과공정 Al-Si 합금의 내마모성 연구

김헌주,정운재 ( Heon Joo Kim,Woon Jae Jung ) 한국주조공학회 1993 한국주조공학회지 Vol.13 No.6

N/A The wear resistance of Hyper-eutectic Al-Si alloy, have recently been noticed as a new automobile material, was investigated. For the purpose of developing wear resistant Al-Si alloy, some factors which attribute to wear resistance are examined as follows; refinement of primary Si particle during solidification, and effect of refinement on wear resistance and other mechanical properties. The most effective refinement was accomplished by adding both NaF and S, and this improve wear-resistance in abrasive wear type. The wear losses of specimens cast in metal mold were ruduced to 80% of those in sand mold. T6 heat treatment increases hardness, which resulted in reduction of wear loss about 3∼18 %.

6061AI 복합재료 마모특성에 미치는 SiC 입자 강화재 체적분율의 영향

김헌주(Heon Joo Kim) 한국열처리공학회 2002 熱處理工學會誌 Vol.15 No.2

N/A In the present investigation wear behavior of the 6061Al composites reinforced with 5, 10, 20% SiC par tides for dry sliding against a SM45C counterface was studied as a function of load and sliding velocity. Sliding wear tests were conducted at two loads(19.6 and 49N) and three sliding velocitiies(0.2, 1 and 2 m/sec) at constant sliding distance of 4000 m using pin-on-disk machine under room temperature. Presence of SiC reinforcement particles in the composites has displayed a transition from mild to severe wear at relatively higher applied load and sliding velocity compare to that of the matrix metal. As the volume fraction of SiC particles increased, the transition moved to a more severe wear conditions. Eventually, mild wear prevailed at a most severe wear conditions in this study, that was 49N load and 2 m/sec sliding velocity in 20% SiC partide/6061Al composite.

B.390 알루미늄 합금의 마모특성에 미치는 초정Si 입자크기와 잔류응력의 영향

김헌주 ( Heon Joo Kim ),김성재 ( Sung Jae Kim ) 한국열처리공학회 2006 熱處理工學會誌 Vol.19 No.1

AC4A 합금의 충격특성 및 피로특성에 미치는 스크랩 함량의 영향

김헌주 ( Heon-joo Kim ) 한국주조공학회 2016 한국주조공학회지 Vol.36 No.6

The effects of scrap content on the impact and fatigue properties were investigated in AC4A alloy. The impact absorbed energy of as-cast specimens were 3.61, 3.56, 3.47, and 3.08 Joules, respectively, when scrap contents of the specimens were 0, 20, 35, and 50%. And, the corresponding energy levels of the T6 heat-treated condition were 3.66, 3.48, 3.25, and 2.96 Joule. In the same way, the fatigue strength values of the as-cast specimens were 53.2, 52.0, 48.4, and 43.8MPa, respectively, and the corresponding fatigue strengths of the T6 heat-treatment specimens were 85.4, 75.7, 60.6, and 51.2 MPa. Impact absorbed energy and fatigue strength decreased as scrap content of the specimen increased. It is assumed that impact absorbed energy decreased owing to the presence of oxide films, which act as branches of 2nd cracks; fatigue strength also decreased with decreased deflection of the fatigue crack path as the scrap content of the specimens increased.

고압 금형 주조용 Al-4 wt%Mg-0.9 wt%Si계 합금의 인장특성에 미치는 Fe, Mn함량의 영향

김헌주 ( Heon Joo Kim ) 한국주조공학회 2013 한국주조공학회지 Vol.33 No.3

Effect of Fe and Mn contents on the tensile properties of Al-4 wt%Mg-0.9 wt%Si alloy system has been studied. Common phases of Al-4 wt%Mg-0.9 wt%Si alloy system were α-Al, Mg2Si, α-Al12(Fe,Mn)3Si and β-Al5FeSi. As Fe content of Al-4 wt%Mg-0.9 wt%Si alloy system increased from 0.15 wt% to above 0.3 wt%, β-Al5FeSi compound appeared. When Mn content of the alloy increased from 0.3 wt% to 0.5 wt%, morphology of plate shaped β-Al5FeSi compound changed to chinese script α-Al12(Fe,Mn)3Si. As Fe content of Al-4 wt%Mg-0.9 wt%Si-0.3 wt%Mn alloy increased from 0.15 wt% to 0.4 wt%, tensile strength of the as-cast alloy decreased from 191 MPa to 183 MPa and, elongation of the alloy also decreased from 8.0% to 6.2%. Decrease of these properties can be explained as the formation of plate shape, β-Al5FeSi phase with low Mn/Fe ratio of the alloy. However, when Mn content of Al-4 wt%Mg-0.9 wt%Si-0.3 wt%Fe alloy increased from 0.3 wt% to 0.5 wt%, tensile strength of as-cast alloy increased from 181 MPa to 194 MPa and, elongation of the alloy increased from 6.8% to 7.0%. These improvements attribute to the morphology change from β-Al5FeSi phase to chinese script, α-Al15(Mn,Fe)3Si2 phase shape-modified from with high Mn/Fe ratio of the alloy.

