Bronze is a metal obtained by mixing molten copper and some other metals and non-metals. As a rule, the amount of copper additive components does not exceed three percent, but there are exceptions to this rule - zinc and nickel can be added in large quantities. Such alloys are called brass and cupronickel (cupronickel), respectively. In other alloys, zinc may also be present, but with a limitation: its amount should not exceed the sum of the other added metals. If this happens, the alloy will be brass.

This metal alloy appeared about five and a half thousand years ago. It was then that the Bronze Age began. Until that time, only copper was smelted - this metal was the basis of all tools. When the melts of copper and tin happened to be combined, another metal was obtained, which was called bronze - an alloy of copper and tin, harder than the original metals. It immediately found wide application in all spheres of human life: it was used to make bladed weapons and kitchen utensils, mirrors and jewelry, coins and sculptors’ creations.

Medieval bronze craftsmen cast bells for the needs of the church and cannons for the army. Specially made bronze was used to cast the cannons. This technology existed until the nineteenth century. Below are some interesting facts about bronze.

Manufacturing methods and characteristics

Physical data

The characteristics of the alloy are determined by its chemical composition and can vary within certain limits. Bronze is less susceptible to corrosion and provides better metal-to-metal glide than brass. It has higher strength and is less susceptible to atmospheric influences (water and air) and better resists salts and organic acids. It is easy to machine, it can be soldered and fastened by welding. Some physical characteristics of bronze:

• specific gravity from 7.8 to 8.7 tons/cu.m. meter;
• melting point of bronze – melts when heated from 930 to 1140 degrees;
• color changes from red - the color of copper, to white - the color of tin;
• wear resistance and good sliding on metal determine the scope of application as sliding bearings; they work well in any temperature conditions;
• There is high electrical conductivity and heat transfer, resistance to steam, which contributes to the manufacture of parts for equipment operating in extreme situations.

How to make bronze

Melting and mixing copper melts and additives of different metals, which make it possible to give the alloy certain required characteristics, leads to the production of an alloy metal such as bronze. In the manufacturing process electric ovens involved induction type and crucible forges, with their help you can make any alloys with copper.

Melting is carried out with flux additives, and the initial raw material for smelting can be either copper ore or copper scrap. Typically, scrap copper is added to the melt along with the filler metal during the smelting process. When smelting only copper ore, the following operations are performed:

When using scrap copper, the procedure for making bronze is the same.

Varieties

Based on the ratio of the content of the main components of bronze - copper and tin, two main types are known: tin, when the main filler material is tin, and tin-free, if tin is present in very small quantities.

Tin bronze

Classic or tin bronze– a universal material not only in industry, but also in other spheres of human activity. In this alloy, there are 80 parts of copper to 20 parts of tin; it melts well, has high strength, is quite hard, does not corrode, is wear-resistant and helps reduce friction between metals.

These advantages of tin bronze lead to difficulties in some other respects: the alloy is difficult to forge and cut, sharpen sharp edges and stamp, but it is easy to make castings from it. The settlement when cooling the pour does not exceed one percent, which allows the material to be used in artistic products of particular precision.

To give the alloy additional properties, its composition may include additives of other metals and non-metals:

• zinc in an amount of up to 10% improves anti-corrosion properties; parts made from this alloy are used in shipbuilding, where the aggressive environment is salt water;
• Lead and phosphorus contribute to better sliding of bronze products over other metals; such an alloy is easier to cut and stamp.

Tin-free

– sometimes the use of tin in an alloy is not allowed, and the required characteristics are obtained by adding other metals. Modern technologies make it possible to select additives in such a way that products made from tin-free bronze completely replace products made from classical bronze.

Lead bronze– an alloy that glides well over metal, withstands high pressure, is very durable and does not melt easily. Its scope of application is bearings operating under high pressure.

Silicon- it is 97% copper, a little tin and five hundredths of a percent silicon, it is added to increase electrical conductivity and such bronze is used as cores of telephone cables. It is non-magnetic, easily soldered, elastic and resistant to low temperatures. Additionally, it may contain manganese.

Beryllium- the hardest. This alloy is very resistant to corrosion and extreme temperatures, both positive and negative. It is a non-magnetic metal and does not produce sparks during collisions. Additionally, nickel or cobalt can be added to it. Elastic products are made from the alloy - springs, membranes, plates.

Aluminum– the composition is simple, five percent aluminum, the rest is copper. The color of bronze is shiny golden, it is resistant to chemicals - acids. It is strong in hardness and heat-resistant, retaining its properties even at extremely low temperatures. It resists corrosion poorly and exhibits significant shrinkage during casting. For its beautiful color it is used in jewelry production, making coins and medals. Physical properties predetermine the use of the alloy in parts of automotive products, gunpowder and pyrotechnic production.

Marking

What metals make up bronze? The basic composition of bronze can be determined by its marking, developed on the basis of state standards. Example: BrOF 7. The first two letters are bronze; alloy composition: O – this is tin; Ph is phosphorus; 7 – additive content, in this case tin, since the content of the second additive substance is not indicated in the marking. Designations of other filler substances: A – aluminum, K – silicon. Mts is manganese, Zh is iron, and so on, according to the first letters of the additive.

