Covers various topics related to the Metal Materials Function Master practice exam, including carburized layer measurement, creep phenomenon, and causes of heat treatment hardening failure.
Includes explanations of the difference between hot working and cold working, the invariant reaction of Fe3C, the general properties of metals, leakage testing, and the S-curve.
Specifically details methods for measuring decarburization layer using a microscope and hardness testing, heat treatment-related problems and solutions, and the characteristics of metallic materials.
1. Describe the methods for measuring decarburization layer. ◑ Measurement method using a microscope A method of measuring the depth of the decarburization layer by etching the cross-section of the test piece and observing it under a microscope.
◑ Measurement method using hardness test A method of measuring the depth of the decarburization layer by conducting a hardness test on the cross-section of the test piece.
2. What is the phenomenon where, at high temperatures, deformation occurs beyond a certain level proportional to the external force over time? ◑ Creep phenomenon
3. Describe the causes of heat treatment hardening failure (hardness failure). ◑ Low quenching temperature ◑ Slow cooling rate ◑ Decarburization and oxidation during quenching
4. Describe two methods for measuring the decarburization layer of heat-treated materials. ◑ Measurement method using a microscope ◑ Measurement method using a hardness test ◑ Measurement method based on carbon concentration
5. Describe the methods for distinguishing between hot working and cold working, and list one advantage of each. ※ Distinguishing method ◑ Based on the metal's recrystallization temperature -. Hot working → Working at a temperature higher than the recrystallization temperature -. Cold working → Working at a temperature lower than the recrystallization temperature
※ Advantages ◑ Hot working
※ Countermeasures ◑ Adding alloying elements (Al, Ti, Zr, V, B with high affinity for nitrogen) to prevent temper embrittlement.
11. List three invariant reactions of Fe3C and write their reaction equations (represent liquid as L). ◑ Eutectic reaction: Liquid (4.3%C) → γ Austenite (2.08%C) + Cementite (6.67%C) ◑ Peritectic reaction: Liquid (0.5%C) + α Ferrite (0.09%C) → γ Austenite (0.17%C) ◑ Eutectoid reaction: γ Austenite (0.8%C) → α Ferrite (0.02%C) + Cementite (6.67%C)
12. Describe five general properties of metals. ※ Physical properties ◑ Exists in solid form at room temperature ◑ Has a high melting point and high strength. ◑ Has a specific density and is generally heavy. ◑ Excellent thermal and electrical conductivity. ◑ Requires a lot of processing time, equipment, and cost.
※ Mechanical properties ◑ High hardness and wear resistance. ◑ Good castability and alloy recovery is possible.
13. List five types of fluid flow in leak testing.
※ Influencing factors of the S-curve ◐ Heating rate ◐ Heating temperature ◐ Segregation ◐ Stress ◐ Alloying elements
18. Describe three methods for drawing an S-curve. ※ Methods for obtaining the S-curve ◐ Metallographic method ◐ Thermal analysis method ◐ Thermal expansion method ◐ Magnetic analysis method