Pub Date : 2014-10-31DOI: 10.7777/JKFS.2014.34.5.170
Sung-Gyoo Kim, Ji-tae Kim, B. Park, Heung-Il Park
Using the Gleeble test, the effects of [Mn/S] ratios and the presence of sulfides on the high-temperature fracture morphology of heavy-section steel castings were analysed via the observations of the microstructures. The specimens for which the [Mn/S] ratio was in the range of 60~80 showed a ductile fracture morphology with an area reduction of more than 60%, while some specimens with similar [Mn/S] ratios showed a brittle fracture morphology with an area reduction of 0.0% due to the liquidation of sulfides at the grain boundary. The fracture morphology was classified into three types in the Gleeble high-temperature tensile test specimens. The first type showed dimple formation at the grain boundary, the formation of globular MnS sulfides, and plastic deformation of sulfides at an elevated temperature, indicating a needle-point type of ductile fracture with area reductions of 96.0~97.8%. The sec-ond type was a knife-edge type brittle fracture with an area reduction of 0.0% due to the film-type liquidation of sulfides at the grain boundary, band-type liquidation, and the liquidation of a terraced nipple pattern. The third type was the typical ductile fracture with an area reduction of 31.3~81.0%, in accordance with the mixture of dimples with in the grains and terraced nipple pattern at the grain boundary.
{"title":"The Influence of [Mn/S] Ratios on the Fracture Morphology of a Heavy-section Steel Castings at Elevated Temperature","authors":"Sung-Gyoo Kim, Ji-tae Kim, B. Park, Heung-Il Park","doi":"10.7777/JKFS.2014.34.5.170","DOIUrl":"https://doi.org/10.7777/JKFS.2014.34.5.170","url":null,"abstract":"Using the Gleeble test, the effects of [Mn/S] ratios and the presence of sulfides on the high-temperature fracture morphology of heavy-section steel castings were analysed via the observations of the microstructures. The specimens for which the [Mn/S] ratio was in the range of 60~80 showed a ductile fracture morphology with an area reduction of more than 60%, while some specimens with similar [Mn/S] ratios showed a brittle fracture morphology with an area reduction of 0.0% due to the liquidation of sulfides at the grain boundary. The fracture morphology was classified into three types in the Gleeble high-temperature tensile test specimens. The first type showed dimple formation at the grain boundary, the formation of globular MnS sulfides, and plastic deformation of sulfides at an elevated temperature, indicating a needle-point type of ductile fracture with area reductions of 96.0~97.8%. The sec-ond type was a knife-edge type brittle fracture with an area reduction of 0.0% due to the film-type liquidation of sulfides at the grain boundary, band-type liquidation, and the liquidation of a terraced nipple pattern. The third type was the typical ductile fracture with an area reduction of 31.3~81.0%, in accordance with the mixture of dimples with in the grains and terraced nipple pattern at the grain boundary.","PeriodicalId":16318,"journal":{"name":"Journal of Korea Foundry Society","volume":"95 1","pages":"170-178"},"PeriodicalIF":0.0,"publicationDate":"2014-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83404966","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-10-31DOI: 10.7777/JKFS.2014.34.5.156
김세준, 현승균, 김세광, 윤영옥
【This study is focused on the effect of $Al_2Ca$ as a modifier on eutectic Si modification of A356 alloy. Microstructural observation was carried out for as-cast, as-solution treated and as-aged samples. Solution treatment and aging were performed for 2, 4, 6 and 10 hrs at $540^{circ}C$ and $170^{circ}C$ , respectively. Although A356 alloy, which $Al_2Ca$ was added, has no significant difference in as-cast phases with normal A356 alloys, it shows much more modified eutectic Si, grain refinement and improved tensile property both in as-cast and as-heat treated conditions. TGA result shows that $Al_2Ca$ added A356 alloy has a certain improvement in oxidation resistance.】
