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  • Title/Summary/Keyword: hardened layer

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Development of Low Pressure Carburizing and High Pressure Gas Quenching System (뺏치식 저압침탄 고압가스냉각 시스템 개발)

  • Jang, Byoung-Lok;Han, Hyoung-Ki;Kim, Won-Bae;Dong, Sang-Keun;Kim, Han-Suck;Cho, Han-Chang
    • 한국연소학회:학술대회논문집
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    • 2005.10a
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    • pp.78-84
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    • 2005
  • The development of eco-friendly low pressure carburizing system with high pressure gas quenching (LPC_GQ, 500kg/charge) led to new stage in the fundamental case-hardening treatments. This is due to its ability to provide tighter tolerances on the carburizing process with notable reductions in distortion of the carburized and hardened workpiece. This system is characteristics by high uniformity and reproducibility of heat treatment results, absence of an intergranular oxidation layer, carburizing of complex shapes, reduced cycle time, low operating costs, simplified production, eliminate post washing, and reduced grinding costs.

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A study on the sensitivity analysis of processing parameters for the laser surface hardening treatment (레이저 표면 경화처리 긍정변수의 민감도 해석에 관한 연구)

  • 이세환;양영수
    • Proceedings of the KWS Conference
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    • 2000.10a
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    • pp.260-263
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    • 2000
  • A methodology is developed and many used to evaluate the response sensitivity of the thermal systems to variations in their design parameters. Technique for computing the sensitivity of temperature distributions to changes in processing parameters needed for deciding the more effective laser input parameters for laser surface hardening treatment are considered. In this study, a state equation governing the heat flow in laser surface treatment is analyzed using a three-dimensional finite element method and sensitivity data of the processing parameter obtained using a direct differentiation method applied for sensitivity analysis. The interesting processing parameter is taken as the laser scan velocity and characteristic beam radius( rb) of the sensitivity of the temperature T versus v and rb is analyzed. And these sensitivity results obtained in another parameters are fixed condition. To verifying the numerical analysis results, hardened layer dimensions (width and depth) of the numerical analysis compared with the results of an experimental data.ata.

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Sensitivity Analysis of Processing Parameters for the Laser Surface Hardening Treatment by Using the Finite Element Method (유한요소법을 이용한 레이저 표면경화처리 공정변수의 민감도 해석)

  • 이세환;양영수
    • Journal of Welding and Joining
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    • v.19 no.2
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    • pp.228-234
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    • 2001
  • A methodology is developed and used to evaluate the response sensitivity of the thermal systems to variations in their design parameters. Technique for computing the sensitivity of temperature distributions to changes in processing parameters needed to decide the more effective laser input parameters for laser surface hardening treatment is considered. In this study, a state equation governing the heat flow in laser surface treatment is analyzed using a three-dimensional finite element method and sensitivity data of the processing parameter obtained using a direct differentiation method is applied to the sensitivity analysis. The interesting processing parameters are taken as the laser scan velocity and laser beam radius ( rb), and the sensitivities of the temperature T versus v and rb are analyzed. These sensitivity results are obtained with another parameters fixed. To verify the numerical analysis results, hardened layer dimensions (width and depth) of the numerical analysis are compared with the experimental ones.nes.

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Development of High Performance Low Pressure Carburizing System (Batch type 가스침탄 열처리로 국산화개발)

  • Kim, Won-Bae;Dong, Sang-Keun;Jang, Byoung-Lok;Han, Hyoung-Ki;Kim, Han-Suck;Cho, Han-Chang
    • Journal of the Korean Society for Heat Treatment
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    • v.19 no.5
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    • pp.262-269
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    • 2006
  • The development of eco-friendly low pressure carburizing system with high pressure gas quenching(LPC-GQ, 500kg/charge) led to new stage in the fundamental case-hardening treatments. This is due to its ability to provide tighter tolerances on the carburizing process with notable reductions in distortion of the carburized and hardened workpiece. This system is characteristics by high uniformity and reproducibility of heat treatment results, absence of an intergranular oxidation layer, carburizing of complex shapes, reduced cycle time, low operating costs, simplified production, eliminate post washing, and reduced grinding costs.

