Welding Flashcards
What is the misalignment defect?
Definition: Amount a joint is out of
alignment at the root
Cause:
Carelessness
Also due to joining different thicknesses
(transition thickness)
What is an undercut?
Definition: A groove cut at the toe of
the weld and left unfilled
Cause: High amperage, electrode
angle, long arc length, rust
Prevention: Clean metal before
welding
Repair: Weld with smaller electrode,
sometimes must be low hydrogen
with preheat
What is an underfill?
Definition: The weld surface is below the
adjacent surfaces of the base metal
Cause: Improper welding techniques
Prevention: Apply proper welding techniques
for the weld type and position
Repair: Simply weld to fill – may
require preparation by grinding
What is excessive concavity or convexity?
Definition: Concavity or convexity of a fillet weld
which exceeds the specified allowable limits
Cause: Amperage and travel speed
Prevention: Observe proper parameters and
techniques.
Repair: Grind off or weld on – must blend
smoothly into the base metal
What is incomplete fusion?
Definition: Where weld metal does not form a
cohesive bond with the base metal
Cause: Low amperage, steep electrode angles, fast
travel speed, short arc gap, lack of preheat, electrode
too small, unclean base metal, arc off seam
Prevention: Eliminate the potential causes
Repair: remove and re-weld, being careful to
completely remove the defective area
Incomplete or insufficient penetration?
Definition: When the weld metal does not extend
to the required depth into the joint root
Cause: Low amperage, low preheat, tight root
opening, fast travel speed, short arc length
Prevention: Correct the contributing factor(s)
Repair: remove and re-weld
What is spatter?
Definition: Small particles of weld metal
expelled from the welding operation
which adhere to the base metal surface
Cause: Long arc length, severe electrode
angles, high amperages
Prevention: Correct the cause; base
metal can be protected with coverings
or high temperature paints
Repair: Remove by grinding or sanding
What do you expect when welding
two hypereutectoid steels with 15%CW (SAW)?
Average hardness of the HAZ lower than the parent material
Which welding process would you select for welding
hypereutectoid carbon steels?
Submerge Arc Welding
Which microstructure do you expect in the parent
material when spot welding an AISI1045?
Alpha + pearlite
Which microstructure do you expect in the parent material when spot welding a carbon steel of 0.76%C with 10% cold work?
Pearlite with 10%CW
3 Most Important Things?
- If a steel tends to form martensite, pre-heating
and post-heating processes should be conducted - An appropriate selection of welding process and
parameters should be conducted to prevent
defects in a weld
3. A weld is not necessarily rejected because it contains flaws (consider Standards)
Outline the electrode classification for shielded metal arc welding.
E -> Electrode/ electric arc
XX -> Minimum tensile strength in
ksi of deposited weld metal in
the as-welded condition
Y -> Weld positions in which
electrode can be used
YZ -> Type of covering
Z -> Current characteristics of
electrode
What is hydrogen cracking?
Hydrogen cracking, also called cold cracking,
requires all three of these factors:
• Hydrogen
• Stress
• Susceptible microstructure (high hardness)
Prevention by:
• Preheat
• Low hydrogen welding process
What does the carbon equivalent show?
The ability to form martensite upon cooling.
Low values of CE mean less likely to form martensite.
High values of CE require preheating to reduce the temperature differential and reduce rate of cooling.
