Bronze alloy composition | Proflazermet
Bronze is an alloy of copper and special additives that are necessary to give the metal certain technological properties. Bronze may contain the following components: Sn (tin), Mn (manganese), Be (beryllium), Pb (lead), Si (silicon), Cr (chromium), P (phosphorus), Fe (iron) and other elements.
Bronze alloy is resistant to abrasion, corrosion, and aggressive environments such as sea water. These properties are achieved by adding alloying components in certain proportions. The ratio of components is regulated by regulatory documents: GOST, industry standards, methods, enterprise standards.
Alloy classification
In accordance with the presence of alloying components in the composition, it is customary to distinguish the following types of bronzes:
- tin - the main alloying component in them is tin;
- not containing tin at all, that is, tin-free.
In addition to the composition of bronze, there is another criterion for their classification - technological parameters. Bronzes stand out:
- deformable, intended for pressure treatment;
- foundries for making castings.
Main alloying components
The main component that determines most of the technical characteristics of bronzes is copper. To give the alloy the necessary parameters, special additives are used - alloying components. One of the common alloying components contained in bronze is tin. It was from tin bronze that bells were cast and called “bell” bronze.
Also the following can be used as an alloying element:
- Be – beryllium. Increases the strength of bronze.
- Si – silicon and Zn, zinc to increase the surface abrasion resistance. These same elements increase the fluidity of bronzes, which has a positive effect on the quality of casting.
- Pb – lead. Increases the anti-corrosion properties of metal.
- Al – aluminum. Increases corrosion resistance, oxidation resistance at high temperatures and reduces metal reaction with sulfur compounds and engine exhaust products.
Brands of bronzes
Bronzes are marked with the abbreviation “Br”, as well as the addition of a letter or several letters that indicate alloying additives. The volume of alloying additives is determined by GOST standards.
Different brands of bronze have their own individual characteristics: chemical composition, technical characteristics, scope of application. By marking bronzes, you can find out what components they contain, and use special tables to determine the purpose of this alloy and its technological parameters.
Marking of alloys using the example of tin bronzes
Some grades of tin bronzes are shown in the table below. Here you can also find important technological parameters of the alloy, as well as the scope of application of each specific grade of bronze.
This table also indicates the method of bronze casting. “K” in the corresponding column means that casting was carried out in a chill mold, “P” – casting was carried out in a sand mold.
The “grade” column shows the names of the alloys. “Br” in the name of the brand means bronze, then the alloying components present in the alloy are indicated.
Based on the markings, it is clear that the metal grades listed in the table contain tin. Some contain zinc, lead and phosphorus in addition to tin.
Percentage of bronze components
The percentage of elements, as well as the chemical composition, is included in the abbreviation of the alloy grade. It does not indicate the percentage of the main element - copper, but indicates the content of all alloying elements in percentage terms.
For example, in the BrO3Ts12S5 brand the content of components is as follows:
tin – 3%;
zinc – 12%;
lead – 5%;
the remaining 80% comes from copper.
The percentage of copper in the alloy affects its color. The more copper, the brighter the golden color the bronze has. With a copper content of 50%, the color of the alloy will become white, close to the color of silver. In accordance with the tasks set, it is possible to obtain different colors of the metal by varying the percentage of alloying elements and copper.
Some varieties of bronze alloys
The most commonly required materials are tin, beryllium, silicon and aluminum bronzes.
Tin bronze
Tin bronze contains tin as the main alloying component. May also contain phosphorus, zinc, lead, nickel, etc.
The table shows the maximum content of elements in some brands:
As can be seen from the table, the alloys contain at least 80% copper. As the volume of tin in the alloy increases, its properties also change:
- the hardness and strength of the metal increases;
- plasticity decreases;
- Impact strength decreases;
- fatigue strength increases.
One of the alloying components is P (phosphorus). A given element is called alloying if its content is more than 0.1%.
When phosphorus enters a copper alloy, it deoxidizes the copper. In addition, it is phosphorus as an alloying additive that increases the wear resistance of the metal. This composition also has a downside. Phosphorus, when its content is exceeded, reduces the ductility of the resulting metal. Therefore, when adding phosphorus as an alloying component to deformable tin bronze, it is extremely important to strictly adhere to GOST and other regulatory documents.
Another alloying component is Zn (zinc). It is added to bronze, which does not contain phosphorus. Zinc is introduced in an amount that can dissolve. Lead may often be administered along with zinc.
Lead is slightly soluble; the resulting alloys BrOTsS4-4-2.5 and BrOTsS4-4-4 are solid solution crystals and undissolved inclusions of lead. The addition of lead increases the anti-friction properties of the metal and the ability to cut it.
However, lead as an alloying element reduces some other mechanical properties of the resulting metal.
Ni (nickel) can also be added. The element increases strength, ductility and deformability.
Beryllium bronze
This type includes tin-free dispersion-hardening alloys of copper and beryllium. This means that the solubility of the alloying element directly depends on temperature. Quenching is carried out from a single-phase region, that is, directly from the melt. It is very important to select the correct process temperature to use.
It is this value that determines how well the melt will transform into a solid solution and how homogeneous it will be, which is important for giving the metal specific properties. The optimal hardening temperature is 760-800 °C. When the temperature increases above the specified range, there is a possibility of an increase in the metal grain size and, as a result, a decrease in technological parameters.
Temperatures below the specified range do not allow the solid solution to be saturated with beryllium to the required extent.
The cooling rate of the solution should be at least 30-60 degrees per second. This is necessary so that the components in the solid solution do not begin to decompose. Sometimes Ni (nickel) and Co (cobalt) can be introduced as an additional alloying additive to reduce the cooling rate limit. These additives increase the stability of the solid solution in case of supercooling. Magnesium can be used for the same purposes.
