Welding variables-welding current,voltage,speed, Mechanical Engineering

WELDING VARIABLES

The following major process variable play an important role in shaping the weld bead and the resultant weld metal in submerged arc welding:

  • a. Welding current
  • b. Welding voltage
  • c. Welding speed
  • d. Electrode stick out or wire extension
  • e. Height of the flux layer
  • f. Joint design
  • g. Electrode polarity


Welding current


Is the most influential process variable. It controls the rate at which the electrode is melted, the depth of fusion and the amount of base metal melted. Excessively high current produces a digging arc and the weld joint may melt through the backing, causing burn through. Other side effects are high current undercuts, highly narrow weld seam and large Heat Affected Zone (HAZ). Too low a welding current produces an unstable arc in the cavity.

Welding voltage

 The welding voltage is a function of arc gap. This primarily determines the shape of the fusion zone and reinforcement. The High welding voltage produces a wider, flatter and less deeply penetrated weld. The wider bead increases the flux consumption and decreases the resistance to porosity caused by rust or scale. However, a wide bead can accommodate a poor joint fit up. Excessively high voltage produces a hat shaped bead which is prone to cracking. Low arc voltage produces a stiffer arc and improves the penetration in a deep groove joint. However, slag removal is poor in such cases. Excessively low voltages produce a high, narrow bead with poor bead shape resulting in very difficult slag removal.

Welding speed


The welding speed has an important influence on the weld bead size and penetration. Very high travel speeds decrease the welding action and increases the possibility of undercuts, arc blow, porosity and uneven bead shapes. Since welding speed, i.e. travel speed determines the amount of weld metal deposited per unit length of the weld, the bead shape is essentially controlled by the welding speed. Too low a travel speed increases the heat input into the weld, produces a heavy reinforcement and  causes slag inclusions. However porosity is advantageously reduced since sufficient time is permitted for the gases to escape into the atmosphere during  slag metal reactions.

Electrode stick out


Stick out or electrode extension plays an important role for current densities higher than 80,000 amps / sq. inch. The electrode stick out is the length of the wire extending beyond the tip of the contact tube upto the surface of the work piece. Higher stick out imparts resistance heating to the wire before it enters the arc, hence deposition rate is increased. Too high a stick out would soften the wire and stiffness of the wire would be lost at higher temperatures resulting in improper bead formation.

Posted Date: 9/14/2012 7:11:33 AM | Location : United States







Related Discussions:- Welding variables-welding current,voltage,speed, Assignment Help, Ask Question on Welding variables-welding current,voltage,speed, Get Answer, Expert's Help, Welding variables-welding current,voltage,speed Discussions

Write discussion on Welding variables-welding current,voltage,speed
Your posts are moderated
Related Questions
#question calculate bending force

What is the spindle and drill The spindle and drill head assembly the taper hole can be create on radial drilling machine with some special attachment likewise quill(The spindl

Explain the autoignition and detonation theory of detonation. What do you mean by preignition ? Describe octane Rating of a fuel. What are the different S.I. engine combustion cham

Find out ratio of  upper end area to lower end area  of bar of uniform strength Sol : The figure given to us shows a bar subjected to external tensile load P. If bar had be

Resultant force with the help of moments: How do you find the position of resultant force with the help of moments? Sol.: At first find the magnitude and direction of t

extraction of refractories

Q. What do you understand by Binders? Binders used in a foundry are : Inorganic and organic binders. Organic binders used for core making and will be discussed later. Clay b

Evaluate the Support required by body on plane: A body having weight 50KN rests in limiting equilibrium on rough plane, whose slope is 30º. The plane is raised to a slope of

A pelton wheel works at the foot of a dam because of which the head available at the nozzle is 400m. The nozzle diameter is 160mm and the coefficient of velocity is 0.98. The diame

Question The three freight cars are rolling along the horizontal track with the velocities shown in the Figure. After the impacts occur the three cars become coupled together a