This study investigated the growth behavior and characteristics of compounds formed at the interface between a liquid Al-Si-Cu alloy and solid cast iron. Through microstructural analyses, it was observed that various AlFe and AlFeSi phases are formed at the interface, and the relative proportion of each phase changes when small amounts of strontium are added to the Al alloy. The results of the microstructural analysis indicate that the primary phases of the interfacial compounds in the Al-Si-Cu base alloy are Al8Fe2Si and Al4.5FeSi. However, in the Sr-added alloys, significant amounts of binary AlFe intermetallic compounds such as Al5Fe2 and Al13Fe4 formed, in addition to the AlFeSi phases. The inclusion of Sr has a slight diminishing effect on the rate at which the interfacial compounds layer thickens during the time the liquid Al alloy is in contact with the cast iron. The study also discusses the nano-indentation hardness and micro-hardness of the interfacial phases.

In order to broaden the range of application of light weight aluminum alloys, it is necessary to enhance the mechanical properties of the alloys and combine them with other materials, such as cast iron. In this study, the effects of adding small amounts of Cu and Zr to the Al-Si-Mg based alloy on tensile properties and corrosion characteristics were investigated, and the effect of the addition on the interfacial compounds layer with the cast iron was also analyzed. Although the tensile strength of the Al-Si-Mg alloy was not significantly affected by the additions of Cu and Zr, the corrosion resistance in 3.5 %NaCl solution was found to be somewhat lowered in this research. The influence of Cu and Zr addition on the type and thickness of the interfacial compounds layer formed during compound casting with cast iron was not significant, and the main interfacial compounds were identified to be Al5FeSi and Al8Fe2Si phases, as in the case of the Al-Si-Mg alloys.

In this study, we collect water control valves that have had accidents due to existing cracks, etc. are collected, and propose investigation items for strengthening the valve structural safety evaluation through a series of analyzes from valve specifications to physicochemical properties are proposed. The results of this study are as follows. First, there was a large variation in the thickness of the body or flange of the valves to be investigated, which is considered to be very important factor, because it may affect the safety of the valve body against internal pressure and the flange connected with the bolt nut. Second, 60% of the valves under investigation had many voids in the valve body and flange, etc. and the decrease in thickness due to corrosion was relatively large on the inner surface in contact with water rather than the outer surface. It is judged that the investigation of depth included voids is very important factor. Third, all valves to be investigated are made of gray cast iron foam, and therefore it is judged that there is no major problem in chemical composition. It is judged that the chemical composition should be investigated. Fourth, as a physical investigation item, the analysis of metal morphology structure seems to be a very important factor for nodular cast iron from rather than a gray cast iron foam water valve with a flake structure. As it was found to be 46.7~68.8% of the standard recommended by KS, it could have a direct effect on damage such as cracks, and therefore it is judged that the evaluation of tensile strength is very important in evaluating the safety of the valve.

This research developed ultra-pressure pump main body by using ductile cast iron FCD500, conducted quantitative analysis on following phenomenon of flow or solidification processing in cast processing for improvement of cast device, after extracting model from cast concluded as follows by brinel hardness test. after selecting the ideal condition of cast and it applied to cast of real product shape, discovered the ideal filling processing under the condition that temperature of molten metal was between 1300℃ and 1280℃. and after finishing filling, solidification was commenced rapidly when percentage of solidification completion was between 40%~50%, at that moment, the termperature was measured 1100℃. moreover under the condition of temperature below 900℃, keeping temperature on the center of parts for a certain period of time brings stability of stabilization of heat in parts and organizational stabilization of ductile cast iron. As the results of the casting method design, it was that the ductile cast parts of pump main body was obtained as the maximum HB of 220 was recorded and good test results were achieved

Currently, there are two main issues regarding the development of core technologies in the automotive industry: the development of environmentally friendly vehicles and securing a high level of safety in the event of an accident. As part of the efforts to address these issues, research into alternative materials and new car body manufacturing and assembly technologies is necessary, and this has been carried out mainly by the automotive industries. Large press molds for producing car body parts are made of cast iron. With the increase of automobile production and various changes of design, the press forming process of car body parts has become more difficult. In the case of large press molds, high hardness and abrasive resistance are needed. To overcome these problems, we attempted to develop a combined heat treatment process consisting of local laser heat treatment followed by plasma nitriding, and evaluated the characteristics of the proposed heat treatment method. From the results of the experiments, it has been shown that the maximum surface hardness is 864 Hv by the laser heat treatment, 953 Hv by the plasma nitriding, and 1,094 Hv by the combined heat treatment. It is anticipated that the suggested combined heat treatment can be used to evaluate the durability of press mold.

