수직 연속주조 공정으로 제조된 Al-8Zn-2Mg-2Cu 빌렛의 표면 결함 형성에 미치는 주조 온도와 주조 속도의 영향

이윤호 ( Yoon-ho Lee ),김용유 ( Yong-You Kim ),이상화 ( Sang-hwa Lee ),김민석 ( Min-seok Kim ),어광준 ( Kwangjun Euh ),이동근 ( Dong-geun Lee ) 한국주조공학회 2021 한국주조공학회지 Vol.41 No.3

7000계 알루미늄 합금은 다른 Al 합금에 비해 강도가 우수하여 주목을 받고있으며, 7000계 알루미늄 빌렛은 일반적으로 Direct-Chill (DC) 주조 공정을 통해 제조된다. DC 주조 공정으로 제조된 알루미늄 빌렛의 표면 결함은 주로 Exudation과 Meniscus freezing 현상과 관련이 있으며, 이는 합금 성분, 주조 속도 및 주조 온도의 영향을 받는다. 특히, 7000계 알루미늄 합금은 응고 과정에서 응고 온도 범위가 넓어 주조 결함이 발생하기 쉽다. 본 연구에서는 DC 주조 공정에 의해 제조된 Al-8Zn-2Mg-2Cu 합금 빌렛에 대한 표면 결함 변화에 대하여 조사하였다. 빌렛의 표면은 "Wavy" 또는 "Dot" 표면으로 관찰되었다. Wavy 표면은 낮은 주조 속도(200mm/min)와 온도(655℃)에서 Meniscus freezing 현상에 의해 형성되었으며, Concave 영역에서 Meniscus freezing 현상으로 인한 조성작 과냉으로 인해 미세한 수지상 조직이 관찰되었다. 반면에, 주조 온도가 높은 조건(675℃)에서는 Dot 표면이 기공 형성에 의해 형성되었으며, 높은 주조 속도(230mm/min)에서 제조된 Dot 표면을 갖는 빌렛에서는 높은 금속 수두압에 의해 Exudation 층이 형성되었다. Exudation 층의 Dot 영역과 Smooth 영역은 각각 미세한 수지상 형태와 주상정 형태의 조직이 관찰되었으며 이는 Dot 영역에서 가스 기공의 형성에 의한 결과이다. 7000-series aluminum alloys are noted for their superior strength compared with other Al alloys, and their billets are generally fabricated by direct-chill (DC) casting. Surface defects in a DC-cast aluminum billet are mainly related to exudation and the meniscus freezing phenomenon, which are influenced by alloy compositions, casting speed, and casting temperature. 7000-series aluminum alloys have a wide freezing range during solidification, which makes it easy for casting defects to occur. In this study, we investigated surface defect evolution in casting billets of Al-8Zn-2Mg-2Cu alloy fabricated by a DC casting process. The billets showed “wavy” or “dotted” surfaces. The wavy surface was formed by meniscus freezing at a lower casting speed (200 mm/min) and temperature (655 ℃). In the wavy surface, refined dendritic cells were observed in a concave region due to the constitutional supercooling caused by meniscus freezing. Meanwhile, at a higher casting temperature (675 ℃), the dotted surface was formed by pore formation. In the dotted surfaces in the billet formed at a high casting speed (230 mm/min), an exudation layer was formed by the high metallostatic head pressure. The dotted region and the smooth region had a refined dendritic morphology and a columnar morphology at the exudation layer, respectively. This is attributed to the formation of gas pores in the dotted region.

Microstructure and mechanical properties of Al-1Mn and Al-10Si alloy circular clad ingot prepared by direct chill casting

Fu, Y.,Jie, J.,Wu, L.,Park, J.,Sun, J.,Kim, J.,Li, T. Elsevier Sequoia 2013 Materials science & engineering. properties, micro Vol.561 No.-

An innovative direct chill casting process to prepare Al-10wt%Si and Al-1wt%Mn alloy circular clad ingots has been developed in the present study. The experimental casting parameters were determined by theoretical analysis, numerical simulation and experimental processes. The interface of clad ingots was investigated by methods of metallographic examination, electron probe microanalysis (EPMA) and transmission electron microscopy (TEM). The results showed that excellent metallurgical bonding of two different aluminum alloys could be achieved by direct chill casting. The Al-1Mn alloy which was poured into the mold earlier served as the substrate for heterogeneous nucleation of Al-10Si alloy. Because of diffusion of Si and Mn elements, a diffusion layer with a thickness of about 40μm on average between the Al-10Si and Al-1Mn alloys could be obtained. The tensile strength of the clad ingot was 106.8MPa and the fractured position was located in the Al-1Mn alloy side, indicating the strength of the interfacial region is higher than that of Al-1Mn alloy.