{"title":"Al2Ca를 함유한 A356 합금에서의 다양한 열처리 조건에 따른공정 Si 개량화 거동","authors":"김세준, 현승균, 김세광, 윤영옥","doi":"10.7777/JKFS.2014.34.5.156","DOIUrl":"https://doi.org/10.7777/JKFS.2014.34.5.156","url":null,"abstract":"【This study is focused on the effect of $Al_2Ca$ as a modifier on eutectic Si modification of A356 alloy. Microstructural observation was carried out for as-cast, as-solution treated and as-aged samples. Solution treatment and aging were performed for 2, 4, 6 and 10 hrs at $540^{circ}C$ and $170^{circ}C$ , respectively. Although A356 alloy, which $Al_2Ca$ was added, has no significant difference in as-cast phases with normal A356 alloys, it shows much more modified eutectic Si, grain refinement and improved tensile property both in as-cast and as-heat treated conditions. TGA result shows that $Al_2Ca$ added A356 alloy has a certain improvement in oxidation resistance.】","PeriodicalId":16318,"journal":{"name":"Journal of Korea Foundry Society","volume":"37 1","pages":"156-161"},"PeriodicalIF":0.0,"publicationDate":"2014-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81635721","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-10-31DOI: 10.7777/JKFS.2014.34.5.162
Heon-Joo Kim
The effect of the mold preheat temperature on the solidification crack strength was investigated in AC2B aluminum alloy. A tension type apparatus as part of a solidification crack test which could measure the stress-strain relationship quantitatively was utilized. The evaluation of the solidification crack strength with varying mold preheat temperatures was performed by the test procedure established in this research. When the mold preheat temperatures were 250C, 150C and 50C, the solidification crack strengths were found to be 7.8 Kgf/cm, 12.9 Kgf/cm and 28.6 Kgf/cm, respectively. In the same way, when the mold preheat temperatures were 250C, 150C and 50C, the corresponding temperatures of the failure sites were 610C, 600C and 571C, and the calculated solid fractions were 14.0%, 29.3% and 50.8% when the specimens failed, respectively. The solidification crack strength increased in proportion to the solid fraction of the failure site. The solidification crack strength obtained in this test is assumed to reflect the effects of metallurgical factors on the thermo-plastic characteristics of a solidifying alloy such as the grain size of the solid, the grain morphology, and the distribution of solid grain.
{"title":"Effect of Mold Preheat Temperature on Solidification Crack Strength of AC2B Aluminum Alloy","authors":"Heon-Joo Kim","doi":"10.7777/JKFS.2014.34.5.162","DOIUrl":"https://doi.org/10.7777/JKFS.2014.34.5.162","url":null,"abstract":"The effect of the mold preheat temperature on the solidification crack strength was investigated in AC2B aluminum alloy. A tension type apparatus as part of a solidification crack test which could measure the stress-strain relationship quantitatively was utilized. The evaluation of the solidification crack strength with varying mold preheat temperatures was performed by the test procedure established in this research. When the mold preheat temperatures were 250C, 150C and 50C, the solidification crack strengths were found to be 7.8 Kgf/cm, 12.9 Kgf/cm and 28.6 Kgf/cm, respectively. In the same way, when the mold preheat temperatures were 250C, 150C and 50C, the corresponding temperatures of the failure sites were 610C, 600C and 571C, and the calculated solid fractions were 14.0%, 29.3% and 50.8% when the specimens failed, respectively. The solidification crack strength increased in proportion to the solid fraction of the failure site. The solidification crack strength obtained in this test is assumed to reflect the effects of metallurgical factors on the thermo-plastic characteristics of a solidifying alloy such as the grain size of the solid, the grain morphology, and the distribution of solid grain.","PeriodicalId":16318,"journal":{"name":"Journal of Korea Foundry Society","volume":"284 1","pages":"162-169"},"PeriodicalIF":0.0,"publicationDate":"2014-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73399123","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-10-31DOI: 10.7777/JKFS.2014.34.5.151
Jeong-Min Kim, N. Kim
The relatively low conductivity of conventional Mg-Al alloys often limits their areas of application. Therefore, several attempts to develop new high-conductivity magnesium alloys have been made recently. In this research, A Ce-rich rare-earth (RE)material and zinc were added to magnesium which contained no aluminum. As the RE and Zn content were increased, both the hardness and tensile strength were gradually increased, despite the fact that the electrical conductivity decreased slightly. The effects of an aging treatment on the conductivity and mechanical properties of Mg-RE-Zn alloys were also investigated. The electrical conductivity did not change according to the heat treatment conditions; however, the mechanical properties could be enhanced by proper aging heat treatments.
