• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2004년도 춘계 학술발표대회 개요집
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• pp.168-170
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• 2004

터빈로터는 발전설비 중에서 가장 핵심 부분이며 동시에 심한 고온 응력을 받는 부분이다. 터빈로터 재료로는 Ni-Cr-Mo-V강과 CrMoV 강등이 사용된다. CrMoV 강은 발전 설비로 장시간 사용 중 열적피로나 크립손상, 고온 부식 등의 문제가 단독 혹은 복합적으로 발생하여 재료에 손상을 입히게 되고 결국에는 설비의 수명을 단축 시키곤 한다. (중략)

• 한국정밀공학회지
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• 제26권6호
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• pp.90-96
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• 2009

Ultrasonic method using SH(shear horizontal) wave has been developed to determine the surface damage in fatigued material. Fatigue damages based on propagation energy were analyzed by multi-regression analysis in interrupted fatigue test specimen including CrMoV and 12Cr alloy steel. From the test results, as the fatigue damage increased the propagation time of the launched waves increased and amplitude of wavelet decreased. Also, analysis for the waveform modulation showed a reliable estimation, with confidence limit of 97% for 12Cr steel and 95% for CrMoV steel, respectively. Therefore, It is thought that SH ultrasonic wave technique can be applied to determine fatigue damage of in-service component nondestructively.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.266-271
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• 2001

Spherical indentation technique was developed to evaluate the flow properties of metallic materials in carbon steel, stainless steel and alloys, etc. Through the spherical indentation test, differently degraded 1Cr-1Mo-0.25V steel's mechanical properties were observed and compared with conventional standard test data. The flow properties of 1Cr-1Mo-0.25V steels were estimated by analyzing the indentation load-depth curve. To characterize the flow property, we used material yield slope and constraint factor index rather than strain-hardening exponent because the variation of strain-hardening exponent was very little and the data showed irregularly. And the constraint factor's effect was small when the material yield slope was taken into account.

• 한국항행학회논문지
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• 제28권4호
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• pp.532-537
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• 2024

본 연구에서는 항공기 및 고속전철 등 대형 수송기기의 제동디스크에 적용되는 Ni-Cr-Mo-V계 및 Ni-Cr-Mo계 저합금강의 합금 성분 변화에 따른 마모 특성을 평가하였다. 경도시험 결과, C-Mo-V강의 경도는 39.4±0.9HRc로 가장 높았고, Ni-Cr-Mo강이 32.4±0.6HRc로 가장 낮았다. 마찰계수는 수직하중이 증가함에 따라 감소하는 경향을 보였으며, 수직하중 1 N에서 Ni-Cr-Mo강의 마찰계수가 0.842, 수직하중 5 N에서 Mn-Cr-V강이 0.696으로 가장 높았다. Ni-Cr-Mo강은 수직하중 1 N에서 마모흔의 폭 711 ㎛, 깊이 8.24 ㎛, 마모량 11 mg, 수직하중 5 N에서 폭 1,017 ㎛, 깊이 19.17 ㎛, 마모량 17 mg으로 가장 큰 마모흔의 폭, 깊이 및 마모량을 보여주었다. 마모기구 분석 결과, 모든 시편에서 패임, 박리 및 응착이 관찰되었고, Ni-Cr-Mo강에서 소성변형이 더 우세하게 관찰되었다.

• Journal of Welding and Joining
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• 제26권3호
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• pp.37-44
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• 2008

Charpy V-Notch test is commonly used to evaluate fracture toughness. However, since the region to be evaluated is limited to bulk material due to the specimen size required, individual evaluation of micro-structures on weldment is very difficult. In this study, ASP(Advanced Small Punch) test was carried out to evaluate material degradation and fracture toughness on the B.M, W.M and each micro-structures of HAZ for X20CrMoV121 and 2.25Cr1Mo steels with artificial aging time. In addition, to evaluate fracture toughness and material degradation of B.M and W.M of X20CrMoV121 steels with aging times, CVN (Charpy V-notch) test was performed. And then the correlation between ASP and CVN test on X20CrMoV121 steels was obtained. Furthermore, through this correlation, material degradation property of each micro-region of the HAZ in weldment, which was impossible to be evaluated by the CVN test, can be estimated and determined.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2002년도 추계학술발표회요약집
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• pp.282.1-282
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• 2002

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.322-327
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• 2000

This paper investigates the time-dependent crack growth in X20CrMoV 12 1 steel weld joints. Crack growth test are carried out $545^{\circ}C$ on side-grooved 1/2T CT specimens under static loads. A simulated material is produced for the intercritical HAZ, where fracture normally occurs. Constitutive properties are obtained for the simulated HAZ material as well as for the base metal and weld metal. Finite element analyses of crack growth are performed on the models with and without a HAZ layer, using the experimental crack length-time history. The inclusion of HAZ layer increase the load line velocities significantly. The crack growth rates are correlated reasonably well with $C^*$. The smallest crack size for the validity of $C^*$ is found much smaller than the ASTM crack initiation size for 1T CT specimen of creep ductile materials.

• 비파괴검사학회지
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• 제20권5호
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• pp.445-450
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• 2000

고온에서 운용 중인 설비의 안전성을 평가하기 위해서는 사용기간동안 열화된 재료의 물성을 측정하여야 한다. 실제 사용되고 있는 화력발전소 터빈의 로터에서 열화도가 다른 여러 종류의 시편을 입수하기 어렵기 때문에, 터빈 로터재로 널리 사용되고 있는 1Cr-1Mo-0.25V 강을 인공열화시켜 시편으로 사용하였다 열화도의 비파괴적 평가를 위하여 교류 섭동 자기장을 인가하여 가역 투자율을 측정하는 자기적 방법을 사용하였다. 열화도의 증가에 따라 경도와 가역 투자율 피크 사이의 간격은 감소하였는데, 경도와 가역 투자율 피크 간격과의 선형관계를 이용하여 비파괴적으로 터빈 로터강의 열화도를 평가할 수 있는 기초를 마련하였다.

• 대한기계학회논문집A
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• 제25권12호
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• pp.2109-2115
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• 2001

Miniaturized specimen technology is useful to characterize the mechanical behavior when it is difficult to sample the material enough for the test. In this study, two kinds of miniaturized Charpy impact specimens(i.e., miniaturized specimen with side groove and without side groove) of aged 1Cr- lMo-0.25V steel were prepared and tested. The relationship between the extent of degradation in terms of ductile brittle transition temperature(DBTT) and the fracture stress of 1Cr-1Mo-0.25V steel was established. The fracture stress obtained from miniaturized specimen without side groove turned out to be linearly related with the DBTT of standard specimen. Therefore the fracture toughness of aged turbine rotor steel might be evaluated by the fracture stress. In addition, the correlation between DBTT of standard specimen and that of miniaturized specimen was investigated. As the results of normalizing DBTT by maximum elastic tensile stress, the normalized DBTT of miniaturized specimen without side groove allows one to estimate that of standard specimen.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.231-236
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• 2001

A newly developed Advanced Indentation System (AIS), which is a portable and nondestructive system for evaluating tensile properties, was used to measure mechanical behavior of materials used under high temperature and pressure conditions. This test measures indentation load-depth curve during indentation and analyzes the mechanical properties related to deformation and fracture. Aging effects of Cr-Mo and Cr-Mo-V steel at high temperature were simulated. Tensile properties including yield strength and tensile strength at various temperature are obtained from the test. For all test materials and conditions, the AIS-derived results were in good agreement with those from conventional standard test method. Examples of the test results ate given and potential applications of the AIS to assess the integrity of aging structures are briefly discussed.