lithium alloys that deform only under the influence of high temperature and pressure during casting. Parts are cast from such material and receive bearings, machine parts, fittings, etc.

Classification based on zinc content is used.

• Red or tombak - the proportion of zinc is 5–20%. The alloy has excellent anti-friction and anti-corrosion properties and is used to produce steel-brass bimetal.
• Yellow - with a zinc content from 20 to 36%. The composition retains high plasticity.
• Technical - with 48–50% zinc, used to produce fittings, machine parts, parts of chemical equipment, and so on.

We will talk about the properties of brass according to GOST below.

How do alloying additives affect

An alloying is an additive to an alloy that changes its composition and, as a result, gives it some new properties, or increases or decreases existing properties. To reduce the loss of metal from the surface of the melt, aluminum is added to it; the resulting oxide film plays a protective role. To increase strength and improve anti-corrosion properties, magnesium is added to the alloy, separately or together with aluminum and iron. Moreover, additives have practically no effect on the density of the metal.

The addition of nickel to the melt eliminates the manifestation of negative aspects in terms of oxidative processes. It is possible to improve the ductility, malleability of the alloy and the conditions for its cutting by introducing an additive such as lead into the brass composition. Silicon in combination with lead improves sliding to such an extent that an alloy alloyed with this additive can be used on equal terms with tin bronze. At the same time, silicon added without other additives specifically increases the hardness and strength of brass. If the metal is planned to be used on a ship, tin is added to it, which makes it resistant to salt water.

TOMPACK is... What is TOMPACK?

• TOMPAC - (French tompac, from Malay tamhaga copper). Alloy of copper and zinc, yellow copper. Dictionary of foreign words included in the Russian language. Chudinov A.N., 1910. TOMPACK is a golden yellow alloy of copper and zinc; the latter is no more than 1 part per ten.... ... Dictionary of foreign words of the Russian language
• tombak - a, m. TOMBAC a, m. tombac m.> German. Tompak. An alloy of copper and zinc, having a golden color; used for the manufacture of cheap jewelry, household items, etc. BAS 1. The word tompak (or tombak) is the name of copper-zinc ... ... Historical Dictionary of Gallicisms of the Russian Language
• TOMPAK - TOMPAK, an alloy of COPPER and ZINC, in which the zinc content is much lower than in brass. Invented by London watchmaker Christopher Pinchbecker (circa 1670-1732). Tompak is often used to imitate gold ... Scientific and technical encyclopedic dictionary
• tompak - arco, argo, alloy Dictionary of Russian synonyms. tompak noun, number of synonyms: 5 • argo (9) • arco (2) ... Dictionary of synonyms
• TOMPACK - (French tombac from Malay tambaga copper), brass with 3 10% Zn (the rest Cu). Good ductility and high corrosion resistance. They produce bimetal (steel and brass), as well as parts for refrigeration and other equipment and artistic products.... ... Big Encyclopedic Dictionary
• TOMPAK - TOMPAK, tompaka, many. no, husband (French tambac from Malay) (special). An alloy of copper and zinc, a type of brass. Ushakov's explanatory dictionary. D.N. Ushakov. 1935 1940 ... Ushakov's Explanatory Dictionary
• TOMPAK - TOMPAK, ah, husband. Alloy of copper and zinc, brass grade. | adj. tompakovy, oh, oh. Ozhegov's explanatory dictionary. S.I. Ozhegov, N.Yu. Shvedova. 1949 1992 ... Ozhegov's Explanatory Dictionary
• TOMPAC is a copper-zinc alloy (brass), containing from 88 to 97% copper and has high corrosion resistance. T. welds well with steel, it is used for the manufacture of bimetal steel-brass, parts of refrigeration equipment, etc. Thanks to ... ... Big Polytechnic Encyclopedia
• Tompak - Jug and dish made from tombak Tombac (French tombac, from Malay tambaga copper) a type of brass with a copper content of 88-97% and zinc ... Wikipedia
• tompak - a; m. [German] Tompak] A type of brass that is an alloy of copper and zinc. ◁ Tompakovy, oh, oh. T. color. That production. T. samovar (made from tombak). * * * tombac (French tombac, from Malay tambaga copper), brass with 3 10% Zn... ... Encyclopedic Dictionary

Effect of impurities on properties

Impurities are not the main alloying elements of simple brasses, but they affect the properties of the alloys. It is almost impossible to obtain an alloy without impurity atoms, since foreign elements are contained in the raw materials for the production of copper and zinc. Ultrapure metals have a high cost and their use is highly specialized and not justified for mass production. The amount of impurities is controlled by standards, which guarantees the mechanical and technological properties of grade copper alloys.

Low-melting impurities, which have limited dissolution in copper-zinc alloys, negatively affect the properties of brass. Low-melting inclusions in the brass composition are released along the grain boundaries and worsen the plastic properties during hot deformation. Single-phase α-brasses are most sensitive to such impurities.

Impurities that do not form independent phases do not negatively affect the mechanical and technological properties of brass.

