[Metal Materials Function Master Practical] 35th Edition Solution

1. Write the procedure for metallographic examination of metal materials..
◑ Specimen sampling - Specimen mounting - Etching - Drying - Microscopic observation

2. Write 3 methods for determining ferrite grain size.
◑ Comparison method
◑ Intercept method
◑ Sectioning method

3. Calculate the packing efficiency of BCC.

4. Draw a diagram and explain the precipitation mechanism during pearlite formation.
◑ Fe3C nucleation and growth at the austenite grain boundary
◑ Fe3C nucleus growth
◑ Ferrite formation around Fe3C
◑ Fe3C formation at the ferrite grain boundary

5. Write the requirements for carburizing steel.
◑ It should be low carbon steel.
◑ It should not contain elements that hinder carburization.
◑ Grain growth should not occur when heated at high temperatures for a long time.
◑ There should be no porosity or cracks during casting.
◑ It should have good machinability and workability.

6. Write the propane gas combustion reaction in a furnace and the gas ratio (air:propane) in case of complete combustion.
◑ C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(l)
◑ In case of complete combustion, gas ratio → 5:1

7. Write the 3 stages that occur when annealing cold-worked metal and their driving forces.
※ 3-stage phenomenon and driving force
◑ Recovery: Stored energy within the metal
◑ Recrystallization: Strain energy accumulated during cold working
◑ Grain growth: Reduction of grain boundary interfacial energy

8. Write 3 mass effects in heat treatment.
◑ Even with the same type of steel, the hardening depth varies depending on the size (mass) of the product.
◑ Hardness decreases continuously from the surface to the center.
◑ When the mass is large, a rapid decrease in surface hardness occurs.

9. What are the microstructures at positions a, b, c, d, e, f in the quenching-tempering microstructure transformation diagram?

10. What is Gibbs' phase rule?
◑ C variable = Number of substances
◑ P equation = Number of substance phases (gas, liquid, solid)
◑ F degree of freedom = C - P + 2
In this case, the reason for adding 2 is that, in addition to the number of substances and the number of phases, the experimenter can independently change P and T, so 2 is added when calculating the degree of freedom.

11. List the following microstructures in order from highest to lowest hardness.
★ From highest to lowest hardness (cementite-martensite-troostite-sorbite-pearlite-austenite-ferrite)
Cementite → Martensite → Troostite → Sorbite → Pearlite → Austenite → Ferrite

☆ From lowest to highest hardness (ferrite-austenite-pearlite-sorbite-troostite-martensite-cementite)
Ferrite → Austenite → Pearlite → Sorbite → Troostite → Martensite → Cementite

12. What is the process of removing graphitic carbon accumulated in a carburizing furnace or a carbonitriding furnace by injecting an appropriate amount of air as needed or regularly because it degrades the function of the carburizing furnace or carbonitriding furnace?
◑ Burn-out

13. When a specimen with a carburizing depth (t) as shown in the figure is to be transferred with an inclination to observe a wider surface, that is, twice the area, calculate the angle of inclination.

14. Write 5 purposes of spheroidizing annealing.
◑ Refinement of microstructure
◑ Increase in toughness
◑ Uniformity of quenching
◑ Reduction of quenching distortion
◑ Increase in machinability

15. Write 5 types of magnetic particle inspection magnetization methods.
◑ Yoke method
◑ Coil method
◑ Magnetic flux leakage method
◑ Central conductor method
◑ Prod method

16. Write the process of solvent removable dye penetrant inspection.
◐ Pre-cleaning - Penetrant application - Cleaning - Developer application - Inspection - Drying - Post-cleaning

17. Write 4 types of stainless steel.
◑ Austenitic
◑ Ferritic
◑ Precipitation hardening
◑ Martensitic

18. Explain the general properties of amorphous alloys.
◐ Mechanical properties
- High toughness, tensile strength, wear resistance, and no crystal defects.
- Very good temperature dependence.
- Work hardening hardly occurs.
- Has high fracture toughness.
- Toughness and ductility change significantly with temperature.
◐ Chemical properties
- Excellent corrosion resistance.

19. Write 5 pieces of equipment used in radiographic testing.