Pub Date : 2015-12-31DOI: 10.7777/JKFS.2015.35.6.178
Hyun-Wook Jo, J. Do, W. Jo, H. Chung, Je-hyun Lee, C. Jo
Due to excellent abrasion resistance the high-chrome white irons are widely used in mining and mineral industries. Minor variation of carbon content in 28% chrome white iron resulted in difference in primarily solidified microstructure. Sub-eutectic (hypoeutectic) composition led to formation of primarily solidified dendrites. Formation of primarily solidified dendrites which were supersaturated with carbon and chrome also caused precipitation of fine secondary carbides that are different from relatively large plate type carbides in the eutectic structure. Small portion of primarily solidified dendrite expected to contribute significantly to the improvement of abrasion resistance of the white iron because the dendrites provided mechanical support to carbides. The relative fraction of primary dendrite increased with reduction of carbon content from the eutectic composition. The increased fraction of primary dendrite increased hardness value of the white irons.
{"title":"Effect of Primarily Solidified Structure on the Microstructure and the Mechanical Properties of High Cr White Iron","authors":"Hyun-Wook Jo, J. Do, W. Jo, H. Chung, Je-hyun Lee, C. Jo","doi":"10.7777/JKFS.2015.35.6.178","DOIUrl":"https://doi.org/10.7777/JKFS.2015.35.6.178","url":null,"abstract":"Due to excellent abrasion resistance the high-chrome white irons are widely used in mining and mineral industries. Minor variation of carbon content in 28% chrome white iron resulted in difference in primarily solidified microstructure. Sub-eutectic (hypoeutectic) composition led to formation of primarily solidified dendrites. Formation of primarily solidified dendrites which were supersaturated with carbon and chrome also caused precipitation of fine secondary carbides that are different from relatively large plate type carbides in the eutectic structure. Small portion of primarily solidified dendrite expected to contribute significantly to the improvement of abrasion resistance of the white iron because the dendrites provided mechanical support to carbides. The relative fraction of primary dendrite increased with reduction of carbon content from the eutectic composition. The increased fraction of primary dendrite increased hardness value of the white irons.","PeriodicalId":16318,"journal":{"name":"Journal of Korea Foundry Society","volume":"125 1","pages":"178-184"},"PeriodicalIF":0.0,"publicationDate":"2015-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86043763","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 : 2015-12-31DOI: 10.7777/JKFS.2015.35.6.147
Heon-Joo Kim
The effects of Sc and Sr elements on the modification of the eutectic phase and the castability were investigated in the Al-4wt%Mg-0.9wt%Si-0.3wt%Mn-0.15wt%Fe alloy. Measurements of the cooling curve and microstructure observations were performed to analyze the additional effects of Sc and Sr minor elements during the solidification process. A prominent effect found on the modification of the eutectic phase with additions of the Sr and Sc elements. Here, a fine eutectic phase and a decrease in the growth temperature of the eutectic phase were evident with an addition of Sc element up to 0.2 wt%. The growth temperature of the eutectic phase decreased and the effect on the modification of the eutectic phase increased with the addition of Sr element up to 0.02 wt%. The addition of 0.02wt%Sr had the strongest effect on the modification of the eutectic phase, and the resulting microstructure of the eutectic phase was found to have a fibrous morphology with a decreased aspect ratio and an increased modification ratio. Fluidity and shrinkage tests were conducted to evaluate the castability of the alloy. The addition of 0.02wt%Sr effectively increased the fluidity of the alloy, while an addition of Sc did not show any effect compared to when nothing was added. The maximum filling length was recorded for 0.01wt%TiB-0.02wt%Sr owing to the effect of the fine -Al grains. The macro-shrinkage ratio decreased, while the micro-shrinkage ratio increased with the addition of various eutectic modifiers. The highest ratio of micro-shrinkage was recorded for the 0.02wt%Sr condition. However, the total shrinkage ratio was nearly identical regardless of the amounts added in this study.