The following alloys are most often used in industry and production:
- BrB2 – with a beryllium content of 2%;
- MNB – copper-nickel-beryllium alloy, beryllium content does not exceed 0.8%
- IBC is a copper-cobalt-beryllium ratio with the same beryllium content as in MNB.
Both BrB2, MNB and MKB have high ductility and strength, and are easily subject to bending and stretching, as well as other types of plastic deformation.
components in some beryllium bronzes are shown in the table:
Silicon Bronze
This tin-free alloy contains Cu (copper) in the amount of 80%, Zn (zinc) 20% and Si (silicon) about 3% and 1% manganese (BrKMts-3-1), and is resistant to compressive and tensile deformation. High mechanical and antifriction properties, ductility at low temperatures allow this alloy to be used for antifriction parts, springs, bearings, etc.
Silicon-containing alloys have another useful property - fluidity. They are widely used in the casting of complex parts. Also, due to its composition, bronze does not produce a spark upon impact.
Aluminum bronze
Aluminum bronze contains aluminum as an alloying component. aluminum can reach 12%. Depending on the aluminum content, the properties of the resulting metal also change.
For example, single-phase bronze, in which up to 9.4% aluminum is easily deformed by pressure at any temperature. This is due to its high plasticity. An example of such a brand is BrA7.
The addition of aluminum as an alloying component significantly increases the strength of the metal and its resistance to corrosion in difficult conditions: salt water, high humidity, etc. This type of metal is used for oil platforms located at sea.
Al also has a significant effect on the thermal conductivity of the metal. As the aluminum content increases, the thermal conductivity of the resulting metal decreases when compared with copper in its pure form. Adding even 10% Al reduces the thermal conductivity of copper from 390-401 W/(m*K) to 75 W/(m*K). Adding additional alloying components further reduces thermal conductivity.
Thus, the following conclusions can be drawn: the technological parameters of bronzes depend on which alloying components and in what ratio were introduced during the manufacture of the metal. The main component is copper, the percentage of alloying additives is regulated by GOSTs and other regulatory documents.
Source: https://proflasermet.ru/article/bronza-sostav-splava/
Bronze: main additives and scope of application
Bronze is an alloy of copper and other alloying metals and non-metals that give the new material certain properties. Currently, almost no industry can do without bronze. However, many people do not know the main components that make up this alloy.
What are the main additives that alloy bronze?
The core component of bronze is copper, which determines the main part of its characteristics.
People began to use this material for various purposes long ago, as evidenced by products found by archaeologists as a result of excavations. Initially, material enriched with tin was used in production. Bells have been cast from a similar compound for centuries, which is why the mixture of copper and tin was called bell bronze.
What is included in bronze?
Today, an alloy that does not contain tin is often used. Bronze contains various metallic and non-metallic elements, which got there for a reason, but serve to improve its quality characteristics. Take the element tin as an example; it is contained to improve the ductility of bronze due to its properties.
With a high percentage of tin, the alloy will become harder. But do not forget that the most important element that affects the strength and hardness of tin is the chemical element beryllium. Alloys containing beryllium can surpass many steels in their strength.
When hardened, beryllium bronze has good elasticity, due to which spring elements and springs are made.
Bronze alloys, which contain aluminum, have high strength and corrosion resistance. Due to the characteristics of bronze with the addition of aluminum, products made from them perfectly withstand the negative effects of sea water and other adverse conditions.
Alloys containing lead are well suited for the manufacture of products that will be used in the future under increased mechanical loads, such as impacts.
In mechanisms with rotating parts, this alloy is used for the manufacture of sliding bearings.
The zinc and silicon included in the composition give the metal fluidity in its molten form. Through casting, such bronze is used to produce parts and products that are complex in their design and structure. It is also worth noting that one of the properties of this alloy is that subsequently there are no sparks when striking the product. Which is an important property when performing many works in conditions of high concentrations of flammable gases.
Due to the development of the industrial sphere associated with oil, new types of bronzes were invented; this type is represented by copper alloys containing such elements as aluminum and nickel.
These alloys are highly resistant to corrosion, and when exposed to salt water, they are able to retain their original appearance and resist the effects of salts.
Thanks to the improvement of the metallurgical industry, it was possible to make such alloys and use them to produce elements intended for oil platforms, which are installed, most often, on ocean shelves.
Classification by processing technologies:
However, in addition to dividing according to their constituent elements, bronze alloys are systematized according to processing technologies:
- deformable (used in various structures subject to plastic deformation);
- foundry (in the manufacture of objects the foundry method is used).
Marking and scope of use of bronze
The current industrial industry produces many grades of bronze alloys. They differ not only in composition and other parameters, but also in their scope of use.
They are most often used in rocketry, mechanical engineering, shipbuilding and aircraft manufacturing. These productions use all the positive properties of the metal. Due to its low abrasion, it is used mainly for making parts of moving parts of structures.
Experienced specialists are able to distinguish the type of metal by color alone. Of course, not everyone is capable of this.
At the same time, an elementary, and most accurate, method of obtaining important information about the composition of the metal and its typical nature is marking decoding, which includes symbols in the form of alphabetic and digital designations.
Modern manufacturers produce bronze alloys exclusively in accordance with GOST, which regulates the quality and ratio of metals in the alloy. Special documentation contains technical tables that contain all the information about the exact composition of each brand of bronze. From these documents you can also learn about other characteristics of bronze alloys and their applications.
To correctly read the relevant regulatory documents, you need to know the formal notations. For example, the first letters in the marking will help you understand what kind of alloy we are talking about. Thus, bronze, for example, would be designated as "Br".
After the first letters you can see what other metals are present in the bronze alloy, that is, the next letter indicates which element is included in the alloy as an alloying additive.
