25-27 Which of the following gases is the least dense? Oxygen Carbon dioxide arg

Question

25-27

Which of the following gases is the least dense? Oxygen Carbon dioxide argon Helium What can be done to counteract the loss of certain alloying elements such as chromium, vanadium, aluminum, titanium, manganese or silicon? Do not use oxygen in the shielding gas. Use less oxygen in the shielding gas. add a deoxidizer to the shielding gas. Add a deoxidizer to the filter wire. The only difference between all GMA welding machines and some FCA welding machines is that all GMA welding machines must have a. cooling water system shielding gas solenoid air cooling fan power contractor to start and stop the current

Explanation / Answer

25: d Helium

26. b Use less Oxygen in the sheilding gas.

Oxygen causes oxidation of the weld, so it is not suitable for welding aluminium, magnesium, copper, and some exotic metals. Increased oxygen makes the shielding gas oxidize the electrode, which can lead to porosity in the deposit if the electrode does not contain sufficient deoxidizers. Excessive oxygen, especially when used in application for which it is not prescribed, can lead to brittleness in the heat affected zone.

27. d : Power Contractor to start and stop the current

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