QUESTION 8: JOINING METHODS (INSPECTION OF WELDS) (SPECIFIC)
8.1 State FOUR causes of spatter as a welding defect that occurs during the welding process - NSC Mechanical Technology Welding and Metalwork - Question 8 - 2020 - Paper 1
Question 8
QUESTION 8: JOINING METHODS (INSPECTION OF WELDS) (SPECIFIC)
8.1 State FOUR causes of spatter as a welding defect that occurs during the welding process.
8.2 Brief... show full transcript
Worked Solution & Example Answer:QUESTION 8: JOINING METHODS (INSPECTION OF WELDS) (SPECIFIC)
8.1 State FOUR causes of spatter as a welding defect that occurs during the welding process - NSC Mechanical Technology Welding and Metalwork - Question 8 - 2020 - Paper 1
Step 1
8.1 State FOUR causes of spatter as a welding defect that occurs during the welding process.
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Answer
Too high current / amperage too high
Too long arc / Arc blow
Not using anti-spatter spray
Wet electrodes
Step 2
8.2.1 Nozzle too far from the surface
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When the nozzle is too far from the surface, it can lead to excessive melting of the top edge leading to an undercut at the top of the cut face. This can negatively affect the integrity and appearance of the weld.
Step 3
8.2.2 Nozzle too close to the surface
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If the nozzle is too close to the surface, the top edge of the cut may become slightly rounded and heavily beaded. This results in a cut face that is usually square but can compromise the cleanliness and quality of the cut.
Step 4
8.3.1 Porosity
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Dirty weld surface - Contaminants on the surface can introduce air pockets.
Wet welding electrodes - Moisture can cause gas entrapment during the welding process.
Step 5
8.3.2 Poor penetration
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Welding current is too low - Insufficient heat can prevent the weld from penetrating the base materials properly.
Travel speed is too fast - Moving too quickly may not allow enough time for the weld to fuse adequately.
Step 6
8.4 Name TWO causes of cracks in the heat-affected zone (HAZ).
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Excessive hydrogen - Hydrogen can lead to cracking upon cooling.
High residual stress levels - Rapid cooling or improper welding sequence can create stresses that lead to cracks.
Step 7
8.5 Name THREE elements that should be inspected during the visual inspection of arc-welded joints.
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Shape of the profile - Ensuring a proper weld profile is crucial for strength.
Uniformity of the surface - A consistent surface indicates a good welding process.
Surface cracks - Any visible cracks can be a sign of underlying problems.
Step 8
8.6 Describe the procedures to be followed when performing an ultrasonic test on a welded joint.
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Gel should be put on the surface of the work piece to ensure good contact for sound transmission.
The sender/receiver is moved in a zigzag motion across the weld to broaden its detection range.
A high-frequency sound wave is sent into the metal, and the receiver monitors the echoes as they reflect off internal flaws.
The oscilloscopes will then indicate the deviations in the waves, helping pinpoint the defects in the metal.