This is followed by numbers indicating the percentage of the additional element.
It is worth knowing that in the marking of bronze alloys for absolutely every brand, you will not find an indication of the amount of copper that is present in the alloy. The percentage of copper is calculated differently. After all, the amount of each metal is indicated in fractions of a percent. Therefore, in order to find out how much copper is present in a bronze alloy, it is necessary to calculate the difference between one hundred percent of the composition and the number of specified elements.
As mentioned above, bronze alloys are used in almost all areas of industry. But the decorative properties of bronze are also widely used. For example, candlesticks were previously made from it, and in many cities there are bronze monuments admiring their grandeur and monumentality.
It is unlikely that in the near future a metal will appear that will surpass bronze alloys in its quality and relative cheapness, so the production of bronze alloys will be relevant in the future.
Source: https://SoproMats.ru/materialyi/metallyi/bronza/
Bronze composition
Bronze is an alloy of copper with other elements, in particular tin, aluminum, silicon, beryllium, lead and others, except zinc and nickel. An alloy of copper with zinc is called brass, and an alloy with nickel is called cupronickel. Despite the fact that the composition of bronze contains the main component (for example, in an alloy of copper and tin, tin is the main component), any bronze also contains additives of other elements - zinc, lead, phosphorus, etc.
Man learned to make bronze back in the 5th millennium BC, which is confirmed by numerous archaeological finds, which include, first of all, ancient bronze products in the form of jewelry and various everyday items. The very first bronze was an alloy of copper and arsenic - arsenic bronze. This type of bronze was in no way inferior to tin bronze, and in some cases even surpassed it.
Over time, towards the end of the Bronze Age, arsenic bronze gradually began to be replaced by tin bronze, as well as other more expensive varieties. This happened for several reasons. Firstly, arsenic bronze had a fairly high toxicity, which inevitably led to disability for people working with it.
Secondly, arsenic bronze turned out to be unsuitable for metallurgy - products made from it broke, this alloy was not subject to remelting due to the fact that during this process a certain percentage of arsenic simply evaporated or was released in the form of slag, which led to increased fragility of the alloy and, as a result, products made from it. At best, melted arsenic bronze could be used for costume jewelry or non-essential parts.
The third reason why this type of bronze disappeared from use was the development of surface deposits that were rich in copper and arsenic. Arsenic was found much less frequently than tin and some other metals that were used to make the alloy, and therefore bronze with arsenic was significantly higher in price.
Thus, when the first horse-drawn transport appeared, which served to develop international economic relations, it became much more cost-effective to import non-arsenic grades of bronze than to spend money on making your own arsenic.
Properties of bronze
The properties and characteristics of bronze are influenced by the composition of the alloy, which determines its varieties.
Based on their composition, the following types of bronze are distinguished:
- tin. These alloys can be either two-component or multi-component, but despite this, tin still remains the second largest element by mass;
- tin-free. These are all other types of bronze that do not contain tin - aluminum, beryllium, silicon, lead, etc. Depending on which component is present in the alloy, bronze acquires certain specific properties. For example, due to the presence of beryllium in the alloy, the material becomes extremely elastic and wear-resistant. But the presence of silicon imparts anti-friction properties.
According to the area of application of bronze there are:
- deformable, i.e. those that can be easily machined - forging, rolling, cutting, etc.;
- injection molding In this case, exclusively casting is used to manufacture the product. This is due to the fact that processing and deformation of alloys of this type is possible only when they are exposed to very high temperatures.
The structure of bronze allows the material to be classified as follows:
- to single-phase, i.e. components in a solid solution, one phase is formed. In this material, the maximum percentage of tin is from 6% to 8%. This structure gives the material elasticity, which allows it to be processed by forging. It is worth noting that bronze, which contains about 2% tin, can be processed by forging in the cold without heating, but with a tin percentage of up to 8%, heating during forging is impossible;
- to two-phase. This type is associated with the appearance of two phases in the solution, which has a radical effect on the properties of the material. If the percentage of tin in the alloy is significantly higher than 15%, which is the maximum indicator of solubility, then two phases are formed in the solid solution. At the same time, in contrast to the single-phase structure, the material becomes completely non-malleable, but on the contrary, it acquires hardness and brittleness. It is bronze, which has a two-phase structure, that is used for casting.
Today, the most common type of bronze is tin.
Main technical characteristics of bronze:
- density of bronze. It has a variable value because it depends on the mass fraction of tin in the alloy. Thus, if the percentage of tin in the material is in the range of 8% - 4%, then the density can vary from 8.6 kg/cm3 to 9.1 kg/cm3;
- the melting temperature ranges from 8800C to 10600C and can vary depending on the composition of the alloy;
- the average heat capacity of bronze is 0.385 kJ;
- most bronzes have a fairly low thermal conductivity, often lower than that of copper - the electrical resistivity value is 0.087 - 0.176 μOhm*m;
- The bronze material is quite resistant to corrosion damage both in the open air and in a humid environment, so the corrosion rate is quite low - 0.002 mm/year in air and 0.04 mm/year in a humid environment.
The main materials for the production of bronze are metals or alloys. The latter are used much more often due to their relatively low cost, as well as the possibility of producing absolutely any cast bronze.
Application of bronze
Today, this alloy has found its very wide application. This is due, first of all, to the presence of unique, diverse properties.