It is not customary to indicate the percentage of copper content in the labeling; it is calculated by calculation as the remainder of the difference. In the example, this is 93%. Its color depends on the chemical composition of bronze. The copper content of the alloy determines its color - the higher it is, the redder the bronze will be, and vice versa. If there is only 50% copper, and everything else is light additives, then the alloy will resemble silver in color.

The main component of bronze is copper, to which other metals (usually tin) are added. At the same time, the share of other substances is no more than 2.5%, which makes it possible to improve the performance of the resulting alloy. If copper is combined with zinc, brass is obtained; when zinc is replaced with nickel, a cupronickel composition is obtained. There are other options. For example, BrA5 is a type of bronze obtained by adding aluminum. We work with the BrO5 brand, made on the basis of tin, since this material fully complies with state requirements.

A little about history

The first bronze products appeared in the 3rd century BC. The Middle East is considered the birthplace of this amazing metal - the oldest finds of a compound of copper and tin were found in Iran, as well as Syria, Turkey and Iraq. Most often, household and work items were made from bronze. The most common surviving items are household, military and jewelry items.

Then came a period when this metal became the main source of the monetary industry - coins of various denominations were made from it. Around the 5th century AD. The production of bronze sculptures began in Hellas. This is where the tradition of making bronze miniatures and figurines originates, which is still relevant today.

With the onset of the Middle Ages, bronze became part of weapons and became the main resource for casting cannons, cannonballs, and shells. Bell casters also paid attention to this metal - bronze makes beautiful products that give a deep and pleasant sound.

Bronze spear tip (7th-4th century BC).

How do the species differ?

Alloys are classified depending on the selected components. Bronze made with the addition of tin often also contains lead or phosphorus - this provides an alloying effect. Due to tin, the alloy becomes harder and more durable, withstands melting better and retains its shape well. The resulting material is easy to grind, and the presence of special components allows you to achieve higher performance and visual performance.

There is also bronze, which does not contain tin. Such options have a new structure that differs from the traditional one, but in terms of their properties they are almost equal to the classic alloy.

The technical properties of a metal can affect its performance.

Casting material is formed by the method of making decorative and stylish products (for example, our products). It is also widely used in the production of bearings, parts of complex mechanisms, as well as components for devices designed to operate in sea water.

Deformable materials are designed to be formed mechanically. In this case, the metal is cut, forged, and covered with corrugation. As a rule, this option is flexible and relatively soft - cables, tapes, rods and sheet products are produced from it.

Bronze rod.

Properties of bronze

When considering this alloy in comparison with other metal mixtures (for example, zinc composition), it is worth noting that real bronze is impervious to natural processes of destruction, lasts a long time and is resistant to aggressive influences (vibration, friction). It also remains durable and beautiful even with prolonged contact with water, air, acidic environments or salt solutions. Most types of bronze can be soldered or welded.

The color of the alloy depends on the components included in its composition. The lightest type is white. Dark classes have a reddish tint.

The following additives affect the tone and quality of bronze:

• zinc and lead reduce susceptibility to friction;
• aluminum and silicon extend service life, protect against corrosion and deformation;
• nickel and iron increase the ability of the alloy to recrystallize, making the substance smooth and homogeneous;
• silicon or manganese is added to increase resistance to rust, oxide deposits and intense heat;
• a material not intended to conduct electricity is made with the addition of chromium or beryllium.

The most popular classes of bronze alloy used in industry are:

1. Beryllium (due to hardness). Can be hardened and is elastic. With the natural or artificial aging of a metal, its increased resistance to mechanical processes is manifested. This indicator is often enhanced by preliminary deformation. Serves for the manufacture of large and small machine parts, as well as for the production of equipment.
2. Aluminum (due to high density). It is resistant to chemicals, does not change under the influence of natural factors, and is suitable for use in sea water. Easy to process and cut, popular in the production of flat and strip products.
3. Silicon-zinc (advantage - excellent fluidity). Does not create sparks during machining (turning, milling). Suitable for casting complex or decorative shapes.
4. Lead - resistant to friction and shock. Due to these indicators, it is more often used for parts that carry a large load.
5. Tin - combines all the above advantages, and therefore is in greatest demand.

How to get bronze

Bronze making is a demanding and rather difficult process in which auxiliary metals are introduced into molten copper. Smelting is carried out in forges or induction furnaces. For heating, natural fuel (coal) or flux is used.

The first stage is placing copper in the furnace and heating it until it reaches a liquid state. After this, phosphorous copper is introduced into the substance, to which alloying components are later added. The resulting alloy is mixed, and a new processing temperature is set. At the final stage, copper phosphorous is again used, which allows you to get rid of any oxidation.

Melting bronze is simple, and therefore this metal is often used for casting art objects and miniatures. Using special forms and filling them out correctly, the specialists of the Bronzamania workshop produce products of ideal appearance. Blanks intended for artistic casting are made in round or flattened format.