AISI 51B20 보론첨가강의 경화능에 미치는 오스테나이트화 온도의 영향

김헌주 ( Heon Joo Kim ),박무용 ( Moo Yong Park ) 한국열처리공학회 2010 熱處理工學會誌 Vol.23 No.6

Effect of hardenability, grain size and microstructural change according to the change of austenitizing temperature was analyzed in Jominy hardenability test of AISI 51B20 steel. Grain growth was small, 7㎛ and 12㎛ austenite grain sizes at austenitizing temperature of 900℃ and 1000℃, respectively, while rapid grain growth was observed up to 30㎛ austenite grain size at austenitizing temperature of 1100℃. As austenitizing temperature increased from 900℃ to 1100℃, hardenability in the region within 15 mm from end-quenched surface decreased due to the grains growth of bainite and martensite mixture, on the other hand the hardenability in the region exceeding 15 mm from end-quenched surface increased. Increased hardenability was attributed to different microstructures; pearlite, fine pearlite and bainite, and bainite and martensite structures at austenitizing temperature of 900℃, 1000℃ and 1100℃, respectively.

AISI 51B20강의 인장 및 충격특성에 미치는 오스테나이트화 온도와 퀜칭,템터링 온도의 영향

김헌주 ( Heon Joo Kim ) 한국열처리공학회 2011 熱處理工學會誌 Vol.24 No.6

Abstract Effects of microstnictura change, tensile properties and impact property according to the change of austenitizing temperature and tempering temperature of AISI 51B20 steel were examined. Regardless of austenite grain size, lath martensite with needle and packet shapes was found at tempering temperature of 300℃~400℃. The needles of lath martensite changed to parallel packet at tempering temperature of 450℃~600℃. As tempering temperature increased, tensile strength, yield strength and hardness decreased, while elongation, ratio of reduction area and Charpy impact energy increased. Grain size increased when quenching temperature was 930℃. Grain size had prominent effect on the mechanical properties of AISI 51 B20 steel. Ratio of tensile strength/yield strength and yield strength autenitized at 880℃ followed by tempering at 350℃-450℃ showed higher values than that of autenization at 930℃ due to fine grain size. (Received September 18, 2011; Revised October 21. 2011; Accepted November 2, 2011)

주조용 Al-4wt%Mg-0.9wt%Si-0.3wt%Mn-0.15wt%Fe 합금의 결정립 미세화와 주조특성에 미치는 Ti, B, Zr 첨가원소의 영향

김헌주 ( Heon Joo Kim ),박수민 ( Su Min Park ) 한국주조공학회 2015 한국주조공학회지 Vol.35 No.5

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 α-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 α-Al solution for shell mold and steel mold were 72.3 μm and 23.5 μm, 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.

주조용 Al-4wt%Mg-0.9wt%Si-0.3wt%Mn-0.15wt%Fe 합금의 공정Mg2Si 개량과 주조특성에 미치는 Sc, Sr 첨가원소의 영향

김헌주 ( Heon Joo Kim ) 한국주조공학회 2015 한국주조공학회지 Vol.35 No.6

The effects of Sc and Sr elements on the modification of the eutectic Mg2Si 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 Mg2Si phase with additions of the Sr and Sc elements. Here, a fine eutectic Mg2Si phase and a decrease in the growth temperature of the eutectic Mg2Si phase were evident with an addition of Sc element up to 0.2 wt%. The growth temperature of the eutectic Mg2Si phase decreased and the effect on the modification of the eutectic Mg2Si 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 Mg2Si phase, and the resulting microstructure of the eutectic Mg2Si 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 α-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.

AC2B 알루미늄 주조합금의 응고균열 강도에 미치는 금형 예열온도의 영향

김헌주 ( Heon Joo Kim ) 한국주조공학회 2014 한국주조공학회지 Vol.34 No.5

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 250℃, 150℃ and 50℃, the solidification crack strengths were found to be 7.8 Kgf/cm2, 12.9 Kgf/cm2 and 28.6 Kgf/cm2, respectively. In the same way, when the mold preheat temperatures were 250℃, 150℃ and 50℃, the corresponding temperatures of the failure sites were 610℃, 600℃ and 571℃, 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.