- bronze is the main material for the manufacture of various sculptures, as well as a huge number of decorative items, which include figurines, ashtrays, lamps, grilles, railing decorations and much more. From cast bronze, castings are produced that are distinguished by their complexity. Thanks to this, it is possible to obtain, for example, a sculpture on which literally the pores of the skin will be depicted;
- jewelry craftsmanship. Despite the fact that in this case today bronze is used somewhat less than in other areas of human activity, there were still times when the alloy was the main material for the production of women's jewelry;
- various accessories. Bronze is used to make overhead hinges, locks, handles, taps, mixers, and plumbing fixtures. This is due to such a feature of bronze as durability and increased resistance to corrosion. In addition, bronze allows you to turn all of these objects into real works of art and make them into an elegant decorative element;
- casting bronze is used for the production of gears, bushings, seals, various equipment, the operation of which takes place in an environment of high humidity and under water;
All of the above applications involve the use of tin bronze. All other types of this alloy are appropriate to use in those areas of human activity where for some reason it is impossible to use tin bronze. An excellent example of this is beryllium bronze, which is used in electrical engineering because it has significantly higher thermal and electrical conductivity than tin bronze.
Thus, it should be said that despite the fact that bronze is the oldest alloy known in human history, due to its diversity and unique properties it has found its wide application in the modern world.
Source: http://mining-prom.ru/cvetmet/med/sostav-bronzy/
What metals make up bronze - Metalist's Handbook
Bronze owes its high popularity not only to its decorative characteristics, but also to a number of other properties. Meanwhile, few of those who use this metal can name the composition of bronze, but it is this that determines the characteristics of this copper alloy.
Foundry bronze BrZTs8S4N1 in ingots is used for the production of anti-friction parts
Main alloying additives
Bronze is a non-ferrous alloy based on copper, which determines most of its characteristics. Man began to produce and use bronze for various purposes since ancient times, as evidenced by the results of archaeological excavations. Initially, bronze was used, the composition of which was enriched with tin. Alloys of this type include, in particular, the so-called bell bronze (bells have been cast from it for many centuries).
In addition to bronzes containing tin, copper alloys that do not contain this chemical element are also actively used today. Instead of tin, the following are used as the main alloying additive in such copper alloys:
- beryllium, which gives bronze increased strength;
- silicon and zinc are elements that make the surface of a bronze product very resistant to abrasion and improve the fluidity of bronze, which is especially important for foundry operations;
- lead, which gives bronze resistance to corrosion;
- aluminum, which gives bronze decent anti-friction properties and high corrosion resistance.
The question about what metal is necessarily present in any bronze can be answered unequivocally: it is copper.
Chemical composition of various grades of bronze (click to enlarge)
In addition to division by chemical composition, there is a classification of bronze alloys according to processing technology:
- deformable (used for the production of products that are processed by plastic deformation);
- foundry (products from them are produced by casting).
Modern industry produces many grades of bronze, differing in their chemical composition and, accordingly, characteristics and scope of application. Many experienced craftsmen can even determine by the color of bronze what type it belongs to.
However, not everyone can do this.
The surest and easiest way to obtain information about what is contained in a certain brand of bronze and what type it is is to decipher the marking, which includes both alphabetic and digital designations.
Guitar strings: on the left from ordinary tin bronze (20% tin), on the right from phosphorus (7.7% tin, 0.3% phosphorus)
All grades of bronze alloys produced by modern enterprises in strict accordance with the requirements of regulatory documents (GOSTs) are listed in special tables, from which you can obtain information not only about the chemical composition of a certain grade of alloy, but also about its areas of application and characteristics. However, even without using such tables, you can determine the type of alloy and its chemical composition if you know the principle by which its designation is formed.
Mechanical properties and applicability of tin bronzes (k - chill casting, p - sand casting)
You can understand that this is bronze, a copper alloy, by the first letters “Br” present in the marking. After them, letters are placed, by which you can find out what other metals, besides copper, are contained in the chemical composition of this alloy. The regulatory document establishes the following rules for designating the chemical elements present in bronze:
Designation of additives in bronze composition
Typically, the marking of bronze of any brand does not indicate the amount of copper contained in its chemical composition. In this case, the numbers present in the designation indicate the quantitative content (in whole fractions of a percent) of the remaining elements.
Accordingly, the amount of copper contained in bronze of a certain brand is calculated as the difference between 100% of the total composition and the amount of additives. For example, bronze grade Br AZh 9-4 contains 9% iron and 4% aluminum, the remaining 87% is copper.
Bronze metal products are produced in the form of tape, wire, pipes, bushings, plates and rods
The amount of pure copper contained in bronze affects not only the technological and operational characteristics of the product, but also the color of its surface.
Thus, products made from the most common brands of bronze alloys, which contain about 85% copper, are distinguished by a golden color. If the amount of copper is reduced to 50%, the result can be white bronze, very similar in color to silver.
If desired, gray and even black bronze can be obtained - this result can be achieved by reducing the amount of copper in the alloy to 35% or lower.
Many old bronze products, the surface of which is almost black, acquired this color not due to the use of an alloy of a certain composition for their production, but as a result of exposure to time and various external factors (fires, prolonged exposure to damp soil, etc.). In ancient times, technologies for the production of bronze simply could not exist, the composition of which is supplemented by rare earth metals, giving it a rich black color.
Brands and areas of their application
Naturally, various chemical elements are introduced into the composition of any bronze not aimlessly, but in order to improve its properties. Thus, the content of a metal such as tin in bronze affects its ductility. The more bronze contains this metal, the harder and, accordingly, more brittle the alloy becomes.
However, the most significant influence on the hardness and strength of bronze is exerted by a chemical element such as beryllium. Some brands of bronze alloys containing beryllium in their chemical composition surpass high-quality steels in their strength characteristics.
If beryllium bronze is subjected to a hardening procedure, it, along with high strength, acquires elasticity, which makes it possible to make springs, springs and membranes for various purposes from this material.
Properties and applications of beryllium bronzes (click to enlarge)
Bronze alloys, the chemical composition of which is enriched with aluminum, are used to produce products that must combine sufficiently high strength with exceptional corrosion resistance.
