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
Q. Explain Machining allowance? Machining allowance or finish allowance indicates how much larger the rough casting should be over the finished casting to allow sufficient mat


Explain Hard or Fixed Automation Mechanical controls consist of numbers of mechanism that create the required relative motion to complete an activity. These mechanisms include:

The tapered, two-cell beam is subjected to a pure torque of 50,000 in-lb counter clockwise. The length of the beam (normal to the figure) is 100 in. The flange areas are 1 sq in an

Describe vortex flow and derive mathmetical equation Z= w 2 r 2 /2g for forced vertex flow ω= angular velocity z= height of parabola r= radius of parabola

m=4.9Kg, K=3694 N/m, x=0.013m. I have this much details, now I want to find the damping constant ''b''. I hv tried so much, but this question needs damping ratio ''zeta'' or damped

what is critical pressure, triple point, degree of super heat...

How many types of Foundations are there Foundations are broadly classified into two types, viz., shallow and deep foundations with respect to  the width (B) and depth (D) below


a) Describe and illustrate the terms with their classification: Mechanism, Kinematic, Machine links and Kinematic pair. b) Discuss the Inversions of double slider crank chain an