• 제목/요약/키워드: Austenitic Alloys

검색결과 68건 처리시간 0.029초

A Study on Fatigue Strength of Austenitic Stainless Steel for Centrifuge (원심분리기용 오스테나이트계 스테인리스강의 피로강도에 관한 연구)

  • Lee, Mee-Hae;Kim, Yong-Soo;Park, Joon-Woo
    • Journal of the Korean Society of Safety
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    • 제23권3호
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    • pp.12-16
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    • 2008
  • For industrial centrifuges, the state of their welding areas, even with a naked-eye observation, offers potential safety problems such as inconsistent bead formation. STS304, which is used mainly in centrifuges, is made of metal alloys with chrome and nickel as the main ingredients, offering excellent corrosion resistance, thermal resistance, and high strength, and thus allowing it to be used for diverse purposes. This paper conducted tensile and fatigue tests of STS304 to improve the safety of centrifuges. In the findings, for the static behavior of the STS304 material, welded specimens increased their yield and tensile strength compared with the base test specimens, but decreased their elongation ratio. Also, the data dispersion phenomenon of welded specimens remarkably increased.

Mn-deprived Phase Transformation in High-Mn Steel during the Dew-point Control Process

  • Hong, Woong-Pyo;Baik, Sung-Il;Kim, Gyo-Sung;Jeon, Sun-Ho;Chin, Kwang-Guen;Oh, Chang-Seok;Kim, Young-Woon
    • Applied Microscopy
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    • 제43권1호
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    • pp.40-45
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    • 2013
  • Phase transformation by the Mn-deprivation was observed in the high-Mn twinning-induced plasticity-aided steel. Mn-depletion was induced by the formation of Mn-O oxide during the dew-point control process at temperature above $-20^{\circ}C$, which changed austenitic parent phase to multi-grained ferrite. Mixture of Al-O, Al-Mn-Si-O oxides were observed at the grain boundaries of transformed ferrite.

Creep Behavior of High Temperature Prestrain in Austenitic 25Cr-20Ni Stainless Steels (오스테나이트계 25Cr-20Ni 스테인리스강의 고온 예변형에 의한 크리프 거동)

  • 박인덕;남기우;안석환
    • Journal of Ocean Engineering and Technology
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    • 제16권3호
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    • pp.59-64
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    • 2002
  • In the present study, we examined the influence of prestrain on creep strength of Class M alloy(STS310S) and Class A(STS310J1TB) alloys containing precipitates. Prestrain was given by prior creep at a higher stress than the following creep stresses. Creep behaviour before and after stress change and creep rate of pre-strained specimens were compared with that of virgin specimens. Pre-straining produced the strain region where the strain rate was lower than that of a virgin specimen both for STS310J1TB and STS310S steels. The reason for this phenomenon was ascribable to the viscous motion of dislocations, the interaction between dislocations and precipitates in a STS310J1TB steel, and the interaction of dislocations with sub-boundaries in a STS310S steen which has the higher dislocation density and smaller subgrain size resulted from pre-straining at higher stress.

Dissimilar Metal Welding of Inconel 600 and STS304 by a continuous wave Nd:YAG Laser (연속파형 Nd:YAG레이저를 이용한 Inconel 600와 STS 304의 이종금속용접)

  • Shin, Ho-Jun;Yoo, Young-Tae;Song, Seong-Wook
    • Proceedings of the KSME Conference
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    • 대한기계학회 2004년도 춘계학술대회
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    • pp.1120-1125
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    • 2004
  • Welding characteristics of STS304 stainless steel and Inconel 600 using a continuous wave Nd:YAG laser are experimentally investigated. Alloy 600 being used in steam generator tubing of pressurized water reactor(PWR) exposed to some corrosion environment, stress corrosion cracking can occur on this material. Presented here are the results from a series of experiments in which dissimilar metal welds were made using the gas tungsten arc welding process with pure argon shielding gas. But It is well known that solidification cracking susceptibility of austenitic alloys depends on the solidification temperature range and amount/distribution of solute rich liquid that exists at the terminal stages of solidification. An experimental study was conducted to determine effects of welding parameters and to optimize those parameters that have the most influence on eliminating or reducing the extent welding zone formation at dissimilar metal welds.

