Historians suggest that primitive people found copper in the form of nuggets, sometimes reaching significant sizes. Copper (Cuprum) got its name in Latin from the island of Cyprus, where the ancient Greeks mined it. Due to the fact that the melting point of copper is not too high and amounts to 1083 ° , nuggets or ore containing copper could be melted on a fire. This ensured the production of copper and made it possible to use it for the manufacture of weapons and household items.
Despite the fact that copper has been widely used by people since ancient times, in terms of distribution in the earth's crust, it takes 23 place among other elements. Most often, it is found in nature in the form of compounds that make up sulfide ores. The most common of them are copper shine and copper pyrite. There are several technologies for producing copper from ore, and for each of them the process occurs in several stages.
As already noted, the low melting point of copper made it possible to successfully process it even at the very initial stage of the development of civilization. And we must pay tribute to the ancient metallurgists, they found options for obtaining and using not only pure copper, but also its alloys. Melting is the transition of a metal from a solid to a liquid state. For this, heating was used, and the low melting point of copper made it possible to successfully carry out a similar operation.
Then, tin was added to liquid copper, or it was reduced from cassiterite (ore containing tin) on the surface of copper. As a result, bronze was obtained, superior in strength to Cuprum and used for the manufacture of weapons. However, now I would like to dwell in more detail on the melting operation, which allows to obtain a sufficiently pure material from ore.
Each metal has a melting point of its own and depends on the presence of impurities in the composition of the starting material. So, copper, the melting point of which is 1083 ° , after adding tin forms bronze, which melts at a temperature of 930-1140 ° depending on the tin content. Brass, an alloy of copper and zinc, has a melting point of 900-1050 ° C.
During the heating of the metal, the crystal lattice is destroyed. Initially, as the temperature heats up, the temperature rises, and then, starting from a certain value, it remains constant, although heating continues. At this moment, melting occurs. This continues throughout the entire time until all the metal has melted, and only then will the temperature begin to rise. This is true for all metals; the melting point of copper also does not change.
When cooling, the opposite is true: first, the temperature decreases before the solidification of the metal begins, then it remains constant and after the metal has completely hardened, it begins to decrease again. This behavior of the metal, if depicted on a graph, is called a phase diagram, which shows the state of the substance at a particular temperature. For scientists, the phase diagram is one of the tools in studying the behavior of metals during melting.
If we continue heating the molten metal, then at a certain temperature a process similar to boiling begins. So, the boiling point of copper is 2560 ° C. The process received this name for its external resemblance to the boiling of a liquid when gas bubbles begin to stand out from it. The same thing happens with the metal, for example, at a sufficiently high temperature, carbon formed during the oxidation of carbon begins to escape from liquid iron.
The article discusses the process of melting metals, describes the concept of melting temperature, its behavior in the process of melting. The effect of the low melting point of copper on the development of civilization and metallurgy is explained.