{"title":"Effect of Sc, Sr Elements on Eutectic Mg 2 Si Modification and Castability of Al-4wt%Mg-0.9wt%Si-0.3wt%Mn-0.15wt%Fe Casting Alloy","authors":"Heon-Joo Kim","doi":"10.7777/JKFS.2015.35.6.147","DOIUrl":"https://doi.org/10.7777/JKFS.2015.35.6.147","url":null,"abstract":"The effects of Sc and Sr elements on the modification of the eutectic phase and the castability were investigated in the Al-4wt%Mg-0.9wt%Si-0.3wt%Mn-0.15wt%Fe alloy. Measurements of the cooling curve and microstructure observations were performed to analyze the additional effects of Sc and Sr minor elements during the solidification process. A prominent effect found on the modification of the eutectic phase with additions of the Sr and Sc elements. Here, a fine eutectic phase and a decrease in the growth temperature of the eutectic phase were evident with an addition of Sc element up to 0.2 wt%. The growth temperature of the eutectic phase decreased and the effect on the modification of the eutectic phase increased with the addition of Sr element up to 0.02 wt%. The addition of 0.02wt%Sr had the strongest effect on the modification of the eutectic phase, and the resulting microstructure of the eutectic phase was found to have a fibrous morphology with a decreased aspect ratio and an increased modification ratio. Fluidity and shrinkage tests were conducted to evaluate the castability of the alloy. The addition of 0.02wt%Sr effectively increased the fluidity of the alloy, while an addition of Sc did not show any effect compared to when nothing was added. The maximum filling length was recorded for 0.01wt%TiB-0.02wt%Sr owing to the effect of the fine -Al grains. The macro-shrinkage ratio decreased, while the micro-shrinkage ratio increased with the addition of various eutectic modifiers. The highest ratio of micro-shrinkage was recorded for the 0.02wt%Sr condition. However, the total shrinkage ratio was nearly identical regardless of the amounts added in this study.","PeriodicalId":16318,"journal":{"name":"Journal of Korea Foundry Society","volume":"10 1","pages":"147-154"},"PeriodicalIF":0.0,"publicationDate":"2015-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84098314","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 : 2015-10-31DOI: 10.7777/JKFS.2015.35.5.120
Heon-Joo Kim, Su-Min Park
The effects of Ti, B and Zr on grain refinement and castability were investigated in Al-4wt%Mg-0.9wt%Si-0.3wt%Mn-0.15wt%Fe alloy. Measurement of cooling curve and micro-structure observation were performed to analyze the effects of the addition of minor elements Ti, B and Zr during solidification. The prominence of effect on grain refinement was in increasing order for Ti, Zr and B element. Fine grain size and an increase of the crystallization temperature for -Al solution were evident as the amount of addition elements increased in this study. Addition of 0.15wt% Ti was most effective for grain refinement, and the resulting grain size of -Al solution for shell mold and steel mold were and , respectively. Fluidity and shrinkage tests were perform to evaluate the castability of the alloy. Maximum fluidity length and minimum ratio of micro shrinkage were recorded for 0.15wt% Ti addition due to the effect of the finest grain size.
