• Title/Summary/Keyword: Cast microstructure

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A Study on the Production of a Compressor Piston for an Automobile Air-Conditioner using Aluminum casting/Forging (알루미늄 주조/단조 공정을 이용한 자동차용 에어컨 컴프레서 피스톤의 생산에 관한 연구)

  • Lee, Sung-Mo;Wang, Shin-Il;Kim, Hyo-Ryang;Bae, Won-Byong
    • Journal of the Korean Society for Precision Engineering
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    • v.17 no.8
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    • pp.53-59
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    • 2000
  • In this study aluminum casting experiments are carried out to reduce the grain size of a cast preform and to spheriodize its dendritic structure by adding Ti+B and Zr and to modify flaked eutectic silicon by adding Sr, And a finite element simulation is performed to determine an optimal configuration of the cast preform to be used in forging of a compressor piston for an automobile air-conditioner. When 0.15% Ti+B Zr and 0.05% Sr are added respectively into the molten aluminum alloy the finest grain in casting of the preform is obtained. It is confirmed that the optimal configuration of the cast preform predicted by FEM simulation is very useful for forging the compressor piston. After forging the cast preform of the compressor piston. the microstructure and the hardness of the cast preform is compared with those of the cast/forged product.

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Effect of Strip-cast Conditions on the Formation of Microstructures in Nd-Fe-B alloys (Strip-cast 조건이 Nd-Fe-B 합금의 미세조직 형성에 미치는 영향)

  • Lee, D.H.;Jang, T.S.;Kim, D.H.;Kim, Andrew S.
    • Journal of the Korean Magnetics Society
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    • v.12 no.1
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    • pp.34-40
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    • 2002
  • In order to improve the microstructure of the strip cast Nd-Fe-B alloys that are frequently used for production of high energy sintered magnets, influence of various strip casting conditions on the microstructure and phase formation and distribution were investigated. Nd-Fe-B strips consisting of microstructures suitable for preparation of high energy sintered magnets could be obtained when the wheel speed was below 5 m/s. The compositional limit that can avoid the crystallization of free iron in the as-cast state was estimated to be Nd$\_$14/Fe$\_$79/B$\_$7/. Regardless of the compositional variation, <001> preferred orientation of Nd$_2$Fe$\_$14/B normal to the strip surface was always occurred below 5 m/s, which would eventually enhance the grain alignment during pressing the powder under a magnetic field. While the coercivity of the strip cast alloys increased with the increase of the wheel speed, mainly due to the refinement of Nd$_2$Fe$\_$14/B grains, it decreased with the reduction of Nd content in the alloy composition as the formation of free iron increased.

A Study on the Improvement of Mechanical Properties for an Engine Piston (엔진피스톤의 기계적 성질의 향상에 관한 연구)

  • 김영호;배원병;변흥석
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1995.10a
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    • pp.113-116
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    • 1995
  • In this experimental study,aluminum hotforging was conduct to get superior pistion to cast piston. Cast structure of billet is destroyed, harmful defects is removed by forging process. We proposed the direction od die design by observing formability of product according to die shape. The microstructure of forged products with different preform was investigated to determine inital billet shape. We proposed appropriate heat treatment condition for improvement of mechanical properties.

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The Effects of Cyclic Heat Treatment Process for Fine Microstructure of TiAl Cast Alloy (주조용 TiAl 합금의 조직 미세화를 위한 반복열처리 공정 조건에 관한 연구)

  • Kong, Man-Sik;Yang, Hyunseok
    • Journal of the Korean Society for Heat Treatment
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    • v.32 no.5
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    • pp.195-200
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    • 2019
  • For expanding the applications and workability of TiAl alloy, elongation is very important property. Fine microstructure is needed for elongation and physical properties of TiAl alloys. In this study, The effects of cyclic heat treatment process for fine microstructure of Ti-46Al-Nb-W-Cr-Si-C alloy, which was made by VAR (vacuum arc remelting) and VIM(vacuum induction melting) centrifugal casting process, was investigated. Cycle heat treatment process was very effective for recrystallization of this TiAl system, which has microstructure size of $50{\sim}100{\mu}m$ through pre-heat treatment, cyclic heat treatment in ${\alpha}+{\gamma}$ phase region and solution heat treatment respectively. Refined grain size was finally confirmed by photos of optical microscope and scanning electron microscope.

