Answer:
When used as pure gases for welding ferrous metals, argon and helium may produce an erratic arc action, promote undercutting, and result in other flaws.
Explanation:
Argon and Helium is belongs to noble gas. Since novel gases are completely filled outer orbital. therefore they are erratic nature. Hence, noble gas are very stable as it neither except electron nor it denote due to it paired of electronic configuration.
Depending on the materials being welded, these atmospheric gases react with welding area and either it reduces the quality of the weld or make the welding more difficult.
Therefore, to protect welding area from atmospheric gases noble gases which are small in size are used.
Thus, argon and helium are used as pure gases during welding ferrous metals.
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