Weld defects, Mechanical Engineering

WELD DEFECTS

The common defects encountered in submerged arc welding are:

  • a. Slag inclusion
  • b. Porosity
  • c. Cracking of welds.

 

a). Slag Inclusion: Slag inclusion is the result of incomplete dislodging of each layer during multiphase welding.  Using Proper cleaning of each  pass, the defect can be avoided. Improper  wire positioning creates under cuts resulting in slag inclusion in those areas.

b). Porosity: Porosity in submerged arc welding occurs mainly due to the presence of contaminants in the metal surface or electrode and due to moisture pick up by the flux. In addition, the gases generated during welding may get entrapped in weld due to improper selection of process parameters such as excessive current, too high welding speed or excessive height of flux layer.

c). Cracking: The main factor in promoting cracking in the weldment is the chemical composition of the steel itself. If the steel is hardemable, cracking  can be avoided by proper selection of preheat and by controlling the hydrogen level during welding. Cracking may also occur due to susceptibility of the material to hot shortness.

This defect is mainly associated with the sulphur content in the weld and can be controlled by the adjustment of manganese content in the flux. The other major cause of cracking could be due to the external restraints forced on to the joint during cooling. In general, the weld metal cracking can be avoided by proper selection of current, voltage and travel speed to yield a weld deposit with a bead formation factor, that is bead width to depth ratio around 3:2.

Posted Date: 9/14/2012 7:20:46 AM | Location : United States






Your posts are moderated
Related Questions
Ratio of applied stress: What should be the ratio of applied stress, s, to yield stress s Y in a large thin plate so that plastic spread along lint of crack is equal to  1 /1

Schedule Evaluation Each continuations of a partial schedule that are produced in step 1 are ranked as per to their respective cost function. This cost function might be dissim

Define Inversion of a mechanism ? Illustrate in detail about any three of the Inversions of the single slider crank chain Mechanism. (a) What do you understand by Degree of Free

Obtain the closed loop transfer function of the system shown:

(a) What do you mean by machinibility ? Discuss the factors which come into play while evaluating the machinability of any metal. Also describe machinability index. (b) Brass co

Calculate pressure on each side of spherical ball : Heavy spherical ball of weight W rests in V shaped trough whose sides are inclined at the angles and to the horizontal

Flight of the Bumblebee Railroad train T a leaves station A at a uniform speed of 30mph toward station B. Train Tb leaves station B at a uniform speed of 20mph toward station

Constructive Solid-Geometry Methods (CSG) Constructive models represent a solid as a combination of primitive solids. This modeling technique combine the volumes occupied by ov

An internal wheel B with 80 teeth is keyed to shaft F. A fixed internal wheel with 82 teeth is concentric with B. A compound wheel DE gear with two internal wheels, D has 28 teeth

Derive steady flow energy equation?Also give applications of steady of steady flow energy mathematical equation?