{"title":"Effect of Ti, B, Zr Elements on Grain Refinement and Castability of Al-4wt%Mg-0.9wt%Si-0.3wt%Mn-0.15wt%Fe Casting Alloy","authors":"Heon-Joo Kim, Su-Min Park","doi":"10.7777/JKFS.2015.35.5.120","DOIUrl":"https://doi.org/10.7777/JKFS.2015.35.5.120","url":null,"abstract":"The effects of Ti, B and Zr on grain refinement and castability were investigated in Al-4wt%Mg-0.9wt%Si-0.3wt%Mn-0.15wt%Fe alloy. Measurement of cooling curve and micro-structure observation were performed to analyze the effects of the addition of minor elements Ti, B and Zr during solidification. The prominence of effect on grain refinement was in increasing order for Ti, Zr and B element. Fine grain size and an increase of the crystallization temperature for -Al solution were evident as the amount of addition elements increased in this study. Addition of 0.15wt% Ti was most effective for grain refinement, and the resulting grain size of -Al solution for shell mold and steel mold were and , respectively. Fluidity and shrinkage tests were perform to evaluate the castability of the alloy. Maximum fluidity length and minimum ratio of micro shrinkage were recorded for 0.15wt% Ti addition due to the effect of the finest grain size.","PeriodicalId":16318,"journal":{"name":"Journal of Korea Foundry Society","volume":"113 1","pages":"120-127"},"PeriodicalIF":0.0,"publicationDate":"2015-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75239005","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 : 2015-10-31DOI: 10.7777/JKFS.2015.35.5.114
Ji-Ho Ahn, Jae-Han Lim, B. Moon
This paper reports the effect of a refractory crucible type on the microstructure of duplex stainless steel (DSS) cast with the addition of gadolinium using air-induction melting. Grade 4A DSSs with 1 wt% of gadolinium (Gd) were fabricated in various crucibles including alumina (), magnesia (MgO), calcia (CaO) coated with yttria () and graphite. The standard free energies of the formation of calcium and yttrium oxide were lower than those of gadolinium oxide and other crucible elements based oxide. The yield of Gd in DSS using , MgO, CaO-coated and graphite was 5, 19, 83 and 96%, respectively. As Gd yield increased, the amount of Gd-based inclusions increased, the size of the inclusions were reduced, and the inclusions became evenly distributed.
{"title":"The Effect of Refractory Crucible on Microstructure of Duplex Stainless Steel Cast with Gadolinium during Air Induction Melting","authors":"Ji-Ho Ahn, Jae-Han Lim, B. Moon","doi":"10.7777/JKFS.2015.35.5.114","DOIUrl":"https://doi.org/10.7777/JKFS.2015.35.5.114","url":null,"abstract":"This paper reports the effect of a refractory crucible type on the microstructure of duplex stainless steel (DSS) cast with the addition of gadolinium using air-induction melting. Grade 4A DSSs with 1 wt% of gadolinium (Gd) were fabricated in various crucibles including alumina (), magnesia (MgO), calcia (CaO) coated with yttria () and graphite. The standard free energies of the formation of calcium and yttrium oxide were lower than those of gadolinium oxide and other crucible elements based oxide. The yield of Gd in DSS using , MgO, CaO-coated and graphite was 5, 19, 83 and 96%, respectively. As Gd yield increased, the amount of Gd-based inclusions increased, the size of the inclusions were reduced, and the inclusions became evenly distributed.","PeriodicalId":16318,"journal":{"name":"Journal of Korea Foundry Society","volume":"2015 1","pages":"114-119"},"PeriodicalIF":0.0,"publicationDate":"2015-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86872378","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 : 2015-10-31DOI: 10.7777/JKFS.2015.35.5.109
Kuk-Jin Kim, Su-gun Lim, H. Ju, S. Pak
In this study, the measurement of FN (ferrite volume fraction) and the solution annealing ratio at a temperature of were determined with 15A elbow fittings of shell cast SSC13, and the corrosion resistance with and without austenitizing solution annealing were investigated in comparison with AISI304. The delta ferrite phase was observed in the material due to the slow cooling effect of the shell mold casting. However, the delta ferrite phase decreased gradually with the solution annealing at a temperature of . The hardness generally decreased with a heat treatment; however, its corrosion resistance was improved with the heat treatment. In addition, when a passivation treatment was applied, its corrosion ratio showed the lowest value. The pattern of general corrosion decreased due to the decrease in the delta ferrite phase with the solution annealing treatment. Consequently, it is suggested that the corrosion resistance of SSC13 elbow fittings can be improved by increasing the ratio of any solution annealing treatment used and by decreasing the ferrite phase. The relationship between the ratio of solution annealing and delta ferrite is expressed as follows: SA (solution annealing ratio,%) = 98 - FN (ferrite volume fraction, %).
