Which of the following is NOT kept out of the weld area by shielding gas when the flux melts?

The correct answer is that metal oxides are not kept out of the weld area by shielding gas when the flux melts. In welding processes that use flux, such as flux-cored arc welding, the flux serves to protect the molten weld pool by creating a barrier to contaminants, notably oxygen and moisture from the air, which can lead to defects in the weld.

Metal oxides are typically a natural component of the base materials being welded, or they can form during the welding process as a result of the reaction of the molten metal with contaminants. Since metal oxides are often already present in the materials being welded, they cannot be excluded from the weld area solely by the application of shielding gas. The shielding gas primarily works to prevent unwanted atmospheric gases from interacting with the heated base and filler metals during the welding process, rather than excluding materials that are already part of the workpieces.

On the other hand, the remaining contaminants like oxygen, dirt, and airborne contaminants are adequately addressed by the shielding effect of the gas. The presence of these other elements in the weld area can lead to issues such as porosity, inclusions, and weakened weld joints, highlighting the importance of effective shielding during welding operations.