• 한국정밀공학회지
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• 제31권1호
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• pp.29-33
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• 2014

Recently, Difficult-to-cut materials are used in many manufacturing industry. But the difficult-to-cut materials are difficult-to-cutting process. So difficult to cut material cutting process was used after heat treatment through preheating for easy cutting process. In this study, Inconel 625 was preheating using laser heat source in computer simulation. Laser heat source temperature applied $1290^{\circ}C$ that suitable preheating temperature for Inconel 625. And temperature effects such as temperature distribution for moving heat source studied apply to similar actual process condition. Simulation results for heat treatment effects through temperature distribution verified.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.438-443
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• 2005

Laser surface hardening is an effective technique used to improve the tribological properties and also to increase the service life of automobile components such as camshafts, crankshatfs, lorry brake drums and gears. High power CO2 lasers and Nd:YAG lasers are employed for localized hardening of materials and hence are of potential application in the automobile industries. The heat is conducted rapidly into the bulk of the specimen causing self-quenching to occur and the formation of martensitic structure. In this investigation, the microstructure features occurring in Nd:YAG laser hardening SM45C steel are discussed with the use of optical microscopic and scanning electron microscopic analysis. Moreover, This paper describes the optimism of the processing parameters for maximum hardened depth of SM45C steel specimens of 3mm thickness by using CW Nd:YAG laser. Travel speed was varied from 0.6m/min to 1.0m/min. The maximum hardness and case depth fo SM45C steel are 780Hv and 0.4mm by laser hardening.

• 열처리공학회지
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• 제8권1호
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• pp.24-31
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• 1995

Heat flow equation and FEM have been used to calculate the hardening section of material in laser transformation hardening. SCM440 used as the diesel engine piston of vessel has been hardened by a $CO_2$ laser with the wavelength of $10.6{\mu}m$. The specimens were inclined from 0 to 70 degree to investigate the characteristics of laser hardening. The geometrical factor of heat flow equation affects the size of hardening area. The case width decreased with increasing travel speed and the case width increased with increasing inclined angle. Maximum case depth was achieved about 1.0mm and maximum hardness of laser hardened area was of 2.8 times than that of base metal. Experimental data show good agreement with the theoretical calculations for given laser hardening conditions.

• Journal of Welding and Joining
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• 제24권4호
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• pp.15-21
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• 2006

The aim of present study is to investigate the effect of welding parameters and heat treatment conditions on the formability of the $CO_2$ laser welded silicon steel sheet. It was found that there is optimum range of the heat input ($0.6{\sim}0.7kJ/cm$) and gap distance ($0.125{\sim}0.150mm$) for the high tensile strength and the avoidance of the fracture in weld metal. Also, it was essential fur the improvement of formability to perform pre- and post-welding heat treatment which cause the uniform mixture of base metal and welding consumable.

• 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.

• 한국재료학회지
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• 제30권9호
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• pp.465-473
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• 2020

For surface hardening of a continuous casting mold component, a fundamental metallurgical investigation on dissimilar laser clads (Cu-NiCrBSi) is performed. In particular, variation behavior of microstructures and mechanical properties (hardness and wear resistance) of dissimilar clads during long-term service is clarified by performing high-temperature post-clad heat treatment (temperature range: 500 ~ 1,000 ℃ and isothermal holding time: 20 ~ 500 min). The microstructures of clad metals (as-clads) consist of fine dendrite morphologies and severe microsegregations of the alloying elements (Cr and Si); substrate material (Cu) is clearly confirmed. During the post-clad heat treatment, the microsegregations are totally homogenized, and secondary phases (Cr-based borides and carbides) precipitated during the short-term heat treatment are also almost dissolved, especially at the heat treatment conditions of 950 ℃ for 500 min. Owing to these microstructural homogenization behaviors, an opposite tendency of the surface mechanical properties can be confirmed. In other words, the wear resistance (wear rate) improves from 4.1 × 10^-2 ㎣/Nm (as-clad condition) to 1.4 × 10^-2 ㎣/Nm (heat-treated at 950 ℃ for 500 min), whereas the hardness decreases from 453 HV (as-clad condition) to 142 HV (heat-treated at 950 ℃ for 500 min).

• 열처리공학회지
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• 제2권1호
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• pp.21-26
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• 1989

• Journal of Advanced Marine Engineering and Technology
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• 제35권5호
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• pp.600-607
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• 2011

고탄소강은 사용자가 요구하는 특성을 만족시키기 위해 침탄, 질화, 고주파담금질 등에 의해 표면처리 되어져 왔다. 그러나 기존의 처리 방법은 모두 처리물 전체를 가열하거나 균일한 가열을 하지 못하여 표면처리 후 변형의 문제와 처리후의 후가공의 경비문제, 그리고 극히 일부분만 경화가 필요한 부품에는 적용하기 어려운 문제점이 있었다. 이러한 문제를 해결할 수 있는 표면처리법으로로써 레이저열처리 방법이 대두대고 있으며, 레이저열처리는 레이저 빔을 피처리물의 표면에 조사하고 적당한 속도로 이동을 하게 되면 레이저조사부위가 급속하게 가열되고 레이저 빔이 통과한 후에는 표면의 열이 내부로 열전도 되어 급속히 자기냉각(self-quenching)됨으로써 표면에 새로운 기계적 성질을 갖게 하는 열처리법이다. 본 연구에서는 기존의 CW Nd:YAG 레이저 열원보다 효율이 좋은 HPDL을 이용한 고효율, 고기능의 고탄소강 열처리 후 재료적 물성을 평가하였다. 그 결과 레이저빔의 조사속도 및 온도변화에 따른 열처리부 및 모재 부분에 대한 경도특성 및 미세조직의 특성을 명확히 할 수 있었다.

• 한국정밀공학회지
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• 제12권10호
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• pp.130-137
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• 1995

With the rapid growth of the die and mold, the new die making method has been developed. Especially, the laser is very useful, because it has a very fast cutting speed and is possible to manufacture complicated geometry. The quality of the laser cut is to be evaluated with respect to some characteristic quality parameters such as kerf width geometry, roughness and heat affected zone. This paper describes the laser cut characteristic(heat-affected zone) of the alloy tool steels(STD11) and the prediction of the kerf width genmetry by the FEM. On using the oxidation heat and laser beam, the prediction of kerf geometry is more accurate than that only by the laser beam. After laser cutting, the heat-affected zone is generated on the cutting cross section. The magnitude of hardness on the cutting cross section was similar to that of the heat treatment. It was possible to predict heat-affected zone by using the FEM program.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2013년도 춘계학술대회 논문집
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• pp.935-936
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• 2013