Welding – Conceptual approach Part - II
#01. In graphite electrodes, in case of carbon arc welding, to prevent oxidation electrodes are coated with ___________________?
To prevent oxidation incase of carbon arc welding electrodes are coated with copper.
#02. What are the factors that determine selection of electrodes?
The factors that determine selection of electrodes are – availability of ac or dc current, composition of base metal, thickness of base metal, welding position, expected physical properties of welded joints, use of electrodes for a particular or specific conditions.
#03. What are carbon electrodes?
These electrodes are used in carbon arc welding and cutting. They are available in two varieties i.e. carbon electrodes and graphite electrodes. Bare carbon and graphite electrodes become hot during welding due to resistance offered by the material to flow current. Their hot surface starts oxidizing by coming in contact with atmosphere and leads to reduction in electrode size. To prevent this copper coating is used.
#04. How electrodes are specified?
According BIS (Bureau of Indian Standards), electrodes are specified by six digits. In the specification first digit shows particular type of covering, second digit shows welding position, third digit shows particular current conditions, fourth digit says about minimum tensile strength of the weld metal, fifth digit shows the percentage elongation of deposited weld metal in tensile testing and last sixth digit shows impact value of weld metal.
#05. What is TIG welding?
TIG Welding stands for Inert Gas Tungsten Arc Welding. It is basically an arc welding process in which the arc is struck between a non-consumable tungsten electrode and the base metal. In this welding a special type of electrode holder is used that carries a passage around electrode for the flow of inert gas to provide the protective shield. It is suitable for the welding of metals that have very low melting point.
#06. What are applications of TIG Welding?
Its specific applications includes welding of Al-alloys, Mg-alloys, Nickel alloys, Zirconium alloys, Titanium alloys, beryllium alloys, refractory metals, carbon steels, alloy steel and stainless steel.
#07. In TIG Welding which current (ac or dc) is used for the welding of aluminum, magnesium or beryllium?
AC current enables good penetration and less surface oxidation hence preferred for case of weld mention in question.
#08. Why DC with straight polarity is least used?
This is because dc provides less penetration, enables flat and wide bead and needs maximum skill. A specific advantage associated with it is that it enables better removal of oxides from work surface.
#09. What is MIG Welding?
MIG Welding is known as Metal inert Gas welding, and it involves welding of metals using a consumable metal electrode in an inert atmosphere. The arc is struck between the metal electrode and the work-piece. The electrode is in the form of a continuous wire which is fed into the arc, by the adjustable speed electric motor, at the same speed at which it is melted and deposited in the weld. A specially designed electrode holder is used which, in addition to a passage for wire electrode, also incorporates passage for supply of inert gas for shielding of electrode, molten weld metal, arc and adjacent hot area of base metal from atmospheric contamination.
#10. Which type of current is used in MIG Welding?
In case of MIG welding dc with reverse polarity is used. Use of dc with reverse polarity provides a deeper penetration and a clean weld surface.
Join Our Group : SSC/DRDO/NTPC/RRB
Follow us @ Facebook For Practice Question
