NARRATIVE - QUESTION AND ANSWER

1. What is the main reason for carrying out PQR?

- To show that the proposed welding joint has the properties to

satisfy the design requirement.

2. What is Essential Variables (Procedure)?

- A change in welding condition which will affect the mechanical

properties of the weldment and requires WPS re-qualification.

3. Give 5 Essential Variables.

a) parent metal f) filler metal (F-number and A-number)

b) welding position g) preheat temperature

c) travel speed h) welding process

d) amperage i) electrode stick out

e) voltage

4. Give 4 factors that contribute hydrogen induce cracking (HIC) in

C-Mn steel.

a) Hydrogen concentration.

b) Susceptible microstrucrture.

c) Residual stress cause by welding.

d) Ambient temperature.

5. What is the distinguishing features of lamellar tearing?

- step-like appearance.

- terrace like appearance.

6. Why hard stamp is a problem?

- because it will cause as a stress risers.

- highly susceptible to corrosion.

- It would damage the material.

7. State 2 methods to minimize lamellar tearing.

a) Apply a buttering layer of weld metal to the surface of

susceptible plate.

b) Change the joint design.

c) Change the quality of parent material.

d) Reducing size weld.

8. Briefly describe the principle of operation TIG process.

- TIG (Tungsten Inert Gas) Welding is a metal joining process in

which coalescence of metal is produced by heat from an electric

arc that is maintained between the tip of non consumable

electrode and the surface of base metal in the weld joint.

9. Give causes of tungsten inclusion.

a) Electrode contact to weld pool.

b) Too long extension of electrode tip which cause an overheat

and result to melting of electrode.

c) Contamination of electrode tip.

d) Thermal shock to the tungsten causing small fragments to enter

the weld pool.

10. Reason why weld was tested.

a) To ensure the soundness of weld metal.

b) To determine the mechanical properties of the weld.

11. How would you remove temporary attachment/support.

- By arc gouging or grinding, leave at least 3 mm for smooth

grinding, carry out NDT such as MPI or DPT to ensure that

weld metal & parent metal are free from defect.

12. Give 2 reasons for the following defect.

a) Undercut.

1. High welding current.

2. high travel speed.

b) Tungsten Inclusion.

1. Electrode contact to weld pool.

2. contamination of electrode tip.

c) Slag Inclusion.

1. Insufficient cleaning between passes.

2. improper manipulation of electrode.

d) Centerline cracking.

1. Weld bead is very narrow & very deep.

2. high restraint transverse to weld axis.

e) Hydrogen cracking.

1. High carbon equivalent on carbon steel.

2. residual stress

13. Highest to lowest hydrogen content of welding process.

1. FCAW

2. SAW

3. MMA

4. MIG

5. TIG

14. Prevention of hydrogen induce cracking (HIC).

a) Pre-heat.

b) Use basic low hydrogen electrode.

c) PWHT

d) Control the rate of cooling.

e) Avoid poor weld profiles.

15. What is the purpose of Nick break test?

a) A butt weld fracture test that is carried out for welder

approval (weld quality is observed/evaluated).

b) An alternative to radiographic testing (welder approval test).

16. Differentiate Micro and Macro Examination.

Micro – asses the grain structure of material and other non-visible

defect where examination is on metallurgical microscope.

Macro – a qualitative method used to determine and asses the internal

quality of the weld at low magnification.

17. Advantages and Disadvantages of UT / RT.

- Advantages of UT

a) A wide variety of material can be tested.

b) Can easily find lack of side wall fusion.

c) Portable with instant result.

d) No safety requirements as compare to RT.

- Disadvantages of UT

a) Requires calibration.

b) Difficult to interpret.

c) No permanent record.

d) High operational skill level.

- Advantages of RT

a) A wide variety of material can be tested.

b) Can assess penetration in small diameter pipe.

c) Gamma ray is very portable.

d) Permanent record of results.

- Disadvantages of RT

a) High safety requirements.

b) Difficult to interpret.

c) Cannot generally identify lack of sidewall fusion.

d) High operator skill level.

18. List items of equipment for semi-automatic welding machine

(MIG/MAG).

a) Power source – transformer/rectifier.

b) Inverter power source.

c) Power hose assembly.

d) Liner.

e) Contact tip.

f) Torch head assembly.

g) Power return cable.

h) Wire spool.

i) Power control panel.

j) External wire feed unit.

19. Explain why the presence of lamination obstruct Ultrasonic testing.

- Weld bead crosses the laminations.

20. Differentiate Semi-automatic, Mechanized and Automatic.

• Semi-automatic – wire speed and arc length are controlled

automatically by the equipment. Travel speed and position

controlled by welder.

• Mechanized – all parameters are under control of the

equipment but may vary during welding, e.g., steering welding

head, adjusting wire feed speed & arc voltage.

• Automatic – parameters cannot be changed during welding.

21. In to which categories may weld testing be divided?

- Destructive & Non-Destructive Testing

22. What is a qualified Welding Procedure Specification ( Oral )?

- an approved WPS that is to be used as a guide by welder and

inspector.

23. What is the testing for full thickness of lamellar tearing?

- Short Transverse Reduction Area (STRA)

24. Differentiate single and multiple qualification (Oral )?

Single qualification