{"title":"Microstructure and Properties of Mg-RE-Zn Alloys for High Conductivity Parts","authors":"Jeong-Min Kim, N. Kim","doi":"10.7777/JKFS.2014.34.5.151","DOIUrl":"https://doi.org/10.7777/JKFS.2014.34.5.151","url":null,"abstract":"The relatively low conductivity of conventional Mg-Al alloys often limits their areas of application. Therefore, several attempts to develop new high-conductivity magnesium alloys have been made recently. In this research, A Ce-rich rare-earth (RE)material and zinc were added to magnesium which contained no aluminum. As the RE and Zn content were increased, both the hardness and tensile strength were gradually increased, despite the fact that the electrical conductivity decreased slightly. The effects of an aging treatment on the conductivity and mechanical properties of Mg-RE-Zn alloys were also investigated. The electrical conductivity did not change according to the heat treatment conditions; however, the mechanical properties could be enhanced by proper aging heat treatments.","PeriodicalId":16318,"journal":{"name":"Journal of Korea Foundry Society","volume":"70 1","pages":"151-155"},"PeriodicalIF":0.0,"publicationDate":"2014-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78684430","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-08-31DOI: 10.7777/JKFS.2014.34.4.123
Dae-hwan Kim, Hyun-Ju Jung, Sung-Yong Shim, Su-gun Lim, Sang-yong Lee
This work presents the results of a thixo-extrusion process applied to aluminum alloy and and reheating characteristics of semisolid A356 Alloy using have been discussed. The reheating experiment was performed using an electric resistance furnace and mul-tistage heating for uniform reheating. The thixo-extrusion was performed at the optimal reheating conditions of the semi-solid A356 alloy, the the extrusion conditions were an extrusion ratio of 33 and ram speed of 6 mm/sec. The results showed that the thixoextrusion of semi-solid A356 alloy fabricated by the cooling slope reduced the extrusion pressure by 180% in comparison with hot extrusion, and that a sound extrusion could be obtained in spite of the same extrusion ratio and strain rate.
{"title":"Thixo Extrusion and Reheating Characteristics of Semi Solid A356 Alloy","authors":"Dae-hwan Kim, Hyun-Ju Jung, Sung-Yong Shim, Su-gun Lim, Sang-yong Lee","doi":"10.7777/JKFS.2014.34.4.123","DOIUrl":"https://doi.org/10.7777/JKFS.2014.34.4.123","url":null,"abstract":"This work presents the results of a thixo-extrusion process applied to aluminum alloy and and reheating characteristics of semisolid A356 Alloy using have been discussed. The reheating experiment was performed using an electric resistance furnace and mul-tistage heating for uniform reheating. The thixo-extrusion was performed at the optimal reheating conditions of the semi-solid A356 alloy, the the extrusion conditions were an extrusion ratio of 33 and ram speed of 6 mm/sec. The results showed that the thixoextrusion of semi-solid A356 alloy fabricated by the cooling slope reduced the extrusion pressure by 180% in comparison with hot extrusion, and that a sound extrusion could be obtained in spite of the same extrusion ratio and strain rate.","PeriodicalId":16318,"journal":{"name":"Journal of Korea Foundry Society","volume":"20 1","pages":"123-129"},"PeriodicalIF":0.0,"publicationDate":"2014-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76886064","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-08-31DOI: 10.7777/JKFS.2014.34.4.130
