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
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.

Q. Use of high temperature materials in Furnaces? Often, furnace tubing and refractory protected membrane walls are fabricated from plain carbon steel with a minimum of 0.25% c

Determine couple - Homogeneous cylinder: Homogeneous cylinder having weight W rests on horizontal floor in contact with wall (Fig ure given below ). If the coefficient of

what is blow hole defect ?

Necessity of Electrical System Lights and horn for safe riding of vehicle even at night. Electricity for ignition of fuel in the engine. Battery Charging.

Edge joints: The flanged edge joint is suit- able for plate 1/4 inch or less in thickness and can only sustain light loads. Edge preparation for this joint may be done.

Human Factor : The human factor is the key factor in the success of CAD system. This concerns the training of the designer or the engineer without whom the CAD system become

RECTIFIER TYPE POWER SOURCES The next popular power sources are of rectifier type. Three phase transformer (step down) connected to a rectifier to give DC output is the simple

determine the shear force and bending moments of 4KN fprce

Deliverables: A QFD chart, showing the relationships between the customer requirements and the engineering specifications. (Refer to the Ullman QFD chart posted on My