{"title":"Effect of Austenitizing Ratio on the Delta Ferrite Volume Fraction and Corrosion Resistance of Shell Mold Cast SSC13 Elbow Fitting","authors":"Kuk-Jin Kim, Su-gun Lim, H. Ju, S. Pak","doi":"10.7777/JKFS.2015.35.5.109","DOIUrl":"https://doi.org/10.7777/JKFS.2015.35.5.109","url":null,"abstract":"In this study, the measurement of FN (ferrite volume fraction) and the solution annealing ratio at a temperature of were determined with 15A elbow fittings of shell cast SSC13, and the corrosion resistance with and without austenitizing solution annealing were investigated in comparison with AISI304. The delta ferrite phase was observed in the material due to the slow cooling effect of the shell mold casting. However, the delta ferrite phase decreased gradually with the solution annealing at a temperature of . The hardness generally decreased with a heat treatment; however, its corrosion resistance was improved with the heat treatment. In addition, when a passivation treatment was applied, its corrosion ratio showed the lowest value. The pattern of general corrosion decreased due to the decrease in the delta ferrite phase with the solution annealing treatment. Consequently, it is suggested that the corrosion resistance of SSC13 elbow fittings can be improved by increasing the ratio of any solution annealing treatment used and by decreasing the ferrite phase. The relationship between the ratio of solution annealing and delta ferrite is expressed as follows: SA (solution annealing ratio,%) = 98 - FN (ferrite volume fraction, %).","PeriodicalId":16318,"journal":{"name":"Journal of Korea Foundry Society","volume":"33 1","pages":"109-113"},"PeriodicalIF":0.0,"publicationDate":"2015-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81277895","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 : 2015-08-31DOI: 10.7777/JKFS.2015.35.4.075
Sung-Gyoo Kim, Byung-chul Lee, Heung-Il Park
Commercial Zr-based amorphous alloy was recycled and oxygen was introduced during the recycling process. The oxygen content can have a great effect on the glass forming ability and the mechanical properties of the alloy. Therefore, it was closely examined. The initial oxygen content in the raw material was 1,244 ppm. It was increased to 3,789 ppm in the alloy after ten recycling processes. As the recycling processes were repeated, the oxygen content increased. Specifically, after four recycling processes, it increased sharply as compared to that after three recycling processes. After ten recycling processes, the glass transition temperature (Tg) increased from 613 K to 634 K and the crystallization temperature (Tx) increased from 696 K to 706 K. On the other hand, the super-cooled liquid region () decreased slightly from 83 K to 72 K while the reduced glass transition temperature (Trg = Tg/Tm) was 0.63, remaining constant even when the oxygen content was increased. These results indicated that the increased oxygen content deteriorated the glass forming ability. The bending strength as determined in a three-point bending test showed a sharp decrease from 3,055 to 2,062 MPa as the oxygen content was increased from 1,244 ppm to 3,789 ppm; the extension was also decreased from 3.02 to 1.74 mm. These findings meant that the alloy became brittle.