• Aluminum is completely in solid solution and, as an impurity, does not deteriorate the properties of brass. Small additions of aluminum during melting form a protective film of aluminum oxide on the surface of the melt. This prevents the evaporation and loss of zinc.
• Nickel and manganese in low concentrations enter the solid solution and have little effect on the physical, mechanical and technological properties of brass. Nickel raises the recrystallization temperature of brasses.
• Iron at room temperature has low solubility in the copper-zinc solid solution and forms an independent γFe phase in brasses. This ferromagnetic phase significantly changes the magnetic properties of brasses. The iron concentration in antimagnetic brass does not exceed 0.03%. Iron improves the strength and technological qualities of alloys, since it makes recrystallization difficult and refines the grain.
• Silicon is an impurity that enters a solid solution. Silicon improves soldering and welding of brass and increases resistance to corrosion cracking.
• Bismuth requires special control; it does not dissolve in brass alloys in the solid state and creates a low-melting eutectic at the grain boundaries, which consists of pure bismuth. Bismuth provokes the hot brittleness of brasses, having a stronger effect on single-phase ones. Its concentration in brasses is limited to 0.002–0.003%
• Lead is slightly soluble in copper-zinc alloys in the solid state and, upon solidification, is released in elemental form at the grain boundaries in the form of small spherical particles. Lead impurities impair the ductility of α-brasses at elevated temperatures. Lead provokes hot brittleness, especially in single-phase brasses, so the lead content in double α-alloys does not exceed 0.03%. Additions of lead to brass improve machinability.
• Antimony is a harmful impurity in copper-zinc alloys. It impairs technological ductility during hot and cold forming. Antimony concentrations of up to 0.1% in two-phase brasses prevent dezincification.
• Arsenic dissolves in solid copper up to 5% by weight at a temperature of 25°C, but in a copper-zinc solid solution its solubility is no more than 0.1%. The brittle intermediate phase As2Zn is formed at an arsenic concentration of more than 0.5%. This phase is released in the form of interlayers at the grain boundaries, which leads to brittleness of brass. Arsenic in small quantities of 0.025-0.06% with microadditives protects brass from corrosion cracking and dezincification in sea water.
• Phosphorus is slightly soluble in copper-zinc alloys during solidification. In a solid solution, phosphorus forms an intermediate phase, which increases the hardness and greatly reduces the plastic properties of brass. Small amounts of phosphorus increase the mechanical properties of brasses and reduce the grain diameter of castings. The rate of grain growth in deformed brasses is increased by phosphorus during recrystallization annealing. Copper-zinc alloys do not require deoxidation with phosphorus, since zinc is a stronger deoxidizer than phosphorus. In industrial grades of brass, the phosphorus content does not exceed 0.005-0.01%

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.

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.

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.

Main selection criteria

You have to solve the problem of choice both when building a new house and when renovating an old one. Heating radiators, just like electricity, water, and sewerage, are the most important part of utilities in any room. When choosing heating devices, experts take into account four main indicators.

• House type. When choosing a radiator, first of all, you need to take into account the type of house. If the apartment is located in a high-rise building, then installing steel panel appliances in it is not recommended. It is worth paying attention to bimetallic models. If the house is low-rise, then both types of radiators can be installed.
• Appearance. The modern design of the device is not only a tribute to good taste, but also a testament to quality. Responsible manufacturers devote a lot of effort and resources to developing optimal shapes that not only give a beautiful appearance, but also improve the thermal characteristics of the radiator.
• Correct power calculation . Underheating or overheating of the room means loss of comfort. To avoid this, it is necessary to correctly calculate the required thermal power of the device. It is calculated using a simple formula: the power (in watts) should be equal to the area of ​​the room in square meters, multiplied by 100. If the room is well insulated and has metal-plastic windows, 200 watts are subtracted from the resulting figure. If the room is corner or has several large windows, then the radiator power is increased by 25%.
• The right choice of manufacturer. Often in life, the pursuit of cheapness turns into problems. This fully applies to heating devices. A radiator made using a semi-handicraft method may not have the same characteristics as stated. After just a couple of heating seasons, it may begin to leak and require replacement.

How to make the right choice? There can be no clear answer. Everyone wants to have beautiful heating devices that combine the advantages of both steel and aluminum. Of course, such a choice is not an easy task, but still feasible even for non-specialists. You only need to have a minimal understanding of the item you are purchasing and adhere to a few of the simple criteria listed above.

Just four of these simple indicators will allow the owner of a house or apartment to choose the optimal radiator configuration, its type and cost, and which will last for a very long time.

Areas of application

Tombak has become widespread in various fields of human activity. Here are the most popular areas.

• Production of jewelry, ornaments, interior items and kitchen utensils . Tompak is valued in this area primarily as a material that imitates gold. Its noble color, pliability and high decorative effect make it an excellent solution for such purposes.
• The production of tableware is especially important in the countries of Central Asia, since here such household items are valued and held in high esteem. Brass does not tolerate contact with liquids, therefore dishes made from the raw materials in question are necessarily subjected to tinning - a technology during which a thin layer of tin is applied to the item.
• Modern industry also actively uses tombac. It is used to make wire for various purposes.
• The creation of technical parts is carried out in various ways. The most commonly used method is based on the principle of mechanical removal of material from the surface. Special turning and milling machines are used for processing. Due to the high relevance of this technology, many tombac blanks began to appear.
• There are a large number of organizations whose production activities are aimed at producing rolled products. The metal in this form is processed on turning equipment. Rolled tombac is characterized by different diameters, which cannot be said about the length and basic properties, which are standardized characteristics. Such features make it easy to select the necessary workpiece for future production.

The area of ​​use of the metal largely depends on its resistance to corrosion.

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