This content covers various problems and solutions related to the Metal Materials Master Craftsman practical exam, providing detailed explanations of crystal defects, pearlite nucleation, ferrite grain size measurement, the five major elements of steel, and the effects of manganese.
It also presents solutions for preventing temper embrittlement, quenching characteristics, calculation formulas for exposure factors in radiographic testing, spheroidizing treatment methods for bearing steel, and methods of microstructure examination, as well as explanations of the definition, purpose, and additives of aluminum modification treatment.
This content serves as a learning resource for preparing for the Metal Materials Master Craftsman practical exam, helping with exam preparation through various problem types and explanations.
1. While a perfect crystal refers to an ideal crystal where atoms or molecules are arranged regularly without any defects, what are the 3 types of lattice defects? ◑ Point defects ◑ Line defects ◑ Interfacial defects
2. Illustrate and briefly explain the pearlite nucleation process with a diagram. ◑ Fe3C nucleation and growth at austenite grain boundaries ◑ Fe3C nucleus growth ◑ Ferrite formation around Fe3C ◑ Fe3C formation at ferrite grain boundaries
3. Write 3 methods for measuring ferrite grain size. ◑ Area measurement method ◑ Intercept method ◑ Point counting method
4. Write the 5 major elements of steel excluding manganese (Mn) and 4 effects of manganese (Mn). ※ 5 Major Elements of Steel ◑ P (Phosphorus) ◑ S (Sulfur) ◑ Si (Silicon) ◑ C (Carbon)
※ 4 Effects of Manganese ◑ Combines with S to exist as MnS, preventing S-related issues and hot shortness. ◑ Inhibits grain growth at high temperatures, preventing a decrease in elongation. ◑ Increases tensile strength and hot workability. ◑ Improves castability and hardenability.
5. When temper embrittlement occurs at 400~500℃, write the countermeasures. ◑ Rapidly cool during high-temperature tempering. ◑ Add a small amount of Mo (alloying element). ◑ Refine austenite grain size. ◑ Ensure complete martensite formation during quenching. ◑ Obtain high toughness through austempering.
6. In the quenching process, write the characteristics of parts (a) and (b) in the figure below (X).
7. Write the formula for calculating the exposure factor in radiographic testing when the tube voltage is Ma, the time is t, and the distance is d.
8. Draw the process flow diagram for the spheroidizing treatment of bearing steel with carbide size of 0.4~0.5μm. ◑ Long-time heating method: Heating just below A1 (650~700℃) and then cooling. ◑ Repeated heating method: Heating and cooling repeatedly around the A1 transformation point. ◑ Slow cooling method: Heating to a temperature above A3 and Acm, dissolving Fe3C, and then rapidly cooling to prevent the precipitation of network Fe3C and achieve spheroidization. ◑ Isothermal holding method: Heating to a temperature above the A1 transformation point and below Acm, then slowly cooling to the A1 transformation point. ◑ Network carbide dissolving method: Heating to a temperature above the A1 transformation point and below Acm, isothermally holding below the A1 transformation point until the transformation is complete, and then cooling.
9. What is the method of measuring the types of phases present and the interfacial area between phases using microstructure examination? -. Types of Phases ◐ Austenite ◐ Ferrite ◐ Cementite ◐ Pearlite ◐ Bainite ◐ Martensite -. Measurement Methods ◐ Point Counting Method ◐ Intercept Method ◐ Area Weight Method
10. Write the definition and purpose of aluminum (Al) modification treatment and list the additives used in it. -. Definition of Modification Treatment ◑ A treatment that enhances the mechanical properties by strengthening the matrix through precipitation of solute atoms as intermetallic compounds by maintaining a supersaturated solid solution at room temperature or slightly above.
-. Purpose of Modification Treatment ◑ To refine the microstructure and improve strength.