A study on the microstructure change during the welding of a cast iron with a Fe-Mn-Al steel powder (주철과 Fe-Mn-Al강 이종금속 용접부의 조직변화에 관한 연구)

  • 김경중;서정현
    • Journal of Welding and Joining
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    • v.8 no.4
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    • pp.35-45
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    • 1990
  • Casting are widely used nodays as complicated and diversified forming materials due to its superior castability. However the welding of cast iron has not been accompaniced satisfactory resulting in an microstructure change happened in the heat affected zone (HAZ), especially the graphite are formed and shaped consecutively in the area and it has great impact on the crack occuring and growth together with martensite forming in this area. It case of gray cast iron welding, it is required for pre-heat treatment or specific welding consumables to restrain forming the martensite in the HAZ. In this study, by applying the plasma surface overlaid welding. Fe-Mn-Al steel powder has been used for improvement of anti-crackability in the HAZ and much attention has been paid to establish the overlaid welding method for gray cast iron so that optimum welding conditions may prevent the cracking. With our experiments, we have found that to prevent defects which may occur in the HAZ, the overlaid welding technique for gray cast iron has been developed.

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Effects of Heat Treatments on Microstructure , Hardness and Abrasive Wear Resistance in 3%C-10%Cr-5%Mo-5%W White Cast Iron (3%C-10%Cr-5%Mo-5%W 백주철에 있어서 열처리가 현미경조직, 경도 및 내마모성에 미치는 영향)

  • Yu, Sung-Kon
    • Journal of Korea Foundry Society
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    • v.19 no.1
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    • pp.33-37
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    • 1999
  • White cast iron of 3%C-10%Cr-5%Mo-5%W was casted, and then heat treated with three different methods such as homogenizing, austenitizing and tempering to observe its effects on the microstructure, hardness and abrasive wear resistance. In uni-directional soldification, bamboo tree-like $M_7C_3$ carbide grew along with the heat flow direction, and fishbone-like $M_6C$ carbide was dispersed randomly among $M_7C_3$ carbides. While almost pearlitic structures were observed in the as-cast specimen, those of the heat treated specimens consisted of secondary carbide, retained austenite and tempered martensite. In austenitized specimen, the amounts of retained austenite were 60.88% due to the higher cooling rate encountered in forced air cooling. On the other hand, the amounts of retained austenite were reduced from 60.88% to 23.85% in tempered specimen due to the transformation of austenite into tempered martensite. The hardness of tempered specimen showed the highest value, and then decreased in the order of austenitized, as-cast and homogenized specimens. But, the abrasive wear resistance of austenitized specimen was the highest, and then decreased in the order of tempered, as-cast and homogenized specimens.

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Effect of Aging Treatment on the Microstructure and Tensile Properties of AZ61-xPd (x = 0, 1 and 2 wt%) Alloys (AZ61-xPd (x = 0, 1 and 2 wt%) Mg합금의 미세조직 및 인장특성에 미치는 열처리의 영향)

