Ni 합금강의 크리프 거동

황경충,김종배,강성수 한국안광학회 2008 한국안광학회지 Vol.13 No.4

목적: 각종 기계 부품에 주로 사용되는 9% Ni 합금강의 고온 크리프 시험과 그 시편들의 파단면을 관찰하고 Larson-Miller 변수를 적용하여 상수 C값을 결정하여 합금강의 수명을 예측하는데 있다. 방법: 본 시험의 장치는 Andrade와 F. Garofalo 등이 고안한 레버-빔 형으로 제작되었고, 크리프시험 설정조건은 시험편에 미치는 영향을 알 아보기 위하여 4가지의 온도조건과 4가지 응력조건을 설정하여 16가지의 조건 하에서 시험을 실시하였다. 결과: 크 리프 시험온도가 증가함에 따라 크리프 변형에 따른 응력의 멱지수(n)는 3.97에서 3.55로 점진적으로 감소하는 경 향을 보였다. 크리프 변형의 활성화에너지는 응력이 증가함에 따라 90.39에서 83.64kcal/mol로 점진적으로 감소하 였다. Larson-Miller 변수의 계산에 의한 상수 C값은 약 22로 계산되었으며, 사용온도가 제시되면 그 수명을 예측할 수 있다. 파단면의 SEM 측정결과 저온과 고온의 경우는 입내파단에 의한 취성파괴 현상이 나타났으며, 중간정도 온도영역에서는 입계파단에 의한 연성파괴현상이 나타났으며, 일부에서는 딤풀현상도 나타났다. 결론: 9% Ni 합금 강에 대한 고온 크리프시험과 그 시편들의 파단면을 관찰한 결과를 제시하여 그 파괴현상을 분석함으로써 설비분 야의 부품활용에 대한 기초설계 자료를 구축하여 장비의 수명예측에 유용하게 응용될 수 있다. Purpose: To observe the high temperature creep test and the fracture surface of the samples of 9% Ni alloy steel generally used for all kinds of mahine parts and predict the durability of that by determining a constant of C with a Larson-Miller variable. Methods: The equipment of this test was made into lever-beam style designed by Andrade and F. Garofalo et al.. The condition of creep test was set under 16 kinds of conditions after fixing 4 kinds of temperature condition and 4 kinds of stress condition to check how it effects the samples. Results: The temperature of creep test was increased, the stress index (n) of creep deformation was gradually decreased from 3.97 to 3.55. The activation energy of creep deformation was decreased from 90.39 to 83.64 kcal/mol when the stress was increased. A constant of C value by calculation of larson-Miller variable was about 22 and if temperature for use is suggested, the durability could be calculated. Conclusions: By analyzing the fracture phenomenon and suggesting the observation result of the fracture surface of the samples and creep test of 9% Ni alloy steel, the basic design data for the practical use of accessories in the field of equipment could be constructed and used to predict the durability of the equipment.

초 두랄루민(Al 2024)의 정적인 크리프 거동

황경충,윤종호 한국공작기계학회 2004 한국공작기계학회 추계학술대회논문집 Vol.2004 No.-

Super-duralumin has widely been used as the part materials of aerospace and automobile industry because it has high specific strength and also is light. But, we have little design data about the creep behaviors of the alloy. Therefore, in this study, every creep test under four constant stress conditions have been conducted for four temperature conditions. A series of creep tests had been performed to get the basic design data and life prediction of super-duralumin products and we have gotten the following results. First, the stress exponents showed the descending trend as the test temperatures increase. Secondly, the creep activation energy gradually decreased as the stresses become bigger. Thirdly, the constant of Larson-Miller parameters on this alloy was estimated about 6. And last, the fractographs at the creep rupture showed both the brittle fracture due to the transgranular rupture.

안경테소재 합금(Ti-6AI-4V)의 크리프 특성

황경충,윤종호 한국공작기계학회 2003 한국공작기계학회 추계학술대회논문집 Vol.2003 No.-

Titanium alloy has widely been used as glasses rim material because it has high specific strength and also is light, harmless to men. But, we have little design data about the creep behaviors of the alloy. Therefore, in this study, an apparatus has been designed and built for conducting creep tests under constant load conditions. A series of creep tests on them have been performed to get the basic design data and life prediction of titanium products and we have gotten the following results. First, the stress exponents decrease as the test temperatures increase. Secondly, the creep activation energy gradually decreases as the stresses become bigger. Thirdly, the constant of Larson-Miller parameters on this alloy is estimated about 13. And last, the fractographs at the creep rupture show both the ductile and the brittle fracture according to the creep conditions.

인코넬 690 합금의 절삭성에 관한 연구

황경충,윤종호,최재하,김성청 한국공작기계학회 2002 한국생산제조학회지 Vol.11 No.2

In domestic industry, there is no manufacturers specialized in the production of cutting tools for the difficult cutting materials. Then, we have few data about them. In this study, the gear driving high speed lathe on which is mounted by a tool dynamometer and high speed CCTV were used to measure the various machining characteristics. Relations among the cutting speed, feed rate per revolution, cutting depth, cutting forces and surface roughness were graphically analyzed under 64 cutting conditions. The process of chip, i.e., generation, development and falling-off also were visualized for the characterization of chip shapes of the difficult-to-cut materials using the CCTV.

