ТОР 5 статей:
Translate the following sentences.
1) The operation of making sand castings is not as is simple as it seems.
2) The foundry industry is as old as our knowledge of brass and iron.
3) As to the physical properties of metals they are crystal structure, electrical conductivity, heat conductivity.
4) Metals have some mechanical properties such as hardness, strength, ductility etc.
5) Sand and clay are mixed to make the molding sand. Water is used as well.
6) The sand as well as the clay must be refractory.
Read Text А. Translate it.
MAKING A SAND MOLD
Sand mold is made by packing the molding sand around a pattern. A pattern of wood, metal or wax is needed to form the cavity in the sand which molten metal will be poured. Patterns are to have the same shape as the finished object (отливаемый предмет), but their size should be a little (немного) larger as the casting shrinks when cooling. A pattern made of metal may be used longer.
If the pattern is made of one piece, it is called a solid pattern. The pattern made in two halves is known as split pattern. The split patterns may be removed from the mold in pieces (по частям).
For a small amount of castings a wooden pattern may be used. It is more economical than a metal pattern. Sand molds are made in the flasks which are wooden or metal boxes consisting of two parts. The upper portion is called the «cope», and the lower portion is called the «drag».
In sand molding two special boards are to be used. The drag is placed on the moldboard. A molding board is smooth and a little larger than the flask opening. The size of the moldboard should be the same as the outside of the drag. The board which is placed on top of the packed drag is called the bottom board because after turning the flask over, it becomes the bottom of the mold.
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