• 한국분말재료학회지
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• 제27권1호
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• pp.31-36
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• 2020

Phosphorus is an element that plays many important roles in powder metallurgy as an alloy element. The purpose of this study is to investigate the influence of phosphorus addition on the microstructures and mechanical properties of sintered low-alloy steel. The sintered low-alloy steels Fe-0.6%C-3.89%Ni-1.95%Cu-1.40%Mo-xP (x=0, 0.05, 0.10, 0.15, 0.20%) were manufactured by compacting at 700 MPa, sintering in H₂-N₂ at 1260 ℃, rapid cooling, and low-temperature tempering in Ar at 160 ℃. The microstructure, pore, density, hardness, and transverse rupture strength (TRS) of the sintered low-alloy steels were evaluated. The hardness increased as the phosphorus content increased, whereas the density and TRS showed maximum values when the content of P was 0.05%. Based on microstructure observation, the phase of the microstructure changed from bainite to martensite as the content of phosphorus is increased. Hence, the most appropriate addition of phosphorus in this study was 0.05%.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 1997년도 춘계학술강연 및 발표대회 강연 및 발표논문 초록집
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• pp.34-34
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• 1997

The effect of alloying mode and porosity on the axial tension-tension fatigue behavior of a P/M steel of nominal composition Fe-4w/o Ni-1.5w/o Cu-O.5w/o Mo-O.5w/o C has been evaluated. Alloying modes utilized were elemental powder mixing, partial alloying(distaloy) and prealloying by water atomization; in each case the carbon was introduced as graphite prior to sintering. Powder compacts were sintered($1120{\circ}C$/30 min.) in 7Sv/o $H_2$/25v/o $N_2$ to densities in the range 6.77-7.2 g/$cm^3$. The dependence of fatigue limit response on alloying mode and porosity was interpreted in terms of the constituent phases and the pore and fracture morphologies associated with the three alloying modes. For the same nominal composition, the three alloying modes resulted in different sintered microstructures. In the elemental mix alloy and the distaloy, the major constituent was coarse and fine pearlite, with regions of Ni-rich ferrite, Ni-rich martensite and Ni-rich areas. In contrast, the prealloy consisted primarily of martensite by with some Ni-rich areas. From an examination of the fracture surfaces following fatigue testing it was concluded that essentially all of the fracture surfaces exhibited dimpled rupture, characteristic of tensile overload. Thus, the extent of growth of any fatigue cracks prior to overload was small. The stress amplitude for the three alloying modes at 2x$l0^6$ was used for the comparison of fatigue strengths. For load cycles <3x$l0^5$, the prealloy exhibited optimum fatigue response followed by the distaloy and elemental mix alloy, respectively. At load cycles >2x$l0^6$, similar fatigue limits were exhibited by the three alloys. It was concluded that fatigue cracks propagate primarily through pores, rather than through the constituent phases of the microstructure. A decrease in pore SIze improved the S-N behavior of the sintered steel.

• 미래기술융합논문지
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• 제2권2호
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• pp.9-14
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• 2023

이 연구는 1050MPa급 경량 연성 주철 주관류 컨트롤 암을 개발하기 위한 첫 해의 결과를 보여줍니다. 첫째, 최적 설계 구조를 위한 레이아웃 설계 및 구성 요소 개발, 그리고 컨트롤 암 강성과 최적 구조 디자인 및 강건성 설계를 통해 예상 응력을 제어하는 중점 영역의 강건성을 달성합니다. 둘째, 높은 강성과 고성능 경량 구조를 반영하는 컨트롤 암을 개발합니다. 중공을 통해 소비자가 요구하는 설계와 강성을 충족시키기 위해 개발된 컨트롤 암은 코어 제작 공정을 개발합니다. 셋째, 최적의 합금 조성과 열처리 방법을 통해 철 합금 (Cu, Ni, Mo)의 양과 Austempered 열처리 및 조화 상태를 도출합니다. 넷째, 저강도, 고강성 구성 요소 개발을 위해 최적의 성형기술 개발을 통해 최적의 주조 기술 개발로 이어지는 구성 요소 개발을 위한 높은 강도의 주조 형성 기술을 개발하기 위한 시도를 합니다.