SLA 쾌속조형 패턴에 의한 직접 주조에 관한 연구

이승채,김우순,김동현 한국공작기계학회 2004 한국공작기계학회 추계학술대회논문집 Vol.2004 No.-

Rapid prototyping technologies have been widely used to reduce the development cost of new products. Manufacturing industries are nowadays characterized by the flexibility and complexity of products. This to due to the rapid development of manufacturing technology and diverse needs of customers. In this paper, the burning condition for getting casting product of resin pattern have been examined experimentally. In generally, the burning conditions have effect on the casting products. Using the direct casting. we directly producted the jewelry.

Mechanical Heterogeneity of Heat-Resistant EV31A Magnesium Alloy with Large Size Processed by Direct-Chill Casting

Deping Zhang,Boqiong Li,Chaojie Che,Baosheng Liu,Peng Cheng,Yali Zhao,Jinhui Zhang,Liren Cheng 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.10

High quality of large-sized EV31A benchmark alloy was fabricated by direct-chill casting, without significant composition segregation along its radial direction. As-cast samples show noticeable mechanical heterogeneity, such as strength decreasing but ductility increasing from the surface to the center positions of the ingot. After heat treatment, however, mechanical properties of the alloy are nearly the same in each position, indicating mechanical homogeneity, which is mainly attributed to the strengthening mechanism transition from grain-boundary hardening in as-cast samples to precipitation hardening in peak-aged samples. In addition, we found that solute hardening is the athermal strengthening which contributes more to high-temperature strength than precipitation hardening, as evidenced by lower strength loss from 25 to 250 °C in T4-treated sample than in peak-aged sample. Solute hardening effect is thermally stable and extends to high temperatures, which favors the retention of linear strain hardening by retarding dynamic recovery. This work thus provides new insight into designing heat-resistant Mg alloys and understanding mechanical heterogeneity of large-scale Mg alloy ingots.

Alloy 625의 특성과 조직에 미치는 원심주조품 두께의 영향

이유정,김병훈,주윤곤,조창용,이재현 한국주조공학회 2022 한국주조공학회지 Vol.42 No.3

The effect of thickness on the microstructure and the mechanical properties of centrifugal cast 625 was investigated. Centrifugal cast 625 with various thickness of 10, 17 and 50mm showed partially columnar grained structure 8, 12.3 and 18.5mm respectively from the outer surface. Secondary dendrite arm spacing in the columnar grains slightly increased with increasing casting thickness. Tensile strength of the columnar region was similar regardless of casting thickness. Solidification behavior of the columnar grained region is similar to that of directional solidification, thus solidification rate in the centrifugal cast tube was extrapolated from the secondary dendrite arm spacing data of the directionally solidified material. The equiax grained region formed interior of the thick castings. The tensile strength of the equiaxed region showed the average value of the columnar region which is presumably orig- inated from the grain structure rather than secondary dendrite arm spacing. 초내열합금 625 튜브의 제조에 필요한 원심주조품의 두께에 따라 응고조직과 기계적 특성에 미치는 영향을 고찰하였다 . 10, 17, 50 mm 두께로 원심주조한 625합금에서 두께의 증가에 따라 주상정 부분의 길이와 2차 수지상 간격이 약간 증가하였으나 상 온 인장특성은 큰 차이를 보이지 않았다 . 주상정 부분의 응고는 일방향응고의 형태로 응고가 진행되기 때문에 일방향응고 조건을 변화시켜 2차 수지상의 간격을 비교하여 각 두께의 주조품에서 응고속도를 계산하였다 . 두꺼운 주조품일수록 내부 다결정 조직의 비율이 증가하였다 . 다결정 부분의 인장특성은 주상정 부분의 평균값과 유사한 값을 보였으며 이는 2차 수지상의 간격보다 결정립 형태의 영향인 것으로 사료된다.

『내가 죽어 누워 있을 때』- 영상화가 불가능한 소설 영화로 만들기 -

최선화 현대영미어문학회 2014 현대영미어문학 Vol.32 No.3

Director James Franco's film, due out in 2013, has adapted Faulkner's stream of consciousness tale of the death of Addie Bundren and her family's journey to grant her dying wish and bury her in Jefferson. Franco has turned it into a film that uses a split-screen technique to tell the narrative from various characters' points of view. Told through multiple voices, the film vividly brings to life Faulkner's fictitious South and is satiated with the impoverished, violent, and fascinating characters that were his trademark. Today he is regarded as an important interpreter of the universal theme of "the problems of the human heart in conflict with itself." The story is discussed in light of Franco's film As I Lay Dying in contrast with Faulkner’s novel As I Lay Dying in order of scriptwriting, casting, and film directing. The film cannot fully depict the remarkably elaborate poetic and philosophical intricacy of Faulkner’s novel but Franco does seem to be trying to stay faithful to Faulkner's vision for the story.