  • Kim, Sang Hyun;Kim, Byeong Ho;Park, Kyung Chul;Park, Yong Ho;Park, Ik Min
    • Korean Journal of Metals and Materials
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    • v.50 no.10
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    • pp.711-720
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    • 2012
  • In this study, the effect of aging treatment on the microstructure and tensile properties of AZ61-xPd (x = 0, 1 and 2 wt%) alloys were investigated. The microstructure of as-cast AZ61-xPd alloys mainly consisted of ${\alpha}-Mg$, $Mg_{17}Al_{12}$ and $Al_4Pd$ phases. After solution treatment, most of the $Mg_{17}Al_{12}$ phases were dissolved into the Mg matrix. Thereafter, $Mg_{17}Al_{12}$ phases were finely formed and distributed near thermally stable $Al_4Pd$ phases and inside the grains through aging treatment at $220^{\circ}C$ during 88 hours. With the aging at $220^{\circ}C$, the peak aged AZ61-xPd alloys showed higher hardness than as-cast and solution treated AZ61-xPd alloys. In particular, the AZ61-1Pd alloy was optimized due to refined $Mg_{17}Al_{12}$ and $Al_4Pd$ phases. Further, the peak aging time was reduced with increasing Pd addition (>1 wt%). Tensile strength was increased by Pd addition at $25^{\circ}C$, $150^{\circ}C$, both as-cast and peak aged AZ61-xPd alloys. After aging treatment, room and high temperature tensile strength were increased more than the as-cast specimens. The AZ61-1Pd alloy especially showed the largest strength increase range. Elongation was decreased with addition Pd at $25^{\circ}C$ and $150^{\circ}C$.

A Study on the Effects of Artifacts on Fatigue Limit of Ductile Cast Iron with Ferritic Structure

  • Kim, Jin-Hak;Kim, Min-Gun
    • Journal of Mechanical Science and Technology
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    • v.14 no.10
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    • pp.1021-1027
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    • 2000
  • In this study, fatigue tests were performed to examine the effects of micro drill hole on fatigue limit of as cast and austempered ductile cast iron (ADI) using the rotary bending fatigue tester. As results, micro drill holes ($diameter{\leq}0.4mm$) did not influence the fatigue limit of ADI, compared to annealed ductile cast iron; the critical defect size of crack initiation, in ADI was larger than as cast. If the ${\sqrt{area}}$ of micro drill hole and graphite nodule in ADI are comparable, crack initiates at the graphite nodule. When the ruggedness developes through austempering treatment process, microstructure on crack initiation at micro drill hole is tougher than that of as cast ductile cast iron.

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A Study on the Development of Aluminum Piston by Forging Process (알루미늄 단조 피스톤의 개발에 관한 연구)

  • Kim, Y.H.;Bae, W.B.;Kim, H.S.
    • Journal of the Korean Society for Precision Engineering
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    • v.14 no.9
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    • pp.30-36
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    • 1997
  • In this study, the development of an aluminum forged piston was tried to substitute the cast piston, in which there were internal defects such as blow hole and shrink pipe. A gasoline engine piston was chosen as an example for developing the forged piston. Before aluminum forging, model, material (plasticine) test was carried out to investigate the forgeability and internal flow pattern of the forged piston at room temperature. From the result of model material test, an aluminum piston to be forged was redesigned. The aluminum pistion was forged in hot process. The quality of a forged piston was compared with that of a cast piston in the point of mechanical properties, internal defect and microstructure. It was proved that the forged piston was superior to the cast piston.

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THE EFFECTS OF ALLOYING ELEMENTS AND COOLING RATES DURING SOLIDIFICATION ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF P-CONTAINED C/V GRAPHITE CAST IRONS

  • Kim, Myung-Ho;Park, Heung-Il;Kim, Woo-Yeol;Bae, Cha-Hurn
    • Journal of Korea Foundry Society
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    • v.15 no.6
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    • pp.546-557
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    • 1995
  • This study was undertaken to obtain an improved understanding of the effects of alloying elements on the residual amounts of Mg in the melt and on the resultant microstructure of compacted vermicular graphite cast irons, and the influence of alloying elements and cooling rates during solidification on the formation of phosphide eutectics, and on the mechanical properties of compacted vermicular graphite cast irons containing copper, tin, molybdenum for producing pearlitic matrix, and also containing phosphorus and boron for increasing wear resistance were evaluated.

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