Jeong-Min Kim, N. Kim, Jesik Shin, K. Kim, Se-Hyun Ko
Abstract Efforts have been made to develop new silicon-free aluminum casting alloys that possess high electrical and thermal con-ductivity. In this research Al-Fe-Cu-Mg alloys with various Cu and Mg contents were investigated for their various properties. Asthe Cu or Mg content was increased, the electrical conductivity gradually decreased, while the tensile strength of the Al-Fe-Cu-Mgalloy tended to be improved. It was found that fluidity was generally inversely proportional to the Cu content, but the alloys con-taining 1%Mg showed considerably low fluidity, regardless of the Cu content. Key words : Aluminum, Casting, Conductivity, Tensile strength, Fluidity 1. 서 론 알루미늄 및 알루미늄합금은 대표적인 경량소재로서 비강도가 높고 전기 및 열 전도도가 우수하므로 자동차, 항공, 전기/전자 산업 등에서 널리 사용되고 있다. 예를 들어, 고출력LED 방열부품소재로서 중요하게 활용되고 있는데, 최근 전기/전자제품의 소형화 및 고집적화가 진행됨에 따라 보다 전도성이 우수한 새로운 알루미늄합금의 출현이 필요한 시점이기도하다. 기존에 주로 사용되는 알루미늄 주조합금은 주조성과 강도가 우수하지만 통상적으로 다량의 Si을 포함하고 있어 전도성이 상대적으로 낮고 주조공정 후 표면처리에 어려움이 있다.상용합금계인 Al-Si계 주조합금은 순수한 알루미늄에 비해 열전도도가 절반 수준까지 낮은 경우가 대부분인 것으로 알려져있으며[1], 따라서 최근 들어 전도성을 현저히 저하시키는 Si을 완전히 배제한 상태에서 양호한 강도와 주조성을 보유한새로운 고전도성 알루미늄합금의 개발연구가 활발하게 진행되고 있다[2,3].방열부품용 알루미늄합금은 보통 높은 강도가 요구되지는 않으나 활용분야에 따라 일정 수준이상의 강도가 필요하므로 새로운 고전도성 합금의 조성에 따른 기계적 성질을 조사할 가치가 있다. 또한 방열부품용 알루미늄합금은 생산성과 경제성이우수한 주조공정으로 대부분 제조되므로 주조특성이 중요하며,특히 주형 충전성을 의미하는 유동도가 낮으면 불량률의 증가와 생산성의 저하가 예상된다. 알루미늄합금에서 Si은 응고 중응고잠열을 다량 방출함으로써 유동도의 증가에 매우 효과적인합금원소이므로 제거할 경우 유동도의 저하가 심각할 수 있어확인이 필요하다. 합금의 유동도는 여러 가지 재료 및 공정변수의 영향을 받는 복잡한 현상으로서 많은 연구에도 불구하고아직도 완전하게 규명되어 있지 못 하다[4-6]. 그럼에도 불구하고 일반적으로 합금의 유동도는 응고구간과 매우 밀접한 관련이 있는 것으로 알려져 있는데, 즉 응고구간이 확대될수록 유동도는 감소하는 일반적인 경향을 보인다[4,7].Received:May. 25, 2014;Revised:Aug. 5, 2014;Accepted:Aug. 18, 2014
Abstract Efforts have been made to develop new silicon-free aluminum casting alloys that possess high electrical and thermal con-ductivityIn this research Al-Fe-Cu-Mg alloys with various Cu and Mg contents were investigated for their various properties。Asthe Cu or Mg content was increased, the electrical conductivity gradually decreased, while the tensile strength of the Al-Fe-Cu-Mgalloy tended to be improved。It was found that fluidity was generally inversely proportional to the Cu content, but the alloys con-taining 1%Mg showed considerably low fluidity, regardless of the Cu content。Key words: Aluminum, Casting, Conductivity, Tensile strength, Fluidity 1。西龙铝合金是典型的轻量材料，鼻腔高，电和热传导优秀，广泛应用于汽车，航空，电气/电子产业等。例如，作为高输出LED防热部件材料被很重要地使用，随着最近电气/电子产品的小型化和高集成化的进行，需要出现导电性更好的新铝合金。现有的主要使用的铝制铸造合金铸造性和强度优秀，但通常含有大量Si，导电性相对较低，铸造工程后表面处理有困难。合金铸造合金关系人al - si界常用的是纯粹的铝相比,低热传导度到一半的情况而大部分为已知,[1],因此,近年来,能大大降低导电的si完全排除的情况下具有良好的强度和铸造省拥有的新古典都城,铝合金的研究非常活跃地进行着开发[2,3]。防热元件用铝合金通常不需要高强度，但根据应用领域的不同，需要一定水平以上的强度，因此值得调查新古典导电合金的组成所带来的机械性质。另外，防热零件用铝合金大部分是生产效率和经济性优秀的铸造工程，因此铸造特性非常重要，特别是意味着模具填充性的流动性低的话，不良率的增加和生产效率的低下是可以预测的。在铝合金中，Si在凝固过程中会释放大量的凝固潜热，是一种对增加流速非常有效的合金元素，如果去除，会严重降低流速，需要进行确认。合金的流动度是一种受多种材料和工艺变数影响的复杂现象，尽管研究了很多，但仍未完全查明[4-6]。尽管如此，人们普遍认为合金的流动度与凝固区间有非常密切的关系，即随着凝固区间的扩大，流动度呈现减少的一般趋势[4,7].Received:May。25、2014;revised: aug。5、2014;accepted: aug。18、2014
