Е. С. Закирова, П. А. Красавин Английский язык для технических вузов
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| JOINING PROCESSES
A mechanical joint is a part of a machine which is used to connect another mechanical part or mechanism. Mechanical joints may be temporary (with the help of bolts, screws, studs, etc.) or permanent (welding, brazing, soldering, and riveting). Bolted joints are considered to be temporary mechanical joints and may be disassembled when required. They consist of fasteners that capture and join other parts, and are secured with the help of screw threads. Welding is a fabrication process that joins materials, usually metals or ther- moplastics, by causing coalescence. This is often done by melting the work pieces and adding a filler material to form a pool of molten material that cools to become a strong joint, but sometimes pressure is used together with heat, or by itself, to produce the weld. Brazing is a joining process in which a filler metal is melted and drawn into a capillary formed by the assembly of two or more workpieces. The filler metal reacts with the workpiece(s) and solidifies in the capillary, forming a strong joint. Unlike welding, the workpiece is not melted. Brazing is similar to solder- ing, but occurs at temperatures in excess of 450 °C (842 °F). Soldering is a joining process that occurs at temperatures below 450°C (842 °F). It is similar to brazing in the fact that filler is melted and drawn into 173 a capillary to form a join, although at a lower temperature. Because of this lower temperature and different alloys used as fillers, the metallurgical reaction between filler and workpiece is minimal, resulting in a weaker joint. Riveting is one of the most ancient metalwork joining processes. Its use has declined markedly during the second half of the 20th century, but it still re- tains important in the 21st century. The earlier use of rivets is being superseded by improvements in welding and component fabrication techniques. Bolted joint Screw joint Stud joint жүктеу/скачать 4,38 Mb. Достарыңызбен бөлісу:
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