Mechanical Engineering - Workshop Technology - Discussion

The correct answer is alternating current (AC) is used.

When TIG (Tungsten Inert Gas) arc welding copper alloys, alternating current (AC) is typically used. This is because AC provides several benefits, including:

- Better cleaning action: AC helps to remove oxidation and other surface contaminants from the copper alloy, resulting in a cleaner weld.
- Reduced porosity: AC helps to reduce porosity in the weld by providing a more consistent and controlled arc.
- Improved weld penetration: AC allows for better weld penetration, especially in thicker sections of copper alloy.

Direct current (DC) with straight polarity (DCEP) or reversed polarity (DCRP) is not typically used for welding copper alloys with TIG, as it can lead to:

- Poor arc stability.
- Increased porosity.
- Reduced weld penetration.

AC, on the other hand, provides a more stable and controlled arc, making it the preferred choice for welding copper alloys with TIG.

DCSP - ELECTRODE NEGATIVE, WORK POSITIVE.
DCRP- ELECTRODE POSITIVE, WORK NEGATIVE.

DURING TIG WELDING -

DCRP CANNOT BE USED AS ELECTRONS WILL FLOW FROM WORK TO ELECTRODE AND WILL HEAT THE ELECTRODE UNNECESSARILY. DCSP CANNOT BE USED FOR ALUMINIUM AND MAGNESIUM AS THERE WILL BE OXIDE FORMATION ON THE WORKPIECE WHICH DISRUPTS THE ELECTRIC ARC (because electrons will flow from electrode to workpiece).

So, for AL and MG only AC welding is used. For other materials, DCSP can be used such as FERROUS ALLOYS and COPPER ALLOYS as there oxides will not promotes further oxidation and will not disrupts the electric arc.

DCRP: The work piece is connected to negative terminal and electrode is connected to positive terminal. The heat generation of work piece is high. High melting point material are easily welded.

DCSP: The work piece is connected to positive terminal and electrode is connected to negative terminal.

DCRP is rarely used. Because it tends to melt the electrode. AC is used for All and Mg DCRP COPPER AND STAINLESS STEEL etc.

AC - used for non-ferrous metal except copper.

DC WITH STRAIGHT POLARITY - used for ferrous metal and also for copper.

DC with reverse polarity used for magnesium.

The AC is more versatile in welding for steel, cast iron, AL & Mg.

DCSP is used for all metals except alloys of Al and Mg, for Al and Mg either DCRP or AC supply is used.

Straight polarity is used for TIG welding.

Reverse polarity is used for ARC welding.

In this used only DC current & strait polarity used for thin base metal.

And strait polarity for thin and low melting base metals.