Defects involving inadequate bonding, Mechanical Engineering

Defects Involving Inadequate Bonding


Lack of fusion

Involves lack of complete melting and fusion of some portion of the weld metal in a joint. It may occur either between parent metal and weld metal or between two layers of weld metal. This can occur in fusion welding and pressure welding. The following are the reasons for incomplete fusion:

  • Improper manipulation of electrodes
  • Incorrect position of electrodes
  • Low welding current
  • Too rapid arc advance
  • Improper joint fit up
  • Improper edge cleaning of slag after flame cutting
  • Impurities on the face of the joints in the case of pressure welding.

 


If lack of internal fusion is severe it is considered to be a serious defect. Incomplete fusion at the surface is of more serious consequence. As lack of fusion in the form of incomplete penetration of unbevelled or bevelled joints is not always revealed by radiography, ultrasonic examination is recommended as a supplementary test when lack of fusion is suspected.

 Incomplete penetration

This is incomplete penetration of the weld through the thickness of the joint. This usually occurs at the root of the weld or between the deposits made from both sides of a joint. In double welded joints lack of penetration may occur within the wall thickness as a 'buried' defect. Incomplete penetration at the root is more severe. The reasons are:

  • Incorrect joint design.
  • Improper welding parameters, particularly current.
  • Incorrect electrode size.
  • Incorrect polarity where DC is used.

 


Inadequate joint penetration is not tolerated to any extent in objects which are subjected to either tension or bending stresses. It can initiate brittle fracture under either static or dynamic loads. The unfused root causes stress concentration which could lead to failure without deformation and cracks are initiated from the unfused root. Lack of fusion and incomplete penetration are not permitted by pressure vessel code. This type of defects are easily detected by ultrasonic or radiography. In case of thin ferrous welds, magnetic particle examination can be used.

Posted Date: 9/17/2012 9:02:34 AM | Location : United States







Related Discussions:- Defects involving inadequate bonding, Assignment Help, Ask Question on Defects involving inadequate bonding, Get Answer, Expert's Help, Defects involving inadequate bonding Discussions

Write discussion on Defects involving inadequate bonding
Your posts are moderated
Related Questions
1. Production Capacity : Machines idled by breakdowns cannot produce thus the capacity of the systems is reduced. 2. Production cost: Labor costs per unit rise beca

Q. Explain about Fired Heaters and Combustion Engines? Fired heaters and combustion engines shall normally be located at a safe distance from hazardous areas as they provide po

Determine the reaction at specific points: A light rod AD can be supported by frictionless pegs at B and C and rests against frictionless wall at A as shown in th

Q. Scope of Materials for sulfuric acid service? This Engineering Practice presents materials of construction commonly used in Sulfuric Acid service. The corrosiveness of sulfu

Angle of Repose(α): It is the maximum angle of inclined plane on which body tends to move down the plane because of its own weight. Consider the equilibrium of body when body

A fictious force or pseudo force is an imaginary force that acts on a body in non inertial frame. it is opposite in direction of accelaration of non inertial frame.

Determine the minimum critical Euler axial compression force,  Pcr and the minimum critical Euler axial compression stress, cru, for the column below which is pinned at the top and

A double shoe brake as shown in the figure is capable of absorbing a torque of 1400 N-m. The diameter of the brake drum is 350mm and the angle of contact of each shoe is 100°. If t

Determine elongation because of self weight of tapering rod: Sol.: Take a tapering rod hung vertically and firmly fixed at top position. The rod is of length L tapers unifor

In motorcycle servicing we studied about various service tips for motorcycle servicing. These steps will ensure proper servicing of motorcycle and as a result customers will trust