{"title":"The Effect of Oxygen Content on the Glass Forming Ability and Mechanical Properties of the Zr-based Amorphous Alloy Return Scrap","authors":"Sung-Gyoo Kim, Byung-chul Lee, Heung-Il Park","doi":"10.7777/JKFS.2015.35.4.075","DOIUrl":"https://doi.org/10.7777/JKFS.2015.35.4.075","url":null,"abstract":"Commercial Zr-based amorphous alloy was recycled and oxygen was introduced during the recycling process. The oxygen content can have a great effect on the glass forming ability and the mechanical properties of the alloy. Therefore, it was closely examined. The initial oxygen content in the raw material was 1,244 ppm. It was increased to 3,789 ppm in the alloy after ten recycling processes. As the recycling processes were repeated, the oxygen content increased. Specifically, after four recycling processes, it increased sharply as compared to that after three recycling processes. After ten recycling processes, the glass transition temperature (Tg) increased from 613 K to 634 K and the crystallization temperature (Tx) increased from 696 K to 706 K. On the other hand, the super-cooled liquid region () decreased slightly from 83 K to 72 K while the reduced glass transition temperature (Trg = Tg/Tm) was 0.63, remaining constant even when the oxygen content was increased. These results indicated that the increased oxygen content deteriorated the glass forming ability. The bending strength as determined in a three-point bending test showed a sharp decrease from 3,055 to 2,062 MPa as the oxygen content was increased from 1,244 ppm to 3,789 ppm; the extension was also decreased from 3.02 to 1.74 mm. These findings meant that the alloy became brittle.","PeriodicalId":16318,"journal":{"name":"Journal of Korea Foundry Society","volume":"21 1","pages":"75-79"},"PeriodicalIF":0.0,"publicationDate":"2015-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75517434","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 : 2015-08-31DOI: 10.7777/JKFS.2015.35.4.088
W. Jung, Daeho Jeong, Youngchai Lee, Jae‐Hyun Lee, Sangshik Kim
The effects of quenching and tempering temperatures on the tensile, impact and corrosion properties of A487 alloy cast with different C contents of 0.16, 0.19 to 0.23 wt.% were examined. The impact tests were conducted at and and the immersion test was performed using 3.5% NaCl solution for 14 days. The quenching temperature affected the mechanical properties of A487 alloy cast, while the magnitude of change varied depending on the C content. The increase in tempering temperature showed the typical trend of decreasing tensile strength and increasing impact properties. The change in quenching and tempering temperature in this study did not affect the corrosion properties of A487 alloy significantly. The change in mechanical and corrosion properties of A487 with different C contents was discussed based on the microstructural and fractographic observation.
{"title":"Effect of Quenching and Tempering Temperatures on Mechanical Properties of A487 Cast with Different C Contents","authors":"W. Jung, Daeho Jeong, Youngchai Lee, Jae‐Hyun Lee, Sangshik Kim","doi":"10.7777/JKFS.2015.35.4.088","DOIUrl":"https://doi.org/10.7777/JKFS.2015.35.4.088","url":null,"abstract":"The effects of quenching and tempering temperatures on the tensile, impact and corrosion properties of A487 alloy cast with different C contents of 0.16, 0.19 to 0.23 wt.% were examined. The impact tests were conducted at and and the immersion test was performed using 3.5% NaCl solution for 14 days. The quenching temperature affected the mechanical properties of A487 alloy cast, while the magnitude of change varied depending on the C content. The increase in tempering temperature showed the typical trend of decreasing tensile strength and increasing impact properties. The change in quenching and tempering temperature in this study did not affect the corrosion properties of A487 alloy significantly. The change in mechanical and corrosion properties of A487 with different C contents was discussed based on the microstructural and fractographic observation.","PeriodicalId":16318,"journal":{"name":"Journal of Korea Foundry Society","volume":"70 1","pages":"88-98"},"PeriodicalIF":0.0,"publicationDate":"2015-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91207485","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 : 2015-08-31DOI: 10.7777/JKFS.2015.35.4.080
Hongling Kang, Jin-young Park, Eok-Soo Kim, Kyung-Mox Cho, I. Park
The Al die casting process has been widely used in the manufacturing of automotive parts when the process requires near-net shape casting and a high productive rate. However, porosity arises in the casting process, and this hampers the wider use of this method for the creation of high-durability automotive components. The porosity can be controlled by the shot condition, but, it is critical to set the shot condition in the sleeve, and it remains difficult to optimize the shot condition to avoid air entrapment efficiently. In this study, the 4.5 mm, 2.0 mm plate die castings were fabricated under various shot conditions, such as plunger velocities of 0.7 m/s ~ 3.0 m/s and fast shot set points of the cavity of -25%, 0%, 25%, and 50%. The mold filling behavior of Al melts in the cavity was analyzed by a numerical method. Also, according to the shot conditions, the results of numerical analyses were compared to those of die-casting experiments. The porosity levels of the plate castings were analyzed by X-ray CT images and by density and microstructural analyses. The effects of the porosity on the mechanical properties were analyzed by tensile tests and hardness tests. The simulation results are in good general agreements with the die-casting experimental results. When plunger velocity and fast shot set point are 1.0 m/s and cavity 25% position, castings had optimum condition for good mechanical properties and a low level of porosity.
