논문 : 제조공정 ; SCM 440 빌렛트의 수평 연속주조시 표면품질에 미치는 인발 사이클과 주조속도의 영향

이병화 ( B. H. Lee ),유병돈 ( B. D. You ),김목순 ( M. S. Kim ),정일권 ( I. K. Jung ),윤황로 ( H. R. Yoon ) 대한금속재료학회 ( 구 대한금속학회 ) 1998 대한금속·재료학회지 Vol.36 No.7

Trial tests were made to examine the effects of casting pattern on the surface quality of SCM 440 billets in horizontal continuous casting. The withdrawal cycle and the casting speed were varied 40~80 cycle/min and 0.7~1.0 m/min respectively. The main results obtained could be summarized as follows: When the withdrawal cycle is low, the withdrawal mark is irregular and the surface of billet is rough due to the formation of the lapped skin. The increase of withdrawal cycle results in the uniform withdrawal mark and the fine surface of cast products. The very low or the very high withdrawal cycle is essential for the prevention of transverse cracks on surface and corner cracks of the billet. For the case of the withdrawal cycle of 50 cycle/min, the effects of casting speed on the formation of transverse cracks and on the surface roughness could not be justified accurately due to the formation of lapped skin. The casting speed does not affect, however, the formation of the corner crack.

Variation of Hot Ductility Behavior in As-Cast and Remelted Steel Slab

서상철,손광석,이성근,김인수,이태진,임창희,김동규 대한금속·재료학회 2008 METALS AND MATERIALS International Vol.14 No.5

Variations in the hot ductility behavior of as-cast and remelted steel slabs were investigated. The specimens were prepared directly from the surface of an as-cast continuous casting slab. The slab was then remelted to assess the effect of the same on the cast structure. A high temperature tensile test was used to obtain hot ductility data. In the case of 0.18 wt.% carbon steel, hot ductility improved with increasing strain rate for both as-cast and remelted slab specimens. Comparing the results obtained from the as-cast and remelted specimens, similar hot ductility values were observed in the low temperature range. At higher temperatures, however, the remelted slab specimen had a higher R/A (reduction of area) value. The decreased R/A value of the as-cast specimens in the high temperature region could be explained by the increase in the initial grain size due to the slow cooling of the large slab during continuous casting. This means a lower hot ductility value than that obtained from remelted specimen should be assumed in the case of the application of lab data to an actual continuous casting process.

연주 주편의 열간 연성에 미치는 변형속도 및 재용해의 영향

변재환,손광석,서상철,김진수,이주동,임창희,김인수,이성근,김동규 대한금속재료학회 2005 대한금속·재료학회지 Vol.43 No.3

The effect of strain rate and remelting on hot ductility of low carbon steel were investigated. The specimen was prepared from as cast continuous casting slab, and also the slab was remelted to assess the effect of remelting by which cast structure would be modified. High temperature tensile test was adopted to get the hot ductility data. In case of 0.18 wt.% carbon steel, hot ductility was markedly improved with increasing strain rate in both specimen obtained from as cast slab and remelted slab. Comparing the results obtained from as cast specimen and remelted specimen, it showed similar value of hot ductility in low temperature range, and in high temperature region, showed higher R/A(reduction of area) value in the specimen obtained from remelted slab. The decreased RA value of as cast specimen in high temperature region could be explained by the increase in initial grain size due to slow cooling of large slab during continuous casting. It means that we should presume lower value of hot ductility than the value obtained from remelted specimen in case of lab data application to actual continuous casting process. (Received November 22, 2004)

Sand Casting Process Design for the Bush Parts of the Continuous Hot Zinc Plating Roll Applied to Wear-Resistant Alloy Cast Steel

Dong-Hwan Park(박동환),Jae-Jung Yun(윤재정),Jin-Tae Hong(홍진태),Hyuk-Hong Kwon(권혁홍) 한국기계가공학회 2017 한국기계가공학회지 Vol.16 No.4

In the sand casting process, the flow of liquid metal affects the quality of casting products and their die life. To determine the optimal bush part design process, this study performed various analyses using commercial finite element analysis S/W. The simulation focused on the molten metal behaviors during the mold filling and solidification stages of sand casting. This study aims to develop methods to reduce the cost and increase the tool life of the continuous hot zinc plating roll.

Study on the possibility of continuous-casting of bimetallic components in condition of direct connection of metals in a liquid state

Marukovich, E.I.,Branovitsky, A.M.,Na, Young-Sang,Lee, Jong-Hoon,Choi, Ki-Young Elsevier 2006 Materials & design Vol.27 No.10

<P><B>Abstract</B></P><P>The possibility of producing bimetals by continuous casting method when composition of components occurs in liquid state without mixing is considered. Contact layers of composite metals were investigated by methods of metallographic, X-ray diffraction, microscopic and ultrasonic analyses. Binary mixtures of eutectic type Al–Zn, Al–Sn, Al–Pb were selected. The numerical estimations for bimetallic casting of some metal-alloy pairs were also conducted to achieve the optimization of casting process condition.</P><P>It was observed that the size of diffusion zone of interface layer was 0.1–0.5mm in producing bimetallic compositions by direct connection of liquid phase components. The microstructures observed in bimetallic binary samples were well accorded to those expected from the phase diagrams. It could be concluded from the mathematical simulation for casting process that qualified bimetallic casting billet and plate can be continuously cast by carefully controlling the casting process condition such as withdrawing speed.</P>