Bronze in a molten state.

Application of bronze

Impeccable performance qualities have made bronze one of the most common materials in mechanical engineering, aviation, shipbuilding and large industry. This metal is not susceptible to moisture, does not wear out, and is almost impossible to deform. Therefore, bronze is used in the production of rolled products intended for use in aggressive chemical environments, as well as for the production of parts and pipes of various profiles.

Reliability and long service life are additional characteristics due to which bronze has become widely known in the field of sculpture and art. Interior parts are made from it - candlesticks, chandelier bodies, decor. Therefore, the specialists of the Bronzamania workshop can guarantee the long service life of all products available for sale - our products retain their beautiful appearance and functionality for decades, without reacting to weather conditions and other adverse factors.

Every person has heard or seen bronze; the composition of the alloy of this metal remains a mystery to many. This article describes the types, what it comes from and where it is used. They learned to obtain metal at the dawn of the third millennium BC. Since then, proportions have changed more than once, technology has improved, but has never lost its importance for human civilization. The metal has unique performance and decorative characteristics, which is why it is still used in various modern fields.

Bronze is an alloy of several components that determine its main characteristics. The result is a material that has no limits in application. The very first products were used by people who lived in Mesopotamia and Southern Iran. This is confirmed by archaeological finds. What the mixture is made from and what components modern masters add, you will learn from the next section.

Compound

To obtain a high-quality bronze alloy, the composition must consist of one or more base substances, as well as alloying additives. The main component is copper, and the rest are needed to improve the performance of the material. The alloying component used is:

• manganese;
• tin;
• lead;
• chromium;
• phosphorus;
• iron.

Zinc and nickel are used in extreme cases, because this combination with copper produces completely different alloys (brass and cupronickel, respectively).

The amount of additives in the mixture may vary. But this is precisely what affects the color of the metal. For example, a fiery red hue indicates the presence of a large amount of copper. By the cold steel color you can understand that the mixture contains no more than 35%.

The number of additional elements should not exceed 2.5 percent of the total mass. In addition to copper, bronze contains other metals: tin, aluminum, lead, silicon and beryllium. Based on the element used, the combination is given a name. Whatever alloying additives are chosen, only copper, which determines most of the characteristics, remains constant.

The chemical composition of bronze determines what kind of alloy and grade it will turn out to be. All types differ in the mass fraction of main components and impurities. The exact quantities are given in a special table, where several are considered and the impurities used are indicated.

Properties and characteristics

Bells were cast from an alloy consisting of copper and tin a few years ago. Today, other types are actively used, which, in addition to tin, include other chemical elements. Each of them gives special qualities to bronze.

Alloys containing beryllium are characterized by increased strength. But silicon, as well as zinc, added in small quantities, improves the fluidity of the metal. Therefore, this composition is often used in foundries, or they cover the surface of various products with it. Why do they become resistant to abrasion?

A small amount of zinc included in the total mass does not change the mechanical properties of the composition. The element reduces the cost of the finished material, so sometimes industry specifically introduces up to 10% zinc to reduce production costs.

Alloys containing lead become resistant to corrosion. Aluminum, as an alloying additive, gives the composition anti-friction properties. What qualities the finished product will have directly depends on the presence of one or more additional elements in it, as well as on their quantity.

Bronze is a metal that has increased strength, corrosion resistance and wear resistance. Products made from it are not afraid of atmospheric conditions, the ingress of salt water, or various solutions containing organic acids. The alloy can be welded and soldered and comes in a variety of shades from red to white.

It differs not only in chemical composition, but also in processing technology. Modern industry is familiar with such methods as: deformable and foundry. If a mixture is required that will withstand cold forging, then the components are processed using the first method. The alloy from which the products are cast is processed using the second method.

Today there are many brands that differ in characteristics and scope of application. Experienced craftsmen who have been working with the mixture for a long time can determine what type it is by taking a quick glance. But people who are simply interested can obtain information by examining the markings, which consist of letters and numbers.

A description of the characteristics will help you better understand what the mixture is, but it is worth studying the pros and cons. It has many more positive aspects than negative ones. Therefore, the material has not lost popularity for such a long time due to the mass of excellent qualities. These include the fact that products made from such metal can be melted down an unlimited number of times. At the same time, the alloy remains of the same quality as after production.

It is popular among sculptors, in the field of instrumentation and machine tools, because it gives minimal shrinkage. In order for it to be amenable to mechanical processing, the composition should not contain more than 5% lead. Since it is this component that provides lightweight chip breaking. The presence of phosphorus in the composition deoxidizes the mixture, but only if no more than 1% of the alloying component is added.

Tin bronze

Tin is most often used as an additive to copper. After all, it is this component that gives copper its special qualities. The combination with tin has the following properties:

• fusibility;
• hardness;
• elasticity.

The finished material is convenient for polishing, and due to the presence of additional components, it is often used for casting. The advantage of tin bronzes is their wide range of applications. But everything depends on the quantitative content of the elements.

