• Title/Summary/Keyword: Ductile-to-brittle transition temperature

Search Result 82, Processing Time 0.025 seconds

A Study on the Fracture Toughness Characteristics of FCAW Weldment of Steel for Offshore Structures (해양 구조물용 강재 FCAW 용접부의 파괴인성 특성에 관한 연구)

  • Kang Sung-Won;Kim Myung-Hyun;Kim Yong-Bin;Shin Yong-Taek;Lee Hae-Woo
    • Journal of Welding and Joining
    • /
    • v.22 no.6
    • /
    • pp.57-63
    • /
    • 2004
  • Fracture toughness is an important parameter in designing offshore structures to ensure resistance to fracture at various temperatures. In this study, a series of experiments is carried out to obtain fracture toughness values (CTOD) of API 2W Gr.50B, welded using FCAW(Flux Cored Arc Weld). In particular, a comparison of absorbed impact energy and CTOD values are made with respect to two different welding groove shapes; double-V-groove and double-bevel-groove. Charpy impact tests are performed for specimens sampled near the root gap, and CTOD tests are carried out for three point bending specimens having the notch at weld zone. While Charpy impact test result is determined to be a good qualitative measure of fracture toughness, no quantitative correspondence between impact absorbed energy and CTOD values was found. Based on the experiment, it is observed that double-V-groove welds give lower transition temperature than those of double-bevel-groove.

Temperature-Dependent Thermal and Chemical Stabilities as well as Mechanical Properties of Electrodeposited Nanocrystalline Ni

  • Zheng, Liangfu;Peng, Xiao
    • Metals and materials international
    • /
    • v.24 no.6
    • /
    • pp.1293-1302
    • /
    • 2018
  • Nanocrystalline (NC) Ni electrodeposits (EDs) with a mean grain size of $34{\pm}12nm$ has been investigated, from room temperature to $800^{\circ}C$ under a purge gas of argon, by both non-isothermal and isothermal differential scanning calorimetry measurements, in combination with characterization of temperature-dependent microstructural evolution. A significant exothermic peak resulting from superimposition of recrystallization and surface oxidation occurs between 340 and $745^{\circ}C$ at a heating rate of $10^{\circ}C/min$ for the NC Ni EDs. The temperatures for recrystallization and oxidation increase with increasing the heating rate. In addition, recrystallization leads to a profound brittle-ductile transition of the Ni EDs in a narrow range around the peak temperature for the recrystallization.

Multi-step Internal Nitriding of Tungsten-titanium Alloys

  • Nagae, Masahiro;Yoshio, Tetsuo;Takada, Jun;Hiraoka, Yutaka;Takida, Tomohiro
    • Proceedings of the Korean Powder Metallurgy Institute Conference
    • /
    • 2006.09b
    • /
    • pp.1157-1158
    • /
    • 2006
  • Internally nitrided dilute W-Ti alloy specimens having a heavily deformed surface microstructure were prepared by a multi-step internal nitriding at 1573-2073 K. Primary nitriding below their recrystallization temperature induced a precipitation of ultrafine TiN particles. After secondary and tertiary nitriding, those precipitates grew into rod-like TiN with a length of 20-60 nm. The recrystallization temperature after nitriding was elevated above 2073 K. The yield strength at 1773 K obtained from nitrided W-0.5 mass% Ti alloy was about 5 times as large as that of the recrystallized specimen. DBTT of the nitrided alloys was about 373 K.