铝压铸工艺在汽车零件的制造中得到了广泛的应用，该工艺要求近净形铸造和高生产率。然而，在铸造过程中会出现气孔，这阻碍了这种方法在高耐久性汽车部件制造中的广泛应用。孔隙度可以通过抛丸条件来控制，但抛丸条件的设置至关重要，而如何优化抛丸条件以有效地避免夹气仍然是一个难题。在柱塞速度为0.7 m/s ~ 3.0 m/s，型腔快冲设定值为-25%、0%、25%和50%的条件下，制备了4.5 mm、2.0 mm板压铸件。用数值方法分析了铝熔体在型腔内的充型行为。根据铸态条件，将数值分析结果与压铸试验结果进行了比较。通过x射线CT图像、密度和显微组织分析分析了板状铸件的孔隙度。通过拉伸试验和硬度试验，分析了孔隙率对力学性能的影响。模拟结果与压铸试验结果基本吻合。当柱塞速度为1.0 m/s，快射设定点为1.0 m/s，型腔位置为25%时，铸件具有良好的力学性能和较低的孔隙率。
{"title":"Effect of Casting Thickness and Plunger Velocity on Porosity in Al Plate Diecasting","authors":"Hongling Kang, Jin-young Park, Eok-Soo Kim, Kyung-Mox Cho, I. Park","doi":"10.7777/JKFS.2015.35.4.080","DOIUrl":"https://doi.org/10.7777/JKFS.2015.35.4.080","url":null,"abstract":"The Al die casting process has been widely used in the manufacturing of automotive parts when the process requires near-net shape casting and a high productive rate. However, porosity arises in the casting process, and this hampers the wider use of this method for the creation of high-durability automotive components. The porosity can be controlled by the shot condition, but, it is critical to set the shot condition in the sleeve, and it remains difficult to optimize the shot condition to avoid air entrapment efficiently. In this study, the 4.5 mm, 2.0 mm plate die castings were fabricated under various shot conditions, such as plunger velocities of 0.7 m/s ~ 3.0 m/s and fast shot set points of the cavity of -25%, 0%, 25%, and 50%. The mold filling behavior of Al melts in the cavity was analyzed by a numerical method. Also, according to the shot conditions, the results of numerical analyses were compared to those of die-casting experiments. The porosity levels of the plate castings were analyzed by X-ray CT images and by density and microstructural analyses. The effects of the porosity on the mechanical properties were analyzed by tensile tests and hardness tests. The simulation results are in good general agreements with the die-casting experimental results. When plunger velocity and fast shot set point are 1.0 m/s and cavity 25% position, castings had optimum condition for good mechanical properties and a low level of porosity.","PeriodicalId":16318,"journal":{"name":"Journal of Korea Foundry Society","volume":"29 1","pages":"80-87"},"PeriodicalIF":0.0,"publicationDate":"2015-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83475325","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 : 2015-08-31DOI: 10.7777/JKFS.2015.35.4.067
D. Ye, Hyun Sik Kim, M. Kang, Hae-Yong Jeong
In this study, Mg-Zn alloys are investigated in terms of their thermal properties after an addition of Cu. Al element is added to improve the mechanical properties and castability in general case. However, it was excluded here because it significantly decreases the thermal conductivity. On the other hand, Zn was added as a major element, which had less influence on reducing the conductivity and can complement the mechanical properties as well. Cu was also added, and it improved the heat transfer characteristics as the amount was increased. The composition ranges of Zn and Cu are 6 wt.% and 0~1.5 wt.%, respectively. Mg-6Zn-xCu alloy was prepared by a gravity casting method using a steel mold and then the thermal conductivity and the microstructure of the as-cast material were investigated. By measuring the density_(), specific heat_(Cp) and thermal diffusivity_(), the thermal conductivity_() was calculated by the equation . As the amount of Cu increased in the Mg-6Zn-xCu alloy, the heat transfer characteristics were improved, resulting in a synergistic effect which is slow when the added Cu exceeds 1 wt.