EXAM COVERAGE SUMMARY
Metallurgy Fundamentals
Crystal structures (BCC, FCC, HCP) and close-packed planes
Solid solutions (interstitial vs substitutional)
Phase diagrams and lever rule calculations
Eutectic systems and phase transformations
Iron-carbon equilibrium diagram
Mechanical Properties
Work hardening and strain hardening mechanisms
Dislocation theory and slip systems
Yield strength and grain size relationship (Hall-Petch)
Recovery, recrystallization, and grain growth
Strain aging and blue brittleness
Thermal Properties
Thermal conductivity and diffusivity
Heat input and cooling rate calculations
Preheating effects on cooling rates
Thermal expansion considerations
Welding Metallurgy
Solidification mechanisms and dendritic growth
Constitutional supercooling
Hot cracking (solidification cracking)
Hydrogen cracking and cold cracking
Lamellar tearing and reheat cracking
Weld Defects and Control
Porosity causes and control methods
Nitrogen and hydrogen porosity
Carbon monoxide porosity in steels
Inclusions and slag entrapment
, Undercut and lack of fusion
Welding Processes
Submerged arc welding (SAW) flux composition
Electroslag welding flux conductivity
GMAW transfer modes
SMAW electrode coatings and functions
FCAW and GTAW characteristics
Weldability of Metals
Carbon steel weldability and CE calculations
Stainless steel sensitization and stabilization
Aluminum welding challenges
Nickel alloys and titanium shielding requirements
Dissimilar metal welding considerations
Welding Consumables
Electrode selection criteria
Flux composition and functions
Shielding gas effects
Tungsten electrode additives (thoria, lanthana)
Filler metal matching and properties
Testing and Inspection
Destructive testing methods
Non-destructive testing techniques
Visual inspection standards
Radiographic interpretation
Ultrasonic testing principles
,SECTION A:
1. Which crystal structure is characterized by close-packed planes and the ability to
undergo extensive plastic deformation?
(a) BCC only
(b) FCC and HCP
(c) BCC and FCC
(d) HCP only
Answer: (b) FCC and HCP
Both FCC and HCP structures contain close-packed planes that allow significant slip
systems, contributing to their excellent ductility and formability compared to BCC structures.
2. What happens to the solubility of one component in another during precipitation
hardening?
(a) It decreases with increasing temperature
(b) It increases with increasing temperature
(c) It remains constant regardless of temperature
(d) It fluctuates randomly with temperature changes
Answer: (b) It increases with increasing temperature
Precipitation hardening requires that the solubility of one component increases with rising
temperature, allowing the alloy to be solution treated and then aged to form fine precipitates
that strengthen the material.
3. Why are thoriated tungsten electrodes preferred for GTAW applications?
(a) They have higher melting points than pure tungsten
(b) They operate at lower temperatures for the same current
(c) They produce more stable arcs in all positions
(d) They are less expensive to manufacture
Answer: (b) They operate at lower temperatures for the same current
Thoria lowers the work function of tungsten, increasing thermionic emission and allowing the
electrode to operate at lower temperatures while maintaining excellent arc starting and
stability characteristics.
4. Which of the following factors would most likely lead to centerline solidification
cracking in structural steel welds?
(a) Insufficient preheat temperature
(b) Welding current and speed too high
(c) Electrode extension too long
(d) Arc voltage too high
, Answer: (b) Welding current and speed too high
High welding current and speed create deep, narrow weld pools with a high width-to-depth
ratio, concentrating impurities and low-melting constituents at the centerline where they
promote solidification cracking.
5. What is the primary cause of porosity in aluminum welds?
(a) Nitrogen from atmospheric contamination
(b) Hydrogen dissolved in the molten metal
(c) Carbon monoxide formation
(d) Oxygen from incomplete shielding
Answer: (b) Hydrogen dissolved in the molten metal
Hydrogen has a much higher solubility in liquid aluminum than solid aluminum, and when
aluminum solidifies rapidly, the excess hydrogen forms gas bubbles that become trapped as
porosity in the weld metal.
6. In the iron-carbon phase diagram, what percentage of pearlite would be present in a
slowly cooled 0.2% carbon steel?
(a) Approximately 50%
(b) Approximately 75%
(c) Approximately 25%
(d) Approximately 10%
Answer: (c) Approximately 25%
Using the lever rule, with the tie line from 0.0% carbon (ferrite) to 0.8% carbon (pearlite), at
0.2% carbon the pearlite fraction is (0.2-0.0)/(0.8-0.0) = 25%, with the balance being
proeutectoid ferrite.
7. Which of the following elements is most likely to form an interstitial solid solution
with iron?
(a) Nickel
(b) Copper
(c) Carbon
(d) Chromium
Answer: (c) Carbon
Carbon atoms are small enough to occupy the interstitial sites between iron atoms in the
crystal lattice, whereas nickel, copper, and chromium have similar atomic sizes to iron and
form substitutional solid solutions.
8. Why does the temperature range of 150°C to 400°C cause problems when forming
steels?
