• Title/Summary/Keyword: 2.25CrMo steel

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Manufacturing 2.25Cr-1Mo Steel In Hot Rolling Strip Mill (2.25% Cr-1%Mo 합금계 열연강판 제조기술)

  • 노태훈
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 1999.08a
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    • pp.390-398
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    • 1999
  • The thermomechanical control process(in hot rolling strip mill) was employed to produce 2.25Cr-1Mo steel, which is to be construction material for the steam generator for power plant. Although the Conventional processes has been the primary means of producing the 2.25Cr-1Mo steel, an alternative method was used to meet the specification of ASTM heat treatment for A387-22-Classl using autotempering after coiling in hot rolling strip mill. The microstructures, tensile properties at various temperatures, and creep-rupture properties have been investigated to compare the properties with those of materials produced by the conventional process and to certify the application of the thermomechanical control process to an actual process of manufacturing 2.25-Cr-1Mo steel, this in turn, will reduce the cost of the process. About 14 to 34% glanular bainite (remainder proetectoid ferrite) formed in a coil, and this variety of volume fraction stems from the different cooling rates, which varies with position of the coil after coiling. Tensile testing from room temperature to 700$^{\circ}C$ indicated that strength increases with test temperature showing peaks at around 600$^{\circ}C$. Creep-rupture properties have been being investigated at the temperature of 500$^{\circ}C$ with 27.5, 32kg/$\textrm{mm}^2$ loads and have showed no rupture for over 1000 hours.

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Changes of Carbide Characteristics and Magnetic Properties in Artificially Aging Heat Treated 2.25CrMo Steel (경년열화 열처리된 2.25CrMo 강에서의 탄화물 특성 및 자기적 성질의 변화)

  • Byeon, Jal Won;Kwun, S.I.
    • Journal of the Korean Society for Heat Treatment
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    • v.14 no.6
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    • pp.323-329
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    • 2001
  • Artificial aging was performed to simulate the microstructural degradation in 2.25CrMo steel arising from long time exposure at $540^{\circ}C$. The carbide morphologies were classified as acicular, pipe and globular type, and the number of carbides per unit area was measured for each type of carbides. The fine acicular carbides were found to diminish drastically in the initial stage of aging. An attempt was made to evaluate the microstructural degradation in artificially aging heat treated 2.25CrMo steel by the magnetic property measurements such as saturation magnetization, coercivity and remanence. The saturation magnetization showed no distinct trend with aging time. However, the coercivity and remanence were observed to decrease rapidly in initial 920 hours of aging time and then decrease slowly afterwards.

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A Study on Evaluation of High Temperature Creep Properties of 9Cr1MoVNb Steel by Small Punch-Creep test (소형펀치-크리프 시험에 의한 9Cr1MoVNb강의 고온 크리프 특성 평가 연구)

  • Yu, Hyo-Sun;Na, Sung-Hoon;Baek, Seung-Se;Kwon, Il-Hyun;Ahn, Byung-Guk;Na, Eui-Gyun
    • Proceedings of the KSME Conference
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    • 2000.11a
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    • pp.99-104
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    • 2000
  • This paper describes the high temperature creep characteristics for virgin material of 9Cr1MoVNb steel using small punch creep(SP-Creep) test technique which is developing recently. In addition, the several results of SP-Creep test are compared with that of 2.25Cr- 1Mo steel which is widely used as boiler materials and that of conventional uniaxial creep test. The obtained SP-Creep curves show the creep behaviors of three regimes like that obtained from conventional uniaxial creep test, and SP-Creep properties are definitely depended on applied load and test temperature. The correlation of SP-Creep rate and creep rupture life with applied load has been determined like the correlation between creep rate/rupture life and stress in uniaxial creep test, and also is satisfied with Power law. The creep rupture times of newly 9Cr1MoVNb steel are higher than those of 2.25Cr1Mo steel at the same creep temperature and applied loading condition, and the decrease extent of creep rupture life with loads is very lower compared with 2.25Cr1Mo steel.

