Welding Defects:

Defects Cause Remedies

1. Undercut: 1. Welding with the arc at high 1. Reduce travel speed and power
Undercut is defined as “A groove voltage input.
melted into the base metal
adjacent to the weld toe or weld 2. Using electrode at the wrong 2. Lower the arc voltage or reduce
face and left unfilled by weld angle the arc length. The voltage should
metal. typically be between 15 to 30 volts.
3. Working at a higher speed of The welding arc length should not
weld. be more than the diameter of the
electrode core.
4. Unclean base metal surface.
3. Keep the electrode angle between
5. Excessive arc length 30 to 45 degrees on the standing leg.

6. Incorrect weaving technique 4. Weld in flat positions.

2. Incomplete Penetration OR (i) Incorrect use of the welding (i) Be sure to allow the proper free

Lack of Penetration: technique. space at the bottom of a weld.

(ii) Wrong electrode size. (ii) Use small diameter electrodes in
A joint root condition in a groove
Improper electrode. a narrow welding groove.
weld in which weld metal does not
(iii)Low deposition rate of core. (iii) Use sufficient welding current
extend through the joint thickness.
(iv) Having too much space to obtain proper penetration.
Incomplete penetration in welding
between the weld. (iv) Do not weld too rapidly.
refers to a situation where the weld
(v) Moving the welding bead (v) Proper heat input
bead does not fully penetrate into the
too fast.
joint, leaving a gap or an un-fused
(vi) Lack of penetration can be
(vi) Using too low amperage
portion between the weld metal and
the base metal. setting, preventing adequate repaired by proper back gouging.
melting of metal. (vii) Increase the groove angle and
root gap.

3. Incomplete Fusion OR 1. Low heat input. 1. Higher welding current and

Lack of Fusion: 2. Contamination of the metal slower travel rate to ensure the
surface. melting process of the metals.
Incomplete fusion, often referred
3. Using incorrect electrode 2. Improving welding positions such
to as “Lack of Fusion” (LOF) in
diameters for the specific as joint angle, torch angle, and bead
welding, occurs when the weld
material thickness. position.
metal does not properly fuse with
4. Too fast travel speed. 3. Clean the welding area and metal
the base metal or with the
5. Large weld pools moving surface before welding.
previously deposited weld
ahead of the arc.
metal. This results in a gap or an
4. Choose the right electrode
6. Incorrect electrode position.
unfused area between the two
diameter that fits the material
7. Incorrect welding parameters.
materials, compromising the strength
thickness.
8. Trapped oxides, slag on weld
and integrity of the weld joint.
face and groove.
5. Optimize the travel speed.

6. Use an adequate weld pool that

does not flood the arc.

4. Slag Inclusion: 1. Excessive weaving and the 1. Use higher welding current.

Inclusions are defined as “Entrapped use of too large an electrode in a 2. Modify groove angle and root

foreign solid material, such as slag, narrow groove and too low gap.

flux, tungsten, or oxide.” The amperage can also cause slag 3. Remove the slag from previous

inclusions may be found as single pockets. bead completely.

particles, aligned particles, or 2. Insufficient cleaning out of 4. Use higher travelling speed.

clustered particles. slag along an undercut toe of a 5. Decrease weaving width.

multipass weld and incorrect 6. Prevent rapid cooling.
electrode manipulation leave
pockets of slag.
3. Welding current is too low.
4. Improper groove shape.
5. Porosity: (i) Excessive hydrogen, (i) Puddling keeps weld metal

Porosity is defined as “Cavity-type nitrogen, or oxygen in welding molten longer and often insures

discontinuities formed by gas atmosphere. sounder welds.

entrapment during solidification or (ii) High solidification rate. (ii) Use low-hydrogen welding

in a thermal spray deposit.” The (iii) Dirty base metal. process; filler metals high in

porosity may be surface or (iv) Dirty filler wire. deoxidizers; increase shielding gas

subsurface, and may be a single (v) Improper arc length, flow.

cavity, aligned, or clustered. welding current, or electrode (iii) Use preheat or increase heat
manipulation. input.
(vi) Excessive moisture in (iv) Use recommended procedures
electrode covering or on joint for baking and storing electrodes.
surfaces. Preheat the base metal.
(vii) High sulfur base metal (v) Use specially cleaned and
(viii) Not sufficient pudding packaged filler wire, and store it in
time to allow entrapped gas to clean area.
escape. (vi) Use electrodes with basic
slagging reactions.
6. Overlap OR Over-Roll: 1. Incorrect welding procedure. 1. Choose the proper welding

Overlap is defined as “The 2. Wrong selection of welding technique for optimal arc length.

protrusion of weld metal beyond the materials. 2. Maintain the right electrode

weld toe or weld root.” Overlap is 3. Improper preparation of base angle.

the excess metal that spreads out metals. 3. Avoid using large-sized

around the bead. The spread-out 4. Too low welding current. electrodes.

filler metal is not properly mixed 5. Too slow travel speed. 4. Try to weld in flat positions.

with the base metals. Typically, it 6. Steep electrode angle. 5. Use low heat input or welding

comes in a round shape over the current.

weld joint. 6. Use proper travel speed.

