• 열처리공학회지
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• 제5권1호
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• pp.23-31
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• 1992

It is investigated that Fe-C-N compound layer, defusion layer, and induction hardened layer produced by nitrocarburizing blend heat treatment in austenitic temperature with high frequency induction heating of mild steel specimen sprayed sursulf salt-bath. As the temperature of blend-heat treatment got increased, the thickness and hardness of compound layer and diffusion layer were increased. Compound layer(max. $35{\mu}m$), diffusion layer (max. 2.5mm) and induction hardened layer were gained in the shortest time 10 sec and in the case of $1000^{\circ}C$ total hardness depth of those was about 3.5mm. When the blend-heat treated specimen was reheated, maximum hardness of compound layer was dropped more than that of the reheated compound layer after sursulf treated, whereas hardness of diffusion layer was increased.

• 대한기계학회논문집A
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• 제37권3호
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• pp.429-436
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• 2013

본 논문에서는 고주파 열처리된 SAE1055 베어링강의 경도에 따른 피로 거동 및 이의 확률론적 평가를 수행하였다. 이를 위하여 경도 수준에 따른 5 종류의 시험편(A : 원재료, B : HV390-전경화, C : HV510-전경화, D : HV700-전경화 및 E : HV-700 표면경화)를 준비하였다. 피로시험은 4 점 회전굽힘 피로시험기를 이용하여 응력비 R=-1 의 조건하에서 수행하였다. 그 결과, SAE1055 강의 피로 거동은 경도에 따라 크게 변화하였으나 HV510 수준이상에서는 피로한도의 증가는 관찰되지 않았다. 또한 피로 파손기구에 대한 경도의 영향을 평가하기 위하여 SEM(scanning electron microscope)을 이용한 파면 관찰을 수행하였다. 피로수명의 통계적 특성은 P-S-N(probabilistic S-N) 곡선을 이용하여 평가되었으며 이에 대한 경도의 영향은 잔류치 해석(residue analysis)을 통하여 수행하였다.

• 한국자동차공학회논문집
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• 제2권6호
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• pp.1-8
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• 1994

To enhance the strength of gears for transmission, Generally caburizing heat treatment is applied. But there are some problems in this technology the distortion of gears during heat treatment process, and the discontinuity of manufacturing process. For these reasons, the high frequency induction hardening process is widely used. This method is one of the surface hardening process to improve the wear resistance and fatigue life of the machine components. In this study, to compare the bending fatigue strength of caburized gear with that of induction hardened gear, bending fatigue testing of gears with two different cases was performed by using an electrohydraulic servo-controlled fatigue testing machine and double tooth bending fatigue test fixture. Fatigue life distributions at constant stress levels were established directly from fatigue data. For gear design, the fatigue strength distribution at specified life is more important. This distribution is obtained by statical transformation from fatigue life distribution. Reliability of bending fatigue strength was estimated by P-S-N curves and Weibull distribution.

• Journal of Advanced Marine Engineering and Technology
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• 제36권1호
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• pp.78-84
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• 2012

금형의 공정 과정에서 금형과 성형품 사이에서 발생하는 마찰로 인해 발생하는 금형의 마모가공차로 작용하여 성형 품질을 저하시킬 수 있다. 따라서 금형의 내마모성을 향상시키기 위해 질화나 침탄처리, 화염 및 고주파 표면처리 등의 방법들이 적용되어 왔다. 하지만 형상의 제한이나 제품의 변형 등과 같은 문제점을 수반하고 있기 때문에, 이러한 문제점을 해결할 수 있는 표면처리 방법으로써 레이저 표면처리 기술이 검토되고 있다. 따라서 본 연구에서는 고출력 다이오드 레이저를 이용, 금형재료용 주철의 표면처리를 시도하였다. 앞서 제1보와 제2보의 논문에서는 금형의 재료 및 형상의 차이에 따른 열처리 특성을 비교하였다면, 본 논문에서는 열처리 후 생성되는 경화부, 경계부위 및 모재의 조직적 차이를 분석하기 위해 광학 현미경 및 전자 현미경을 이용하여 미세조직을 관찰하고, EDS를 통해 조직의 상태를 파악하였다. 미세조직 관찰 결과, 경화부는 침상의 마르텐사이트 조직이 형성되어 있었다.