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Microstructural Characterization for Structural Health Monitoring of Heat-Resisting Rotor Steels (로터용 내열강의 구조 건전성 모니터링을 위한 미세 조직 평가)

  • Kim, C.S.;Byeon, Jae-Won;Park, Ik-Keun
    • Journal of the Korean Society for Nondestructive Testing
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    • v.28 no.2
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    • pp.177-183
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    • 2008
  • The typical heat-resisting rotor steels such as 2.25CrMo, 9CrMo and 12CrW steel were experimentally studied in order to understand their materials degradation under high temperature and pressure during the long-term service, and then use the basic studies for the structural health monitoring. In order to monitor the materials degradation, it was conducted by the isothermal aging for 2.25CrMo steel, creep-fatigue for 9CrMo steel and creep for 12Cr steel with the incremental step test. The ultrasonic wave properties, electrical resistivity and coercivity were interpreted in relation to microstructural changes at each material and showed strong sensitivity to the specific microstructural evolution.

Microstructure and Mechanical Properties of Cr-Mo Steels for Nuclear Industry Applications

  • Kim, Sung-Ho;Ryu, Woo-Seong;Kuk, Il-Hiun
    • Nuclear Engineering and Technology
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    • v.31 no.6
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    • pp.561-571
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    • 1999
  • Microstructure and mechanical properties of five Cr-Mo steels for nuclear industry applications have been investigated. Transmission electron microscopy, energy dispersive spectrometer, differential scanning calorimeter, hardness, tensile, and impact test were used to evaluate the Cr and W effect on the microstructure and mechanical properties. Microstructures of Cr-Mo steels after tempering are classified into three types : bainitic 2.25Cr-lMo steel, martensitic Mod.9Cr-lMo, HT9M, and HT9W steels, and dual phase HT9 steel. The majority of the precipitates were found to be M$_{23}$C$_{6}$ carbides. As minor phases, fine needle-like V(C,N), spherical NbC, fine needle-like Cr-rich Cr$_2$N, and Cr-rich M$_{7}$C$_3$were also found. Addition of 2wt.% W in Cr-Mo steels retarded the formation of subgrain and dissolution of Cr$_2$N precipitates. Hardness and ultimate tensile strength increased with increasing Cr content. Though Cr content of HT9W steel was lower than that of HT9 steel, the hardness of HT9W was higher due to the higher W content. W added HT9W steel had the highest ultimate tensile strength above $600^{\circ}C$. But impact toughness of W added steel (HT9W) and high Cr steel (HT9) was low.w.w.

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Evaluation of Thermal Degradation of 2.25Cr-1Mo Steel Using Ultrasonic Nonlinear Effect and X-ray Diffraction Method (초음파 비선형 음향 효과 및 X-선 회절법을 이용한 2.25Cr-1Mo 강의 열화 손상 평가)

  • Kim, Duk-Hee;Park, Un-Su;Park, Ik-Keun;Byeon, Jai-Won;Kwun, Sook-In
    • Journal of the Korean Society of Safety
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    • v.17 no.4
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    • pp.71-79
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    • 2002
  • It was attempted to evaluate the degree of degradation of thermally aged 2.25-1Mo steek by ultrasonic monlinear parameter(UNP) measurement and X-ray diffraction analysis of extracted carbide. Artificial aging was performed to simulate the microstructural degradation in 2.25Cr-1Mo steel arising from long time exposure at $540{\circ}C$. Microstructural analysis (number of carbides per unit area) and measurements of mechanical properties(Vickers hardness, DBTT) and degradation evaluation parameters(UNP and intensity ration of X-ray diffraction peak of electrolytically extracted carbide) were performed. Both of UNP and intensity ratio of X-ray diffraction peak for M6C carbide to that of M23C6 carbide(IR) increased abruptly in the initial 1000 hour of aging and then changed little. UNP and IR were proposed as potential parameters to evaluate the degree of aging degradation of 2.25Cr-1Mo steel.

Ultrasonic Nondestructive Evaluation of Microstructural Degradation in Artificially Aging Heat Treated 2.25CrMo Steel (인공 열화 열처리된 2.25CrMo 강의 미세조직 변화에 대한 초음파 비파괴평가)

  • Byeon, Jai Won;Kwun, S.I.;Park, Un-Su;Park, Ik-Keun
    • Journal of the Korean Society for Heat Treatment
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    • v.14 no.2
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    • pp.110-117
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    • 2001
  • Artificial aging was performed to simulate the microstructural degradation in 2.25CrMo steel arising from long time exposure at $540^{\circ}C$. It was found that the carbides became coarser and spheroidized as aging time increased. An attempt was made to evaluate the microstructural degradation in artificially aging heat treated 2.25CrMo steel by the ultrasonic attenuation and velocity measurements. Ultrasonic velocity was found essentially insensitive to the microstructural changes resulting from aging heat treatment. However, the ultrasonic attenuation was observed to increase with increasing aging time. Also, it was noticed that the change of ultrasonic attenuation with aging time was more sensitive at high frequency regions.