7. Burn Through: 1. High welding current and 1. Maintaining a proper root gap.

“Burn through” in welding refers to heat input. 2. Control in the application of

a situation where excessive heat and 2. Thin material. welding current.

welding parameters cause a hole or 3. Lack of proper joint 3. It can be repaired in some cases

penetration through the base metal preparation. wherein the hole is removed and re-

being welded. It occurs when the 4. Extreme gap to the root. welded.

welding process generates more heat 5. Not enough root face metal. 4. Reduce heat input by increasing

than required for the thickness and travel speed, use of a heat sink, or

type of material being joined. This by reducing welding parameters.

excessive heat melts the base metal,

creating a hole or opening that can
compromise the structural integrity
of the weld joint. An open hole is
exposed when the welding process
accidentally penetrates the whole
thickness of the base metal, creating
a burn-through or melt-through. This
is one of the common weld defects
when welding thin metals.

8. Spatters: 1. High welding current. 1. Use the right polarity and adjust
2. Long weld arc. the weld current.
Spatters are visible small weld metal
3. Contaminated welding 2. Use the proper shield gas and
particles sticking around the weld
surface. better shielding technique.
bead in a scattered manner. The
4. Wrong selection of welding 3. Increase electrode angle and
small particles are the molten weld
polarity. decrease arc length.
metal droplets expelled from the
5. Shielding gas was not proper. 4. Clean the metal surface before
welding electrode. Commonly found
6. Using a wet electrode and a welding.
in ARC, GAS, and tack welding
larger arc length.
processes. They can also appear,
though less frequently, in MIG
welding.

9. Distortion: 1. Excessive weld size. 1. Stick to an appropriate

2. Improper set-up and fixture. temperature gradient for welding.
Residual stresses in weldments 3. Overheating of base plate. 2. Use correct welding orders.
produce distortion and may be the 4. Excessive layers. 3. Maintain an arc travel speed of 10
cause of premature failure in 5. Worn out tip. to 20 inches per minute for rotating
weldments. Distortion is caused 6. Wire feeder does work workpieces, and 4 to 10 inches per
when the heated weld region smoothly. minute for orbital welding
contracts non-uniformly, causing 7. Feed roller not fasten equipment.
shrinkage in one part of the weld to properly. 4. Optimize the design for your
exert eccentric forces on the weld 8. Varying temperature sheet metal part for an adequate
cross section. It is changes in the gradients during welding. number of weld passes.
position and dimensions of metal 9. Using an incorrect welding 5. Use the right amount of weld
plates. This defect is more order. metal to decrease contraction forces.
pronounced in thinner plates, as their 10. Slow arc travel speed. 6. Clamp the parts securely.
limited surface area hampers 11. Too many welds pass with Use thicker base plate.
effective heat dissipation. small diameter electrodes. 7. Replace the worn out electrode.
12. High residual stress in the 8. Grease wire feeder.
metal plate to be welded. 9. Adjust feed roller properly.

10. Cracks: 1. Electrode is not of good 1. Use suitable metal materials and

A crack is defined as “A fracture quality or may be damped. clean their surfaces before welding.

type discontinuity characterized by a 2. Base metal contains over 2. Use the right welding speed and

sharp tip and a high ratio of length carbon and manganese content. current.

and width to opening displacement.” 3. Base metal having higher 3. Preheat the base metal and reduce

Cracks are usually considered the Sulphur content. the cooling speed joint.

most severe discontinuity because of 4. Welding is done without pre 4. Use the appropriate sulfur and

their tendency to propagate under or post heating. carbon mixture.

stress. 5. Too large welding current. 5. Reduce the gap between weld
6. Thickness of base metal is joints.
much more. 6. Use proper electrode.
7. Too strong restraint for 7. Use low hydrogen type electrode
groove. with higher basicity.
8. Poor ductility or 8. Reduce welding current.
contamination of given base 9. Modify the groove design.
metals.
9. Combining high welding
 speed with low current.
10. High residual stress
solidification from shrinkage.
11. Lack of preheating before
starting welding.
12. The high content of sulfur
and carbon in base metals.
13. Using hydrogen as shielding
gas for welding ferrous metals.

Questions:
1. Describe the principle of Thermit welding with net sketch.
2. State it's field of application. Give their advantage and limitation.
3. Write down the common defects of welding. Mention their remedies in short.