Question

Question 05
(a) i) What are the three type of general defects in welding?
ii) Explain each of them.
iii) State the significance of each defect on the quality of welding.
(b) i) What are the three basic categories of inspection and testing techniques used for welding inspector?
ii) Name some typical inspections and/or tests in each category.
(c) i) Distinguish between soldering and brazing.
ii) What is the purpose of a flux in soldering?
  iii) Under what circumstances would brazing be selected rather than soldering?
iv) What filler metals are generally used in brazing?
(d) i) Explain the procedure for the adhesive application.
ii) What are some of the methods used to cure adhesives?
iii) How does mechanical assembly differ from the other methods of assembly?
iv) What is the technical difference between a screw and a bolt?

Answer 1

a.I. The three type of general defects in welding are

1. External welding defects

2. Internal welding defects

3. Incomplete penetration

II. External welding defects - Defects occur on the upper surface of weld work. There are different types of defects occur in this defect type here i will explain one of the type i.e Weld crack

Weld crack-  Welding cracks can be present at the surface, inside of the weld material or at the heat affected zones.

Causes Of Weld Crack:1. Poor ductility of the given base metal.
2. The presence of residual stress can cause a crack on the weld metal.
3. The rigidity of the joint which makes it difficult to expand or contract the metals.

Remedies for Weld crack:1. Using appropriate materials may decrease the chances of crack.
2. Preheating the weld and reducing the cooling speed joint helps in reducing crack.
3. Reduce the gap between the weld joints by using reasonable weld joints.

Internal welding defects - Defects occur under the surface of weld work. There are different types of defects occur in this defect type here i will explain one of the type i.e Slag Inclusion

Slag Inclusion - If there is any slag in the weld, then it affects the toughness and metal weldability of the given material. This decreases the structural performance of the weld material.

Causes Of Slag:1. Slag is formed if the welding current density is very small, as it does not provide the required amount of heat for melting the metal surface.
2. If the welding speed is too fast then also slag may occur.
3. If the edge of the weld surface is not cleaned properly then also slag may form.

Remedies for Slag Inclusion:1. Increase the current density
2. Adjust the welding speed so that the slag and weld pool do not mix with each other.
3. Clean the weld edges and remove the slags of previous weld layers

III. The significance of each defect on the quality of welding is very important. For example defects in a bead greatly affect not only appearance but also strength. This means that appearance defects such as pits, undercut, overlap, insufficient reinforcement, surface cracking, bead meandering, remaining groove and arc strike directly represent defects in welding quality.

b.I. The different types of inspection of welding are

X-ray Inspection - X-ray inspection is a critical, non-destructive evaluation method allowing the inspector to see the inside and underside of welded materials, according to Weld Procedures. Recorded on radiographic film, x-ray readings give the inspector a clear indication of how durable and well-constructed welded materials are well beyond what can be viewed with the naked eye.

Ultrasonic Inspection - Ultrasonic inspection uses audio waves to test for proper echoing and vibration within welded pipe, according to Weld Procedures. Essential methods of non-destructive inspection, ultrasonic waves are generated into the pipe to match the density and length of the materials being tested.If an inspector notes any abnormalities in sound wave frequency such as hearing reflected sound in the a portion of the pipe where no echo should be heard it may be grounds for rejecting the weld.

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