Effect of Slime on Engineering Characteristics of Large-Diameter Cast-in-Place Pile

허옹,윤여원,도진웅 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.1

Slime forms at the bottom of boreholes under the effect of groundwater. The larger the borehole, the more the slime. The demand for large-diameter cast-in-place (CIP) piles has increased as the number of large structures has increased. Excessive slime management can delay construction. However, the effect of slime on the engineering characteristics of large-diameter CIP piles is not understood. In this study, the strength of slime–concrete mixtures was investigated by varying the volume ratio of slime. Field-scale testing was performed to evaluate the behavior of the large-diameter CIP pile using bidirectional load testing. A numerical analysis was performed to assess the compressibility of the slime under the self-weight of the pile. The results revealed that the general levels of slime at the bottom of the borehole had an insignificant influence on the engineering characteristics of the large-diameter CIP pile because the slime is susceptible to being mixed with poured concrete and compressed by the self-weight of the pile.

Simulation and Experiment on Direct Continuous Casting Process of Lead Frame Copper Alloy

Huang Guojie,Xie Shuisheng,Cheng Lei 한국소성가공학회 2010 기타자료 Vol.2010 No.6

Direct Continuous Casting (D.C.C) is an important method in casting lead frame copper alloy. In this paper, numerical simulation is adopted to investigate the casting process in order to optimize the D.C.C technical parameters, such as the casting temperature, casting speed and cooling intensity. According to the numerical results, the reasonable parameters are that the casting temperature is between 1413K~1413K, the casting speed is between 8m/h~10m/h and the speed of cooling water is between 4.2m/s~4.6m/s. And the depth of liquid-solid boundary is measured in different casting temperature and casting speed by experiments. The results show the actual measurements have a little deviation with the numerical simulation. The results of numerical simulation provide the significant reference to the actual experiments.

신속한 주물 시제품 개발을 위한 전산모사 기술과 산업용 단층촬영기 및 쾌속조형기의 적용

유승목(S. M. Yoo),임채호(C. H. Lim),조인성(I. S. Cho),최정길(J. K. Choi) 한국정밀공학회 2006 한국정밀공학회 학술발표대회 논문집 Vol.2006 No.5월

Direct laser sintering (DLS) technology for the resign coated sand is one of attractive technologies to produce molds and cores for the foundry industry rapidly and cost effectively. The objective of this case study is to develop casting pilot models using computer simulation technology, DLS RP machine and industrial computed tomography. The proposed casting design was verified by the Z-Cast software in the fields of fluid flow and solidification during the casting process. Casting parts with aluminum alloy using the post-curing treated sand moulds and cores are accurate to dimension and defect free.

Twin-Roll Strip Casting 공정으로 제조된 Al 7075 합금의 미세조직 및 마모 특성

김경욱,백민석,어광준,이기안 대한금속·재료학회 2021 대한금속·재료학회지 Vol.59 No.12

Al 7075 alloy was manufactured using the twin-roll strip casting (TRC) process, and the mechanical and wear properties of the fabricated TRC process were investigated. To compare the properties of the alloy manufactured by TRC, another Al 7075 alloy was fabricated by conventional direct chill (DC) casting as a comparative material. Based on initial microstructure observations, the Al 7075 alloy manufactured by the DC process showed relatively elongated grains compared to the Al 7075 alloy by TRC process. In both alloys, η(MgZn2) phases were present at the grain and grain boundaries. In the Al 7075 alloy manufactured by the DC process, the η(MgZn2) phases were coarse with a size of ~86 nm and were mainly concentrated in the local area. However, the Al 7075 alloy manufactured by TRC had relatively fine η(MgZn2) phases size of ~40 nm, and they were evenly distributed throughout the matrix. When the mechanical properties of the two alloys were compared, the TRC process showed higher hardness and strength properties than the DC process. In room temperature wear test results, the TRC process exhibited lower weight loss and wear rates compared to the DC process at all wear loads. In other words, the TRC process resulted in relatively superior wear resistance properties compared to the conventional DC process. The wear behavior of both alloys changed from abrasive wear to adhesive wear as the wear load increased. However, the TRC process maintained abrasive wear up to higher loads. Based on the above results, a correlation between the microstructure and wear mechanism of the Al 7075 alloy manufactured by TRC is also suggested.