Due to the characteristics of bronze alloys of this type, products made from them are successfully used in the most unfavorable conditions (high humidity, exposure to sea water, etc.).
In cases where it is necessary to make a product from bronze, which during operation will be subject to significant impact and frictional loads, it is better to use alloys containing lead in their chemical composition. In particular, bearings used in mechanisms for various purposes are made from such bronze.
Features of tin-free aluminum bronzes
Bronze, which, in addition to copper, contains silicon and zinc, is characterized by increased fluidity in the molten state, so they are used primarily for the production of complex parts by casting. A distinctive property of bronzes of this type is that no sparks are formed during mechanical impact on the products that are made from them. This quality is very important in many cases.
Such bronzes, characterized by exceptional corrosion resistance, are often called marine bronzes, because products made from them are able to retain all their original characteristics even after prolonged use in salty sea water.
It was possible to obtain such alloys, which are actively used for the production of elements of oil platforms installed on sea and ocean shelves, thanks to the development of the metallurgical industry.
Most brands of bronze alloys are not magnetic, which makes it possible to successfully use them for the production of electrical products.
How is bronze made?
Over the long period of existence of bronze production technology, only the tools and equipment have changed, but the essence has remained the same. As in ancient times, the raw material for producing this copper alloy can be a charge or bronze waste, and the flux, which prevents too intense oxidation of the metal in the molten state, is charcoal.
This centrifugal casting installation will allow the production of bronze blanks weighing up to 50 kg
The smelting process itself, as a result of which bronze is obtained, is performed in the following sequence.
- The crucible with the feedstock is placed in a furnace preheated to the required temperature.
- To prevent the metal from oxidizing too much after melting, crushed charcoal - flux - is added to it.
- After the metal has completely melted and warmed up well, phosphorous copper is introduced into its composition, which plays the role of an acid catalyst.
- After some exposure in a heated state, alloying and binding elements (ligatures) are added to the molten metal, after which the resulting alloy is thoroughly mixed.
- Before casting the molten metal, phosphorous copper is again added to it, which in this case is necessary to reduce the activity of oxidative processes.
At all stages of production, it is necessary to carefully monitor compliance with the correct temperature conditions in the furnace and the alloy itself. The amount of alloying and binding components added to the molten metal should also be controlled.
Do-it-yourself waterjet cutting of metal
Natural and artificial patination
Many people have probably wondered why old bronze items look not like ordinary bronze, but like green-white bronze. This color appears due to the formation of a film called patina. The factor that influences the process of formation of such a film and the intensity of its occurrence is the interaction of the surface of the bronze product with the surrounding air and the components contained in it (exhaust gases, smoke, water vapor, etc.).
Patina, which can be of oxide or carbonate origin, is a protective film. Its presence makes the product look more noble (just look at the photo of old bronze objects to understand this).
Sugar bowl made of patinated bronze
Today, technologies have been developed that make it possible not only to remove a layer of patina from the surface of a bronze item, but also to perform artificial patination in order to give the bronze item some vintage appearance. This patination is performed using preparations containing sulfur. After they are applied to the surface of the product, it is heated to a certain temperature.
In addition to artificial patina, the surface of bronze products can be covered with a layer of varnish, gilding, chrome or nickel.
Source: https://ssk2121.com/kakie-metally-vhodyat-v-sostav-bronzy/
Bronze: composition and marking, types of alloys and their properties, areas of application
Bronze, which has been known to people for so long, is a valuable alloy with unique characteristics. The article will discuss in detail the composition of bronze, its types and the special properties of each of them. It will also be interesting to learn about the modern scope of application of this alloy.
What is bronze?
Bronze is a multicomponent alloy consisting of two or more elements, the main one being copper. The remaining elements are called alloying elements and are used to improve the properties of the metal. The share of alloying compounds in bronze can be from 2.5% . Manganese, tin, lead, chromium, phosphorus, iron and other elements, except zinc, are used in this capacity. The combination of copper and zinc is called brass.
Depending on the quantitative content of copper additives in the alloy, bronze will have a different color shade. Fiery red shades indicate a high percentage of copper, but a cold steel color indicates the presence of no more than 35% copper in bronze.
History of bronze alloy
Bronze, as is known from school textbooks, has been used since very ancient times. The most ancient alloys made by people were alloys of copper and tin. Finds in the area of Mesopotamia and Southern Iran indicate that the first bronze objects date back to the 3rd millennium BC .
Everything was made from copper: dishes (plates, jugs and pots), weapons (swords, arrowheads and axes), mirrors, money in the form of coins and, of course, a wide variety of jewelry. Ancient Greek sculptors (V-IV centuries BC) also appreciated the qualities of bronze when casting large-sized statues.
Similar technology is still used today.
In the Middle Ages, so abundant in wars, cannons and shells for artillery were cast from an alloy of copper and tin. The most famous embodiment of bronze is the bell; by varying the composition, size and thickness of the walls, the craftsmen achieved the most pleasant sounds of the bronze bell, which flowed throughout the area.
Serving people with its unique properties, it does not lose its popularity. The origin of the word is associated with the Persian word for copper - berenj. It was later transformed into the Italian word bronzo.
Bronze markings
To designate a particular alloy, it is marked as follows:
- At the beginning there is the letter combination “Br” - bronze;
- Next, letters indicating the main alloying elements;
- At the end there are numbers determining the content of alloying elements in the material.
So, an example is the marking BrO5 - the content of the alloy is 5% tin, BrA5 - 5% aluminum.
