2. Answer the questions to the text.

1. What arc did the powdered fluxes produce?

2. How is the molten deposit protected in this process?

3. What wire is used in submerged-arc welding?

4. What material is deposited to cover the joint from atmosphere?

5. Are there any sparks, spatter and flash during the welding action?

6. How and where is the welding heat generated?

7. What current is used in submerged-arc welding?

8. Is submerged-arc welding a manual or automatic process?

9. Is it possible to produce overhead welds by this process?

10. Where is submerged-arc welding used?

11. What advantages does this process have?

3. Give the short summary of the text.

Text 3.

ARC CUTTING

New words and word combinations.

1. carbon-arc cutting – дуговая резка угольным электродом

2. metal-arc cutting – дуговая резка металлическим (плавящимся) электродом

3. oxygen cutting – газопламенная (кислородная) резка

4. to be the least expensive – быть наименее дорогими

5. scrap metal – металлолом

6. provision – условие

7. to permit – позволять

8. without causing – не вызывая

9. a short circuit – короткое замыкание

10. to use up – расходовать, использовать

11. tubular electrode – трубчатый электрод

12. to blow away – выдувать

13. ferrous and nonferrous metals – черные и цветные металлы

14. arc-air gouging – воздушно-дуговая поверхностная резка (строжка)

15. rough grinding – грубое шлифование

16. chipping – рубка

17. precautions – предосторожность

1. Read the text and try to understand it.

Three different processes are used for arc cutting, namely, carbon-arc cutting, metal-arc cutting and arc oxygen cutting.

The carbon-arc cutting. The carbon-arc-cutting process is the least expensive, but, since it produces the roughest cut edges, it is used only for rough work; such as cutting up scrap metal. The equipment used is similar to that employed for carbon-arc welding. A graphite electrode is preferred and direct current with straight polarity is used in order to create a majority of the heat on the workpiece. The arc simply melts the metal and provision must be made to allow the molten metal to drop by gravity out of the cut. All metals which can be readily melted can be cut.

Metal-arc cutting. This process is similar to carbon-arc cutting except that a metal electrode (usually steel) with an electrical insulating covering is used. The insulating covering permits the insertion of the electrode into the cut without causing a short circuit at the sides of the electrode. This covering also serves as an arc stabilizer and concentrates the arc. The cost of metal-arc cutting is higher than that for carbon-arc cutting since the metal electrodes are used up during the cutting. For this reason metal-arc cutting is not used often.

Arc-oxygen cutting. Arc-oxygen cutting is accomplished with a tubular electrode. Thus a stream of oxygen passes through the central hole of the electrode and assists the cutting by oxidizing and blowing away molten metal. The electrode may be steel or of a ceramic material which conducts electricity. An insulating covering prevents short circuiting of the sides of the electrode against the edges of the cut. Direct current with straight polarity is prefered. The cutting is much faster than with thе other two arc-cutting processes. The edges are also smoother but not as smooth as those obtained with oxyacetylene-oxygen cutting. Both ferrous and nonferrous metals of moderate thickness can be cut in any position. Instead of oxygen, air is used in a process known as arc-air gouging. This is useful for cleaning the surfaces of steel castings, and it is generally faster and more economical than rough grinding or chipping.

Underwater arc cutting. Underwater arc cutting can be accomplished with any of the cutting processes: however, the arc-oxygen cutting process is much preferred. Electrode sides must be waterproofed by applying a coating of suitable plastic, and precautions must be taken to protect the diver-welder from the hazards of the electric current. The equipment used for underwater arc cutting is essentially the same as that used for arc cutting in air. However, the electrode holders used must be fully insulated, and direct current with straight polarity must be used to protect the electrode holder and metal parts of the diver's outfit from electrolytic corrosion.

Notes to the text.

1. since —так кaк, c тех fop как, co вpeмeни

2. in order to - чтобы

3. readily - легко

4. for the reason — no пpичинe