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Read and translate the text in a written form. Welding is a method of causing fusion between two like pieces of metal to form one homogeneous mass of metalWelding is a method of causing fusion between two like pieces of metal to form one homogeneous mass of metal. Fusion of two masses of metal may be brought about by four different processes, namely: 1) Forge or blacksmith welding; 2) Thermit welding; 3) Electric welding; 4) Gas welding. Forge or Blacksmith Welding. — Forge welding is a process whereby the two masses of metal to be welded are heated in a blacksmith's forge or appropriate furnace until the metal reaches a plastic stage. At that time the two masses are quickly joined and fused together by force from-a hand or power hammer. Such a process is limited to fairly low carbon steels of solid plain shape. It is obvious that such welding has a narrow range of application, although there is still a large quantity of forge welding done in railrod shops and country blacksmith shops. Thermit Welding. — Thermit welding is not a common process. The process consists of a chemical reaction obtained by igniting finely divided aluminium and iron oxide. A mold is formed around the pieces to be welded, and the metal is then preheated to a dull red colour. The aluminium and iron oxide are retained in a funnel-shaped holder which can be tapped into the mold when the aluminium and iron oxide have been made molten by the chemical reaction which is started by a fuse. The temperature of the molten metal is high enough to fuse the broken sections, thus forming a homogeneous mass of metal. The equipment for thermit welding is simple and inexpensive but the quality of the weld is not such as to recommend it for extensive use. The process can be used only on low carbon steels and wrought iron. Word List:
Questions: 1. What is welding? 2. What kind of welding can you name? 3. What does Forge or Blacksmith welding consist of? 4. What is Forge or Blacksmith welding limited to? 5. Thermit welding is not a common process, is it? 6. What does Thermit welding welding consist of? 7. What is the temperature of the molten metal? 8. What is the equipment for the Thermit welding?
IW # 9.1«WELDING»
Welding is a process when metal parts are joined together by the application of heat, pressure, or a combination of both. The processes of welding can be divided into two main groups: • pressure welding, when the weld is achieved by pressure and • heat welding, when the weld is achieved by heat. Heat welding is the most common welding process used today. Nowadays welding is used instead of bolting and riveting in the construction of many types of structures, including bridges, buildings, and ships. It is also a basic process in the manufacture of machinery and in the motor and aircraft industries. It is necessary almost in all productions where metals are used. The welding process depends greatly on the properties of the metals, the purpose of their application and the available equipment. Welding processes are classified according to the sources of heat and pressure used. The welding processes widely employed today include gas welding, arc welding, and resistance welding. Other joining processes are laser welding, and electron-beam welding. Arc Welding Arc-welding is the most important welding process for joining steels. It requires a continuous supply of either direct or alternating electrical current. This current is used to create an electric arc, which generates enough heat to melt metal and create a weld. Arc welding has several advantages over other welding methods. Arc welding is faster because the concentration of heat is high. Also, fluxes are not necessary in certain methods of arc welding. The most widely used arc-welding processes are shielded metal arc, gas-tungsten arc, gas-metal arc, and submerged arc. Поиск по сайту: |
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