Many people know about bronze only that sculptures and monuments are cast from it. In fact, this metal is deprived of people's attention undeservedly. It is not in vain that in the history of mankind there was even a Bronze Age - a whole era during which the alloy occupied a dominant position. This is one of the few materials used both in industry and in art. The qualities possessed by the alloy of copper with tin are simply indispensable 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.
The use of bronze in the past
The first mention of the alloy of copper and tin dates back to the 4th millennium BC. It is this technological breakthrough, according to historians, that allowed the civilization of Mesopotamia to take a leading position at that time. Archaeological excavations conducted in southern Iran indicate the widespread use of bronze for the manufacture of arrowheads, daggers, spears, axes, swords. Among the finds there are even interior items, for example, furniture and mirrors, as well as jugs, amphorae, vases and plates. The same alloy was used for minting ancient coins and making jewelry.
In the Middle Ages, bronze began to be actively used in Europe. Massive objects such as guns and church domes are made from it. In a later period, with the development of mechanical engineering, such a universal 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, significantly impairing its quality.
The 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 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 technology is practically reduced to zero.
In most cases, the ratio of copper to tin in the proportions of 85 to 15 percent is considered acceptable. The decrease in the proportion of the second component below the indicated level gives rise to a number of problems, the main of which is segregation. This term metallurgists call the process of separation of the alloy and its uneven solidification.
The influence of the color of the alloy on its quality
Knowledgeable people can learn a lot about the material only by looking at the color that bronze has. Composition directly affects this parameter. As you might guess, copper gives a red tint to the alloy. Therefore, a decrease in its percentage in favor of other components will mean a gradual transition of color to more dull tones.
With the usual balance of components (85% copper), bronze casts with yellowness. This kind of it can be found most often. The white alloy is obtained after adjusting the ratio to a ratio of 50:50. But in order for bronze to become gray, it is necessary to reduce the amount of copper to 35%.
As for the change in the practical characteristics of the alloy when experimenting with its composition, the situation here is as follows. The ductility of the material will directly depend on the tin content in it. The smaller it is, the more pliable the bronze will be, but this statement is true only to a certain limit. So, when the mark of 50% is reached, the alloy becomes soft again.
Bronze in art
Strong and durable material, which at the same time possessed a sufficiently low melting point and good ductility, could not fail to interest creative people, in particular sculptors. Already in the 5th-4th centuries BC, Greece worked out to the smallest detail the manufacturing technology of bronze statues, which is still relevant today.
It consists in the fact that the statue of the fire-resistant material is initially replaced by wax, which is destroyed immediately during casting. To do this, the gypsum model must first be made according to the drawing, and then the mold for casting. When exposed to temperature, the wax content simply melts, and bronze takes its place, which cools and hardens. After which it remains only to process and bring to perfection.
Artillery metal
For the manufacture of guns, and later on other military equipment, bronze was always used. The composition of the alloy that is used for these purposes, as a rule, 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 tensile strength. These qualities are possessed by the bronze brand BrAZhMts10-3-1.5. In addition to the main components, its composition contains 1-2% manganese, which increases the antifriction and temperature characteristics.
Making Church Bells
Bell ringing must be melodic, and its sound should delight your hearing at a great distance. Oddly enough, but bronze has such musical talents. To improve the sound of the bell, it is made of an alloy with a high tin content (from 20 to 22%). Sometimes it also adds a little silver. Brands of bronze, which 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 fragility.
Phosphor 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 phosphor bronze, and the material found its application mainly in mechanical engineering. Various parts of machines 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 perfectly fills any recesses during casting.
Aluminum bronze, the composition of which 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 indisputable advantages. So, for example, the addition of 5% aluminum allows the alloy to withstand exposure to aggressive media such as high acidity for a long time.
As a material for the manufacture of various parts of machines, this metal almost everywhere displaced phosphor bronze in paper mills and in powder production due to the higher resistance to tearing.
Silicon and Manganese Bronze
Silicon is added to the alloy to increase electrical conductivity. This quality is used in the manufacture of telephone wires. The reference composition of silicon bronze is as follows: 97.12% copper, 1.14% tin, 0.05% silicon.
The most difficult process to obtain boasts an alloy containing manganese. The whole procedure takes place in several stages. Ferromanganum is first added to molten copper. Then, having maintained the specified temperature, tin is added, and, if necessary, zinc. The English company Bronce Company produces several grades of manganese bronze with different viscosity and hardness. A similar alloy can be used in almost all industries.