METAL “All that glitters is not gold”

Metal is called chemical elements characterized as being good conductors of heat and electricity.

Materials science defines a metal as a material in which there is an overlap between the valence band and the conduction band in its electronic structure. MATERIALS SCIENCE VALENCE BAND

Metal concept relates both to the pure elements and metal alloys with features like.. STEELBRONZE

metal HISTORY

Metals like gold, silver and copper, were used since prehistoric times. At first, only the easily used were pure. The first breakthrough came with the discovery of bronze, resulting from the use of copper ore with tin raids between 3500 a. C. and C., in different regions of the world, the so-called emerging Bronze Age happens to the Stone Age. Another important event in history was the use of iron, around 1400 a. C. The Hittites were one of the first people to use it to develop weapons such as swords, and civilizations that were still in the Bronze Age, as the Egyptians. Around 1400 began to use the furnaces equipped with bellows, which allow reaching the melting point of iron, about 1535 ° C. Henry Bessemer discovered a way to produce steel in large quantities at a reasonable cost. After numerous failed attempts. Shortly after aluminum and magnesium, which helped to develop much lighter and stronger alloys are used. Titanium is the last of the abundant and stable metals with which it is working and it is expected that in a short time, the use of titanium technology becomes widespread.

Properties of the metal

Specific gravity. The specific gravity can be absolute or relative: the first one is the weight of the unit of volume of a homogeneous body. The relative specific gravity is the relation between the peso of a body and the peso of equal volume of a taken substance as it indexes; for the solid and liquid ones the distilled water is cited as an example to 4°C. Specific heat. It is the necessary quantity of heat to raise in 1°C the temperature of 1 kg of certain substance. The specific heat changes with the temperature. In practice it is considered to be the average specific heat in a temperatures interval.

Melting point. It is the temperature to which a material goes on from the solid state to the liquid, transformation that takes place with heat absorption. The hardening point is the temperature to which a liquid happens to the solid state, during the transformation there is heat transfer. Almost always there coincide the points of merger and of hardening. Latent merger heat. It is the necessary heat to conquer the molecular forces of the material (to the merger temperature) and to transform it of solid into liquid.

Resistance wing corrosion. The corrosion of the metals can originate for: · Chemical reactions with the corrosive agents · Reactions electroquímicas produced by electrolytic currents generated in galvanic elements formed in the surface with different potential. The electrolytic currents take place with displacement of metallic ions. The electrolytic corrosion can take place for: · Heterogeneity of the crystalline structure · Internal tensions produced by cold deformation or thermal treatments badly carried out. · It differs in the external ventilation

THE END BY: María Puentes Ortiz José María Cuesta José Antonio