• 열처리공학회지
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• 제15권4호
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• pp.178-187
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• 2002

Austempered Ductile Iron (ADI) castings having various chemical composition and heat treatment conditions were investigated. Especially, this study was investigated the influence of various parameters on austempering temperature and alloying elements. The addition of Mo, Cu, and Ni individually or combined in these alloys also investigated. The alloying elements influence the austempering reaction, the microstructures, mechanical properties and amount of retained austenite. In this study, the mechanical properties (ultimate tensile strength(UTS), hardness, elongation) are analysed to show the relationship between alloying elements, austempering temperatures and amount of retained austenite. The amount of retained austenite was the range of 15 - 40%. In case of the alloy to witch Mo, Cu, and Ni was added, the amount of retained austenite was the largest at a constant austempering temperature.

• 대한치과보철학회지
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• 제32권3호
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• pp.378-395
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• 1994

The purpose of this study was to investigate the effect of various metal surface treatments and adhesive systems on the flexural bond strength of composite resin to Au-Ag-Cu-Pd alloy. The specimens were divided into nine groups by the combinations of surface treatment methods and adhesive systems. The types of surface treatment in this study were alumina blasting only, alumina blasting-Sn plating, alumina blasting-heating and three kinds of adhesive system used in this study were Silicoater system(Heraeus Kulzer GmbH,Germany), Superbond C & B(Sun Medical Co.,Ltd.,Japan) and Cesead opaque primer(Kurary Co.,Ltd.,Japan). After surface treatments and adhesive systems were applied, each specimen was built up with Dentacolor composite resin (Heraeus Kulzer GmbH,Germany). Four-point flexural bond strength was measured by Instron universal testing machine (Model 4301,U.S.A.) and modes of failure were observed by SEM(JEOL,SSM-840A,Japan). The obtained results were as follows: 1. The group that was bonded with Superbond C & B after alumina blasting-heating shelved the highest bond strength with significant difference among the groups, except the group with Cesead opaque primer after alumina blasting-Sn plating(P<0.05). 2. In the groups bonded with Cesead opaque primer, there was significant difference only in the bond strength between the alumina blasting-Sn plating group and alumina blasting group, where the former showed a higher bond strength(P<0.05). 3. In the groups bonded with Silicoater system, there were no significant differences in bond strength regardless of the surface treatment method(P<0.05). 4. In SEM evaluation, the groups of high bond strength, especially bonded with Superbond C & B after alumina blasting-heating and Cesead opaque primer after alumina blasting-Sn plating, revealed mainly cohesive-adhesive failure, whereas the others showed the tendency of adhesive failure.

• 한국결정성장학회지
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• 제4권2호
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• pp.169-177
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• 1994

결정성장된 시편의 농도분포를 제어하기 위해서는 초기융액의 농도를 균일하게 하여야 한다. 용질농도가 초기융액에 있어서 균일하지 않다면, 성장된 시편에 예측한 것과 다른 거시편석이 발생할 수 있다. 위 쪽의 온도가 높은 온도 구배를 갖고 아래로부터 응고를 진행시키는 Bridgman 방법으로 Al-Cu 합금을 성장시키는 경우, 성장된 시편의 어용질 농도분포가 초기응고 부분이 높고 을고가 진행됨에 따라 감소하는 경향을 갖는 것으로 관찰되었다. 이런 현사은 주괴가 녹으면서 도가니와 주괴의 틈으로 스며나온 Cu의 농도가 높은 융액이 주괴가 완전히 녹은 후의 대류에 의해 아래부분에 축적됨으로 발생했다. Al-Mg 합금의 경우 도가니와 주괴의 틈으로 스며나온 Mg의 농도가 높은 융액이 주괴가 완전히 녹은 후의 대류에 의해 떠오르면서 용질 농도분포가 성장중에 최소값을 가지는 것으로 나타났다. 이러한 거시편석을 억제하기 위하여, 균질화 처리 또는 도가니와 주괴의 틈을 없게 함으로 균일한 농도의 초기유액을 얻었다.