(a) Excessive grain growth occurs in this range
(b) Dynamic strain aging causes blue brittleness
Metallurgy Fundamentals
Crystal structures (BCC, FCC, HCP) and close-packed planes
Solid solutions (interstitial vs substitutional)
Phase diagrams and lever rule calculations
Eutectic systems and phase transformations
Iron-carbon equilibrium diagram
Mechanical Properties
Work hardening and strain hardening mechanisms
Dislocation theory and slip systems
Yield strength and grain size relationship (Hall-Petch)
Recovery, recrystallization, and grain growth
Strain aging and blue brittleness
Thermal Properties
Thermal conductivity and diffusivity
Heat input and cooling rate calculations
Preheating effects on cooling rates
Thermal expansion considerations
Welding Metallurgy
Solidification mechanisms and dendritic growth
Constitutional supercooling
Hot cracking (solidification cracking)
Hydrogen cracking and cold cracking
Lamellar tearing and reheat cracking
Weld Defects and Control
Porosity causes and control methods
Nitrogen and hydrogen porosity
Carbon monoxide porosity in steels
Inclusions and slag entrapment
, Undercut and lack of fusion
Welding Processes
Submerged arc welding (SAW) flux composition
Electroslag welding flux conductivity
GMAW transfer modes
SMAW electrode coatings and functions
FCAW and GTAW characteristics
Weldability of Metals
Carbon steel weldability and CE calculations
Stainless steel sensitization and stabilization
Aluminum welding challenges
Nickel alloys and titanium shielding requirements
Dissimilar metal welding considerations
Welding Consumables
Electrode selection criteria
Flux composition and functions
Shielding gas effects
Tungsten electrode additives (thoria, lanthana)
Filler metal matching and properties
Testing and Inspection
Destructive testing methods
Non-destructive testing techniques
Visual inspection standards
Radiographic interpretation
Ultrasonic testing principles
,SECTION A:
1. Which crystal structure is characterized by close-packed planes and the ability to
undergo extensive plastic deformation?
(a) BCC only
(b) FCC and HCP
(c) BCC and FCC
(d) HCP only
Answer: (b) FCC and HCP
Both FCC and HCP structures contain close-packed planes that allow significant slip
systems, contributing to their excellent ductility and formability compared to BCC structures.
2. What happens to the solubility of one component in another during precipitation
hardening?
(a) It decreases with increasing temperature
(b) It increases with increasing temperature
(c) It remains constant regardless of temperature
(d) It fluctuates randomly with temperature changes
Answer: (b) It increases with increasing temperature
Precipitation hardening requires that the solubility of one component increases with rising
temperature, allowing the alloy to be solution treated and then aged to form fine precipitates
that strengthen the material.
3. Why are thoriated tungsten electrodes preferred for GTAW applications?
(a) They have higher melting points than pure tungsten
(b) They operate at lower temperatures for the same current
(c) They produce more stable arcs in all positions
(d) They are less expensive to manufacture
Answer: (b) They operate at lower temperatures for the same current
Thoria lowers the work function of tungsten, increasing thermionic emission and allowing the
electrode to operate at lower temperatures while maintaining excellent arc starting and
stability characteristics.
4. Which of the following factors would most likely lead to centerline solidification
cracking in structural steel welds?
(a) Insufficient preheat temperature
(b) Welding current and speed too high
(c) Electrode extension too long
(d) Arc voltage too high
, Answer: (b) Welding current and speed too high
High welding current and speed create deep, narrow weld pools with a high width-to-depth
ratio, concentrating impurities and low-melting constituents at the centerline where they
promote solidification cracking.
5. What is the primary cause of porosity in aluminum welds?
(a) Nitrogen from atmospheric contamination
(b) Hydrogen dissolved in the molten metal
(c) Carbon monoxide formation
(d) Oxygen from incomplete shielding
Answer: (b) Hydrogen dissolved in the molten metal
Hydrogen has a much higher solubility in liquid aluminum than solid aluminum, and when
aluminum solidifies rapidly, the excess hydrogen forms gas bubbles that become trapped as
porosity in the weld metal.
6. In the iron-carbon phase diagram, what percentage of pearlite would be present in a
slowly cooled 0.2% carbon steel?
(a) Approximately 50%
(b) Approximately 75%
(c) Approximately 25%
(d) Approximately 10%
Answer: (c) Approximately 25%
Using the lever rule, with the tie line from 0.0% carbon (ferrite) to 0.8% carbon (pearlite), at
0.2% carbon the pearlite fraction is (0.2-0.0)/(0.8-0.0) = 25%, with the balance being
proeutectoid ferrite.
7. Which of the following elements is most likely to form an interstitial solid solution
with iron?
(a) Nickel
(b) Copper
(c) Carbon
(d) Chromium
Answer: (c) Carbon
Carbon atoms are small enough to occupy the interstitial sites between iron atoms in the
crystal lattice, whereas nickel, copper, and chromium have similar atomic sizes to iron and
form substitutional solid solutions.
8. Why does the temperature range of 150°C to 400°C cause problems when forming
steels?
(a) Excessive grain growth occurs in this range
(b) Dynamic strain aging causes blue brittleness
