WELDING METALLURGY II QUESTIONS AND CORRECT
DETAILED ANSWERS (VERIFIED ANSWERS) ALREADY
GRADED A+
Heat affected zone Ans✓✓✓The HAZ is the zone of the base metal that
has been heated to high temperatures just below its melting point during
the welding process
ZONE 1 Ans✓✓✓zone 1 represents metal that has been heated to
temperatures in excess which will give a structure that is coarse grained.
This large grain structures is due to grain growth at this temperature.
ZONE 2 Ans✓✓✓zone 2 represents metal that has been heated to give a
fully austenite structure but grain growth has not occurred only some
grain refinement may occur
ZONE 3 Ans✓✓✓zone 3 represents metal that has been heated above
the A3 line (or austenite) region, but temperatures are not high enough to
completely homogenize the austenite
ZONE 4 Ans✓✓✓zone 4 represents metal that has been heated to a
region between the A3 and A1 lines, which result in a structure which is
only partially converted to austenite.
,Depending upon the temperature reached very little ferrite
transformation. (* this partially transformed section has poor notch
toughness)
ZONE 5 Ans✓✓✓zone 5 represents metal that has been heated to a
region below the A1 transformation line with no austenite being formed.
Instead the base metal may have a spheroidized pearlite, may be
softened (tempered, stress-relieved) or may have some recrystallization
Weld Metal Ans✓✓✓-columnar grains and growth in direction of
thermal flow
-mostly ferrite and small amount of pearlite
-widmanstatten pattern (geometrical pattern of ferrite-interlaced masses
distributed throughout the grains, resulting from the precipitation of
ferrite in long continuous plates along the crystallographic planes)
-numerous dislocations (not observable with microscope)
Fusion Zone Ans✓✓✓What you see optically looks more like a line
possesses characteristics of widmanstatten pattern and some grain
growth appearances
,Coarse Grained (grain growth zone) Ans✓✓✓-large regions of pearlite
and smaller grains of ferrite
-very coarse structure near fusion zone - widmanstatten pattern with
lines of ferrite breaking up pearlite areas (it occurs from large austenite
grains during a medium fast rate of cooling)
-Large austenite grains have more tendency to form martensite on rapid
cooling
-Microstructure of the grain growth (gg), above all others determine the
properties of the weld
Fine Grained (FG) Ans✓✓✓-Ferrite and pearlite grains are both much
finer than original grains of base metal
-Base metal has austenitized during welding but temperatures are too
low and time at temperature too short to allow for grain growth
Partially Transformed (PT) Ans✓✓✓-Mixture of old microstructure and
new microstructure
-Typically has the lowest notch toughness properties
, -consists of relatively coarse ferrite grains that have not been completely
dissolved
-much finer clusters of ferrite and pearlite grains occupying former large
pearlite grains
-transformation starts in centers of pearlite grains, where cementite is
dissolved to give austenite containing about 0.8%C
-if cooling is very fast, these regions are transformed to martensite
surrounded by partly dissolved cementite in ferrite
Tempered Zone Ans✓✓✓-Often we do not see any microstructural
changes but will may see some mechanical changes (found doing
hardness)
-cementite has a tendency to spheroidized into larger particles but
welding speed is usually too high
-if the steel has been cold worked before welding ferrite will
recrystallize
Rate of Heating Ans✓✓✓Dependent on:
-Different processes (eg FCAW, GTAW, SAW) all have different heat
inputs
DETAILED ANSWERS (VERIFIED ANSWERS) ALREADY
GRADED A+
Heat affected zone Ans✓✓✓The HAZ is the zone of the base metal that
has been heated to high temperatures just below its melting point during
the welding process
ZONE 1 Ans✓✓✓zone 1 represents metal that has been heated to
temperatures in excess which will give a structure that is coarse grained.
This large grain structures is due to grain growth at this temperature.
ZONE 2 Ans✓✓✓zone 2 represents metal that has been heated to give a
fully austenite structure but grain growth has not occurred only some
grain refinement may occur
ZONE 3 Ans✓✓✓zone 3 represents metal that has been heated above
the A3 line (or austenite) region, but temperatures are not high enough to
completely homogenize the austenite
ZONE 4 Ans✓✓✓zone 4 represents metal that has been heated to a
region between the A3 and A1 lines, which result in a structure which is
only partially converted to austenite.
,Depending upon the temperature reached very little ferrite
transformation. (* this partially transformed section has poor notch
toughness)
ZONE 5 Ans✓✓✓zone 5 represents metal that has been heated to a
region below the A1 transformation line with no austenite being formed.
Instead the base metal may have a spheroidized pearlite, may be
softened (tempered, stress-relieved) or may have some recrystallization
Weld Metal Ans✓✓✓-columnar grains and growth in direction of
thermal flow
-mostly ferrite and small amount of pearlite
-widmanstatten pattern (geometrical pattern of ferrite-interlaced masses
distributed throughout the grains, resulting from the precipitation of
ferrite in long continuous plates along the crystallographic planes)
-numerous dislocations (not observable with microscope)
Fusion Zone Ans✓✓✓What you see optically looks more like a line
possesses characteristics of widmanstatten pattern and some grain
growth appearances
,Coarse Grained (grain growth zone) Ans✓✓✓-large regions of pearlite
and smaller grains of ferrite
-very coarse structure near fusion zone - widmanstatten pattern with
lines of ferrite breaking up pearlite areas (it occurs from large austenite
grains during a medium fast rate of cooling)
-Large austenite grains have more tendency to form martensite on rapid
cooling
-Microstructure of the grain growth (gg), above all others determine the
properties of the weld
Fine Grained (FG) Ans✓✓✓-Ferrite and pearlite grains are both much
finer than original grains of base metal
-Base metal has austenitized during welding but temperatures are too
low and time at temperature too short to allow for grain growth
Partially Transformed (PT) Ans✓✓✓-Mixture of old microstructure and
new microstructure
-Typically has the lowest notch toughness properties
, -consists of relatively coarse ferrite grains that have not been completely
dissolved
-much finer clusters of ferrite and pearlite grains occupying former large
pearlite grains
-transformation starts in centers of pearlite grains, where cementite is
dissolved to give austenite containing about 0.8%C
-if cooling is very fast, these regions are transformed to martensite
surrounded by partly dissolved cementite in ferrite
Tempered Zone Ans✓✓✓-Often we do not see any microstructural
changes but will may see some mechanical changes (found doing
hardness)
-cementite has a tendency to spheroidized into larger particles but
welding speed is usually too high
-if the steel has been cold worked before welding ferrite will
recrystallize
Rate of Heating Ans✓✓✓Dependent on:
-Different processes (eg FCAW, GTAW, SAW) all have different heat
inputs