• 열처리공학회지
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• 제8권4호
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• pp.333-339
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• 1995

The reduction and diffusion process(R-D process) is an economical way to produce the functional materials which contain rare-earth elements and has been applied to the production of rare-earth magnet meterials($SmCo_5$, $Nd_{15}Fe_{77}B_8$), magneto-optical(MO) target materials and hydrogen storage alloy, etc. However, because of difficult to control of the final composition, the R-D process has not been applied to production of the 2-17 type rare earth permanent magnet materials which contain several elements. Therefore, this work was as a basic study for the production of the 2-17 type rare earth permanent materials with composition $Sm(Co_{0.72}Fe_{0.21}Cu_{0.05}Zr_{0.03})_{7.9}$ by the R-D process, the following were mainy examined ; the amount of metallic calcium as a reductant, homogenization condition of the alloy after the R-D reaction, masuring of magnetic properties of the sample after step aging. The sample prepared by the R-D process contained a little more oxygen than that prepared by the melting method, however, showed almost the same magnetic properties.

• 한국분말재료학회지
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• 제14권4호
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• pp.230-237
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• 2007

The fabrication of Fe alloy-40 wt.%TiC composite materials using spark plasma sintering process after ball-milling was studied. Raw powders to fabricate Fe alloy-TiC composite were Fe alloy, $TiH_{2}$ and activated carbon. Fe alloy powder was Distaloy AE (4%Ni-1%Cu-0.5%Mo-0.01%C-bal.%Fe) made by Hoeganes company with better toughness and lower melting point. These powders were ball-milled in horizontal attrition ball mill at a ball-to-powder weight ratio of 30 : 1. After that, these mixture powders were sintered by using spark plasma sintering apparatus for 5 min at $1200-1275^{\circ}C$ in vacuum atmosphere under $10^{-3}$ torr. DistaloyAE-40 wt.%TiC composite was directly synthesized by dehydrogenation and carburization reaction during sintering process. The phase transformation of as-milled powders and sintered materials was confirmed using X-ray diffraction (XRD) and transmission electron microscope (TEM). The density and harness materials was measured in order to confirm the densification behavior. In case of DistaloyAE-40 wt.%TiC composite retained for 5 min at $1275^{\circ}C$, it has the relative density of about 96% through the influence of rapid densification and fine TiC particle reinforced Fe-based composites materials.

• Journal of Welding and Joining
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• 제10권3호
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• pp.63-72
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• 1992

The joining methods of ceramics to metals which can be expected to obtain high temperature strength are mainly classified into the solid-state diffusion bonding method and the active brazing method. Between these two, the solid-state diffusion bonding method is given attentions as substituting method for active brazing method due to being capable of obtaining higher bonding strength at high temperature and accurate bonding. In this paper, the solid-state diffusion bonding of $Al_{2}$O$_{3}$ ceramics to Ni-Cr-Mo alloy steel (SNCM21) using insert metal was carried out. The insert metal employed in this study was experimentally home-made, Ag-Cu-Ti alloy. Influence of several bonding parameters of $Al_{2}$O$_{3}$SNCM21 joint was quantitatively evaluated by bonding strength test, and microstructural analyses at the interlayer were performed by SEM/EDX. From above experiments, the optimum bonding condition of the solid-state diffusion bonding of $Al_{2}$O$_{3}$/SNCM21 using Ag-Cu-Ti insert metal was determined. Futhermore, high temperature strength and thermal-shock properties of $Al_{2}$O$_{3}$/SNCM21 joint were also examined. The results obtained are as follows. 1. The maximum bonding strength was obtained at the temperature of 95% melting point of insert metal. 2. The high temperature strength of $Al_{2}$O$_{3}$/SNCM21 joint appeared to bemaximum value at test temperature 500.deg.C and the bonding strength with increasingtemperature showed parabolic curve. 3. The strength of thermal-shocked specimens was far deteriorated than those of as-bonded specimens. Especially, water-quenched specimen after heated up to 600.deg. C was directly fractured in quenching.

• Corrosion Science and Technology
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• 제6권4호
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• pp.211-218
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• 2007

In this paper, evaluation and development of corrosion resistant materials for smokestacks is summarized mainly on the basis of the author's experimental results. Operating environments of smokestacks and the problems of conventional lining materials for smokestacks are described briefly. The emphasis is focused upon the evaluation and development of recently developed corrosion resistant steels such as YUS260 for heavy oil fired smokestacks, WELACC5 for LNG fired smokestacks and NSL310MoCu Clad steel for coal fired smokestacks. Corrosion resistance of these steels under laboratory corrosion testing environments and actual environments are evaluated. Finally future problems of corrosion resistant materials for smokestacks are touched on briefly.