Because this parameter changes the performance characteristics. For example, when only 5% tin is added, the ductility is reduced. If the amount of an element is quadrupled, the material becomes brittle. Depending on this, the finished product can be used in different ways.

A mixture where the proportion of tin exceeds 6 percent is sent for casting, but it is not suitable for forging or rolling. The metal, which has a pleasant silvery-white color, contains 33% tin. If this parameter decreases/increases, the shade of the material will also change, from red to yellow. Photos of non-ferrous metal can be seen in a variety of places, from school textbooks to modern museums.

Tin free bronze

If the mixture does not contain tin, then it is called special or tin-free. In this case, elements such as:

• aluminum;
• iron;
• lead;
• silicon;

The scope of application of this combination is also extensive. But the mixture itself is very different from tin. The main difference is superior quality and the fact that copper without tin has an even richer range of colors.

If you combine copper with aluminum, you get a mixture that has superior quality characteristics. It is also highly resistant to chemicals. The combination of copper with silicon and zinc gives the metal fluidity. Due to its liquid state, it is easy to process.

The beryllium type is superior to all others in elasticity and high hardness. The material also has such qualities as high weldability and chemical resistance. It is convenient to work with this type of cutting tool. After high-quality processing, the following parts are made from it:

• membranes;
• springs;
• contacts with spring properties.

They are durable, simple and reliable to use. This is not the entire list of products that are produced by craftsmen.

Application

Thanks to experiments with the proportions of alloying components, it was discovered that the use of non-ferrous metal is possible almost everywhere. All because of the properties it possesses. For example, the aluminum type is used when metal pipes and strips are needed. The products are easy to cut, but at the same time they are not afraid of corrosion. Even when the pipes are in seawater, the conditions do not affect their quality. Lead bronze is used in the manufacture of bearings, since the alloy perfectly resists shock loads and has anti-friction properties.

When it is necessary to produce parts of complex shapes that should not produce sparks during operation, think about the zinc-silica mixture. The material can be given any shape because it is highly fluid.

There are not only classic compositions, but also completely unique in their properties, which were discovered quite recently. Such material is aluminum-nickel bronze or marine bronze. The only property that makes this combination similar to the classic one is the presence of copper as the main element. The material was obtained as a result of the development of foundry production and is used in the construction of platforms for oil production located in the seas and oceans. Fire pumps, the metal parts of which are made of nickel-aluminium, withstand specific environmental conditions.

The most famous way to use bronze is to create sculptures and other decorative objects. In homes or on the pages of fashion magazines you can often see products such as:

• figurines;
• lamps;
• railings for stairs;
• grates for fireplaces.

Thanks to the casting method, it is possible to obtain the most complex castings that convey the surface of the template in the smallest detail. Previously, the material formed the basis of almost all women's jewelry, but today its use in jewelry has noticeably decreased.

But plumbing and the production of entrance and interior doors cannot do without bronze fittings. A strong and beautiful mixture of components creates reliable, durable hinges, locks, handles, taps and mixers. It is convenient and easy to work with, so craftsmen are able to produce elegant decorative elements of any size or design.

Products for aircraft navigation instruments and car circuits are made from beryllium bronze, because it can withstand dynamic variable loads. There was a place for using this type in water supply, despite the high cost. It is used to produce structures for particularly critical areas. Because they will last much longer and will not require urgent repairs.

Although new consumables have been invented, metal does not lose its position. Because its use guarantees a high-quality result, regardless of the area. This is due to the properties and variety of products due to which bronze is in great demand.

Bronze is an alloy of copper with tin, aluminum, lead, silicon and beryllium. The composition of the alloy can include a variety of metals, the names of which give the name: tin bronze, aluminum. The percentage of impurities should not exceed 2.5%. The exceptions are nickel and zinc - copper alloys with these elements are called cupronickel and brass, respectively. However, a small amount of zinc may still be present in the composition - its amount must be lower than the sum of all other impurities, otherwise the alloy will be considered brass.

The name itself comes from the Italian “bronzo”. The alloy was first used back in the 35-33rd century BC. (exact dates have not been established) when the Bronze Age began, which replaced the Copper Age. Thanks to improved processing of copper and tin, it was possible to obtain a fairly durable and beautiful alloy, which lasted almost until the 11th century BC. It was used for the production of arrow and spear tips, daggers, knives, swords and other bladed weapons, for the production of furniture parts, mirrors, dishes, vases, jugs, jewelry, statues and coins.

In the Middle Ages, bronze was used to make church bells and cannons; the latter were made from special gun bronze until the 19th century.

Physical properties

The physical properties of an alloy depend on its composition and can vary significantly. Unlike brass, bronze has higher anti-corrosion resistance and anti-friction properties. It is more durable and has strong resistance to air, water, salt, and organic acids. Also bronze easy to solder and weld.

Receipt

Bronze is made by fusing copper with various metals to enhance certain characteristics. For this they use induction furnaces and crucible forges, suitable for melting any copper alloys. Melting is usually carried out under a layer of charcoal or flux. For smelting, either fresh ore that has not yet been processed or secondary waste can be used. The latter are usually added to fresh copper during the smelting process.