{"title":"Influence of Cu and Zn Contents on the Properties of Al-Fe-Cu-Mg Based Casting Alloys","authors":"Jeong-Min Kim, N. Kim, Jesik Shin, K. Kim, Se-Hyun Ko","doi":"10.7777/JKFS.2014.34.4.130","DOIUrl":"https://doi.org/10.7777/JKFS.2014.34.4.130","url":null,"abstract":"Abstract Efforts have been made to develop new silicon-free aluminum casting alloys that possess high electrical and thermal con-ductivity. In this research Al-Fe-Cu-Mg alloys with various Cu and Mg contents were investigated for their various properties. Asthe Cu or Mg content was increased, the electrical conductivity gradually decreased, while the tensile strength of the Al-Fe-Cu-Mgalloy tended to be improved. It was found that fluidity was generally inversely proportional to the Cu content, but the alloys con-taining 1%Mg showed considerably low fluidity, regardless of the Cu content. Key words : Aluminum, Casting, Conductivity, Tensile strength, Fluidity 1. 서 론 알루미늄 및 알루미늄합금은 대표적인 경량소재로서 비강도가 높고 전기 및 열 전도도가 우수하므로 자동차, 항공, 전기/전자 산업 등에서 널리 사용되고 있다. 예를 들어, 고출력LED 방열부품소재로서 중요하게 활용되고 있는데, 최근 전기/전자제품의 소형화 및 고집적화가 진행됨에 따라 보다 전도성이 우수한 새로운 알루미늄합금의 출현이 필요한 시점이기도하다. 기존에 주로 사용되는 알루미늄 주조합금은 주조성과 강도가 우수하지만 통상적으로 다량의 Si을 포함하고 있어 전도성이 상대적으로 낮고 주조공정 후 표면처리에 어려움이 있다.상용합금계인 Al-Si계 주조합금은 순수한 알루미늄에 비해 열전도도가 절반 수준까지 낮은 경우가 대부분인 것으로 알려져있으며[1], 따라서 최근 들어 전도성을 현저히 저하시키는 Si을 완전히 배제한 상태에서 양호한 강도와 주조성을 보유한새로운 고전도성 알루미늄합금의 개발연구가 활발하게 진행되고 있다[2,3].방열부품용 알루미늄합금은 보통 높은 강도가 요구되지는 않으나 활용분야에 따라 일정 수준이상의 강도가 필요하므로 새로운 고전도성 합금의 조성에 따른 기계적 성질을 조사할 가치가 있다. 또한 방열부품용 알루미늄합금은 생산성과 경제성이우수한 주조공정으로 대부분 제조되므로 주조특성이 중요하며,특히 주형 충전성을 의미하는 유동도가 낮으면 불량률의 증가와 생산성의 저하가 예상된다. 알루미늄합금에서 Si은 응고 중응고잠열을 다량 방출함으로써 유동도의 증가에 매우 효과적인합금원소이므로 제거할 경우 유동도의 저하가 심각할 수 있어확인이 필요하다. 합금의 유동도는 여러 가지 재료 및 공정변수의 영향을 받는 복잡한 현상으로서 많은 연구에도 불구하고아직도 완전하게 규명되어 있지 못 하다[4-6]. 그럼에도 불구하고 일반적으로 합금의 유동도는 응고구간과 매우 밀접한 관련이 있는 것으로 알려져 있는데, 즉 응고구간이 확대될수록 유동도는 감소하는 일반적인 경향을 보인다[4,7].Received:May. 25, 2014;Revised:Aug. 5, 2014;Accepted:Aug. 18, 2014","PeriodicalId":16318,"journal":{"name":"Journal of Korea Foundry Society","volume":"104 1","pages":"130-135"},"PeriodicalIF":0.0,"publicationDate":"2014-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80640169","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-08-31DOI: 10.7777/JKFS.2014.34.4.136
Heon-Joo Kim
Numerical solution of thermal stress by CAE analysis could be an effective method in product development stage of castings to predict and treat the problem of solidification cracking of castings. Quantitative stress-strain data are necessary, in this case. Tension type apparatus of a solidification crack test which can measure stress-strain relationship quantitatively was developed and the test procedure was established by this research. Solidification crack strength obtained from the following test procedure could be utilized to evaluate it in terms of effect factors on thermo-plastic characteristic of solidifying alloy such as grain size of solid, grain morphology, distribution of solid grain, etc. Proposed test procedure is as follow: Prediction of temperature at the failure site of solidification cracked specimen by computer simulation of solidification, Calculation of solid fraction of the failure site from thermodynamic solution of solidification under Scheil condition.