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Effect of KCl(s) and K2SO4(s) on Oxidation Characteristics of the 2.25Cr-1Mo Steel in 10%O2+10%CO2 Gas Environment at 650 ℃ (650 ℃의 10%O2+10%CO2 가스 환경에서 2.25Cr-1Mo강의 산화특성에 미치는 KCl(s)과 K2SO4(s)의 영향)

  • Jung, Kwang-Hu;Kim, Seong-Jong
    • Corrosion Science and Technology
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    • v.19 no.1
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    • pp.43-50
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    • 2020
  • In this study, the effects of KCl(s) and K2SO4(s) on the oxidation characteristics of 2.25Cr-1Mo steel were investigated for 500 h in 10O2 + 10CO2 (vol%) gas environmen at 650 ℃. Oxidation kinetics were characterized by weight gain, oxide layer thickness, and fitted models for the experiment data were proposed. The fitted models presented considerable agreement with the experimental data. The oxide layer was analyzed using the scanning electron microscope, optical microscope, and energy dispersive X-ray spectroscopy. The oxidation kinetics of 2.25Cr-1Mo steel with KCl and K2SO4 coatings showed significantly different oxidation kinetics. KCl accelerated the oxidation rate very much and had linear oxidation behavior. In contrast, K2SO4 had no significant effect, which had parabolic kinetics. The oxide layer was commonly composed of Fe2O3, Fe3O4, and FeCr2O4 spinel. KCl strongly accelerated the oxidation rates of 2.25Cr-1Mo steel in the high-temperature oxidation environment. Conversely, K2SO4 had little effect on the oxidation rates.

Experimental Study on Corrosion Characteristics of 1.25Cr-0.5Mo in the 1st-mathanator reactor for Synthetic Natural Gas according to Gas Compositions (1.25Cr-0.5Mo강을 이용한 합성가스 조성 변화에 따른 SNG 1차반응기의 부식특성에 관한 실험적 연구)

  • Kim, Jin-Hyun;Cho, Honghyun
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.17 no.5
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    • pp.709-716
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    • 2016
  • Recently, the operating conditions of the various mechanical structures have become more severe and the running time has become longer as the development of plant equipment increases with the introduction of high technology. Thus, the reliability of the system and its accessories is becoming a problem. Normally, synthetic natural gas (SNG) plants use 1.25Cr-0.5Mo or 2.25Cr-1Mo heat resistant steel according to the operating conditions. In this study, a lab-scale reactor was set up using 1.25Cr-0.5Mo steel, in order to carry out corrosion tests for producing synthetic natural gas. The corrosive characteristics were investigated under 1st-methanator operating conditions and fundamental data about the durability and reliability were obtained by using the experimental test. The analysis of results obtained on the durability of the reactor under emission and injection compositions showed that the hydrogen embrittlement caused by hydrogen and the oxidation corrosion caused by H2O had the most effect on the durability of 1.25Cr-0.5Mo steel in the SNG reactor. However, the hydrogen embrittlement and oxidation corrosion occurred simultaneously under emission conditions, so that the corrosion of the material increased suddenly after a long operating time. Besides, the corrosion of the 1.25Cr-0.5Mo steel under the injection composition was faster than that under the emission composition.

Evaluation of Microstructure and Ductile-Brittle Transition Temperature in Thermally aged 2.25Cr-1Mo Steel by Electrical Resistivity Measurement (전기비저항을 이용한 2.25Cr-1Mo 강 열화재의 미세조직 및 연성-취성천이온도 평가)

  • Byeon, Jai-Won;Kwun, S.I.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.22 no.3
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    • pp.284-291
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    • 2002
  • An attempt was made to evaluate the degree of aging degradation in thermally aged 2.25Cr-1Mo steel by electrical resistivity measurement. Artificial aging was performed to simulate the microstructural degradation in 2.25Cr-1Mo steel arising from long time exposure at $540^{\circ}C$. Microstructural parameter (amount of solid solution element), mechanical property (ductile-brittle transition temperature) and electrical resistivity were measured to investigate the mutual relationship among these parameters. Depletion of solid solution element(Mo and Cr) in matrix was detected after aging. The ductile-brittle transition temperature(DBTT) increased rapidly in the initial stage of aging and then saturated afterward. On the other hand, the electrical resistivity decreased rapidly in the beginning and then saturated in the later stage of aging.