When using only fresh ore, the following order is observed: coal or flux is placed in a preheated furnace, copper is loaded and heated until it melts - 1150Co - 1170Co. Then the metal is oxidized by adding copper phosphorous, sometimes it is introduced in several stages - 50% immediately, 50% in a ladle. After deoxidation, additional additives are added, heated to 100С - 120С.

If additional metals are refractory, then they are first completely dissolved in liquid copper and then heated to a certain temperature. Having pulled the alloy out of the furnace, it is deoxidized by introducing 50% phosphorous copper to get rid of oxides.

If secondary metals or waste are used, then pure copper is first melted, deoxidized with phosphorous copper and secondary metals are added. After melting the latter, additives are introduced into the liquid copper and wait until they melt. After heating to a certain temperature, the alloy is deoxidized with phosphorous copper and covered with dried flux or calcined charcoal. The mixture is heated and left for 20-30 minutes, stirring occasionally. When the time is up, the protruding slag is removed from the surface and poured into molds.

Tin

Tin bronze is most widely used in modern industry. This copper-tin alloy(in the classic ratio of 80% to 20%), which has good strength and hardness, melts easier and has high anti-corrosion resistance and anti-friction properties.

Tin bronze is difficult to forge, roll, cut, sharpen, and stamp and is generally only suitable for solid casting. A small draft (no more than 1%) allows the material to be used when creating particularly precise products in artistic casting.

Optional for rafting may add other metals.

1. Zinc (no more than 10%) increases the corrosion resistance of the alloy and is used to create elements of ships and vessels that will often come into contact with sea water.
2. Thanks to the addition of lead and phosphorus, the antifriction properties of bronze can be significantly improved, and the alloy is also easier to process by pressure and cutting.

Tinless

In some cases, the use of tin is unacceptable. In this case, other metals come to the rescue, the addition of which allows you to obtain the necessary characteristics. And although tin bronze is the standard and most in demand, tin-free bronzes are not inferior to it.

Leaded or leaded

Lead bronze is an excellent anti-friction alloy, it resists pressure well, has increased strength and refractoriness. It is used for the manufacture of bearings that are subject to the greatest pressure during operation.

Kremnetzinc

Silica-zinc bronze consists of copper (97.12%), silicon (0.05%) and tin (1.14%). It is quite fluid and plastic, which allows it to be used as a material for products of complex shapes. It has increased resistance to compression, is not magnetic and does not produce sparks during processing. It is distinguished by elasticity and anti-friction properties, does not lose plasticity at low temperatures, and is well soldered. Often contains nickel or manganese.

Bronze is used in the manufacture of springs, bearings, grilles, guide bushings, evaporators and networks.

Beryllium

Beryllium bronze is the hardest of all types. It has increased anti-corrosion properties and heat resistance, is stable at low temperatures, does not produce sparks on impacts and is not magnetic. The metal is hardened at 750Co - 790Co, aged at 300Co - 325Co. Nickel, iron or cobalt are sometimes added to beryllium bronze to facilitate the hardening technology. In addition, beryllium can be replaced with nickel.

The material is used to create springs and spring parts, membranes, and for watch parts.

Aluminum

Aluminum bronze consists of copper (95%) and aluminum (5%). It has a pleasant golden color and shine, and can withstand prolonged exposure to aggressive environments, such as acids. The alloy has a higher casting density, heat resistance and increased strength, and tolerates low temperatures well. Among the disadvantages, it is worth noting weaker corrosion resistance, stronger shrinkage, as well as strong gas absorption in the liquid state.

Bronze is used to make car parts and in gunpowder production; gears, bushings, coins and medals are smelted.

Other metals

In addition to those mentioned above, bronze may also contain other elements. Nickel and iron increase the recrystallization temperature and promote grain refinement. Chromium and zirconium reduce electrical conductivity and increase the heat resistance of bronze.

Marking

To choose the right metal option, just look carefully at its markings. This will help to accurately determine the features and characteristics of the selected species.

The first letters are “Br” - this means “Bronze”. Then one or more letters are located in a row, behind which additives are hidden: O - Tin, A - Aluminum, K - Silicon, N - Nickel, Mts - Manganese, F - Iron, S - Lead, F - Phosphorus, C - Zinc, B - Beryllium. Next, numbers are written through a hyphen - this is the percentage of each additive in turn.

For example, the designation Br A J N -10 -4 -5 can be deciphered as follows: Bronze containing Aluminum (10%), Iron (4%) and Nickel (4%).

Application

Bronze is actively used in industry and in a variety of fields. First of all, bronze is used in rolled products of the same name: it is produced in the form of pipes, wire, sheets and rods. The metal can also be found in the automotive, chemical, food, construction and fuel industries. It is used to produce gears, bearings, bushings, springs and other parts that are exposed to aggressive environments and often operate under high pressure. Unlike brass, bronze is excellent tolerates mechanical loads and more plastic.