Effect of Heat Treatment Conditions and Densities on Residual Stresses at Hybrid (FLN2-4405) P/M Steels

  • Kafkas, Firat;Karatas, Cetin;Saritas, Suleyman
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09a
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    • pp.566-567
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    • 2006
  • The characteristics of residual stresses occurring in PM steel based nickel (FLN2-4405) was investigated. The measurements of residual stresses were carried out by electrochemical layer removal technique. The values and distributions of residual stresses occurring in PM steel processed under various densities and heat treatment conditions were determined. In most of the experiments, tensile residual stresses were recorded in surface of samples. The residual stress distribution on the surface of the PM steels is affected by the heat treatment conditions and density. Maximum values of residual stresses on the surface were observed sinter hardened condition and 7.4g/cm3 density. Minimum level of recorded tensile residual stresses are150 MPa and its maximum level is 370 MPa.

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Effects of Annealing Temperature on Interface Properties for Al/Mild Steel Clad Materials (어닐링 온도 변화가 Al/연강 클래드재의 계면 특성에 미치는 영향)

  • Jeong, Eun-Wook;Kim, Hoi-Bong;Kim, Dong-Yong;Kim, Min-Jung;Cho, Young-Rae
    • Korean Journal of Materials Research
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    • v.22 no.11
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    • pp.591-597
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    • 2012
  • For heat exchanger applications, 2-ply clad materials were fabricated by rolling of aluminum (Al) and mild steel sheets. Effects of annealing temperature on interface properties, especially on inter-layer formation and softening of strain hardened mild-steel, for Al/mild steel clad materials, were investigated. To obtain optimum annealing conditions for the Al/mild steel clad materials, annealing temperature was varied from room temperature to 600C. At the annealing temperature about 450C, an inter-layer was formed in an island-shape at the interface of the Al/mild steel clad materials; this island expanded along the interface at higher temperature. By analyzing the X-ray diffraction (XRD) peaks and the energy dispersive X-ray spectroscopy (EDX) results, it was determined that the exact chemical stoichiometry for the inter-layer was that of Fe2Al5. In some samples, an X-layer was formed between the Al and the inter-layer of Fe2Al5 at high annealing temperature of around 550C. The existence of an X-layer enhanced the growth of the inter-layer, which resulted in the delamination of the Al/mild-steel clad materials. Hardness tests were also performed to examine the influence of the annealing temperature on the cold deformability, which is a very important property for the deep drawing process of clad materials. The hardness value of mild steel gradually decreased with increasing annealing temperature. Especially, the value of hardness sharply decreased in the temperature range between 525C and 550C. From these results, we can conclude that the optimum annealing temperature is around 550C under condition of there being no X-layer creation.

Electrical Resistivity Imaging for Upper Layer of Shield TBM Tunnel Ceiling (쉴드 TBM터널 상부 지반 연약대 전기탐사)

  • Jung, Hyun-Key;Park, Chul-Hwan
    • Proceedings of the Korean Geotechical Society Conference
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    • 2005.03a
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    • pp.401-408
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    • 2005
  • Recently shield TBM tunnellings are being applied to subway construction in Korean cities. Generally these kinds of tunnellings have the problems in the stability of ground such as subsidence because urban subway is constructed in the shallow depth. A sinkhole occurred on the road just above the tunnel during tunneling in Kwangju, so a survey for upper layer of the tunnel was needed. But conventional Ground Probing Radar can't be applicable due to the presence of steel-mesh screen in the shield segment, so no existent geophysical method is applicable in this site. Because the outer surface of each shield segment is electrically insulated, dipole-dipole resistivity method which is popular in engineering site investigation, was tried to this survey for the first time. Specially manufactured flexible ring-type electrodes were installed into the grouting holes at an interval of 2.4 m on the ceiling. The K-Ohm II system which has been developed by KIGAM and tested successfully in many sites, was used in this site. The system consists of 1000Volt-1Ampere constant-current transmitter, optically isolated 24 bit sigma-delta A/D conversion receiver - maximum 12 channel simultaneous measurements, and graphical automatic acquisition software for easy data quality check in real time. Borehole camera logging with circular white LED lighting was also done to investigate the state of the layer. Measured resistivity data lack of some stations due to failing opening lids of holes, shows general high-low trend well. The dipole-dipole resistivity inversion results discriminate (1) one approximately 4 meter diameter cavity (grouted but incompletely hardened, so low resistivity - less than 30Ωm), (2) weak zone (100-200Ωm), and (3) hard zone (high resistivity - more than 1000Ωm) very well for the distance of 320 meters. The 2-D inversion neglects slight absolute 3-D effect, but we can get satisfactory and useful information. Acquired resistivity section and video tapes by borehole camera logging will be reserved and reused if some problem occurs in this site in the future.

