2023 As the electrode extension is shortened the welding cur

20-23

As the electrode extension is shortened, the welding current decreases increases stays the same varies erratically When used a pure gases for welding ferrous metals may produce an erratic arc action, promote undercutting, and result in other flaws. oxygen carbon dioxide active gases argon and helium High gas flow rates provide better weld coverage. waste shielding gases decrease the venturi effect decrease contamination When CO_2 is being used as a shielding gas and the voltage is set near the maximum, excessive spatter may occur the welding arc may become too short to control arc below the electrode wire may begin to feed erratically the weld penetration will burn through the plate

Solution

20.Current remains constant.The SMAW process is constant current process with drooping VI characteristic.The arc voltage is dependent on arc length.So there is slight change in welding current with change in arc length but not with change in electrode extension

21.Argon and Helium:Pure argon produces a narrow and fingerlike weld, so it is easy to miss joints and fail to penetrate as deep as needed in the right direction.

22.all are true:if the gas flows out of the torch at too high a velocity, it leads to bouncing off the surface being welded and starts a swirling motion parallel to the torch cup called a venturi.venturi effect sucks air into the gas flow, creates an impure weld atmosphere. This results in pinholes in the weld.