Recently, metal molding has become essential not only for automobile parts, but also mass production, and has greatly influenced production costs as well as the quality of products. Its surface has been treated by carburizing, nitriding and induction hardening, but these existing treatments cause considerable deformation and increase the expense of postprocessing after treatment; furthermore, these treatments cannot be easily applied to parts that requiring the hardening of only a certain section. This is because the treatment cannot heat the material homogeneously, nor can it heat all of it. Laser surface treatment was developed to overcome these disadvantages, and, when the laser beam is irradiated on the surface and laser speed is appropriate, the laser focal position is rapidly heated and the thermal energy of surface penetrates the material after irradiation, finally imbuing it with a new mechanical characteristic by the process of self-quenching. This research estimates the material characteristic after efficient and functional surface treatment using HPDL, which is more efficient than the existing CW Nd:YAG laser heat source. To estimate this, microstructural changes and hardness characteristics of three parts (the surface treatment part, heat affect zone, and parental material) are observed with the change of laser beam speed and surface temperature. Moreover, the depth of the hardened area is observed with the change of the laser beam speed and temperature.

0.5%C-25.0%Cr-1.0%Si(합금1), 0.5%C-5.0%Cr-1.0%Si(합금2) 및 2.0%C-5.0%Cr-1.0%Si(합금3)의 3종류 크롬백주철에 있어서 기지조직 및 탄화물에 분푀도는 Cr 및 Si의 거동을 연구하였다. 15kg 용량의 고주파 유도용해로에 선철, 고철, Fe-Cr, Fe-Si 등을 장입시켜 용해시킨후 슬래그를 제거시키고 1550˚C에서 펩 주형에 주입시킨후 실온까지 냉각시켜 SEM으로 응고조직을 관찰하였으며 EPMA분석을 통하여 Cr 및 Si 의 분포거동을 관찰하였다. 합금1의 경우 초정으로 δ페라이트가 정출후 δ페라이트와 용액의 입계에서 δ페라이트와 M7C3탄화물이 공정으로 정출하였으며 합금2의 경우 용액에서 초정으로 거의 δ페라이트가 정출된 수 극히 일부분만이 δ페라이트와 M7C3탄화물의 공정으로 정출하였다. 반면 합금 3의 경우 오스테나이트가 초정으로 정출된 후 오스테나이트와 M3C탄화물이 공정으로 정출하였다. Cr은 주로 M7C3 및 M3C탄화물에 , 그리고 Si는 기지조직에 선택적으로 분배되었으며 Cr의 기지조직에 대한 분배계수는 0.56-0.68, 그리고 Si는 1.12-1.28의 범위에 걸쳐있었다. 또한 Cr의 기지조직에 대한 분배계수는 C 함량이 2.0%일때가 0.5%의 경우보다 낮았으며 M7C3탄화물내의 Cr 함량은 Cr함량이 25.0% 일때가 5.0%의 경우보다 높은값을 나타내었다. 나타내었다.

3%C-10%Cr-5%Mo-5%W, 3%C-10%V-5%Mo-5%W 및 3%C-17%Cr-3%V의 3종류 고합금백주철에 있어서 열처리후의 기지조직의 변태거동을 연구하였다. 15kg 용량의 고주파 유도용해로에 선철, 고철, Fe-Cr, Fe-V, Fe-Mo 및 Fe-W 등을 장입시켜 용해시킨 후 슬래그를 제거시키고 1550˚C에서 Y-block의 펩 주형에 주입시켰다. 적당한 크기로 절단한 시편을 진공분위기하에950˚C에서 5시간동안 우선 균질화처리를 실시하였다. 그 후 다시 이 시편을 1050˚C에서 2시간동안 오스테나이징시킨 후 강제공냉을 행하였다. 강제공냉된 시편을 300˚C에서 3시간 유지시킨 후 템퍼링을 실시하였다. 주방상태에서의 기지조직은 3합금 공히 퍼얼라이트이었으며 강제공냉후에는 마르텐사이트 및 오스테나이트로 변태하였다. 또한 기지조직내에 무수히 많은 이차탄화물 입자들의 석출되었다. 템프링 후 일부 오스테나이트 및 마르텐사이트는 템퍼드마르텐사이트로 변태하였다. 변태하였다.

다합금계백주철의 성분원소인 Cr, V, Mo 및 W 의 첨가량을 변화시켜 응고조직을 관찰하였다. MC탄화물은 초정 austenite dendrite 내에 괴상 및 구상으로 M7C3탄화물은 intercellular boundary에 꽃형태 또는 bar 형태로, 그리고 M2C 탄화물은 M7C3탄화물과 마찬가지로 intercellular boundary에 침상으로 정출하였다. 기지조직은 주방상태에서 pealite 또는 (pearlite + austenite)의 혼합조직으로 구성되어 있었으며, 또한 EPMA 분석결과 MC탄화물은 V, M7C3 탄화물은 Cr 그리고 M2C탄화물은 Mo 및 W가 주성분으로 되어 있음을 알 수 있었다. 냉각곡선을 측정한 결과 액상에서 MC, M7C3, M2C 순으로 공정반응이 일어나고 있었으며 또한 X-선 회절시험을 통해 각 탄화물의 회절 peak를 관찰하였는바 응고조직의 사진과 잘 일치하고 있음을 알 수 있었다.