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UNDERLIGNING THERMOCAPILLARY EFFECTS BY ELECTRON BEAM MELTING OF THIN SPECIMENS

  • Domergue, L.;Camel, D.;Marya, S.
    • Proceedings of the KWS Conference
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    • 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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    • pp.199-204
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    • 2002
  • Extensive investigations on cast to cast variations observed in steels have underlined the role of thermocapillary or surface tension driven fluid flow in welding operations. The behavior of weld pool under the electric arc is however affected by possible arc modifications linked to microchemistry variations in materials & this limits to some extent the real contribution from surface tension effects. Thus, electron beam welding with high vacuum was used to investigate thermo-capillary effects on thin austenitic stainless steels & nickel based alloys. The weld pool was monitored by video observations to estimate the importance of fluid flow during the melting & solidification phase. The results underline the importance of fluid flow on [mal solidification.

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An Investigation on the Microstructure Evolution and Tensile Property in the Weld Heat-Affected Zone of Austenitic FeMnAlC Lightweight Steels (오스테나이트계 FeMnAlC 경량철강의 용접열영향부 미세조직 변화 및 인장특성에 관한 연구)

  • Moon, Joonoh;Park, Seong-Jun
    • Journal of Welding and Joining
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    • 제35권1호
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    • pp.9-15
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    • 2017
  • IMicrostructure evolution and tensile property in the weld heat-affected zone (HAZ) of austenitic Fe-30Mn-9Al-0.9C lightweight steels were investigated. Five alloys with different V and Nb content were prepared by vacuum induction melting and hot rolling process. The HAZ samples were simulated by a Gleeble simulator with welding condition of 300kJ/cm heat input and HAZ peak temperatures of $1150^{\circ}C$ and $1250^{\circ}C$. Microstructures of base steels and HAZ samples were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and their mechanical properties were evaluated by tensile tests. The addition of V and Nb formed fine V and/or Nb-rich carbides, and these carbides increased tensile and yield strength of base steels by grain refinement and precipitation hardening. During thermal cycle for HAZ simulation, the grain growth occurred and the ordered carbide (${\kappa}-carbide$) formed in the HAZs. The yield strength of HAZ samples (HAZ 1) simulated in $1150^{\circ}C$ peak temperature was higher as compared to the base steel due to the formation of ${\kappa}-carbide$, while the yield strength of the HAZ samples (HAZ 2) simulated in $1250^{\circ}C$ decreased as compared to HAZ 1 due to the excessive grain growth.

Analysis of CTOD Tests on Steels for Liquefied Hydrogen Storage Systems Using Hydrogen Charging Apparatus (수소 장입 장치를 활용한 액체수소 저장시스템 강재의 CTOD 시험 분석)

  • Ki-Young Sung;Jeong-Hyeon Kim;Jung-Hee Lee;Jung-Won Lee
    • Journal of the Korean Society of Industry Convergence
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    • 제26권5호
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    • pp.875-884
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    • 2023
  • Hydrogen infiltration into metals has been reported to induce alterations in their mechanical properties under load. In this study, we conducted CTOD (Crack Tip Opening Displacement) tests on steel specimens designed for use in liquid hydrogen storage systems. Electrochemical hydrogen charging was performed using both FCC series austenitic stainless steel and BCC series structural steel specimens, while CTOD testing was carried out using a 500kN-class material testing machine. Results indicate a notable divergence in behavior: SS400 test samples exhibited a higher susceptibility to failure compared to austenitic stainless steel counterparts, whereas SUS 316L test samples displayed minimal changes in displacement and maximum load due to hydrogen charging. However, SEM (Scanning Electron Microscopy) analysis results presented challenges in clearly explaining the mechanical degradation phenomenon in the tested materials. This study's resultant database holds significant promise for enhancing the safety design of liquid hydrogen storage systems, providing invaluable insights into the performance of various steel alloys under the influence of hydrogen embrittlement.

