Welding speed is the linear rate at which the arc moves with respect to plate along the weld joint. Welding speed generally conforms to a given combination of welding current and arc voltage. If welding speed is more than required • Heat input to the joint decreases. • Less filler metal is deposited than requires, […]

Weld quality, and weld deposition rate both are influenced by various welding parameters and joint geometry. These parameters are the process variables as given below : 1. Welding current 2. Arc Voltage 3. Welding speed. 4. Electrode Feed rate 5. Electrode extension (stick-out) 6. Electrode diameter 7. Joint geometry. Each of the above parameters affects, […]

General Controlling Parameters • Most structural metals and their alloys form a cold cathode, its area is small but large quantities of energy are generated to release the electrons needed to support an arc. • High m. p. materials like carbon, tungsten and molybdenum easily supply electrons to sustain the arc due to their temperature. […]

• This technique is an alternative of dip transfer for welding in positions and when thin plates are to be welded. This type of transfer is shown in Fig. 3.21 (a) and (b). Fig. 3.21 (a) Output current wave form of the pulsed current power supply; Metal transfer sequence is also shown Low-current arc keeps […]

• Helium, although inert gas, does not produce axial spray transfer. The transfer is globular with both polarities at all current levels. • Helium arcs are useful, nevertheless, because they provide deep penetration. • Spray transfer can be obtained by mixing small quantities of Argon (about 20 per­cent). With helium, the deep penetration is still […]

3.8.1 Metal Transfer • Shielded metal arc welding processes are used extensively since filler metal is depos­ited more efficiently and at higher rates than is possible with other processes. • For better efficiency, the spatter losses should be reduced to minimum and uncon­trolled short circuits between the electrode and work should be avoided. • Metal […]

3.7.1 Introduction • For all practical purposes a welding arc may be regarded as a gaseous conductor which converts electrical energy into heat. • Arc is a heat source for many welding processes because it produces heat at HIGH INTENSITY. The heat can be easily controlled by controlling the electrical parameters. • In welding, the […]

Welding energy sources can be grouped into the following five categories: — Electrical sources — Chemical sources — Optical sources — Mechanical sources — Solid state sources. Of the above sources, electrical sources of energy are more commonly used. Arc and resistance welding will now be highlighted in the following paragraphs. 3.6.1 Arc Welding • […]

The following factors must be considered when selecting a power source for welding. 1. Initial cost. 2. Cost of periodic maintenance and repair. 3. Mains supply available: 220 V, 440 V or not available. 4. Steady output current even with input voltage fluctuation. 5. Whether machine causes imbalance in the power load. 6. Machine’s inherent […]

• Many modern arc-welding power supply units contain solid-state circuits for regulat­ing the output or replacing the reactors found in conventional systems, or in some cases, as a means of compensating for fluctuations in the mains output voltage. This provides a means of obtaining a stable and consistent operation of the arc in GMA Welding. […]