Shielded Metal Arc Welding: Working, Advantages, Disadvantages and Applications

Shielded Metal Arc Welding

The shielded metal arc welding (SMAW) is a type of electric arc welding in which coalescences of metals is produced by heat from an electric arc created between the tip of a consumable electrode and the surface of the base material at point of welding.

The shielded metal arc welding (SMAW) is also known as manual metal arc welding (MMAW), flux shielded arc welding or stick welding. The shielded metal arc welding is a manual arc welding process which uses a consumable electrode coated in flux to lay the weld. An electric current, either AC or DC, is used to create an electric arc between the coated electrode and metals to be welded. As the weld is laid, the flux coating of the electrode disintegrates, giving off vapors that serve as a shielding gas and forming a layer of slag, both of which protect the weld area the atmospheric contamination.

Working of Shielded Metal Arc Welding

In case of shielded metal arc welding, in order to strike the arc, the electrode is brought into contact with the workpiece by a very light touch of the electrode to the base metal and then pulled back slightly. This process initiates the electric arc and hence, the metaling of the workpiece and the consumable electrode. This causes droplets of the electrodes to be passed from the electrode to the weld pool.

During the welding process, the coated electrode melts, thus the flux covering it disintegrates producing shielding gases and molten slag that covers the filler metal, both of which protect the weld area from the oxygen and other atmospheric gases. As the slag floats on the surface of the weld pool and protects the weld from contamination as it solidifies. Once the slag is hardened, it must be chipped away to reveal the finished weld.

As the welding progresses and the electrode melts, the welder must periodically stop welding to remove the remaining electrode stub and insert a new electrode into the electrode holder.

Advantages of Shielded Metal Arc Welding

The advantages of the shielded metal arc welding (SMAW) are as follows −

• The shielded metal arc welding is a versatile welding process, i.e. this method can be used for welding of various metals.

• The equipment used for shielded metal arc welding is cheap and simple.

• Shielded metal arc welding is suitable for outdoor applications.

Disadvantages of Shielded Metal Arc Welding

The disadvantages of the shielded metal arc welding are given as follows −

• With this welding method, the welding process is discontinuous as the electrode needs to be replaced.

• Fumes produced make the welding process control difficult.

• With the SMAW, the weld may contain slag inclusions.

Applications of Shielded Metal Arc Welding

The shielded metal arc welding is used in the following applications −

• For welding processes in the maintenance and repair industry.

• Used in the construction of the steel structure and in industrial fabrication.

• Used to weld iron and steel (including stainless steel).

• Also used to weld aluminium, nickel and copper alloys.