{"title":"Quantitative Evaluation of Solidification Crack Strength of AC2B Aluminum Casting Alloy","authors":"Heon-Joo Kim","doi":"10.7777/JKFS.2014.34.4.136","DOIUrl":"https://doi.org/10.7777/JKFS.2014.34.4.136","url":null,"abstract":"Numerical solution of thermal stress by CAE analysis could be an effective method in product development stage of castings to predict and treat the problem of solidification cracking of castings. Quantitative stress-strain data are necessary, in this case. Tension type apparatus of a solidification crack test which can measure stress-strain relationship quantitatively was developed and the test procedure was established by this research. Solidification crack strength obtained from the following test procedure could be utilized to evaluate it in terms of effect factors on thermo-plastic characteristic of solidifying alloy such as grain size of solid, grain morphology, distribution of solid grain, etc. Proposed test procedure is as follow: Prediction of temperature at the failure site of solidification cracked specimen by computer simulation of solidification, Calculation of solid fraction of the failure site from thermodynamic solution of solidification under Scheil condition.","PeriodicalId":16318,"journal":{"name":"Journal of Korea Foundry Society","volume":"1 1","pages":"136-142"},"PeriodicalIF":0.0,"publicationDate":"2014-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88809772","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-06-30DOI: 10.7777/JKFS.2014.34.3.100
D. Ye, Hyun Sik Kim, M. Kang, Jung Dae Kim, Haeyoung Jeoung
In recent years, Mg and its alloys have attracted a great deal of attention due to their low density, relatively excellent castability, and straightforward recyclability. Mg alloys have been widely applied to various industrial fields, and are representatively used in automotive and electronic parts. According to previous researches, the electrical conductivity of Mg alloys greatly decreases with increasing Al content. However, with the addition of Zn and/or Cu, the electrical conductivity of Mg alloys is maintained or slightly increased, and improved mechanical properties are obtained as well. On this basis, Mg-Zn-Cu alloys have been investigated in the present study with a focus on the effect of adding Zn and Cu on the electrical conductivity. The Zn and Cu contents ranged from 4 to 6wt.% and 0 to 1.5wt.%, respectively. Ternary Mg-Zn-Cu alloys have been prepared by gravity casting in a steel mold. In the as-casting condition, the electrical conductivity of Mg-Zn-Cu alloys showed a linear increasing trend with decreasing Zn and increasing Cu contents. Furthermore, impact values of Zn = − 1.5 and Cu = 2.5 were determined for these alloys by electrical conductivity tests.