연주크랙 저감을 위한 API X-50 강의 고온연성에 대한 미세조직의 영향

金成圭,金俊星,金洛준 대한금속재료학회 2002 대한금속·재료학회지 Vol.40 No.2

The rapid cooling in continuous casting process produces large thermal stress in the slabs, due to steep thermal gradient between the interior and the exterior of the slabs and a mechanically induced stress caused by friction in the mold, roll pressure, etc. There is also an occurrence of tensile stress at the upper region and compressive stress at the lower region of the slabs at the straightening zone at around 700℃-900℃ in the case of vertical continuous casters. In the case of steels with poor hot ductility, the combination of the stresses mentioned above quite often results in the formation of cracks. Among various types of steels, it is known that steels containing strong carbide formers such as Nb are particularly susceptible to cracking during continuous casting. The present study is concerned with microstructural analyses of the Nb containing steel (A steel) and Nb+B containing steels (B steel) to reduce the transverse corner crack at the straightening zone, with emphasis on elucidating the mechanism of hot ductility. There are differences in the microstructures between the A steel and the B steel. The B steel has a smaller amount of ferrite films along the prior austenite grain boundaries than the A steel. Also, the B steel contains proeutectoid ferrite within the prior austenite grains and 5-㎛-sized coarse Fe_23(B, C)_6 along the prior austenite grain boundaries as well as within the prior austenite grains. The ductility trough is virtually non-existent in the B steel, although variation of values of reduction of area (RA) with temperature shows that the A steel has a trough of RA between 700℃ to 850℃. It is believed that the presence of intraganular ferrite improves the homogeneity of deformation and accordingly the hot ductility of the B steel.

연속주조한 구상흑연주철의 미세조직과 기계적 성질

최경환 ( Choe Gyeong Hwan ),조규섭 ( Jo Gyu Seob ),이경환 ( Lee Gyeong Hwan ),김기영 ( Kim Gi Yeong ) 한국주조공학회 2004 한국주조공학회지 Vol.24 No.1

N/A Microstructure and mechanical properties of ductile cast iron were investigated in terms of diameter change of samples that gives rise to modify the microstructure due to different cooling rate in the continuous casting process. The chemical composition used in this study was GCD 400 grade. From the microstructural observation, we have found a large number of graphite with small size in diameter which is comparable to the microstructure of the sample produced by conventional sand casting. The major reason of this would he due to high cooling rate. In the sample with 26 ㎜ in diameter, the microstructure was composed of pearlite, iron carbide, and graphite. In the samples with 60 and 100 ㎜ in diameter, however, we have observed a dissimilar microstructure that consisting of ferrite and graphite. Concerning the mechanical property, the sample with 26 ㎜ in diameter showed higher hardness and strength compared to those samples with 60 and 100 ㎜ in diameter. The result obtained for ductility appeared a reversal. Much more works such as inoculation, process design and chemical composition would be required in order to have a sound product even in a small diameter of samples.

Effects of a moving weir on tundish flow during continuous-casting grade-transition

전수환,Sangseung Lee,Sanghyun Ha,Sungjool Kim,Donghyun You 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.9

A moving weir to reduce the time for grade transition is proposed. To investigate benefits of the proposed moving weir, tundish flow subject to various conditions of a moving weir was numerically investigated. First, an optimal travelling path of a horizontally moving weir was determined in a water model. Investigation of various cases shows that the shortest transition time is obtained when new molten steel is injected after the weir returns to its original position after a round-trip. Using this travelling path, the speed of the moving weir was investigated in a real-scale model to determine an optimal speed that stabilizes the surface height while the transition time is minimized. As a result, intermixing of steel with dissimilar grades has been reduced by 14.5 % by using the optimal conditions of the moving weir. Lastly, the performance of vertically moving weirs was assessed by comparing with that of the horizontal counterpart.

Relationship Between Fluid Flow Stability and Submerged Entry Nozzle Port Angle in a Conventional Slab Continuous-Casting Mold

Won‑hyuk Lee,Kyung‑woo Yi 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.10

Fluid flow patterns within a conventional slab continuous-casting mold are closely linked to the port angle of the submergedentry nozzle (SEN). Fluid flow is unstable below a certain port angle, with large fluctuations near the port outlet as wellas jet stream oscillation and repeated vortex formation and dissipation within the mold. However, such phenomena are notobserved above a certain port angle, at which the flow pattern becomes stable. This behavior was investigated via bothnumerical simulation and water model experimentation; two different regions were identified with flow patterns varyingaccording to the SEN port angle. In addition, a close quantitative relationship was identified between changes in the portangle and fluid velocity variations. For SEN port angles in the range 0°–15°, the flow velocity in the upper circulation zoneoscillated in an unstable manner. For port angles of 20° or more, the flow velocity of the same zone decreased significantlyand stabilized. When the gas was injected, the unstable region elongated to 0°–20°. The present study offers insight towarddeveloping a clearer understanding of the complex flow patterns in casting molds, as well as of the conditions necessary forstable flow patterns.

연주 ROLL 육성부의 기계적 성질에 미치는 Nb, V의 영향

김창규(CHANG-GYU KIM),윤재홍(JAE-HONG YOON),황동수(DONG-SOO WHANG) 한국해양공학회 2004 韓國海洋工學會誌 Vol.18 No.2

In the steel marking industry, most companies have adopted the continuous casting process, due to its economical benefit. Casting rolls are utilized for frictional drive and the transport of solidifying slap. Dimensional tolerances, mechanical stability, and surface condition of the casting rolls can affect both the surface and the internal quality of the product being cast. To overcome these problems, the industry now is focused on accelerating the rate of technological improvements. This study has been undertaken for the development of casting rolls overlaid materials (SAW FCW wire), with the addition of Vanadium and Molybdenum to the martensitic stainless steel, in order to increase tensile strength and hardness at elevated temperatures.