  • PDF

Influence of Oxidation Inhibitor on Carbon-Carbon Composites: 9. Studies on Impact Properties of the Composites (산화억제제 첨가에 의한 탄소/탄소 복합재료의 물성에 관한 연구: 9. 복합재료의 충격특성에 관한 연구)

  • 박수진;서민강;이재락
    • Composites Research
    • /
    • v.16 no.3
    • /
    • pp.41-48
    • /
    • 2003
  • In this work, the effect of molybdenum disilicide(MoSi$_2$) content on the impact properties of carbon-carbon composites(C/C composites) was investigated in the presence of MoSi$_2$. The content of MoSi$_2$ was varied in 0, 4, 12 and 20 wt% on the basis of resin matrix for anti-oxidation properties of the composites under high temperature. As a result, the composites made with MoSi$_2$ resulted in an increase of interfacial adhesion between fibers and matrix, which could improve the impact properties of the composites. Especially, 12 wt% Mosi$_2$ composites showed the highest impact properties in the present system. This was probably due to the existence of brittle-to-ductile transition(BDT) properties of MoSi$_2$ in the vicinity of 90$0^{\circ}C$, resulting from increasing the interfacial adhesion force among fibers, filler, and matrix in the composites.

Evaluation of degradation in aged 2.25CrMo steel by electrical resistivity, magnetic Barkhausen noise and carbide analysis (전기비저항, 바크하우젠노이즈 및 탄화물 분석법을 이용한 2.25Cr-1Mo 강의 열화도 평가)

  • Byeon, Jai-Won;Pyo, S.W.;Kwun, S.I.
    • Proceedings of the KSME Conference
    • /
    • 2001.11a
    • /
    • pp.210-215
    • /
    • 2001
  • The ferritic 2.25CrMo steel has been used for high temperature structure applications such as turbine rotors, boilers and pressure vessels in fossil plant and petroleum chemical facilities. However, this steel is known to result in aging degradation due to temper embrittlement, carbide induced brittleness and softening of matrix after long time exposure to high temperature. This research investigated the microstructural and mechanical changes after artificial degradation treatment and evaluated the degree of degradation by several nondestructive methods. The decrease of electrical resistivity and increase of magnetic Barkhausen noise(RMS voltage) with increasing aging time were observed. The change of electrical resistivity and Barkhausen noise showed a good correlation with the ductile-brittle transition temperature.

  • PDF

Evaluation of Impact Characteristics for High Strength Structural Steel at Low Temperature (고강도 구조용강의 저온 충격특성 평가)

  • 김재훈;김덕회;김후식;조성석;전병완;심인옥
    • Journal of the Korean Society of Propulsion Engineers
    • /
    • v.5 no.3
    • /
    • pp.1-9
    • /
    • 2001
  • Impact tests are performed on the high strength structural steel that is being developed for the submarine material. Especially, the impact characteristics of this structural steels at low temperatures are investigated by charpy impact testing. Hyperbolic tangent curve fitting method is used to evaluate the LSE(lower shelf energy), USE(upper shelf energy) and DBTT(ductile-brittle transition temperature). Proportional equations between charpy impact energy and lateral expansion are obtained using the test results. Effect of temperature on the fracture appearance is investigated by using SEM.

  • PDF

Program Development for Material Degradation Evaluation Using Grain Boundary Etching Method (입계부식법을 이용한 열화도 평가 프로그램 개발)

  • Yu, Hyo-Seon;Baek, Seung-Se;Na, Seong-Hun;Kim, Jeong-Gi;Lee, Hae-Mu
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.25 no.7
    • /
    • pp.1064-1072
    • /
    • 2001
  • It is very important to evaluate material degradation like temper and carbide embrittlements to secure the reliable and efficient operational conditions and to prevent brittle failure in service. The extent of material deterioration can be accurately evaluated by mechanical test such as impact test or creep test. But it is almost impossible to sample a large specimen from in-service plants. Thus, the material degradation evaluation by a non-destructive method is earnestly required. Recently the non-destructive test technique which uses the grain boundary etching characteristics owing to the variation of material structures has been proposed. However the program for material degradation evaluation using the grain boundary etching method(GEM) in Windows 98 domain doesnt be developed now. The aims of this paper are to develop the program and to complete the new master curve equations for the evaluation of material degradation on in-serviced high temperature components.

