자동차용 Al-Mg-Si 합금의 페인트베이크 경화능 및 성형성에 미치는 미량원소와 시효처리의 영향

최일동,강석봉,진선화,조권도 대한금속재료학회(대한금속학회) 2000 대한금속·재료학회지 Vol.38 No.7

Al-Mg-Si series aluminum alloys for automobile applications are capable of obtaining high strength due to age hardening during paint bake process. However, auto body sheet should go through storage procedure. During storage, hardness is increased by natural aging. Therefore, it is hard to get formability at pressing process and get the sufficient effect of age hardening at the paint bake treatment because of short process time. In order to prevent an adverse effect of natural aging, the effect of alloying elements and pre-aging treatment on the age hardening behavior was investigated in this study. The hardness increment during natural aging was greatly suppressed by addition of Cu+In, Cu+Cd and Cu+Sn. These results might be explained by the fact that In, Cd and Sn can pick up vacancies during the natural aging. Therefore, the diffusion rate of Mg and Si is slowing down gradually and age hardening is also delayed. Hardness during natural aging was stabilized and Vickers-microhardness over 130 was achieved with short artificial aging(paint baking) time by pre-aging treatment. Elongation was over 30% which gives enough formability at press stage by addition of Cd and Sn. The formability (LDH(Limiting Dome Height) and FLC(Forming Limit Curve)) test was performed by the punch stretch test. It is considered that alloying element of Sn is effective to enhance formability.

조성조절 금속박막의 Supermodulus 효과

최일동 한국마린엔지니어링학회 1992 한국마린엔지니어링학회지 Vol.16 No.4

조성조절한 박막금속합금에서 supermodulus효과가 관찰되었음을 소개하였다. 이 현상을 Fermi표면과 Brillouin 대의 접촉, 그리고 정합변형효과에 의해 설명하였으나 합금계에 따라 어느 한쪽으로만 설명이 가능하며 아직도 명쾌한 해석은 어려운 상황이다. Fermi표면으로 해석한 측면에서 보면 조성조절한 박막에서 측정되는 supermodulus 현상으로 그 합금계의 Fermi표면의 구조와 크기를 예측할 수 있고, 또는 그 반대로, Fermi표면의 조성에 따른 구조와 크기를 알면 supermodulus 효과를 나타내는 합금계를 설계할 수도 있을 것이다. 지금까지는 강성계수의 향상에 대해서만 관찰되었으나 그 반대로 강성계수가 급격히 감소하는 현상도 관찰될 가능성은 남아있어 앞으로의 연구가 기대된다.

자동차 차체용 1.2GPa급 TRIP 강의 Weld-bond부 너깃경에 따른 인장전단특성에 관한 연구

최일동,박지연,김재원,강문진,김동철,김준기,박영도,Choi, Ildong,Park, Jiyoun,Kim, Jae-Won,Kang, Mun-Jin,Kim, Dong-Cheol,Kim, Jun-Ki,Park, Yeong-Do 대한용접접합학회 2015 대한용접·접합학회지 Vol.33 No.2

High strength steels have been continually being developed to improve in fuel economy in automotive and ensure safety of passengers. New bonding and welding methods have been required for improving weldability on high strength steels. In this study, resistance spot welding and Weld-bond with nugget diameters of 4.0mm, 5.0mm, 6.0mm and 7.0mm were produced and tested, respectively. In order to confirm the effect of nugget diameters on tensile shear characteristic of the Weld-bond, tensile shear characteristics of Weld-bond were compared with those of resistance spot welding and adhesive bonding. Peak load of Weld-bond were increased as the nugget diameter increases. After appearing maximum peak load continuous fracture followed with second peak owing to load being carried by resistance spot weldment. Fracture modes of the adhesive layer in Weld-bond fractures were represented by mixed fracture mode, which are cohesive failure on adhesive part and button failure at resistance spot welds. The results showed that the tensile shear properties can be improved by applying Weld-bond on TRIP steel, and more apparent with nugget diameter higher than 5${\surd}$t.

