2015-02-18
804
Welding 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:
| 1. | a method of causing fusion | Метод сплавления |
| 2. | like pieces | Одинаковые куски |
| 3. | may be brought about | Может быть осуществлён |
| 4. | two masses of metal | Две массы (два куска) металла |
| 5. | are quickly joined and fused together by force | Соединяются и сплавляются вместе под действием силы |
| 6. | is limited to fairly low carbon steels | Ограничивается сталями с довольно низким процентом углерода (низкоуглеродистые стали) |
| 7. | of solid plain shape. | Простой формы в твёрдом состоянии |
| 8. | is not a common process | Необычный процесс |
| 9. | A mold is formed | Образуют форму |
| 10. | a dull red colour | Тускло-красный цвет |
| 11. | funnel-shaped receptacle | Воронкообразное пространство |
| 12. | can be tapped into | Может отбираться в |
| 13. | thus forming a homogeneous mass of metal | Так что образуется однородная масса металла. |
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?