Metal is used to produce art objects, sculptures, forged items, jewelry, dishes and artistic objects.

BRONZE and BRONZE ROLLED

Classification of bronze alloys

Bronzes are copper-based alloys in which the main alloying elements are tin, aluminum, iron and other elements (except zinc, alloys with which are classified as brasses). The marking of bronzes consists of a combination of “Br”, letters indicating the main alloying elements and numbers indicating their content.

According to the chemical composition, bronzes are classified according to the name of the main alloying element. In this case, bronzes are conventionally divided into two classes: tin (with the obligatory presence of tin) and tin-free.

Based on their application, bronze is divided into deformable bronze, the technological properties of which allow the production of rolled products and forgings, and foundry bronze, used for casting. At the same time, many bronzes from which rolling products are made are also used for casting.

The chemical composition and grades of bronze alloys are defined in the following GOSTs:

Foundries: tin in GOST 613-79, tin-free in GOST 493-79.

Deformable: tin in accordance with GOST 5017-2006, tin-free in GOST 18175-78

The variety of bronzes is reflected in the table below. It presents almost all wrought bronzes and some cast bronzes. Bronzes used exclusively as foundries are marked with an “asterisk”. In what follows, we will consider mainly deformable bronzes. The structure of bronze alloys is briefly discussed in - Structure and properties of alloys.

TIN BRONZES
BrO5 *	BrOF4-0.25	BrOTs4-3	BrOS8-12 *	BrOTsS4-4-2.5
BrO10 *	BrOF6.5-0.15	BrOTs8-4 *	BrOS5-25 *	BrOTsS4-4-17 *
BrO19 *	BrOF7-0.2	BrOTs10-2 *	BrOS10-10 *	BrOTsS5-5-5 *
	BrOF10-1 *		BrOS6-15 *	BrOTsS6-6-3 *
ALUMINUM BRONZES
BrA5	BrAMts9-2	BrAZH9-4	BrAZhMts10-3-1.5	BrAZHN10-4-4
BrA7	BrAMts10-2 *		BrAZHNMts10-4-4-1	BrAZHN11-6-6 *
SILICON	BERYLLIUM	CADMIUM	MAGNESIUM	CHROME
BrKMts3-1	BrB2	BrKd1	BrMg0.3 (0.5 and 0.8)	BrХ0.8
BrKN1-3	BrB2.5	BrKdH0.5-0.15		BrH1
BrKN0.5-2	BrBNT-1.9			BrKh1Tsr
SILVER	ZIRCONIUM	LEAD	MANGANESE
BrSr0.1	BrTsr0.2	BrS30 *	BrMts5

Physical properties of bronze alloys

Elastic modulus E of different brands varies widely: from 10,000 (BrOF, BrOTs) to 14,000 (BrKN1-3, BrTsr). Shear modulus G varies between 3900-4500. These values ​​strongly depend on the condition of the bronze (casting, rolling, before and after refining). For cold-worked strips, anisotropy is observed with respect to the rolling direction.

Machinability almost all bronzes are20% (relative to LS63-3). The exception is tin-lead bronzes BrOTsS with very good machinability ( 90% for BrOTsS5-5-5).

Impact strength varies widely, generally it is less than for copper (for comparability of results, all values ​​are given for chill casting):

BroOF 10-1	BrOF 6.5-0.4	BrAZH 9-4	BrA5	Copper	BrMts5
Brotss 6-6-3	BrOTsS 4-4-2.5	BrAZhMts	BrA7
BrOS 5-25	BrOTs4-3	BrAMts 9-2	BrKMts3-1
Impact value>> increase >>
1 – 3	4 – 6	6 – 8	15 – 16	16 – 18	20

Electrical conductivity Most bronze alloys are significantly lower than those of pure copper and many brasses (resistivity values ​​are given in µOhm*m):

	BrKd
Copper	BrMg	L63	BrOTs4-3	BrAMts	BrKMts	BrOF7-0.2
BrSr	BrTsr	LS59-1	BrOTsS5-5-5	BrA7		BrAZhMts
	BrH			BrAZH9-4		BrAZHN
Electrical resistivity values >> deterioration of electrical conductivity>>
0.02	0.02 - 0.04	0.065	0.09-0.1	0.1-0.13	0.15	0.19

The resistance of silver bronze (copper alloyed with silver up to 0.25%) is the same as that of pure copper, but such an alloy has a high recrystallization temperature and low creep at high temperatures.

The low-alloy bronze alloys BrKd, BrMg, BrTsr, BrKh have low resistivity. The magnitude of electrical conductivity is significant for bronzes used for the manufacture of collector strips, electrodes of welding machines, and for spring-loaded electrical contacts. The given values ​​are approximate, because The resistance value is influenced by the condition of the material. It can change especially strongly under the influence of gentrification (downward, this applies to BrKh, BrTsr, BrKN, BrB2, etc.). For example, the electrical resistance of BrB2 before and after refining is 0.1 and 0.07 μOhm*m.

