Question 64 3AE02 - Third Assistant Engineer (Alt)

The Correct Answer is B **Explanation for Option B (reduce oxidation):** The flux coating on an arc welding electrode (especially Stick/SMAW) serves multiple critical functions, but its primary chemical role is to protect the molten weld pool from contamination by atmospheric gases (oxygen and nitrogen). When the electrode is consumed, the flux melts and decomposes, creating a gaseous shield around the arc and the weld puddle. Simultaneously, it forms a liquid slag that floats atop the molten metal. This slag solidifies after the weld is complete, preventing atmospheric gases from reaching the hot, newly deposited metal until it cools below the temperature where rapid oxidation can occur. By excluding oxygen, the flux prevents the formation of oxides and nitrides, which would weaken the weld and cause porosity. **Explanation for Incorrect Options:** * **A) reduce metal fatigue and warpage:** While proper welding procedures and techniques (like pre-heating or peening) are used to manage distortion (warpage) and residual stress (which affects fatigue), the flux itself does not directly reduce these mechanical issues. It is a chemical and metallurgical shield, not a physical stress reliever. * **C) increase heat transfer:** The flux actually *decreases* heat loss from the molten pool (it acts as an insulator via the slag) but does not significantly increase the heat transfer *into* the weld. The heat is generated by the electrical resistance across the arc. * **D) control penetration:** Penetration is primarily controlled by the amperage (current), arc length, travel speed, and electrode angle. While certain flux ingredients can slightly influence the fluidity of the molten pool, the flux's main purpose is chemical protection, not physical control over the depth of penetration.