PVD법에 의한 TiAlN코팅의 절삭공구에의 적용특성

황경충,윤종호 한국공작기계학회 2003 한국공작기계학회 춘계학술대회논문집 Vol.2003 No.-

As the machine tool industry progresses, the performance of cutting tools also needs to be of good quality and specialized. If the existing metal cutting tool tip is coated properly, its life would be longer and the machining of a difficult-to-cut material also could be possible. For the development of the high quality cutting tool, the applicabilities of TiAlN coating deposited by PVD on the cutting insert were experimentally investigated. The various measurements, such as, SEM micrograph, XRD pattern, AFM surface morphology, and hardness were performed to cross-check the possibility and availability of TiAlN coated tool in the field. The effects of it is successful and we hope to see good results in many fields.

2상 스테인리스강(STS 329J1)의 크리프 특성

황경충,권종완,윤종호 한국공작기계학회 2005 한국생산제조학회지 Vol.14 No.2

Micro duplex stainless steel is used to denote a fine scale two-phase micro structure consisting austenite and ferrite. The development of this structure was done by proper thermo-mechanical processing. The objective of present investigation is to study creep characteristics of this alloy. Since we have little design data about the crap behaviors of the alloy. An apparatus has been designed and built for conducting creep tests under constant load conditions. A series of creep tests on them have been performed to get the basic design data and life prediction of micro duplex stainless steel products and we have gotten the following results. First, the stress exponents decrease as the test temperatures increase. Secondly, the creep activation energy gradually decreases as the stresses become higher. Thirdly, the constant of Larson-Miller parameters on this alloy is estimated as about 5. Last, the fractographs at the creep rupture show both the ductile and brittle fracture modes according to the creep conditions.

인코넬 690 합금의 크리프거동

황경충,윤종호,최재하,김성청 한국공작기계학회 2002 한국생산제조학회지 Vol.11 No.4

Inconel 690 alloy has widely been used in power plant and high temperature facilities because it has high thermal resistance and toughness. But, we have little design data about the creep behaviors of the alloy. Therefore, in this study, an apparatus has been designed and built for conduction creep tests under constant load conditions. A series of creep tests on Inconel 690 alloy have been performed to get the basic design data and life prediction of inconel products and we have gotten the following results. First, the stress exponents decrease as the test temperatures increase. Secondly, the creep activation energy gradually decreases as the stresses becomes bigger. Thirdly, the constant of Larson-Moller parameters on this alloy is estimated about 10. And last, the fractographs at the creep rupture show both the ductile and the brittle fracture according to the creep conditions.

SM45C鋼의 CNC旋削時 表面組度 考察

윤종호,황경충 경일대학교 산업기술연구소 1994 産業技術硏究所 論文集 Vol.4 No.-

It has been found experimentally by a number of workers that for some given cutting conditions there are a variety of relationships among cutting speed, cutting force and surface roughness. But, most of them have been studied through manual lathe. And so, a series of cutting experiments by suing home products are performed through CNC lathe which has more advantage than the former. In this study, for the optimal selection of cutting conditions many experimental graphical data were obtained. That is, cutting force, tool life and surface roughness were measured and investigated as the depth of cut and feed rate under the same cutting area varies. And also, size effect was examined as the depth of cut varies.

CNC旋削時 SM45C鋼의 切削特性 硏究

尹鍾鎬,黃敬忠 慶一大學校 1996 論文集 Vol.13 No.2

A series of cutting experiments for domestic products are performed by using CNC lathe which has more advantages than teh manual lathe, such as, constant cutting speed control, etc. We have gotten the following results through this experimental study. Under a constant cutting area, tool wea progress for high feedrate than low feedrate is later, and the progress goes more rapid as the cutting speed is greater. This is considered due to friction between workpiece and bite. Averaged cutting force becomes great as the feedrate goes rapid, and becomes small as the cutting speed goes rapid. This is considered because effective rake/shear angle becomes smaller as the feedrate becomes higher. The larger are as the cutting speed and aspect ratio(the ratio of cut-depth to feedrate), the smaller become cutting force and surface roughness. And also, for the optimal selection of cutting conditions many experimental graphical data were obtained. That is, cutting force, tool life and surface roughness were measured and investigated as the depth of cut and feed rate changes. And also, size effect ws examined as the depth of cut varies.

SM45C鋼의 CNC旋削時 切削力과 工具磨滅 考察

윤종호,황경충 경일대학교 산업기술연구소 1994 産業技術硏究所 論文集 Vol.4 No.-

It has been found experimentally by a unmber of workers that for some given cutting conditions there are a variety of relationships among cutting speed, cutting force and tool wear. But, most of them have been studied for the foreign materials and tools through manual lathe, And so, in this study, a series of cutting experiment using domestic products are performed through CNC lathe which has advantages, such as , constant cutting speed control, etc. We have gotten the following results through experiments. First, under a constant cutting area, tool wear progress for large feedrate than small feedrate is later, and the progress goes more rapid as the cutting speed is greater. This is considered due to friction between workpiece and bite. Secondly, under a constant cutting area, averaged cutting force becomes great as the feedrate goes rapid, and becomes small as the cutting speed goes rapid. This is considered because effective rake and shear angle becomes smaller as the feedrate becomes larger. Lastly, the larger are as the cutting speed and aspect ratio (the ratio of cut-depth to feedrate), the smaller become cutting force and roughness