Thermal conductivity Most bronzes are significantly lower than the thermal conductivity of copper and lower than the thermal conductivity of brasses (values ​​are given in cal/ cm*s * WITH):

Copper	BrKd	BrKN1-3	L63	BrAZHN	BrAMts	BrOF10-1	BrKMts
BrSr	BrMg	BrA5	LS59-1	BrB2	BrAZH		BrMts5
	BrH			BrOTs4-3	BrAZhMts
Thermal conductivity values ​​>> deterioration >>
0.9	0.8-0.6	0.25	0.25	0.25-0.18	0.17-0.14	0.13-0.12	0.1-0.09

Low-alloy bronzes have high thermal conductivity. Refinement improves thermal conductivity. High thermal conductivity is especially important for ensuring heat removal in friction units and electrodes of welding machines. Low thermal conductivity facilitates the welding process of bronze parts.

Mechanical properties of rolled bronze

If, out of the entire variety of brass, only two grades are mass-produced (LS59-1 and L63), then for the mass production of semi-finished bronze products a significantly larger number of grades are used. Bronze products include circles, pipes, wire, tapes, strips and plates.

Bronze circles

Bronze wheels are produced by pressed, cold-formed and continuous casting methods. The production method and the range of diameters produced are determined by the technological properties of a particular bronze. The table shows the correspondence between bronze grades, rod diameter and production method.

The following histogram gives a general idea of ​​the basic mechanical properties of bronze circles.

Continuously cast circles .

BrOTsS5-5-5, BrAZh9-4, less commonly BrOF10-1 and BrAZhMts10-3-1.5 are mass produced using the continuous casting method. Products obtained by this method do not have defects characteristic of casting in a chill mold or sand mold. Therefore, in terms of their properties, continuously cast semi-finished products are significantly superior to chill castings and are close to pressed semi-finished products.

The circles IZBrOTsS5-5-5 and BrOF10-1 have a relatively smooth surface, disturbed by shallow dents from the pulling device. Wheels of these brands are produced only continuously cast way.

Wheels made of BrAZh and BrAZhMts, produced by continuous casting, may have encircling cracks up to 1 mm deep on the surface. In terms of hardness, strength and ductility, continuously cast wheels are slightly inferior to extruded ones, their antifriction properties are almost the same, and their cost is significantly lower. If necessary, high-quality circles with large diameters (over 100 mm) and short lengths can be cast by centrifugal casting.

Pressed Andcold-formed circles . Heat-strengthening (ennobled) bronzes

In some bronzes, as the temperature decreases, the solubility of the alloying component drops sharply and its separation from the solid solution leads to the effect of dispersion hardening. This process is accompanied by a sharp change in physical and mechanical properties.

Bronzes capable of dispersion hardening allow products made from them to be strengthened through special heat treatment (aging, refining). As a result, hardness, yield strength and strength increase, corrosion resistance improves, and thermal and electrical conductivity increases.

Bronzes with the effect of dispersion hardening include beryllium, chromium, zirconium, silicon-nickel and some complex alloys (see table of bronze grades). Semi-finished products from such bronzes (rods, strips, plates, wire) have the following delivery states:

- No heat treatment.

These are hot-rolled slabs or pressed rods that have cooled at the rate of natural cooling.

- With heat treatment (hardening).

In this case, the semi-finished product is heated to a certain “high” temperature, after which it is quenched in water to obtain a supersaturated solid solution. These are hardened semi-finished products, the condition of which is usually marked with the letter “M”. This heat treatment increases plasticity and allows further operations of bending, drawing, rolling and other types of cold deformation. The hardness, yield and strength limits, and ductility of hardened bronzes are somewhat higher than those of pressed bronzes.

-With heat treatment (quenching) and subsequent cold deformation.

Cold deformation increases the yield and strength limits and increases the hardness of hardened semi-finished products. A cold-worked semi-finished product after hardening is usually marked with the letter “T”.

The second stage of heat treatment - tempering, is usually carried out already on the product. Tempering is carried out at “low temperature” for a certain time. During the release process, there is a releaseexcess phase with an ordered distribution of the alloying element. These precipitates are associated with significant stresses in the crystal lattice, which cause an increase in strength and hardness.

Thus, the refining of this class of bronzes consists of two operations. First, rapid hardening is carried out, then long tempering. Between quenching and tempering, cold work hardening or part manufacturing can take place. Refining regimes strongly depend on the chemical composition of bronze. For BrB2, the hardening temperature is 750-790 C, the tempering temperature is 300 - 350 Sv for 2 - 4 hours. For BrKh0.5, the hardening temperature is 950 C, the tempering temperature is 400 C for 4 hours.

The effect of heat treatment for a BrB2 rod is shown in the histogram, and for strips - in the table. The table also shows the effect of refining for chromium bronze BrKh0.5.