Marking is necessary not only to determine the composition and properties of bronze, but also its specific gravity. To do this, just use the table from the reference book. But if the brand is unknown, then chemical analysis will help. This is necessary to calculate the volume of the workpiece, since its formula reflects the ratio of mass to volume. Knowing the specific gravity of a particular alloy, you can calculate the volume of a part with a certain mass and, conversely, what the weight of a bar of a given size will be.
Bronze composition
Not every combination of copper and another element in an alloy is bronze. Copper and zinc, as already mentioned, form a yellowish-golden alloy called brass. But copper and nickel are embodied in cupronickel, which was once used for wonderful-sounding spoons, and mostly for coins. It is valued for the fact that it does not lose its silvery hue and shine for a long time.
Special bronze (no tin)
Alloys with copper that do not contain tin as an alloying component are called special or tin-free bronze. Such alloys of copper with aluminum, iron, lead, silicon, etc. There are a variety of purposes. They can significantly exceed the quality of tin alloys, and their color range is even richer in variety.
Aluminum bronze has superior mechanical properties compared to tin bronze. At the same time, aluminum alloys are chemically stable . An alloy of copper with silicon and zinc shows excellent fluidity in the liquid state.
Beryllium bronze surpasses all others in elasticity, while possessing high hardness. In addition, the beryllium-copper alloy has high weldability and chemical stability. It works great with the cutting tool, allowing it to be processed. For this reason, this alloy is suitable for the manufacture of parts and elements such as membranes, springs, and contacts with spring properties. They are easily and reliably welded and are durable.
Technological characteristics
According to their technological properties , bronze can be:
- Deformable or easily susceptible to mechanical action. Alloys containing no more than 6% tin have these properties. Their ductility allows for stamping, forging and the production of grooved bronze materials. It is from deformable alloys that bronze wire, tape and sheets, etc. are made;
- Foundry - designed for shaped casting. These copper- and tin-based casting bronzes are used to make machine parts that can operate in seawater, as well as gears and bearing shells.
Thermal conductivity of bronze alloys
If we talk about thermal conductivity, it decreases with the introduction of alloying additives. Despite the fact that copper conducts heat very well, its alloys with other components lose a greater percentage of this indicator. Low thermal conductivity makes bronze unsuitable for friction units, welding electrodes and other elements where rapid heat transfer and removal are required. However, low-alloy bronze alloys are close in thermal conductivity to copper.
Bronze production
The process of producing this metal occurs in electric induction furnaces or crucible furnaces, where copper is alloyed with alloying additives. The smelting takes place under a layer of flux or charcoal. The smelting feedstock mixture can be prepared from either fresh metals or recycled materials.
Bronze production process:
- A certain portion of coal or flux is placed in a heated furnace;
- Copper is loaded into the furnace, where it is melted and heated to the desired temperature;
- The molten material is deoxidized using copper phosphorous;
- Alloying components are added to the deoxidized melt and brought to a hot state. Refractory alloying additives are introduced in the form of alloys;
- Everything is mixed until the components are completely dissolved and heated to the temperature according to the technology;
- Before casting begins, repeated deoxidation with phosphorous copper is performed to remove its oxides;
- The resulting bronze alloy melts perfectly and fills molding containers in the form of standard and round ingots;
- Ingots undergo rolling or press processing.
Areas of application
Due to its diverse properties, bronze is used in mechanical engineering, rocket and aircraft manufacturing, shipbuilding and many other industries.
The quality of anti-corrosion resistance, wear resistance and low friction coefficient have made it an indispensable material for machines and units that are involved in moving parts with high friction. On the other hand, bronze parts need periodic updating.
Due to their chemical resistance, tin-free bronze alloys are used for rolling elements of chemical devices and manufacturing control valves for various pipelines .
The continued popularity of using bronze in sculpture is due to its suitability for casting, as well as its weather resistance, durability and strength. An important factor in the external attractiveness of a bronze sculpture is the color and shine that attracts the eye. In addition, bronze gives the product solidity with an antique effect. For this reason, complex chandeliers , candelabra and other decorative elements in theaters and palaces are made from bronze alloys.
Source: https://stanok.guru/cvetnye-metally-i-splavy/bronza/sostav-svoystva-i-primeneniya-bronzy.html
Beryllium bronze BrB2
BrB2 is a tin-free beryllium bronze that is processed by pressure.
The chemical composition of the BrB2 alloy is described in GOST 18175-78 and includes the following components: copper 96.9-98.0%, beryllium 1.8-2.1%, nickel 0.2-0.5% and up to 0. 5% impurities. The alloy stands out among other bronzes due to its high wear resistance and resistance to corrosion fatigue.
Along with other bronzes, BrB2 has good antifriction and springing properties, as well as average heat and electrical conductivity, which determines the use of BrB2 tape and wire. In addition, the mechanical properties of this alloy can be improved by subjecting it to hardening and aging procedures. For example, BrB2T rod is widely used.
Properties of BrB2
Let's consider the properties of beryllium bronze grade BrB2 - chemical, technological, mechanical, physical.