High-Rate Tensile Properties of Si-Reduced TRIP Sheet Steels

최일동,박영도,손동민,김성준,문만빈 대한금속·재료학회 2010 METALS AND MATERIALS International Vol.16 No.1

There have been efforts to develop Si-reduced TRIP steels to improve the wettability of Zn coatings, since the conventional CMnSi-TRIP steels suffer from poor galvanizability. In addition, for the development of potential applications of Si-reduced TRIP steels in vehicle crash management, a better understanding of high strain rate properties is required. In the present study, the effects of alloying elements, such as Cu, Al, Si,and P, on the high-rate tensile properties of Si-reduced TRIP sheet steels were investigated. Tensile tests were performed with a servo-hydraulic tensile testing machine at strain rates ranging from 10−2to 6 × 102s−1, and the ultimate tensile strength, elongation, strain rate sensitivity, and absorbed energy were evaluated. The retained austenite volume fractions and carbon content of the specimens were measured using neutron diffraction. The UTS was increased with Cu, Al, Si, and P alloying throughout the strain rate range, and the alloying effect on UTS was considerable with Cu and P. The effects of alloying on the microstructure were not significant. All the steels tested in this study exhibited positive strain rate sensitivity, and the m value at strain rates higher than 10 s−1was at least two times higher than that at lower strain rates.

자동차용강의 고속변형거동에 대한 예비변형과 소부경화의 영향

최일동,김동민,Bruce, D. M.,Matlock, D. K.,Speer, J. G.,박성호 대한금속재료학회 2005 대한금속·재료학회지 Vol.43 No.4

The high speed deformation behavior of TRIP steels and HSLA steels has been investigated at strain rates ranging from 10^(-2) to 10³/sec. The effects of metallurgical factors such as prestrain (2%) and bake hardening condition (170℃, 20 min) on tensile properties at various strain rates are being evaluated. Ultimate tensile strength (UTS), total elongation, strain rate sensitivity, and absorbed energy are reported. In general, UTS increases with increasing strain rate, that is, it shows positive strain rate sensitivity. And strain rate sensitivity increases sharply over 100/sec. Strength increases with increasing the amount of prestrain. The bake hardening treatment slightly influences UTS values. The absorbed energy decreases with increasing prestrain but it is not affected by bake hardening treatment. Received February 14, 2005)

Al-Mg 합금의 Luders Line 형성에 미치는 제인자의 영향

최일동,강석봉,한공 대한금속재료학회(대한금속학회) 1996 대한금속·재료학회지 Vol.34 No.4

The formation of Lu¨ders lines was characterized in Al-4.5%Mg and Al-5.6%Mg alloys. All of the test specimens of Al-4.5%Mg and Al-5.6%Mg alloys showed type B Lu¨ders line in the strain rate range from 2×10^(-4)/sec to 2×10^(-1)/sec. Type B Lu¨ders line was identified as serration on stress-strain curves. However, type A Lu¨ders line was not observed. The critical strain(ε_c) for the occurrence of the Portevin Le Chatelier effect(type B Lu¨ders line) in Al-4.5%Mg alloy increased with increasing the strain rate. It was considered that dislocation locking was delayed at high strain rates because dislocations moved faster than solute atoms. Specimens were reheat-treated at 400℃, 450℃ and 500℃ for 30 minutes to study the effect of microstructure on the formation of type A Lu¨ders line. It was shown that Al-4.5%Mg alloy showed type A Lu¨ders line but Al-5.6%Mg alloy didn't. It was considered that the formation of type A Lu¨ders line in Al-4.5%Mg alloy was caused by the grain refinement, increasing the quantity of soluble solute atoms and formation of cell structure after reheat-treatment.