	BrB2		BrХ0.5
	After hardening(M)	After hardeningand vacations	After hardening(M)	After hardeningand vacations
Elastic modulus E, MPa	9500	10500	11200
Yield strength, MPa	200 - 350	950 - 1350	500	270
Ultimate strength, MPa	400 - 600	1100-1500	240	410
Relative extension
Hardness HV	< 130	330		130
Electrical resistance		0.04 - 0.07	0.04	0.02

Dispersion hardening of products made from heat-strengthened bronzes (BrB2, BrKh, BrKhTsr, BrKN) and alloys (MNMts20-30) significantly increases strength and hardness in comparison with the original supply material. Products made of beryllium bronze have the greatest effect from refining.

APPLICATION OF BRONZE ALLOYS FOR THE MANUFACTURE OF SPRINGS

(Elastic properties of bronze alloys)

For the manufacture of springs, materials with a high elastic limit and a minimum level of inelastic phenomena (elastic hysteresis, low level of relaxation, etc.) are used.

For the manufacture of springs and spring parts, tapes, rods and wires from BrKMts3-1, BrOF6.5-0.15, BrOF7-0.2, BrOTs4-3, and beryllium bronzes are used. The high ductility of these bronzes, even in the solid state, makes it possible to use not only wire, but also rods with a diameter of up to 10-15 mm for winding springs.

Depending on the type of spring, its material is subject to normal (compression-tension) or tangential stresses. The spring stiffness is determined by the elastic modulus E or shear modulus G respectively. The greater the corresponding elastic (yield) limit, the greater the area of ​​permissible loads, but in calculations, permissible loads and deformations are calculated based on the tensile strengthtaking into account the calculated coefficients.

The table shows the properties of tapes made of BrOF, BrOC, BrKMts (in the solid state) and BrB2 (after dispersion hardening from the “T” state).

GOST	4748-92	1761-79		1789-70
Bronze grade	BrKMts 3-1	BrOF 6,5-0,15	BrOC 4-3	BrB2
Elastic modulus E, MPa	12000	9500	9500	12000
Elastic limit? 0.005, MPa	260 - 530	320- 480	300-450
Yield strength? 0.2, MPa	510 - 750	550 - 720	520-680	1150-1600
Tensile strength? IN, MPa	600 - 770	580 - 760	550-700	1150-1600
Relative elongation?	2	3	2	-
Hardness H.V.	(GOST 1048-79 ) practically coincide with those for BrKMts bronze, but BrA7 is distinguished by a very high creep strength. After producing springs from refined materials ( beryllium bronzes and alloy MNMts20-20) their dispersion hardening is carried out. The technological process for manufacturing helical cylindrical springs from materials of this group includes the following basic operations: hardening, winding of blanks, cutting long blanks into individual springs, processing of the ends of the springs, dispersion hardening. The process of manufacturing flat springs includes: cutting the material into strips of the required width, hardening, stamping of springs, dispersion hardening. As a result of this heat treatment, the hardness, elasticity, wear resistance increases and the fatigue strength of the spring material increases significantly. APPLICATION OF BRONZE ALLOYS FOR ELECTRODES AND CURRENT CONDUCTORS (Electrode and conductive alloys) Among the numerous grades of bronze, a group of alloys with a low (0.3 – 1%) content of alloying elements stands out. They are distinguished by the fact that they have almost the same electrical and thermal conductivity as pure copper, but at the same time they have greater hardness, yield strength, wear resistance, fatigue limit, and remain operational up to higher temperatures due to increased (compared to pure copper) temperature of the onset of recrystallization. Such alloys include: Cadmium bronze (Cd: 0.9-1.2%) - rods, tapes and collector strips. Chromium-cadmium bronze (Cd: 0.2-0.5%, Cr: 0.35-0.65%) - rods Magnesium bronzes(Mg: 0.3-0.8%) - collector strips and wire. Silver bronze (Ag up to 0.25%) – rods, wire, strips. Chrome bronze (Cr: 0.5 – 1.0) – rods, plates, strips for collector plates, wire. Zirconium(Zr: 0.2 – 0.7%) – collector strips, pipes, strips Chromium-zirconium bronze – rods, plates These bronzes have two main uses. 1. Use in the production of power movable contacts (slip rings, commutator plates). What is primarily important here is high wear resistance, as well as performance at elevated temperatures. 2.For the manufacture of electrodes for welding machines. Electrode alloys must have a high softening point, high hardness and yield strength in the operating temperature range (500 - 700 C). Figure (B) shows the change in hardness of copper, cadmium and chromium bronzes with increasing temperature. One can see the undoubted advantage of BrC at high temperatures. BrKhTsr, BrBNT and other alloys have even better results, but their use is limited by high price and availability. In the adjacent figure (A) you can see the fundamental difference between refined chromium bronze on the one hand and ordinary bronze (BrKd) or copper on the other. Annealing cold-worked copper or BrKd rods reduces hardness. At temperatures above the recrystallization temperature, the texture is destroyed and the metal softens. At the same time, in BrH at 400 o C, dispersion hardening occurs and its hardness after annealing, on the contrary, increases. If dispersion hardening did not occur, then the hardness would decrease along the dotted curve (softening would occur). This means that after the manufacture of electrodes from alloys such as BrKh, BrKhTsr, they must be appropriately heat treated to improve their physical and mechanical properties.