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Shielded metal arc welding (SMAW)

SMAW

The Process:-

Shielded metal arc welding (SMAW) is a process that melts and joins metals by heating them with an arc established between a sticklike covered electrode and the metals, as shown in Figure below. It is often called stick welding. The electrode holder is connected through a welding cable to one terminal of the power source and the workpiece is connected through a second cable to the other terminal of the power source (Figure a). The core of the covered electrode, the core wire, conducts the electric current to the arc and provides filler metal for the joint. For electrical contact, the top 1.5 cm of the core wire is bare and held by the electrode holder. The electrode holder is essentially a metal clamp with an electrically insulated outside shell for the welder to hold safely. The heat of the arc causes both the core wire and the flux covering at the electrode tip to melt off as droplets (Figure b). The molten metal collects in the weld pool and solidifies into the weld metal. The lighter molten flux, on the other hand, floats on the pool surface and solidifies into a slag layer at the top of the weld metal.
 
FUSION WELDING
SMAW
In short:- 
  •       An electric Arc struck between electrode and base metal joint
  •       Base metal melts under arc
  •       Electrode tip melts in drops and transfers to molten pool of base metal
  •       Electrode with Arc moves along the joint keeping constant arc length
  •       On cooling pool solidifies

Advantages and Disadvantages of SMAW:-

       The welding equipment is relatively simple, portable, and inexpensive as compared to other arc welding processes. For this reason, SMAW is often used for maintenance, repair, and field construction. However, the gas shield in SMAW is not clean enough for reactive metals such as aluminium and titanium. The deposition rate is limited by the fact that the electrode covering tends to overheat and fall off when excessively high welding currents are used. The limited length of the electrode (about 35 cm) requires electrode changing, and this further reduces the overall production rate.

Advantages:-
  •          Versatile
  •          Welding in all positions
  •          Areas of restricted access
  •          Wide variety of materials can be welded
  •          Material thickness above 3 mm
  •          Equipment: simple and light

Limitations:-
  •          Low productivity
  •          Automation not possible
  •          Dependent on welder skill
  •          Non-availability of Consumables for exotic material
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