AISI 4140강의 템퍼링 온도에 따른 기계적 성질과 임피던스 특성과의 관계에 관한 연구 = Study on the Relationship between Mechanical Properties and Impedance Characteristics with respect to Tempering Temperatures in AlSl 4140 Steel

다국어 초록 (Multilingual Abstract)

This study has been carried out to establish the relationship between mechanical properties and impedance characteristics by using nondestructive testing techniques.
The results obtained from the experiment are as follows;
1. Optical micrographs have been shown that as tempering temperatures increase from 200℃ to 750℃, various microstructural changes such as the precipitation and growth of ∈-carbides, the formation of lower bainite from the decomposition of retained austenite, the formation and coarsening of cementite particles that occurs after ∈-carbides, and the recrystallization of ferrite grains are involved.
2. Hardness measurement has revealed that Vickers hardness values almost linearly decrease with increasing tempering temperatures.
3. It has been shown from tensile test that as tempering temperature increases, both tensile strength and yield strength decrease almost linearly whereas elongation and reduction of area tend to increase.
4. Values for the relative impedance are shown to repidly increase for a range of tempering temperature of 200 to 350℃, give a maximum value at 450℃, then decrease almost linearly for a temperature range from 450℃ to 700℃, and finally increase again after showing a minimum value at 700℃. Those changes in impedance are related to the precipitation of carbides and the microstructural changes that occur during tempering.
5. The relation between relative impedance and hardness depends on tempeing temperatures and yields
for tempering temperatures below 350℃
Irel. = -0.247H + 150,
for a temperature range of 450 ~ 700℃
Irel. = 0.117H + 42.
6. The relation between relative impedance and tensile strength gives for tempering temperatures below 350℃
Irel. = -0.58 σ + 115,
for a temperature range of 450 ~ 700℃
Irel. = 0.36 σ - 39.
7. Changes in microstructures and mechanical properties cause some influences on electromagnetic properties and hence some variation of the relative impedance of electromagnetic induction coil.

목차 (Table of Contents)

• 목차 = 1
• Ⅰ. 서론 = 2
• Ⅱ. 실험방법 = 4
• 1. 시편준비 = 4
• 2. 현미경 조직 관찰 = 6
• 3. 기계적 성질 시험 = 6
• 4. 전자기유도 시험 = 7
• 가. 전자기유도 시험의 원리 = 7
• 나. 임피던스 측정 = 9
• Ⅲ. 실험결과 및 고찰 = 12
• 1. 현미경 조직 = 12
• 2. 기계적 성질 = 17
• 3. 기계적 성질과 코일의 임피던스와의 관계 = 18
• 가. 탄화물 석출과 임피던스의 변화 = 18
• 나. 기계적 성질과 임피던스 = 20
• Ⅵ. 결론 = 24
• 참고문헌 = 26
• SUMMARY = 28