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Bronze


Bronze
In the 3rd Millennium BC people started to use widely in their business activities metals. The transition from stone tools to metal had enormous significance in the history of mankind. Perhaps, no other discovery has not led to significant social shifts.

the First metal, widespread, was copper. They need constantly looking for the stones, our ancestors, presumably, already in ancient times drew attention to a reddish-green or greenish-grey pieces of native copper. In the cliffs of the coasts and cliffs they came across copper pyrites, copper glitter and red copper ore (cuprite). At first, people used them as ordinary stones and processed accordingly. They soon discovered that when processing the copper strikes of the stone hammer its hardness is greatly increased and it is suitable for the manufacture of tools. Thus came into use the techniques of cold processing of metal or primitive forging. Then it made another important discovery — a piece of native copper or surface rocks containing metal, falling into the fire, found new, characteristic stone features: strong heating of the metal melt and cooling down, acquired a new form. If the form is done artificially, it was necessary for a person product. This property of copper ancient masters used first for the casting of jewelry, and then for the production of copper tools. Such was the origin of metallurgy. Melt steel to be implemented in special high temperature furnaces, representing a somewhat modified construction well known pottery kilns. Generally speaking, copper is a soft metal, much inferior in hardness to the stone. But copper tools can be quickly and easily sharpened. (According to the observations of S. A. Semenov, the replacement of the stone axe on the copper cutting speed increased by about three times.) The demand for metal tools began to grow rapidly. People have started a real "hunting" for copper ore. It turned out that it is not common everywhere. In those places, where he discovered rich deposits of copper, have caused intensive development, has appeared and ore mining business. As shown by the discoveries of archaeologists, in ancient times, the mining process ore were delivered on a large scale. For example, near Salzburg, where copper mining started around 1600 BC, the mine reached the depth of 100 meters, and the total length extending from each of the mine tunnels were several kilometers. The ancient miners had to solve all the problems that face modern miners: the strengthening of arches, ventilation, lighting, and climbing the mountain of ore mined. Gallery strengthened wooden props. The extracted ore was smelted in nearby low clay ovens with thick walls. Such centers of metallurgy existed in other places.

At the end of the 3rd Millennium BC by ancient craftsmen began to use the properties of the alloys, the first of which was the bronze. At the opening of the bronze men had to push an accident, unavoidable in mass production of copper. Some varieties of copper ores contain minor (up to 2%) admixture of tin. Smelted this ore, the master noticed that the copper obtained from it, is much harder than normal. Tin ore could fall into smelting furnace for another reason. Anyway, observations of the properties of the ores has led to the development of the value of tin, which were added to the copper, forming an artificial alloy bronze. When heated with tin and copper melted better and easier subjected to casting, as they become more fluid. Bronze tools were harder than copper, well and easily sharpened. Metallurgy of bronze allowed several times to improve productivity in all sectors of human activity. The very production tools has become much simpler: instead of long and hard work to unjam and grind stone, the people were filled of the mold with liquid metal and received the results in a dream never dreamed of their predecessors. The casting technique is gradually improved. First casting made in an open clay or sand molds, representing a simple hole. They were replaced by open forms, carved from stone that could be used repeatedly. However, the big disadvantage of open forms was that they could only flat items. For casting products with complex shape, they were not good. The solution was found when he invented a closed separable form. Before casting the two halves of the shape are firmly joined. Then through the hole was filled with molten bronze. When the metal cooled and hardened, the form was dismantled and received the finished product. This method allowed to cast parts of complex shape, but he was not fit for figure casting. But this difficulty was overcome when he invented a closed form. In this method of casting was first sculptured in wax the exact model of the future product. Then she daubed clay and fired in a kiln. The wax is melted and evaporated, and the clay took an accurate impression of the model. In the thus formed void was filled with bronze. When it cooled, the form was broken. Thanks to all these operations the master had the opportunity to cast hollow objects even very complex shapes. Gradually opened new techniques of working with metals, such as drawing, riveting, soldering and welding, complementing already known forging and casting.

With the development of bronze metallurgy products everywhere began to displace stone. But do not think that it happened very quickly. Non-ferrous metal ores were everywhere. And tin were found much less frequently than copper. The metals had to be transported long distances. The cost of metal tools remained high. All this prevented their widespread. Bronze was not able to replace stone tools. It was only iron.

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