%. In order to investigate the relative thermal conductivity/emission of the Mg-6Zn-xCu alloy, AZ91 and AZ31 were experimentally evaluated and compared using a separate test equipment. As a result, the Mg-6Zn-1.5Cu alloy when compared to AZ91 showed improvements in the thermal conductivity ranging from 30 to 60% with a nearly 20% improvement in the thermal emission.
{"title":"Effect of Cu Addition on Thermal Properties of Mg-6Zn-xCu alloys","authors":"D. Ye, Hyun Sik Kim, M. Kang, Hae-Yong Jeong","doi":"10.7777/JKFS.2015.35.4.067","DOIUrl":"https://doi.org/10.7777/JKFS.2015.35.4.067","url":null,"abstract":"In this study, Mg-Zn alloys are investigated in terms of their thermal properties after an addition of Cu. Al element is added to improve the mechanical properties and castability in general case. However, it was excluded here because it significantly decreases the thermal conductivity. On the other hand, Zn was added as a major element, which had less influence on reducing the conductivity and can complement the mechanical properties as well. Cu was also added, and it improved the heat transfer characteristics as the amount was increased. The composition ranges of Zn and Cu are 6 wt.% and 0~1.5 wt.%, respectively. Mg-6Zn-xCu alloy was prepared by a gravity casting method using a steel mold and then the thermal conductivity and the microstructure of the as-cast material were investigated. By measuring the density_(), specific heat_(Cp) and thermal diffusivity_(), the thermal conductivity_() was calculated by the equation . As the amount of Cu increased in the Mg-6Zn-xCu alloy, the heat transfer characteristics were improved, resulting in a synergistic effect which is slow when the added Cu exceeds 1 wt.%. In order to investigate the relative thermal conductivity/emission of the Mg-6Zn-xCu alloy, AZ91 and AZ31 were experimentally evaluated and compared using a separate test equipment. As a result, the Mg-6Zn-1.5Cu alloy when compared to AZ91 showed improvements in the thermal conductivity ranging from 30 to 60% with a nearly 20% improvement in the thermal emission.","PeriodicalId":16318,"journal":{"name":"Journal of Korea Foundry Society","volume":"63 1","pages":"67-74"},"PeriodicalIF":0.0,"publicationDate":"2015-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86867894","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 : 2015-06-30DOI: 10.7777/JKFS.2015.35.3.053
In-Je Hwang, Jung-Hyun Moon, J. Jun, Young-Jig Kim
Effects of Zn addition on the microstructure and corrosion behavior of Mg-8%Al-(0-1)%Zn casting alloys were investigated. With increasing Zn content, the amount of β(Mg17Al12) phase increased, while α-(Mg) dendritic cell size became reduced. The corrosion rate decreased continuously with the increase in the Zn content. The evaluation of the microstructural evolution indicates that the improved barrier effect of β particles formed more continuously along the dendritic cell boundaries and the incorporation of more ZnO into the surface corrosion product, by which the absorption of Cl− ions is impeded, are responsible for the better corrosion resistance in relation to the Zn addition.
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