• 비파괴검사학회지
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• 제11권1호
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• pp.38-43
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• 1991

The relationship between eddy current response and case hardening depth has been studied on SM40C(KS D-3752) and SCM440(KS D-3711) steels which were surface hardened by high frequency induction hardening. The results obtained in this study were as follows ; 1) Case hardening depth was successfully measured by observing the eddy current impedance changes of each steel. The impedance decreased linearly with increasing case hardening depth. 2) For large impedance gradient between the hardened surface and core metal, the eddy current response was more sensitive to case hardening depth than for low impedance gradient.

• 열처리공학회지
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• 제10권3호
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• pp.165-171
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• 1997

Laser hardening for the piston ring groove of ductile cast iron was tried. Mechanical and microstructural investigation for the hardened area indicated that the laser heating technique could replace conventional induction hardening process completely and further showed that post grinding process would be eliminated by minimizing bulging of heat treated area. In laser hardening, the volume increase caused by martensitic phase transformation proved to be less than $10{\mu}m$, which insures no post machining on the hardened surface. As expected, the depth of hardening was inversely proportional to the beam scanning velocity and the highest surface hardness was obtained at the beam velocity of 0.75m/min. Heat treatment using phosphate coating demonstrated quite comparable result to the case of graphite suscepter.

• 대한기계학회논문집A
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• 제34권5호
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• pp.645-649
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• 2010

고주파열처리(induction hardening)는 엔진의 구동력을 차동장치에서 바퀴까지 전달해주는 부품인 액슬축(axle shaft)의 비틀림 강도를 증가시키기 위해 적용되는 열처리 방법이다. 고주파 열처리 과정의 급속가열과 급속냉각은 소재에 잔류응력과 물성치를 변화시켜 액슬축의 허용 전달토크를 변화시킨다. 본 연구에서는 고주파 열처리한 액슬축의 잔류응력의 분포와 열처리 깊이에 따른 비틀림 강도 변화를 열물성 및 상변태를 고려한 유한요소 해석을 통해 예측하였으며 이를 시험과 비교하였다.

• 한국정밀공학회지
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• 제23권10호
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• pp.74-79
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• 2006

In this study, the tempering effect on the wear characteristics of induction-hardened SPS5 steel was investigated. For this purpose, three tempering conditions were applied to control the hardness of heat-treated SPS5 steel. Ball-on-disk wear tests have been performed using zircornia balls on the tempered specimens to determine the variation of wear characteristics. The results showed that friction coefficient decreased with increasing hardness for induction hardening conditions. This seems to occur because real contact area between specimen and mating ball was affected by the specimen hardness.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.409-410
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• 2006

In this study, the tempering effect on the wear characteristics of induction-hardened SPS5 steel was investigated. For this purpose, three tempering conditions were applied to control the hardness of heat-treated SPS5 steel. Ball-on-disk wear tests have been performed using zircornia balls on the tempered specimens to determine the variation of wear characteristics. The results showed that friction coefficient decreased with increasing hardness for induction hardening conditions. This seems to occur because real contact area between specimen and mating ball was affected by the specimen hardness.

• 대한금속재료학회지
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• 제48권12호
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• pp.1103-1108
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• 2010

We fabricated flanged outer races for wheel bearing units using 0.52%C clean steels, and then characterized and studied the transformation behavior. The outer races produced by hot forging and high frequency induction hardening in this study were analyzed through microstructural characterization using OM, SEM, TEM, and X-ray diffractometer and their microhardness depth profiles of the raceway contacted by balls were measured using MVH tester. The surface hardened layers with a uniform hardness profile in the raceway consisting of very fine martensite with sub-micron sized retained austenite could be formed for very short time during high frequency induction hardening after hot forging. The very fine martensite may be transformed on rapid cooling, from the inhomogeneous austenite nucleated on rapid heating in small particles of pearlitic cementite fragmentated by hot forging. On the other hand the sub-micron sized retained austenite may be chemically stabilized due to their extremely small size, from the small austenite nucleated at the grain boundaries.