Chemical composition of BrB2 alloy according to GOST 18175 - 78| Fe | Si | Ni | Al | Cu | Pb | Be | Impurities |
| up to 0.15 | up to 0.15 | 0.2 — 0.5 | up to 0.15 | 96.9 — 98 | up to 0.005 | 1.8 — 2.1 | only 0.5 |
Note: Cu is the base; the percentage of Cu is given approximately
| Melting point of BrB2 | 955 °C |
| Hot processing temperature BrB2: | 750 - 800 °C |
| Annealing temperature BrB2: | 530 – 650 °C |
| Assortment | Short-term strength limit sв | Proportional limit (yield strength for permanent deformation) sT | Elongation at break d5 |
| — | MPa | MPa | % |
| Soft wire, GOST 15834 - 77 | 343-686 | 15-60 | |
| Hard wire, GOST 15834 - 77 | 735-1372 | ||
| Soft strip, GOST1789-70 | 390-590 | 20-30 | |
| Hard strip, GOST 1789-70 | 590-930 | 2.5 | |
| Soft alloy, GOST1789-70 | 400-600 | 196-344 | 40-50 |
| Hard alloy, GOST1789-70 | 600-950 | 588-930 | 2-4 |
The hardness of BrB2 rods is specified in GOST 15835-2013 (replacing GOST 15835-70)
Hardness BrB2| Hardness BrB2, soft rod GOST 15835-2013 | HB 10 -1= 100 – 150 MPa |
| Hardness BrB2, Hard rod GOST 15835-2013 | HB 10 -1= 150 MPa |
HB - Brinell hardness of beryllium bronze
Physical properties of BrB2 (beryllium bronze)| Temperature T | Modulus of elasticity of the first kind E 10-5 | Coefficient of thermal (linear) expansion a10 6 | Heat capacity l | Density | Specific heat capacity C | Electrical resistivity R 109 |
| hail | MPa | 1/Grad | W/(m deg) | kg/m3 | J/(kg deg) | Ohm m |
| 20 | 1.31 | 84 | 8200 | 70 | ||
| 100 | 16.6 | 419 |
Analogues of BrB2
| USA | Germany | Japan |
| DIN,WNr | JIS |
Application of beryllium bronze BrB2
Rods made of BrB2 bronze are used in instrument making and automotive industry. BrB2 tapes are also used in instrument making and the production of elastic and spring parts. Wire has found a similar application in mechanical engineering and instrument making.
Bronze BrB2 is used in various areas of production. Antifriction parts and spring parts are made from it: spring parts and springs. Critical parts are made from it.
Non-sparking tools are also made from it.
Technological characteristics make it possible to produce complex high-quality castings from beryllium bronzes, but usually parts from them are made from blanks subjected to preliminary plastic deformation (sheets and strips, wire, tapes, etc.). The widespread use of beryllium group alloys is also due to the fact that they lend themselves well to various types of processing, and all known methods (welding and soldering) can be used to connect parts made from them.
Soldering and welding BrB2
Soldering of beryllium bronzes should be performed immediately after thorough mechanical cleaning of the elements to be joined has been performed.
When performing such a technological operation, silver-based alloys are used as solder, and the protective flux, the use of which is necessary, must necessarily contain fluoride salts.
High quality soldering of parts made of these alloys is ensured by a technology that involves performing the connection in a vacuum and using a layer of protective flux.
Parts made of beryllium bronzes are not joined using electric arc welding; other technologies are successfully used for this: spot, seam, roller and inert gas welding. This limitation in the use of electric arc welding is due to the fact that the alloys of this group have a large crystallization temperature range. In addition, welding of beryllium group bronzes cannot be performed after heat treatment, which is due to their special mechanical properties.
Wear resistance and corrosion resistance of BrB2 bronze
Parts made of beryllium bronze do not wear out and at the same time have a gentle effect on the mating mechanisms, fit well with each other, are polished and interact perfectly in the mechanisms under given parameters.
But even if operating conditions are violated, parts made of BrB2 are able to withstand heavy friction loads and other mechanical influences.
During the operation of mechanisms during wear, BrB2 does not break off in large pieces, but wears out gradually, producing very small chips.
Corrosion fatigue is one of the indicators of the corrosion resistance of metals. When parts operate under the influence of large mass, cyclic dynamic loads in a corrosive environment, there is a high probability of failure of the structures in which they are used.
The BrB2 alloy performs well in various corrosive environments and can be used for the manufacture of critical parts, since corrosion manifests itself quite slowly and does not have a significant effect on the mechanical and physical properties of parts made from this material for a long time.
However, under the influence of moist ammonia vapor and air, beryllium bronzes are prone to intercrystallization corrosion and cracking. In a gas environment saturated with halogens (fluorine, bromine, chlorine and iodine), beryllium halides form on their surface, which causes a decrease in its concentration in the alloy.
The process of interaction with halogens occurs especially actively at elevated temperatures. In this regard, beryllium bronze BrB2 is not recommended for use in the manufacture of parts used in these gases.
Upgrading and hardening of BrB2
By refining, products made from BrB2 are harder and more ductile. Accordingly, semi-finished products are produced in soft (M) and hard (T) states. During the hardening procedure, the metal is heated to a certain temperature, after which it is cooled in water. As a result, the plastic properties of the metal increase and it is used for the manufacture of parts by rolling, forging, drawing and cold bending.
Semi-finished products from BrB2 with hardening and cold deformation are also produced. BrB2 is hardened at a temperature of 750-790 °C, after which the alloy is tempered at a temperature in the range of 300-350 °C. After cold deformation, the mechanical properties of hardness, strength and fluidity are improved. BrB2 T stands out among other bronzes for its highest tensile strength.
Copper-beryllium alloy BrB2, subjected to thermal hardening, becomes more durable, elastic and ductile. Initially, it is brought into a soft state by heating to 760-780°C, and then subjected to aging in water at a temperature of 310-330°C for 3 hours. When the alloy is heated and then cooled to room temperature, beryllium dissolves in copper to form a saturated solid solution.
Subsequent hardening leads to its precipitation, as a result of which BrB2 bronze acquires high hardness up to 350 - 400 HB.
Source: https://poliasmet.ru/svoystva-bronzyi/bronza-brb2.html
Bronze - composition, properties and characteristics of the alloy
Bronze owes its high popularity not only to its decorative characteristics, but also to a number of other properties. Meanwhile, few of those who use this metal can name the composition of bronze, but it is this that determines the characteristics of this copper alloy.
Foundry bronze BrZTs8S4N1 in ingots is used for the production of anti-friction parts
What metals make up bronze?
