Welding quality and performance

Welding is one of the principle activities in modern fabrication, ship building and offshore industry. The performance of these industries regarding product quality, delivery schedule and productivity depends upon structural design, production planning, welding technology adopted and distortion control measures implemented during fabrication. The quality of weld­ing depends on the following parameters:

1. Skill of Welder

2. Welding parameters

3. Shielding medium and

4. Working environment

5. Work layout

6. Plate edge preparation

7. Fit-up and alignment

8. Protection from wild winds during-on-site welding

9. Dimensional accuracy

10. Correct processes and procedures

11. Suitable distortion control procedures in place Selection of Welding Process and Filler Metal:

The welding process and filler metal should be so selected that the weld deposit will be compatible with the base metal and will have mechanical properties similar to or better than the base metal.

Comparison of high energy density welding processes and TIG welding for plate thick­ness 6 mm.

Parameter

TIG

Plasma

Laser

EB

Power input to workpiece

2 kW

4 kW

4 kW

5 kW

Total power used

3 kW

6 kW

50 kW

6 kW

Traverse

Speed

2 mm/s

5.7 mm/s

16 mm/s

40 mm/s

Positional

Good

Good

Yes

Requires

Welding

penetration

penetration

Requires optics to move the beam

mechanism to move the beam

Distortion

Nominal

Nominal

Small

Minimum

Shrinkage

Significant in V-shaped weld

significant in V-shaped weld

Minimum

Minimum

Special

Normal

Normal

Safety interlock

Vacuum

Process

Light

Light

against misplaced

chambers,

Requirements

Screening

Screening

beam reflection

X-ray

Screening

Surface

Underside

Underside

Very fine

Ruffled swarf

Geometry

Protrusion

protrusion

ripples

on back face

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