Defects involving inadequate bonding, Mechanical Engineering

Assignment Help:

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.


Related Discussions:- Defects involving inadequate bonding

Explain applications welding process, Applications. The  welding  process ...

Applications. The  welding  process  finds  widespread  applications  in almost all branches of industry and construction. fabrication and creation of steel structures

Key words related to railway line, Keywords related to railway line: ...

Keywords related to railway line: Railway Station : A facility along a railway line where trains stop and passengers are serviced, and cargo is handled. Platform : A fa

Estimate what fraction of heat loss by the fin, A tube assembly constructed...

A tube assembly constructed of Cu with an inside diameter of 1.25 cm, wall thickness of 0.8 mm and circumferential fins around the periphery. The fins have thickness of 3 mm, and a

Boiler classification, BOILER CLASSIFICATION : (1 )  According to Tub...

BOILER CLASSIFICATION : (1 )  According to Tube Contents:   Boilers can be water tube or fire tube type. In water tube boilers water flows in tubes and in Fire Tube Boilers h

Calculate the primary voltage and real power measurements, Question: A ...

Question: A 7.2kVA single phase 50Hz, 480Vrms: 240Vrms transformer can be modelled using the primary referred approximate equivalent circuit shown in Figure 1 below. Fi

Thermodynamic equilibrium - thermodynamics, Thermodynamic equilibrium - The...

Thermodynamic equilibrium - Thermodynamics: Equilibrium is the state of a system in which the state does not undergo any change in itself with the passage of time without the

Vibration damping and size-factors in clutch design , Vibration Damping : ...

Vibration Damping : Suitable mechanism should be incorporated within the clutch to eliminate (to reduce it drastically) noise produced in the transmission. Size : The size of

Working principle of the petrol engine, W orking Principle of the Petrol E...

W orking Principle of the Petrol Engine: OTTO CYCLE     5-1 Suction Stroke 1-2 Adiabatic Compression Stroke 2-3 Heat Addition at the constant Volume.

Boiler, What is scale formation in case of a boiler

What is scale formation in case of a boiler

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd