레이져 표면 경화 공정에서 신경회로망을 이용한 경화층 깊이 예측

우현구,조형석,한유희,Woo, Hyun Gu,Cho, Hyung Suck,Han, You Hie 한국정밀공학회 1995 한국정밀공학회지 Vol.12 No.11

In the laser surface hardening process the geometrical parameters, especially the depth, of the hardened layer are utilized to assess the integrity of the hardening layer quality. Monitoring of this geometrical parameter ofr on-line process control as well as for on-line quality evaluation, however, is an extremely difficult problem because the hardening layer is formed beneath a material surface. Moreover, the uncertainties in monitoring the depth can be raised by the inevitable use of a surface coating to enhance the processing efficiency and the insufficient knowledge on the effects of coating materials and its thicknesses. The paper describes the extimation results using neural network to estimate the hardening layer depth from measured surface temperanture and process variables (laser beam power and feeding velocity) under various situations. To evaluate the effec- tiveness of the measured temperature in estimating the harding layer depth, estimation was performed with or without temperature informations. Also to investigate the effects of coating thickness variations in the real industry situations, in which the coating thickness cannot be controlled uniform with good precision, estimation was done over only uniformly coated specimen or various thickness-coated specimens. A series of hardening experiments were performed to find the relationships between the hardening layer depth, temperature and process variables. The estimation results show the temperature informations greatly improve the estimation accuracy over various thickness-coated specimens.

SM45C의 레이저 표면경화특성

신호준,유영태,안동규,임기건 한국공작기계학회 2005 한국공작기계학회 춘계학술대회논문집 Vol.2005 No.-

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.

Ti-6Al-4V 합금의 표면 경화 시 경화기구 및 공정변수가 표면 경화에 미치는 영향

서동명,윤혜정,황태우,문영훈 한국소성∙가공학회 2019 소성가공 : 한국소성가공학회지 Vol.28 No.1

The effect of hardening methods and process parameters on surface hardening of a Ti-6Al-4V Alloy has been investigated in this study. To characterize the effectiveness of the respective surface hardening methods, samples of a Ti-6Al-4V alloy were self-quenched, laser-nitrided, laser-carburized, laser-carbonitrided at the same laser irradiation conditions. This experimental procedure was followed by comparing the microstructural evolutions and mechanical properties of the respective samples after the laser surface hardenings. The hardening characteristics of the respective laser surface hardenings were well defined in this study, and the hardness was significantly influenced by the reaction compounds and laser energy density.

다이오드 레이저를 이용한 탄소강 환봉의 표면변태 경화특성

김종도(Jong-Do Kim),강운주(Woon-Ju Kang),이수진(Su-Jin Lee),윤희종(Hee-jong Yoon),이제훈(Jae-Hoon Lee) 한국레이저가공학회 2008 한국레이저가공학회지 Vol.11 No.4

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(A₃), 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 CO₂or 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.

Fiber laser를 이용한 공구강 AISi H13의 표면경화 연구

이재호(Jae Ho Lee),장정환(Jeong Hwan Jang),주병돈(Byeong Don Joo),손영명(Young Myung Son),문영훈(Young Hoon Moon) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5

Laser surface heat treatments comprise a wide variety of techniques by which hard and wear-resistant layers can be obtained on surface without affecting the bulk material. It is known that the performance of these kinds of treatments is highly influenced by the different parameters involved in the process, such as the thermophysical properties of the material or the laser beam settings: pulse width, power and scan rate to the workpieces. In this research, an attempt has been made to improve the surface hardness and wear properties of AISI H13 tool steel through solid solution hardening and refinement of microstructures using a 200W fiber laser as a heat generating source. The hardness of laser melted zone was investigated. As a result, the hardness of as-received AISI H13 tool steel was approximately 240Hv, the hardness of after laser surface heat treatment was around 480~510Hv. In order to identify the effect of heat input on the laser melting zone, many scanning conditions were controlled. The hardening depth and width were increased with the increase in the heat input applied. After investigation, application of experimental results will be considered for mold industry.

CW Nd:YAG 레이저를 이용한 SM45C강의 표면경화특성

김지환,유영태,신호준,노경보 조선대학교 에너지.자원신기술연구소 2003 에너지·자원신기술연구소 논문지 Vol.25 No.1

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 CO_(2) 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 4.5㎜, 10㎜ thickness by using CW Nd:YAG laser. Travel speed was varied from 0.6m/min to 1.5m/min. The maximum hardness and case depth of SM54C steel are 76Hv and 0.688㎜ by laser hardening. When the surface of specimens was melted during laser hardening, the surface hardness of SM45C steel was decreased.

레이저를 이용한 Ti-6Al-4V 합금의 경화 공정에서 공정 변수의 영향분석 및 모델링

김은성,김홍석 한국정밀공학회 2019 한국정밀공학회지 Vol.36 No.8

The objective of this study was to perform surface hardening experiments of titanium alloy using laser. The surface hardness value after laser hardening treatment was observed to increase with respect to the inflow of laser energy. However, when the laser energy exceeded the critical value, damage and cracks were observed on the surface of the material. The relationship between surface hardness values and process variables such as laser energy, scan speed, and number of laser scans was quantitatively modeled through the design of experiments and analysis of variance. Using the established mathematical model, the surface hardness value of the material can be predicted accurately with an average of 10% error over various process conditions. Analysis of the surface composition of the material using energy dispersive spectrometry showed that titanium oxide was the main cause of the increasing surface hardness. Further studies will be conducted to improve the accuracy and predictability of the model using nonlinear modeling techniques.

SKD61 열간합금강의 레이저 표면 합금화 경화처리 공정에서 SKH51 분말 송급속도에 따른 균열 형성에 대한 고찰

최성원 ( Seong-won Choi ),이광현 ( Kwang-hyeon Lee ),서정 ( Jeong Suh ),오명환 ( Myeong-hwan Oh ),강정윤 ( Chung-yun Kang ) 대한금속재료학회(구 대한금속학회) 2016 대한금속·재료학회지 Vol.54 No.3

A laser surface-melting alloying process using a laser beam is a new surface-hardening process of obtaining an alloying layer that melts the surfaces of substrates and alloying powder at the same time. This study used SKD61 hot die steel as a substrate and SKH51 powder as an alloying powder. The laser beam speed and the laser power were fixed at 70 mm/sec and 2 kW. The power feeding rate was changed from 0 rpm to 6 rpm (step: 1 rpm). The alloying layer showed high hardness (710~830 Hv), but cracks occur at a high powder feeding rate. Cracks occur at more than 5 rpm, and the lengths of cracks become longer as the powder feeding rate increases. Moreover, cracks were observed at the dendrite boundary, and dendrite protrusions were observed on the fracture surfaces. As the powder feeding rate increases, the concentration of the Mo, V, and W in alloying layer increase. The liquidus and solidus temperatures decreased by as much as 6 ℃ and 26 ℃. As a result of calculating the aspect ratio (penetration depth/width) of the molten zone, it was found that there is no difference as the powder feeding rate increases. Therefore, strain by solidification contraction was constant with an increase in the powder feeding rate, but cracks occur, and the number of cracks increases because the solidus temperature decreases and the ductility of alloying layer reduces.

SM45C 와 STD_(11)의 CW Nd:YAG 레이저 표면경화 특성비교

김지환,유영태,신호준,오용석 조선대학교 에너지.자원신기술연구소 2003 에너지·자원신기술연구소 논문지 Vol.25 No.1

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 CO_(2) 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 microstructrual features occurring in Nd:YAG laser hardening SM45C and STD_(11) steel are discussed with the use of optical microscopic and scanning electron microscopic analysis. Moreover, This paper describes the optimisation of the processing parameters for maximum hardened depth of SM54C and STD_(11) steel specimens of 4.5㎜, 10㎜ thickness by using CW Nd:YAG laser.

$CO_2$ 레이저 분산빔에 의한 표면경화가 구상흑연주철의 피로특성에 미치는 영향

박근웅,한유희,이상윤 한국레이저가공학회 1999 한국레이저가공학회지 Vol.2 No.2

This study has been performed to investigate into some effects of the output power and traverse speed of laser beam on the microstructures, hardness and fatigue resistance of the ductile iron surface-hardened by $CO_2$ laser defocussed beam. Optical micrographs have shown that with increasing the output power and decreasing the traverse speed, the martensite was coarsened and some retained austenite were appeared in ductile iron. The microstructures of hardening zone were composed of bull's eye and some nodular graphite dissolved structures by the effect of self quenching. Fatigue fracture characteristics of ductile iron have appeared in the high stress and low stress ranges. The fracture initiated at nodular graphites in the surface hardened layer due to the stress concentration caused by a notch effect. The interior graphite nodules were broken away or popped out during crack propagation. Fatigue test has shown that values of fatigue strength considerably increased with increasing output power at a given traverse speed.