무가압침투법에 의한 전자패키징 재료용 Al / SiCp 복합재료의 제조

최일동,김성준,박익민 ( Il Dong Choi,Sung Joon Kim,Ik Min Park ) 한국주조공학회 1996 한국주조공학회지 Vol.16 No.1

N/A Infiltration behavior of Al-Mg alloys in SiC_p powder bed using pressureless infiltration technique have been studied. The manufacturing of Al/SiC_p composites by pressureless infiltration was successful when Mg was added over 8% in Al alloy matrix. Processing time and temperature to complete Infiltration through SiC_p bed was decreased with increasing Mg content in Al alloy. When Mg powder was added in SiC_p bed, processing temperature for successful infiltration was decreased. Volume fraction of SiC_p in composites was increased with increasing the mixing ratio of coarse SiC particles.

Al-Mg-Si 합금에서 Cu, Sn, 합금 원소 및 예비시효처리가 페인트 베이크 경화성에 미치는 영향

최일동,강석봉,김형욱,진선화 대한금속재료학회(대한금속학회) 2000 대한금속·재료학회지 Vol.38 No.5

The Al-Mg-Si alloys for autobody sheet application are capable of providing a good paint bake hardenability. However, in practical usages, it is difficult to perform paint bake cycle immediately after solution heat treatment and a delay at room temperature before the paint bake cycle is usually unavoidable. Also, the condition of paint bake cycle is insufficient to exert completely their age hardenability, although the alloys have a hardening potential. Therefore, in order to improve the paint bake hardenability, it is necessary to prevent the detrimental effect of natural aging before paint bake cycle. In this study, effects of Cu and Sn alloying elements and pre-aging treatment on paint bake hardening in Al-Mg-Si alloys have been studied by means of micro-hardness measurement and transmission electron microscopy. The results showed that the paint bake hardenability of the Al-0.5Mg-1.3Si-0.1Zr alloy is enhanced by the addition of Cu and Sn alloying elements and the adoption of the preaging treatments. It suggested that the clustering process occurred during natural aging is effectively inhibited by Cu and Sn alloying elements and the preaging treatments.

스파크 점화기관에서 흡입 공기 중 산소체적분율의 변화가 연소 및 배기가스 조성에 미치는 영향에 관한 연구

최일동(il Dong Choi),김치원(Chi Won Kim),이병호(Byung Ho Lee) 한국자동차공학회 2016 한국자동차공학회 지부 학술대회 논문집 Vol.2016 No.10

The change in the oxygen volume fraction of the inlet air of the spark ignition engine configuration an experimental apparatus to interpret the effects of combustion and the exhaust gas composition and was experiments using a suitable measuring instrument, in this chapter discusses the experimental apparatus and method. When the volume fraction of oxygen in the intake air increases as described above, the combustion pressure was measured as a way to ensure that the combustion temperature rises, and increase the combustion speed. And the stability of combustion and analyzed using the apparatus for continuously acquired by the average number of cycles than the pressure of the pressure cycle. Depending on the combustion chamber geometry of the spark ignition engine is the ignition position, the flow in the cylinder, the ignition characteristics that are affected. But allows the case that the oxygen volume fraction as in the study change in factors related to the engine and the factor associated with the flow are able to determine the characteristics of the combustion, and analysis using the pressure change of the engine when the fraction of oxygen volume change since the same condition

스파크점화 기관에서 흡기 조성 중 연소 및 배기 특성에 관한 연구

최일동(il Dong Choi),김치원(Chi Won Kim),이병호(Byung Ho Lee) 한국자동차공학회 2016 한국자동차공학회 학술대회 및 전시회 Vol.2016 No.11

The multi-point fuel injection in a spark ignition engine is applied is guided through the inlet valve into the cylinder is mixed with fuel and the air before the intake valve, the piston rises and compresses the mixture through the crankshaft rotational motion. It is generated by the discharge in the spark plug in the compression top dead center electrode spark nuclear propagates in the compressed mixture. Thus, very important because the damage to the living organisms or environmental contaminants in the exhaust gas generated when the mixture is burned. While maintaining good fuel economy from the stoichiometric operation, it reduces both carbon monoxide and nitrogen oxide emissions, combustion instability or unstable behavior due to a misfire by the operating parameters are generating lots of exhaust substances that pollute the earth. And the engine constitute a damage.