• 대한기계학회논문집
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• 제1권2호
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• pp.113-124
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• 1977

By spplying the ultrasomic wave to the solidifing liquid metal, grain sizes of the ingot are refined and the structures are homogenized. One of the reason is the enhancement of nucleation by ultrasonic vibration. According to the reports on this subject, the uncleating conditions are formed by the increse of melting point which is produced by the high pressure due to caviation. In this paper we study whether the caviations are the orgin of the nucleation and analized whether the nucleating conditions are formed by the increase of melting point or not and also compared the analytical result with the experim nt. We analized the pressure change induced by cllaphsing of cavity and the motion of cavith in oscillating pressure field. And we further analized the variation of melting point with pressure change.

• 한국세라믹학회지
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• 제49권2호
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• pp.191-196
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• 2012

In this study, tin phosphate glass system($SnO_2-(1-x)P_2O_5-xB_2O_3$) that occur during the melting of the metal oxide inhibition of the oxidation reaction, and to reduce oxides of high melting temperature in the following three methods were melting. The first is the general way in the atmosphere, and the second by injecting $N_2$ gas under a neutral atmosphere, and finally in the air were melted by the addition of a reducing agent Melt in the atmosphere when the oxidation of the metal oxide is inhibited by low temperatures were melting. In addition, the deposition of crystals within glassy or inhibit devitrification phenomenon is also improved over 80% transmittance. This phenomenon, when the melting of glass, many of $Sn^{4+}$ ions are reduced to the $Sn^{2+}$ was forming oxides SnO, because it acts as a modifier oxide.

• Nuclear Engineering and Technology
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• 제47권3호
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• pp.227-239
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• 2015

The thermal, mechanical, and neutronic performance of the metal alloy fast reactor fuel design complements the safety advantages of the liquid metal cooling and the pool-type primary system. Together, these features provide large safety margins in both normal operating modes and for a wide range of postulated accidents. In particular, they maximize the measures of safety associated with inherent reactor response to unprotected, doublefault accidents, and to minimize risk to the public and plant investment. High thermal conductivity and high gap conductance play the most significant role in safety advantages of the metallic fuel, resulting in a flatter radial temperature profile within the pin and much lower normal operation and transient temperatures in comparison to oxide fuel. Despite the big difference in melting point, both oxide and metal fuels have a relatively similar margin to melting during postulated accidents. When the metal fuel cladding fails, it typically occurs below the coolant boiling point and the damaged fuel pins remain coolable. Metal fuel is compatible with sodium coolant, eliminating the potential of energetic fuel-coolant reactions and flow blockages. All these, and the low retained heat leading to a longer grace period for operator action, are significant contributing factors to the inherently benign response of metallic fuel to postulated accidents. This paper summarizes the past analytical and experimental results obtained in past sodium-cooled fast reactor safety programs in the United States, and presents an overview of fuel safety performance as observed in laboratory and in-pile tests.

• 한국공작기계학회논문집
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• 제17권1호
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• pp.126-131
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• 2008

In this investigation, various factors affecting manufacturing conductive inks are presented, examined and discussed. The discussion includes inherent difficulties in making conductive inks successful and at the same time offers ways in which these difficulties might be overcome. One of the solutions to overcome such difficulties is to use low melting metals and alloys. This aspect is also detailed.

• 방사성폐기물학회지
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• 제15권2호
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• pp.181-189
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• 2017

방사성금속폐기물의 관리 옵션들을 안전성, 경제성, 작업자 피폭, 부피 감용 등의 선별 기준을 적용하여 비교 평가하였다. 원전 해체로부터 발생하는 금속폐기물의 관리 옵션에는 무구속 방출, 제한적 재사용, 그리고 직접 처분이 있다. 고려된 각각의 옵션들은 금속폐기물의 절단과 용융에 의한 부피감용을 수반한다. AHP기법을 적용하여 각 옵션들의 순위를 부여하였다. 방사성금속폐기물을 용융하여 금속 잉곳을 제조한 후 제한적 재이용 또는 무구속 방출하는 방안이 가장 효율적인 옵션으로 도출되었다.

• 한국주조공학회지
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• 제27권3호
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• pp.120-125
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• 2007

The microstructure, mechanical properties and melting range of Ni-Cr-Mo based alloys were investigated to develop Be-free Ni-Cr-Mo base dental alloys for Porcelain-Fused-to-Metal Firing(PFM). All as-cast alloys showed dendritic structure. Rockwell hardness of 20Cr7Mo was increased with addition of Si and Ti. On the contrary, it was decreased with addition of Co. The duplex alloying elemental addition such as 3Co + xTi, 2Si + xCo and 2Si + xTi to 20Cr7Mo resulted in much increase of hardness. Rockwell hardness and compressive strength for 20Cr3CoSiTi or 17Cr6CoSiTi alloy that add Si-Ti had similar values compared to the commercial alloys. Melting range for 20Cr3CoSiTi and 17Cr6CoSiTi alloy that add Si-Ti showed similar or lower than commercial alloys. In conclusion, 20Cr3CoSiTi and 17Cr6CoSiTi alloys can be applied for commercial use.