A Study on the Charpy Impact Performance of Structural Steel Considering the Leakage of Cryogenic Liquefied Gas (극저온 액화가스 누출에 의한 선체 구조용 강재의 샤르피 충격성능에 관한 연구)

  • Dong Hyuk Kang;Jeong-Hyeon Kim;Seul-Kee Kim;Tae-Wook Kim;Doo-Hwan Park;Ki-Beom Park;Jae-Myung Lee
    • Journal of the Korean Society of Industry Convergence
    • /
    • v.26 no.2_2
    • /
    • pp.333-340
    • /
    • 2023
  • Environmental regulations are being strengthened worldwide to solve global warming. For this reason, interest in eco-friendly gas fuels such as LNG and hydrogen is continuously increasing. However, when adopting eco-friendly gas fuel, liquefying at a cryogenic temperature is essential to ensure economic feasibility in storage and transportation. Although austenitic stainless steel is typically applied to store cryogenic liquefied gas, structural steel can experience sudden heat shrinkage in the case of leakage in the loading and unloading process of LNG. In severe cases, the phase of the steel may change, so care is required. This study conducted Charpy impact tests on steel material in nine different temperature ranges, from room to cryogenic temperatures, to analyze the effects of cryogenic liquefied gas leaks. As a result of the study, it was not easy to find variations in ductile to brittle transition temperature (DBTT) due to the leakage of cryogenic liquefied gas. Still, the overall impact toughness tended to decrease, and these results were verified through fracture surface analysis. In summary, brittle fracture of the steel plate may occur when a secondary load is applied to steel for hull structural use exposed to a cryogenic environment of -40 ℃ or lower. Therefore, it needs to be considered in the ship design and operating conditions.

Estimation of fracture toughness of cast steel container from Charpy impact test data

  • Bellahcenea, Tassadit;Aberkane, Meziane
    • Steel and Composite Structures
    • /
    • v.25 no.6
    • /
    • pp.639-648
    • /
    • 2017
  • Fracture energy values KV have been measured on cast steel, used in the container manufacture, by instrumented Charpy impact testing. This material has a large ductility on the upper transition region at $+20^{\circ}C$ and a ductile tearing with an expended plasticity before a brittle fracture on the lower transition region at $-20^{\circ}C$. To assess the fracture toughness of this material we use, the $K_{IC}$-KV correlations to measure the critical stress intensity factor $K_{IC}$ on the lower transition region and the dynamic force - displacement curves to measure the critical fracture toughness $J{\rho}_C$, the essential work of fracture ${\Gamma}_e$ on the upper transition region. It is found, using the $K_{IC}$-KV correlations, that the critical stress intensity factor $K_{IC}$ remains significant, on the lower transition region, which indicating that our testing material preserves his ductility at low temperature and it is apt to be used as a container's material. It is, also, found that the $J_{\rho}-{\rho}$ energetic criterion, used on the upper transition region, gives a good evaluation of the fracture toughness closest to those found in the literature. Finally, we show, by using the ${\Gamma}_e-K_{IC}$ relation, on the lower transition region, that the essential work of fracture is not suitable for the toughness measurement because the strong scatter of the experimental data. To complete this study by a numerical approach we used the ANSYS code to determine the critical fracture toughness $J_{ANSYS}$ on the upper transition region.

Effects of TMCP on the microstructure and mechanical properties of low carbon HSLA steels (저탄소.저합금 강의 미세구조 및 기계적 성질에 미치는 가공 열처리 조건의 영향)

  • Kang, J.S.;Huang, Yusen;Lee, C.W.;Park, C.G.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
    • /
    • 2006.05a
    • /
    • pp.172-175
    • /
    • 2006
  • Effects of deformation at austenite non-recrystallization region and cooling rate on the microstructure and mechanical properties of low carbon (0.06 wt. %) high strength low alloy steels have been investigated. Average grain size decreased and polygonal ferrite transformation promoted with increasing deformation amount due to increase of ferrite nucleation site. As cooling rate increased, the major microstructure changed from polygonal ferrite to acicular ferrite and the fraction of M/A constituents gradually increased. Discontinuous yielding occurred in highly deformed specimen due to the formation of polygonal ferrite. However, small grain size of highly deformed specimen caused lower ductile-to-brittle transition temperature than slightly deformed specimen.

  • PDF