Name:
Score:_________
Course/Section
Date:_________
Essay: Discuss the causes , the effects and the correction of the following defects on the welded
joint after operation such; as the undercut , misalignment and the over-roll . Answer this with your
own understanding or ideas. (Write your answer on the space provided with at least minimum of
20 words per statement on causes, effects and correction on the following welded joint defects
15pts each statement with a total of 45 credit score pts).
1. Undercut - In welding, undercutting is when the weld reduces the cross-sectional thickness of
the base metal. This type of defect reduces the strength of the weld and workpieces. A third
reason is using an incorrect filler metal, because it will create greater temperature gradients
between the center of the weld and the edges.
One of the causes is the electrode’s speed and direction of movement, to a great extent,
determines the quality of the weld. Should you go with a high speed, the end product will have
several points of weakness and incomplete metal fusion. This substandard outcome is a result
of the very thin molten metal along the joint area.
The possible correction it has been established through practice that the electrode’s angle
should be between 30 and 45 degrees to the horizontal surface for optimum performance. This
would provide an appropriate position for the molten metal to get deposited smoothly and
evenly. It is also possible to balance movements at this angle rather than vertically having them.
2. Misalignment - The consequence of linear misalignment can, when welding is carried out
from one side, be lack of root or sidewall fusion to give a sharp continuous imperfection along
the higher weld face toe.
One of the reason This problem arises when there has been insufficient filler metal current or
wire feed too low or too high a travel speed so that the joint has not been sufficiently filled. The
result is that the thickness of weldment is less than that specified in the design, which could lead
to failure.
The remedies is Increasing the welding current and decreasing the travel speed helps in
removing the chances of incomplete fusion. Reducing the deposition rate. Increasing the joint
angle. Try to position the electrode and torch angle properly so that the edges of the plate melt
away.
3. Over-roll - This is weld metal at the toe of the weld that covers the parent metal surface but
has not fused to it. Generally caused by slow travel speed and wrong torch angle.
The causes Low travel speed also causes overlap. The filler deposition rate is constant during
the weld, so if you go too slow, filler will accumulate in the weld pool and cause overlapping.
The remedies No matter how attentive you are, weld defects will occur now and then. In the
event you do have some overlap, fear not. You can fix it with a bit of elbow grease. First identify
the boundaries of your weldment or the weld toe, and mark it. Then grind off the overlap up to
the line. Take care not to harm the joint in the process.