Welding cable connector Welding cable  Generator Electrode holder Ground cable Metal being welded Ground cable connector 5-3 Figure 5-3.  Stick welder–Shielded Metal Arc Welder (SMAW). Figure 5-2. Typical arc welding circuit.  Low-voltage, high-current DC is typically used with GMAW  welding.  Figure 5-5  shows the equipment required for a  typical MIG welding setup.  The molten flux covers the weld and hardens to an airtight slag that protects the weld bead as it cools. Some aircraft  manufacturers, such as Stinson, used this process for the  welding of 4130 steel fuselage structures. This was followed  by heat treatment in an oven to stress relieve and normalize  the structure. Shown in  Figure 5-3  is a typical arc welding  machine with cables, ground clamp, and electrode holder. This method of welding can be used for large volume  manufacturing and production work; it is not well suited to  repair work because weld quality cannot be easily determined  without destructive testing.  Figure 5-6  depicts a typical power  source used for MIG welding. Gas metal arc welding (GMAW) was formerly called gas  inert gas (MIG) welding. It is an improvement over stick  welding because an uncoated wire electrode is fed into and  through the torch and an inert gas, such as argon, helium,  or carbon dioxide, flows out around the wire to protect the  puddle from oxygen. The power supply is connected to the  torch and the work, and the arc produces the intense heat  needed to melt the work and the electrode.  [Figure 5-4] Gas tungsten arc welding (GTAW) is a method of electric arc  welding that fills most of the needs in aircraft maintenance  and repair when proper procedures and materials are used. It  is the preferred method to use on stainless steel, magnesium,  and most forms of thick aluminum. It is more commonly  known as Tungsten Inert Gas (TIG) welding and by the trade  names of Heliarc or Heliweld. These names were derived  from the inert helium gas that was originally used. The first two methods of electric arc welding that were  addressed used a consumable electrode that produced the  filler for the weld. In TIG welding, the electrode is a tungsten  rod that forms the path for the high amperage arc between it  and the work to melt the metal at over 5,400 °F. The electrode  is not consumed and used as filler so a filler rod is manually  fed into the molten puddle in almost the same manner as  when using an oxy-acetylene torch. A stream of inert gas,  such as argon or helium, flows out around the electrode and  envelopes the arc thereby preventing the formation of oxides  in the molten puddle.  [Figure 5-7] Gas Tungsten Arc Welding (GTAW) Gas Metal Arc Welding (GMAW)