{"title":"Electrical Conductivity by Addition of Zn and Cu on Mg-Zn-Cu Alloys","authors":"D. Ye, Hyun Sik Kim, M. Kang, Jung Dae Kim, Haeyoung Jeoung","doi":"10.7777/JKFS.2014.34.3.100","DOIUrl":"https://doi.org/10.7777/JKFS.2014.34.3.100","url":null,"abstract":"In recent years, Mg and its alloys have attracted a great deal of attention due to their low density, relatively excellent castability, and straightforward recyclability. Mg alloys have been widely applied to various industrial fields, and are representatively used in automotive and electronic parts. According to previous researches, the electrical conductivity of Mg alloys greatly decreases with increasing Al content. However, with the addition of Zn and/or Cu, the electrical conductivity of Mg alloys is maintained or slightly increased, and improved mechanical properties are obtained as well. On this basis, Mg-Zn-Cu alloys have been investigated in the present study with a focus on the effect of adding Zn and Cu on the electrical conductivity. The Zn and Cu contents ranged from 4 to 6wt.% and 0 to 1.5wt.%, respectively. Ternary Mg-Zn-Cu alloys have been prepared by gravity casting in a steel mold. In the as-casting condition, the electrical conductivity of Mg-Zn-Cu alloys showed a linear increasing trend with decreasing Zn and increasing Cu contents. Furthermore, impact values of Zn = − 1.5 and Cu = 2.5 were determined for these alloys by electrical conductivity tests.","PeriodicalId":16318,"journal":{"name":"Journal of Korea Foundry Society","volume":"35 1","pages":"100-106"},"PeriodicalIF":0.0,"publicationDate":"2014-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75083841","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-06-30DOI: 10.7777/JKFS.2014.34.3.087
Tae-young Choi, Dae-hwan Kim, Soo-Bae Kim, Sung-Young Shim, Su-gun Lim
Thixo-extrusion of semi-solid 7075 aluminum alloy and the mechanical properties of its extrudates were investigated. The semisolid alloy was prepared by a cooling slope cast. In other to perform thixo-extrusion, semi-solid 7075 aluminum alloy billets were reheated at the reheating conditions reported in a previous study. The maximum extrusion pressure in thixo-extrusion was 615MPa. This was lower than that of conventional hot extrusion (P max = 940MPa) at the same extrusion conditions due to the increased fluidity of the alloy billet in the semi-solid state. The values of Rockwell hardness (scale B) at the extrusion direction of the as thixoextruded bar were 48~53HRB and the difference in Rockwell hardness between the transverse direction and the extrusion direction was 5HRB or less. The results show that thxio-extrusion of semi-solid 7075 Al alloy improves the workability and anisotropic with the extrusion direction compared with hot extrusion of the conventional alloy.
