As is known, any substance may be in gaseous, solid or liquid, and can move from one state to another.Suffice it to recall the water.Usually at positive temperatures is liquid at negative - solid, and at high temperatures, it turns into steam, i.e.in the gaseous state.The transformation from solid to liquid state is called melting and the temperature at which this process occurs - melting point.
How is the process of melting?If we consider the metal, we can see that its structure is a lattice whose atoms are arranged in a certain order relative to each other, making small fluctuations.When a foreign power or heating of the body increases the energy of atoms, and they begin to vibrate with greater amplitude.When the body temperature and the melting temperature of the substance will be equal, it begins the process of destruction of the metal structure, that is the melting process.
However, what began the process of melting, does not mean that it will continue on its own.To maintain it is necessary to constantly supply the heat that is spent on the destruction of the bonds of the crystal lattice.
Every matter its characteristics.And each metal has its own melting temperature.It is determined by the crystal lattice and composition of matter.For pure substances the temperature alone, alloys, consisting of several metal - different.For example, the melting point of iron is 1100-1130 ° C.Such a range of values determined by the fact that the content of impurities in the metal changes to the same form when heated refractory oxides.They have a melting point higher than that of iron.
For copper, this temperature is 1084 ° C, zinc - 419 ° C.Melting brass being an alloy of copper and zinc - about 1000 ° C.This is an approximate value of the temperature is determined by the fact that it depends on the percentage of the components.If the alloy composition is more copper, this will lead to the fact that the melting point of the alloy will be higher if more zinc - below.
It should be noted that the temperature at which the material is melted, depends not only on its purity, but also on the pressure.With increasing pressure, it increases the pressure drop decreases.
As already noted, melting requires a constant supply of heat.In practice, it looks like that the heating of the material is constant, but the temperature remains constant.And only after a certain amount is consumed heat, called the heat of fusion, it will further increase the temperature, but the liquid substance.
There is another feature in the melting metals.If you stop the supply of heat, the melting process is terminated and the reverse process - the liquid metal passes into the solid state.This process is called crystallization.On cooling the liquid metal and making it a solid is released the same amount of heat which is consumed during its melting.
role of fusion in nature, science and technology is difficult to overestimate.Through this process we can obtain metals or alloys with required properties.Virtually the whole of human civilization is based on the metal and its alloys, and hence on the physical constants such as melting point.After all, virtually no one industry which is not consumed to the metal.
Thus, we have considered that such a melting point, determined what it depends on, and described the process of melting.The article also defines the crystallization of metals.
