• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.2
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• pp.119-124
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• 2013

In this study, the two-dimensional transient temperature of printed Ag nanoparticle ink during continuous wave laser sintering was calculated. Ag nanoparticle ink was printed on a glass substrate by inkjet printing. Then, a 532-nm continuous wave laser with different laser intensities was irradiated on the printed Ag nanoparticle ink for 60 s. During laser irradiation, the in-situ specific resistance of the sintered ink was measured. To obtain the transient temperature of the sintered ink during the laser sintering process, a two-dimensional transient heat conduction equation was derived by applying the Wiedemann-Franz law. It was found that the specific resistance of the sintered ink decreased with an increase in the sintering temperature of the printed ink.

• Proceedings of the Korean Society of Laser Processing Conference
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• 2002.05a
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• pp.57-60
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• 2002

• Proceedings of the Korean Society of Laser Processing Conference
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• 2002.11a
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• pp.45-49
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• 2002

• Journal of the Korean Society for Precision Engineering
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• v.12 no.6
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• pp.87-95
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• 1995

In order to predict the case depth and case width in laser transformation hardening, a finite element method was used to analyze the temperature distribution on the material. Laser hardening of the specimens of SM45C and STE11steels was experimented by using the continuous wave CO$_{2}$ laser with the various travel speeds and the defocused Gaussian beam mode. Phosphate coating was adopted on the surface of SM45C to increase the absorption of 10.6 .mu. m laser energy. Experimental data show good agreement with the theoretical predictions. The maximum possible case depth can be predicted for the given laser hardening conditions, such as laser power, and travel speed.

• Proceedings of the KWS Conference
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• 1992.10a
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• pp.156-161
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• 1992

• Journal of the Korean Society for Precision Engineering
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• v.10 no.4
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• pp.64-72
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• 1993

Analytical models for the prediction of the size of hardened zone in laser surface hardening are presented. The models are based on the solutions to the problem of three-dimensional heat flow in plates with infinite thickness. The validity of the model was tested on medium carbon steel for Gaussian mode of beam. Then the model for rectagular beam was used for the predicition of the size of hardened zone on various hardening process parameters. From the calculation results it appeared that the size and shape of the hardened zone are strongly dependent on process parameters such as beam mode, beam size, and traverse speed.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.41.1-41.1
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• 2009

최근 금형은 자동차뿐만 아니라 여러 산업에서 필수적이며 제품의 품질은 물론 제조원가에 막대한 영향을 미친다. 이러한 금형은 침탄, 질화, 고주파담금질등에 의해 표면처리 되어져 왔으나, 이와 같이 기존의 처리 방법은 모두 처리물 전체를 가열하거나 균일한 가열을 하지 못하기 때문에 변형의 문제와 처리후의 후가공의 경비 문제, 그리고 극히 일부분만 경화가 필요한 부품에는 적용하기 어려운 문제점이 있다. 이러한 문제를 해결할 수 있는 표면처리로서 레이저 표면처리 방법이 대두되고 있으며, 레이저 표면처리는 레이저 빔을 피처리물의 표면에 조사하고 적당한 속도로 이동을 하게 되면 레이저조사부위가 급속하게 가열되고 레이저빔이 통과한 후에는 표면의 열이 내부로 열전도 되어 급속히 자기냉각(Self-quenching)됨으로서 표면에 새로운 기계적 성질을 갖게 하는 표면처리법이다. 이와 같이 레이저를 이용한 표면처리로 기존의 CW Nd:YAG 레이저 열원보다 효율이 좋은 HPDL(High Power Diode Laser)를 이용한 고효율, 고기능 금형 표면처리 후 재료적 물성을 평가하고자 한다. 평가방법은 레이저빔의 조사속도 및 온도변화에 따른 표면처리부, 열영향부 그리고 모재 부분에 대한 경도특성 및 미세조직 변화를 관찰하였다. 또한 조사속도 및 온도변화에 대해 경화깊이를 관찰하였다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.176-183
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• 2005

Laser heat treatment technology is used for improving the feature of fatigue resistance and wear resistance in mobile parts. The purpose of this study is to compare the characteristics of laser heat treatment and high frequency heat treatment, which is commonly used in industrial place. For the preemptive experiment, the distribution, depth and size of hardening and its micro-structural features were compared between surface heat treatment case by defocusing and variables of each process for heat treatment by exclusively manufactured heat treatment optical system. As a result, high frequency heat treatment has wide distribution of hardening depth and width about 3 times larger than laser heat treatment, however, its average hardness showed 621.4Hv which is smaller than the average hardness of laser heat treatment with 691Hv.

• Laser Solutions
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• v.11 no.4
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• pp.7-12
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• 2008

Laser Transformation Hardening(LTH) is one branch of the laser surface modification processes. A lot of energy is needed for the LTH process to elevate workpiece surface to temperature of the austenite transformation($A_3$), which results from utilizing a beam with a larger size and lower power density comparatively. This study is related to the surface hardening for the rod-shaped carbon steel by the high power diode laser whose beam absorptivity is better than conventional types of lasers such as $CO_2$ or Nd:YAG laser. Because a beam proceeds on the rotating specimen, the pretreated hardened-phase can be tempered and softened by the overlapping between hardened tracks. Accordingly, the longitudinal hardness measurement and observation of the micro structure was carried out for an assessment of the hardening characteristics. In addition, a hardening characteristics as a hardenability of materials was compared in the point of view of the hardness distribution and hardening depth and width.

• Laser Solutions
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• v.18 no.2
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• pp.1-4
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• 2015

This study is related to the surface hardening treatment to spheroidal graphite cast iron for die by using high power diode laser. Laser device used in this experiment is capable of real-time laser power control. This is because the infrared temperature sensor (two color pyrometer) attached to the optical system measures the surface temperature of specimen and adjusts the laser power in real time. The surface treatment was carried out with the change of heat treatment temperature at the beam travel speed 3 mm/sec. Hardened width and depth was measured and hardened zone was analyzed by micro vickers hardness test in order to research the optimum condition of heat treatment. The changes in microstructure of the hardened zone also was examined. As a result of hardness measurement and observations on microstructure of hardened zone, hardness increased over three times as compared with base metal because the martensite was formed on the matrix structure.