Study on the Microstructural Degradation of the Boiler Tubes for Coal-Fired Power Plants

  • Yoo, Keun-Bong;He, Yinsheng;Lee, Han-Sang;Bae, Si-Yeon;Kim, Doo-Soo
    • KEPCO Journal on Electric Power and Energy
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    • 제4권1호
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    • pp.25-31
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    • 2018
  • A boiler system transforms water to pressured supercritical steam which drives the running of the turbine to rotate in the generator to produce electricity in power plants. Materials for building the tube system face challenges from high temperature creep damage, thermal fatigue/expansion, fireside and steam corrosion, etc. A database on the creep resistance strength and steam oxidation of the materials is important to the long-term reliable operation of the boiler system. Generally, the ferritic steels, i.e., grade 1, grade 2, grade 9, and X20, are extensively used as the superheater (SH) and reheater (RH) in supercritical (SC) and ultra supercritcal (USC) power plants. Currently, advanced austenitic steel, such as TP347H (FG), Super304H and HR3C, are beginning to replace the traditional ferritic steels as they allow an increase in steam temperature to meet the demands for increased plant efficiency. The purpose of this paper is to provide the state-of-the-art knowledge on boiler tube materials, including the strengthening, metallurgy, property/microstructural degradation, oxidation, and oxidation property improvement and then describe the modern microstructural characterization methods to assess and control the properties of these alloys. The paper covers the limited experience and experiment results with the alloys and presents important information on microstructural strengthening, degradation, and oxidation mechanisms.

Smart Composite Beams with Shape Memory Alloy Strips Having TWSME (2방향 형상기억효과 SMA 띠가 부착된 복합재 보의 거동)

  • Kim, Jung-Taek;Kim, Cheol;Yoon, Ji-Won
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 한국복합재료학회 2005년도 춘계학술발표대회 논문집
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    • pp.51-54
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    • 2005
  • Shape memory alloys (SMAs) find many applications in smart composite structural systems as the active components. Their ability to provide a high force and large displacement makes them an excellent candidate for an actuator for controlling the shape of smart structures. In this paper, using a macroscopic model that captures the thermo-mechanical behaviors and the two-way shape memory effect (TWSME) of SMAs smart morphing polymeric composite shell structures like shape-changeable UAV wings is demonstrated and analyzed numerically and experimentally when subjected to various kinds of pressure loads. The controllable shapes of the morphing shells to that thin SMA strip actuator are attached are investigated depending on various phase transformation temperatures. SMA strips start to transform from the martensitic into the austenitic state upon actuation through resistive heating, simultaneously recover the prestrain, and thus cause the shell structures to deform three dimensionally. The behaviors of composite shells attached with SMA strip actuators are analyzed using the finite element methods and 3-D constitutive equations of SMAs. Several morphing composite shell structures are fabricated and their experimental shape changes depending on temperatures are compared to the numerical results. That two results show good correlations indicates the finite element analysis and 3-D constitutive equations are accurate enough to utilize them for the design of smart composite shell structures for various applications.

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Effects of carbon concentration and temperature on the sliding wear resistance in austenitic Fe-10Cr-10Ni-xC alloys

  • Sin, Gyeong-Su;Kim, Seon-Jin
    • Proceedings of the Materials Research Society of Korea Conference
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    • 한국재료학회 2009년도 추계학술발표대회
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    • pp.35.1-35.1
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    • 2009
  • 오스테나이트계 Fe-10Cr-10Ni-xC(x=0.2, 0.5, 0.6and 0.7wt.%)합금에서 변형유기마르텐사이트상변태가 Sliding 마모저항성에 미치는영향을 탄소 및 온도에 따라 조사하였다. 변형유기마르텐사이트상변태가 미치는 영향을 살펴보기 위해 석출물적고 grain의 크기가 비슷한 합금내에서 조사하였다. 변형유기마르텐사이트상변태가 일어나는데 필요한 에너지를 변형률-응력 곡선을 통해 구할 수 있으며, 이를 임계변형에너지라 규명했다. 그 결과, 상온에서 Carbon 함량에 따라 변형유기마르텐사이트상변태가 일어나는데 필요한 임계변형에너지는 증가하였으며, Sliding 마모저항성은 저하되었다. 이는 carbon이 오스테나이트 안정화원소(austenite stabilityelement)이므로 carbon 함량이 증가할수록 변형유기마르텐사이트상변태가 유발하기위해서는 많은 에너지가 필요하기 때문에 low C에 비해 high C의 마모저항성이 저하된 것으로 사료된다. 또한 변형유기마르텐사이트상변태가 고온 Sliding 마모저항성에 미치는 영향을 살펴보기 위해 Fe-Cr-Ni-xC(x=0.2, 0.5, 0.6 and 0.7wt.%)합금을 온도별(25, 100, $300^{\circ}C$)로 조사하였다.

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