As a non-consumable electrodes tungsten or carbon electrodes can be used. In gas-tungsten arc welding a tungsten electrode is used in place of the metal electrode used in shielded metal-arc welding. A chemically inert gas, such as argon, helium, or carbon dioxide is used to shield the metal from oxidation. The heat from the arc formed between the electrode and the metal melts the edges of the metal. Metal for the weld may be added by placing a bare wire in the arc or the point of the weld. This process can be used with nearly all metals and produces a high-quality weld. However, the rate of welding is considerably slower than in other processes.
Gas-Metal Arc
In gas-metal welding, a bare electrode is shielded from the air by surrounding it with argon or carbon dioxide gas and sometimes by coating the electrode with flux. The electrode is fed into the electric arc, and melts off in droplets that enter the liquid metal of the weld seam. Most metals can be joined by this process.
Submerged Arc
Submerged-arc welding is similar to gas-metal arc welding, but in this process no gas is used to shield the weld. Instead of that, the arc and tip of the wire are submerged beneath a layer of granular, fusible material that covers the weld seam. This process is also called electroslag welding. It is very efficient but can be used only with steels.
Resistance Welding
In resistance welding, heat is obtained from the resistance of metal to the flow of an electric current. Electrodes are clamped on each side of the parts to be welded, the parts are subjected to great pressure, and a heavy current is applied for a short period of time. The point where the two metals touch creates resistance to the flow of current. This resistance causes heat, which melts the metals and creates the weld. Resistance welding is widely employed in many fields of sheet metal or wire manufacturing and is often used for welds made by automatic or semi-automatic machines especially in automobile industry.
Vocabulary
gas-tungsten
inert
edge
bare
rate .
gas-metal arc
considerably ,
surrounding
carbon dioxide
droplet
liquid ,
beneath , ,
layer
weld seam
resistance
clamp ,
sheet
fusible
granular
semi-automatic
to create
to submerge
General understanding:
1. What is the difference between the arc-welding and non-consumable electrode arc welding?
2. What are the disadvantages of the non-consumable electrode arc welding?
3. How is electrode protected from the air in gas-metal arc welding?
4. What is submerged arc welding?
5. What is the principle of resistance welding?
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6. Where is semi-automatic welding employed?
Exercise 6.2. Translate into English:
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Exercise 6.3. Translate into Russian:
1. In resistance welding, heat is obtained from the resistance of metal to the flow of an electric current.
2. The heat from the arc melts the edges of the metal.
3. A bare electrode is shielded from the air by surrounding it with argon or carbon dioxide gas.
4. Submerged-arc welding is similar to gas-metal arc welding.
5. Electrodes are clamped on each side of the parts to be welded.
6. Resistance causes heat which melts the metals and creates the weld.