研究了7075半固态铝合金的触点挤压及其挤压物的力学性能。采用冷却斜铸法制备了半固态合金。在另一种进行触点挤压的方法中，在先前研究中报道的再加热条件下对半固态7075铝合金坯料进行再加热。触相挤压的最大挤压压力为615MPa。在相同挤压条件下，由于合金坯料在半固态状态下的流动性增加，这一数值低于常规热挤压(P max = 940MPa)。触变挤压棒材在挤压方向的洛氏硬度(标尺B)值为48~53HRB，横向与挤压方向的洛氏硬度差不超过5HRB。结果表明:与常规合金热挤压相比，半固态7075铝合金热挤压在挤压方向上改善了加工性能和各向异性;
{"title":"Thixo-extrusion of Semi Solid 7075 Aluminum Alloys and Mechanical Properties of The Extrudates","authors":"Tae-young Choi, Dae-hwan Kim, Soo-Bae Kim, Sung-Young Shim, Su-gun Lim","doi":"10.7777/JKFS.2014.34.3.087","DOIUrl":"https://doi.org/10.7777/JKFS.2014.34.3.087","url":null,"abstract":"Thixo-extrusion of semi-solid 7075 aluminum alloy and the mechanical properties of its extrudates were investigated. The semisolid alloy was prepared by a cooling slope cast. In other to perform thixo-extrusion, semi-solid 7075 aluminum alloy billets were reheated at the reheating conditions reported in a previous study. The maximum extrusion pressure in thixo-extrusion was 615MPa. This was lower than that of conventional hot extrusion (P max = 940MPa) at the same extrusion conditions due to the increased fluidity of the alloy billet in the semi-solid state. The values of Rockwell hardness (scale B) at the extrusion direction of the as thixoextruded bar were 48~53HRB and the difference in Rockwell hardness between the transverse direction and the extrusion direction was 5HRB or less. The results show that thxio-extrusion of semi-solid 7075 Al alloy improves the workability and anisotropic with the extrusion direction compared with hot extrusion of the conventional alloy.","PeriodicalId":16318,"journal":{"name":"Journal of Korea Foundry Society","volume":"44 1","pages":"87-93"},"PeriodicalIF":0.0,"publicationDate":"2014-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76430504","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-06-30DOI: 10.7777/JKFS.2014.34.3.107
N. Reddy, Yong-Hyun Baek, Seong-Gyeong Kim, B. Hur
Abstract Permeability is the ability of a material to transmit fluid/gases. It is an important material property and it depends on mouldparameters such as grain fineness number, clay, moisture, mulling time, and hardness. Modeling the relationships among thesevariable and interactions by mathematical models is complex. Hence a biologically inspired artificial neural-network technique witha back-propagation-learning algorithm was developed to estimate the permeability of green sand. The developed model was used toperform a sensitivity analysis to estimate permeability. The individual as well as the combined influence of mould parameters onpermeability were simulated. The model was able to describe the complex relationships in the system. The optimum processwindow for maximum permeability was obtained as 8.75-10.5% clay and 3.9-9.5% moisture. The developed model is very useful inunderstanding various interactions between inputs and their effects on permeability.Key words: Green sand mould, Permeability, Neural networks, Sensitivity analysis
{"title":"Estimation of Permeability of Green Sand Mould by Performing Sensitivity Analysis on Neural Networks Model","authors":"N. Reddy, Yong-Hyun Baek, Seong-Gyeong Kim, B. Hur","doi":"10.7777/JKFS.2014.34.3.107","DOIUrl":"https://doi.org/10.7777/JKFS.2014.34.3.107","url":null,"abstract":"Abstract Permeability is the ability of a material to transmit fluid/gases. It is an important material property and it depends on mouldparameters such as grain fineness number, clay, moisture, mulling time, and hardness. Modeling the relationships among thesevariable and interactions by mathematical models is complex. Hence a biologically inspired artificial neural-network technique witha back-propagation-learning algorithm was developed to estimate the permeability of green sand. The developed model was used toperform a sensitivity analysis to estimate permeability. The individual as well as the combined influence of mould parameters onpermeability were simulated. The model was able to describe the complex relationships in the system. The optimum processwindow for maximum permeability was obtained as 8.75-10.5% clay and 3.9-9.5% moisture. The developed model is very useful inunderstanding various interactions between inputs and their effects on permeability.Key words: Green sand mould, Permeability, Neural networks, Sensitivity analysis","PeriodicalId":16318,"journal":{"name":"Journal of Korea Foundry Society","volume":"23 1","pages":"107-111"},"PeriodicalIF":0.0,"publicationDate":"2014-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79453045","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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