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Extract A. Welding is one of the most important operations that are used in industry

Welding is one of the most important operations that are used in industry. Many parts of machines, automobiles, airplanes, ships and buildings are welded.

In order to join two metal pieces it is necessary to soften them with heat and then to press, hammer or fuse them together. The most widely used method of welding is electric arc welding where the workpieces are joined by means of electricity at the temperature of about 7,232 õF. This is the hottest heat that can be obtained for engineering purposes.

In electric arc welding two workpieces are welded by an electric arc. In order to create the arc a powerful electric current should be provided. The current must be at least 60A and for thicker workpieces it may be 250A or more.

To supply the current it is necessary to use a transformer. The latter must be switched on to strike the arc. To join the workpieces the electrode must brush against the workpiece at 80õ to its surface. As a result current flows between the electrode and the workpiece the tip of the electrode melts and falls onto the workpiece. Thus a joint is created.

It is essential to hold the electrode approximately 4 mm from the surface of the workpiece. One should not leave the electrode too long in the same position because it will become attached to the workpiece. The electrode must be moved across the joint continuously backwards in a straight line. However, if it is moved too quickly neither the electrode nor the workpiece will melt.

And it is important to remember that to weld plates by an electric arc is quite dangerous. In order to protect yourself you should follow certain safety rules. For example, it is absolutely necessary to wear overalls with long sleeves, gloves, an apron, a cap and rubber boots. A mask or helmet is used to protect the face and especially eyes from sparks.

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