• 한국생산제조학회지
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• 제20권6호
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• pp.679-684
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• 2011

Recently, STS 301L joints of side panels to frames for stainless steel rolling stock have been made out by using existing welding methods including Resistance Spot Welding, Laser Welding and Arc Welding. Most of the processes were jointed by spot welding because it is faster at welding and comparatively less expensive for investment in welding facilities than other methods. During spot welding, however, indentation of the metal surface was made due to pressure and melting property of welding. Moreover, since the melting metal was forced to periphery of the plate as indentation was made, sheet separation, which cracked apart between jointed sheets, was carried out. A slight deformation which resulted from sheet separation deteriorated the emotional quality of railway vehicles. This paper suggests that by processing conventional spot electrode tip appropriately, melting metal is able to push up around the processed part (Hollow Spot Electrode Tip) and prevent from being dislodged from first place to periphery. Consequently, sheet separation is remarkably decreased. Also, the emotional quality of appearance of stainless steel rolling stock is enhanced considerably.

• 자원리싸이클링
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• 제4권1호
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• pp.25-30
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• 1995

본 연구에서는 Al 스크랩으로부터 재생지금 제조시 시료의 예비처리, 용제첨가 및 용해분위기가 Al 회수율에 미치는 영향을 조사하였다. 실험결과에 따르면 Al 드로스는 용탕표면에서의 산화반응에 의해 발생하였다. 예비처리의 영향에 다르면 탈지하지 않고 압착한 칩 bale 시료의 경우에는 압착하지 않은 칩 시료에 비해 약 14%의 회수율이 증가하였으며, Al seed 용해공법을 채택하는 경우에는 탈지하지 않고 단지 세편과 압착만을 행하여도 97%의 높은 회수율을 얻을 수 있었다. Al 스크랩 용해시 7wt%까지 첨가된 염에 의해 회수율은 최대 95%까지 증대되었으며, 탄소 및 질소분위기에서도 역시 회수율은 증가하였으나, 염과 탄소의 혼합분 첨가시 과잉 첨가된 탄소는 오히려 회수율을 감소시켰다.

• 한국주조공학회지
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• 제22권5호
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• pp.265-270
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• 2002

A novel jewelry master pattern manufacturing process which reduce manufacturing steps by employing a Duraform rapid prototyping mold and a low melting alloy has been suggested. The novel process follows the steps of 'jewelry 3D CAD design ${\rightarrow}$ Durafrom RP mold ${\rightarrow}$ low melting alloy master pattern' while the previous process follows more complicated steps of 'jewelry idea sketch ${\rightarrow}$ detailed drawing ${\rightarrow}$ wax carving ${\rightarrow}$ flask ${\rightarrow}$ silver master pattern.' An upper and a lower part of molds have been manufactured of Duraform powder, of which melting point is $190^{\circ}C$. A maser pattern was manufactured by pouring a low melting alloy of Pb-Sn-Bi-Cd, so called Woods Metal, of which melting point is $70^{\circ}C$, into the mold. The master pattern is a shape of a disk of 20mm diameter that contains various design factors. The variations of dimensions, surface roughness, surface pore ratio were measured by an optical microscope, a surface roughness profilometer, and a Rockwell hardness tester. The pattern made of were maeasured by an optical microscope, a surface roughness profilometer, and a Rockwell hardness tester. The pattern made of low melting alloy has sufficient surface hardness, and surface pore ratio to be used as the jewelry master pattern.

• 대한치과기공학회지
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• 제45권1호
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• pp.1-7
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• 2023

Purpose: To evaluate the marginal and internal fit of metal coping fabricated by a metal three-dimensional (3D) printer that uses selective laser melting (SLM). Methods: An extraoral scanner was used to scan a die of the prepared maxillary right first molar, and the coping was designed using computer-aided design software and saved as an stereo lithography (STL) file. Ten specimens were printed with an SLM-type metal 3D printer (SLM group), and 10 more specimens were fabricated by casting the castable patterns output generated by a digital light processing-type resin 3D printer (casting the 3D printed resin patterns [CRP] group). The fit was measured using the silicon replica technique, and 8 points (A to H) were set per specimen to measure the marginal (points A, H) and internal (points B~G) gaps. The differences among the groups were compared using the Mann-Whitney U-test (α=0.05). Results: The mean of marginal fit in the SLM group was 69.67±18.04 ㎛, while in the CRP group was 117.10±41.95 ㎛. The internal fit of the SLM group was 95.18±41.20 ㎛, and that of the CRP group was 86.35±32 ㎛. As a result of statistical analysis, there was a significant difference in marginal fit between the SLM and CRP groups (p<0.05); however, there was no significant difference in internal fit between the SLM group and the CRP group (p>0.05). Conclusion: The marginal and internal fit of SLM is within the clinically acceptable range, and it seems to be applicable in terms of fit.