Why is SMAW referred to as a “shielded” process?
Because the workpiece is enclosed in a protective shield.
Because the electrode coating vaporizes to form a protective gas shield.
Because it requires an external gas shield.
Because the electrode itself is made of shielding metal.
The correct answer and explanation is:
The correct answer is:
Because the electrode coating vaporizes to form a protective gas shield.
Explanation:
Shielded Metal Arc Welding (SMAW), commonly known as stick welding, is referred to as a “shielded” process because the electrode coating vaporizes when heated by the arc, creating a protective gas shield around the weld area. This shield prevents contamination from the surrounding air, particularly from oxygen and nitrogen, which can negatively affect the quality of the weld. The electrode itself is made up of a core of metal, but its outer coating, usually composed of various materials like cellulose, potassium, and other compounds, serves as the key to shielding.
When the arc forms between the electrode and the workpiece, the intense heat causes the coating to break down. This releases gases, such as carbon dioxide, hydrogen, and water vapor, which form a barrier around the molten weld pool. This barrier protects the weld from atmospheric contaminants like oxygen and nitrogen, which can cause defects such as porosity, brittleness, and oxidation. Additionally, the coating forms a slag that covers the completed weld, further protecting it as it cools and solidifies.
Unlike processes like Gas Tungsten Arc Welding (GTAW) or Gas Metal Arc Welding (GMAW), which use an external gas supply (such as argon or carbon dioxide), SMAW relies solely on the vaporization of the electrode coating to generate the protective atmosphere. This is why it is considered a “shielded” process and makes SMAW versatile for various outdoor applications, where external shielding gases might be difficult to control.