Figure 3-2. - 0xyfuel gas welding (OFW).

source is called a welding machine or simply, a welder. This should not be confined with the same term that is also used to describe the person who is performing the welding operation. The welder (welding machine) is either electric- or motor-powered. In the Naval Construction Force (NCF), there are two main types of arc-welding processes with which you should become familiar. They are shielded metal arc welding and gas shielded arc welding.

Shielded Metal Arc Welding (SMAW)

Shielded metal arc welding (fig. 3-3) is performed by striking an arc between a coated-metal electrode and the base metal. Once the arc has been established, the molten metal from the tip of the electrode flows together with the molten metal from the edges of the base metal to forma sound joint. This process is known as fusion. The coating from the electrode forms a covering over the weld deposit, shielding it from contamination;

Figure 3-3.-Shielded metal arc welding (SMAW).

therefore the process is called shielded metal arc welding. The main advantages of shielded metal arc welding are that high-quality welds are made rapidly at a low cost. You will learn more about shielded metal arc welding in chapter 7.

Gas Shielded Arc Welding

The primary difference between shielded metal arc welding and gas shielded arc welding is the type of shielding used. In gas shielded arc welding, both the arc and the molten puddle are covered by a shield of inert gas. The shield of inert gas prevents atmospheric contamination, thereby producing a better weld. The primary gases used for this process are helium, argon, or carbon dioxide. In some instances, a mixture of these gases is used. The processes used in gas shielded arc welding are known as gas tungsten arc welding