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Fabrication of Nickel Oxide Film Microbolometer Using Amorphous Silicon Sacrificial Layer (비정질 실리콘 희생층을 이용한 니켈산화막 볼로미터 제작)

  • Kim, Ji-Hyun;Bang, Jin-Bae;Lee, Jung-Hee;Lee, Yong Soo
    • Journal of Sensor Science and Technology
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    • v.24 no.6
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    • pp.379-384
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    • 2015
  • An infrared image sensor is a core device in a thermal imaging system. The fabrication method of a focal plane array (FPA) is a key technology for a high resolution infrared image sensor. Each pixels in the FPA have Si3N4/SiO2 membranes including legs to deposit bolometric materials and electrodes on Si readout circuits (ROIC). Instead of polyimide used to form a sacrificial layer, the feasibility of an amorphous silicon (αSi) was verified experimentally in a 8×8 micro-bolometer array with a 50μm pitch. The elimination of the polyimide sacrificial layer hardened by a following plasma assisted deposition process is sometimes far from perfect, and thus requires longer plasma ashing times leading to the deformation of the membrane and leg. Since the amorphous Si could be removed in XeF2 gas at room temperature, however, the fabricated micro-bolomertic structure was not damaged seriously. A radio frequency (RF) sputtered nickel oxide film was grown on a Si3N4/SiO2 membrane fabricated using a low stress silicon nitride (LSSiN) technology with a LPCVD system. The deformation of the membrane was effectively reduced by a combining the αSi and LSSiN process for a nickel oxide micro-bolometer.

The Influence of Ar Gas in the Nitriding of Low Temperature Plasma Carburized AISI304L Stainless Steel. (AISI304L 스테인리스강의 저온 플라즈마 침탄처리 후 질화처리 시 Ar 가스가 표면 경화층에 미치는 영향)

  • Jeong, Kwang-ho;Lee, Insup
    • Korean Journal of Metals and Materials
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    • v.46 no.3
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    • pp.125-130
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    • 2008
  • Conventional plasma carburizing or nitriding for austenitic stainless steels results in a degradation of corrosion resistance. However, a low temperature plasma surface treatment can improve surface hardness without deteriorating the corrosion resistance. The 2-step low temperature plasma processes (the combined carburizing and post nitriding) offers the increase of both surface hardness and thickness of hardened layer and corrosion resistance than the individually processed low temperature nitriding and low temperature carburizing techniques. In the present paper, attempts have been made to investigate the influence of the introduction of Ar gas (0~20%) in nitriding atmosphere during low temperature plasma nitriding at 370C after low temperature plasma carburizing at 470C. All treated specimens exhibited the increase of the surface hardness with increasing Ar level in the atmosphere and the surface hardness value reached up to 1050 HV0.1, greater than 750 HV0.1 in the carburized state. The expanded austenite phase (γN) was observed on the most of the treated surfaces. The thickness of the γN layer reached about 7μm for the specimen treated in the nitriding atmosphere containing 20% Ar. In case of 10% Ar containing atmosphere, the corrosion resistance was significantly enhanced than untreated austenitic stainless steels, whilst 20% Ar level in the atmosphere caused to form CrN in the N-enriched layer (γN), which led to the degradation of corrosion resistance compared with untreated austenitic stainless steels.

Phytosociological Classification and its Ecological Characteristics of Pinus sylvestris Plantations in Eifel, Germany (독일(獨逸) Eifel 지방(地方) 구주적송(九州赤松)(Pinus sylvestris) 조림지(造林地)의 식물사회학적(植物社會學的) 분류(分類)와 생태적(生態的) 특성(特性))

  • Lee, Young-Geun;Cho, Hyun Je
    • Journal of Korean Society of Forest Science
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    • v.89 no.3
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    • pp.378-383
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    • 2000
  • Pinus sylvestris plantations in the Eifel mountains, Germany, were studied and classified phytosociologically. Ecological characteristics(soil, natural regeneration & succession) of the plant communities classified were analyzed and described with emphasis on the forest management. According to soil and topographic characteristics, this plantations were divided into four categories ; Vaccinium myrtillus-Pinus sylvestris community of the adequate moisture area, Pteridium aquilium-Pinus sylvestris community of the moisture area, Molinia caerulea-Pinus sylvestris community of the hardened soil layer B and Festuca tenuifolia-Pinus sylvestris of the dry area. Tree species growing below the shrub layer was analyzed. The results were considered as Vaccinium mytillus-Pinus sylvestris, Pteridium aquline-Pinus sylvestris and Molinia caerulea-Pinus sylvestris will be changed into Fagus sylvatica forest following Quercus forest, and Festuca tenuifilia-Pinus sylvestris will be changed into Pinus sylvestris-dominated climax forest.

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