Many people know about bronze only that sculptures and monuments are cast from it. In fact, this metal is undeservedly deprived of popular attention. It is not for nothing that in the history of mankind there was even a Bronze Age - an entire era during which the alloy occupied a dominant position.
It is one of the few materials used in both industry and art. The qualities possessed by the alloy of copper and tin are simply irreplaceable in many industries. It is used in the manufacture of tools, in mechanical engineering, casting church bells, and so on.
Moreover, today there are a large number of metal grades, each of which has certain, pre-modeled properties.
Use of bronze in the past
The first mention of an alloy of copper and tin dates back to the 4th millennium BC. It was this technological breakthrough, according to historians, that allowed the Mesopotamian civilization to occupy a leading position at that time.
Archaeological excavations carried out in Southern Iran indicate the widespread use of bronze for the manufacture of arrowheads, daggers, spears, axes, and swords. Among the finds there are even interior items, such as furniture and mirrors, as well as jugs, amphorae, vases and plates.
The same alloy was used to mint ancient coins and make jewelry.
Bronze began to be actively used in Europe in the Middle Ages. It is used to make such massive objects as cannons and church domes. In a later period, with the development of mechanical engineering, such a versatile metal also did not go unnoticed.
It was appreciated mainly for its anti-friction and anti-corrosion properties. However, it should be noted that the material used earlier was somewhat different from what bronze is today.
The composition of the alloy contained many minor impurities that significantly deteriorated its quality.
Chemical composition of modern bronze
Today in materials science, bronze is an alloy of two metals: copper and tin, which can be used in a wide variety of proportions. To give the metal the desired qualities, zinc, phosphorus, magnesium, lead and silicon can be added to this pair. The presence of random impurities with the help of modern technologies is practically reduced to zero.
In most cases, a copper to tin ratio of 85 to 15 percent is considered acceptable. A decrease in the share of the second component below the specified level gives rise to a number of problems, the main of which is segregation. Metallurgists use this term to describe the process of stratification of the alloy and its uneven solidification.
The influence of alloy color on its quality
Knowledgeable people can learn a lot about the material just by looking at the color that bronze has. The composition directly affects this parameter. As you might guess, copper gives the alloy a red tint. Therefore, reducing its percentage in favor of other components will mean a gradual transition of color to duller tones.
With the usual balance of components (85% copper), bronze has a yellowish tint. This variety can be found most often. The white alloy is obtained after bringing the ratio to 50:50. But for bronze to turn gray, it is necessary to reduce the amount of copper to 35%.
As for changing the practical characteristics of the alloy when experimenting with its composition, the situation is as follows. The malleability of the material will directly depend on the tin content in it. The less it is, the more malleable the bronze will be, but this statement is true only to a certain limit. So, when the 50% mark is reached, the alloy becomes soft again.
Bronze in art
A strong and durable material, which at the same time has a fairly low melting point and good malleability, could not but interest creative people, in particular sculptors. Already in the 5th-4th centuries BC in Greece, the technology for making bronze statues was perfected to the smallest detail, which is still relevant today.
It consists in the fact that the sculpture made of fire-resistant material is initially replaced with wax, which is destroyed directly during casting. To do this, a plaster model must first be made according to the drawing, and then a mold for casting. The wax content simply melts when exposed to temperature, and its place is taken by bronze, which cools and hardens.
After which all that remains is to process it and bring it to perfection.
Artillery metal
Bronze has always been used to make cannons, and later other military equipment. The alloy composition used for these purposes usually contains 90% copper and only 10% tin.
This is due to the fact that the material for the tools must be very durable and have increased tear resistance. Bronze grade BrAZhMts10-3-1.5 has these qualities.
In addition to the main components, it contains 1-2% manganese, which increases anti-friction and temperature characteristics.
Making church bells
The ringing of a bell must be melodious, and its sound must please the ear from a great distance. Oddly enough, bronze has such musical talents. To improve the sound of the bell, it is made from an alloy with a high tin content (from 20 to 22%).
Sometimes a little silver is also added to it. The grades of bronze that are used in the manufacture of bells and other percussion instruments are absolutely unsuitable for practical use in other industries.
This is due to the fact that such an alloy has a fine-grained structure and increased brittleness.
Phosphorus and aluminum bronze
For the first time, an alloy consisting of 90% copper, 9% tin and 1% phosphorus was used by Künzel in 1871. It was called phosphorus bronze, and the material found its application mainly in mechanical engineering. Various machine parts that are subject to increased friction are cast from it. Phosphorus is necessary to increase elasticity and increase anti-corrosion properties. The main advantage of this metal is that it ideally fills any cavities during casting.
Aluminum bronze, whose composition is characterized by a high copper content (up to 95%), is very similar in appearance to gold. In addition to beauty, it has a number of other undeniable advantages. For example, the addition of 5% aluminum allows the alloy to withstand exposure to an aggressive environment, such as high acidity, for a long time.
As a material for the manufacture of various machine parts, this metal has almost universally replaced phosphorus bronze in paper mills and in gunpowder production due to its higher resistance to rupture.
Silicon and manganese bronze
Silicon is added to the alloy to increase electrical conductivity. This quality is used in the production of telephone wires. The reference composition of silicon bronze is as follows: 97.12% copper, 1.14% tin, 0.05% silicon.
The most complex production process is an alloy containing manganese. The whole procedure takes place in several stages. First, ferromanganate is added to the molten copper. Then, after maintaining the specified temperature, tin is added, and, if necessary, zinc. The English company Bronce Company produces several types of manganese bronze, which have different viscosity and hardness. This alloy can be used in almost all industries.
Source: http://ooo-asteko.ru/kakie-metally-vhodyat-v-sostav-bronzy/
