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최정길,홍준표 ( Jeong Kil Choi,Chun Pyo Hong ) 한국주조공학회 1990 한국주조공학회지 Vol.10 No.3
주철의 중력금형주조에서 반복작업에 따른 응고과정의 변화를 3차원의 수치해석적 방법에 의하여 컴퓨터해석을 하였다. 수치해석적 방법으로는 차분법을 채택하였다. 반본작업과정에 따라 변화되어지는 주물의 응고시간과 미세조직, 기계적성질과의 관계가 조사 되어졌다. 컴퓨터에 의해 계산된 각싸이클의 냉각속도로 부터 주물의 공정셀의 수, 경도, 인장강도등의 변화를 예측하였으며 또한 반복싸이클에 따른 금형 및 주물의 온도분포와 최종응고부위등을 예측하였고 이들은 실제주조시험에서 얻어진 결과와 비교적 잘일치하였다. 중력금형주조에서 회주철의 응고시간, 공정셀, 기계적성질 및 응고속도에 미치는 냉각수의 영향이 또한 컴퓨터해석에 의하여 잘예측되었으며 컴퓨터해석에 의한 냉각수 라인의 적절한 설계에 의하여 주물의 미세조직 및 기계적성질과 결함발생 가능위치를 효과적으로 제어할수 있음을 확인하였다. N/A
최정길,김성빈,홍준표 ( Jeong Kil Choi,Seoung Bin Kim,Chun Pyo Hong ) 한국주조공학회 1992 한국주조공학회지 Vol.12 No.1
N/A A computer simulation of mold filling has been performed in order to analyze the fluid flow pattern in a mold cavity since casting defects such as cold shut formation, entrapment of air or gas, and inclusions are closely related to the fluid flow phenomena. The flow of molten metal entering the mold cavity with free surface has been modeled by SMAC(Simplified Marker and Cell) method. Two dimensional analysis was carried out on plate shape castings with two types of gate system. The calculation results were compared with those of water modeling experiments and showed relatively good agreement.
최정길,김동옥 ( Jeong Kil Choi,Dong Ok Kim ) 한국주조공학회 1986 한국주조공학회지 Vol.6 No.1
The gating design of gray cast iron was programmed in a Personal computer. By this program, casting test was done. The results obtained are as follows. 1. Gating design that can calculate the velocity of metal flow and size in each gate section by knowing the loss coefficient caused by friction loss and bend loss was programmed. 2. In the test casting, the gating ratio was changed into 1.1:1.3:1, 1:2:2, 1:4:4. And sound casting, free of sand washing defect, was obtained at the velocity of 35.5㎝/sec in ingate.
파라메트릭 모델에 의한 주강의 수축공 결함 예측의 Quality Criteria
이재경,최정길,홍준표 ( Jae Kyung Lee,Jeong Kil Choi,Chun Pyo Hong ) 한국주조공학회 1998 한국주조공학회지 Vol.18 No.1
N/A Criteria functions using the prediction parameters, such as t_f, G and G/√R which can be evaluated from the heat transfer and solidification analyses of castings, are of great importance in the prediction of shrinkage defects in steel castings. The critical values of these prediction parameters are found to be dependent upon the shape and size of castings. A new additional parameter, shrinkage potential, was proposed to evaluate the formation of shrinkage defects quantitatively. A coupling method of the prediction parameters with shrinkage potential was adopted to predict shrinkage defects in steel castings. The calculated results on several castings were compared with the experimental castings. (Received January 14, 1998)
김지준,최정길,홍준표 ( Ji Joon Kim,Jeong Kil Choi,Chun Pyo Hong ) 한국주조공학회 1995 한국주조공학회지 Vol.15 No.1
N/A Prediction of shrinkage cavity in shaped castings considering solidification contraction has been considered to be one of the most important subjects in casting design. Several methods of prediction of the position and shape of shrinkage cavity in castings by computer simulation have been reported. However, most of them did not fully consider solidification contraction. Casting defects caused by volume contraction during solidification of molten metal are categorized into shrinkage cavity and porosity, depending on their generation mechanism. This paper describes in detail a method for predicting the shape and position of shrinkage cavities and porosities in shaped castings both for pure metals and alloys. A computer program was developed to calculate the shape and dimension of shrinkage cavities in shaped castings. The potential of the present method has been successfully demonstrated by comparing predicted cavity shapes with those obtained in a series of experimental castings.
반복 금형주조용 자동 금형냉각장치 개발 및 적용 2 : 실험적 검증
이상목,이영철,최정길,홍준표 ( Sang Mok Lee,Young Chul Lee,Jeong Kil Choi,Chun Pyo Hong ) 한국주조공학회 1998 한국주조공학회지 Vol.18 No.2
N/A The effects of water cooling channels in the metal mold on the cyclic casting process were examined experimentally in order to control the temperature variation in the mold and to improve the soundness of castings. An automatic control system for the water cooling channels was developed based on the computer simulation. Optimum cooling water can be supplied to maintain a quasi-steady state of the mold temperature during the cyclic casting process, leading to the prevention of hot spots and resultant casting defects. Various water cooling conditions were examined for obtaining better quality castings and reduced casting cycle time, and the results were compared with the computational results which was reported in paper I. It was found that the calculated results were in good agreement with those obtained experimentally. Microstructure and hardness variations were also investigated as a function of the distance from the casting center line. (Received March 2, 1998)
주강품 압탕 설계에 체적 수축을 고려한 응고해석의 적용
김지준,김기영,최정길,홍준표 ( Ji Joon Kim,Ki Young Kim,Jeong Kil Choi,Chun Pyo Hong ) 한국주조공학회 1995 한국주조공학회지 Vol.15 No.5
N/A Test castings in plate, disc, and cubic shaped castings for 0.2wt.% carbon and stainless steel have been poured to examine the effects of the riser dimensions including riser neck on the casting soundness. Three empirical methods were chosen in risering of steel castings. A computer program of solidification analysis considering liquid and solidification contraction was developed to apply for riser-design calculated by using their methods in plate, disc, and cubic shaped castings, and to calculate the position and dimension of shrinkage cavity in complex shaped casting. The potential of present method has been successfully demonstrated by comparing predicted cavity shapes with those obtained in a series of experimental castings. Three empirical methods can be used in a practical way to make a rapid estimation of tie minimum riser diameter, but they can not provide a criterion of casting soundness with shape and material on all occasions. The shape and position of shrinkage cavity can be successfully predicted both using the present method and using risering calculated by their methods regardless of the shape and cast material.
반복 금형주조용 자동 금형냉각장치 개발 및 적용 1 : 용탕충진거동 및 응고해석
이영철,이상목,최정길,홍준표 ( Young Chul Lee,Sang Mok Lee,Jeong Kil Choi,Chun Pyo Hong ) 한국주조공학회 1998 한국주조공학회지 Vol.18 No.2
N/A A three dimensional simulation program based on the SOLA-VOF technique was developed for the modeling of mold filling and solidification sequences of the AC4B alloy in the cyclic permanent mold casting process. The geometries and mesh diagrams of the casting and the mold were automatically generated using a pre-processor based on the commercial Auto-CAD system. The solidification time of the casting and the temperature variation of the mold with cyclic casting were evaluated using the present scheme. The effects of the local water cooling of the metal mold on the cyclic casting process were also examined in order to control the temperature variation in the mold and to improve the soundness of the castings. The minimization of the casting cycle time was also confirmed by the present program for an improved productivity. It can be concluded that the present program can be used for obtaining the optimum casting parameters and the local cooling condition for obtaining sound castings without shrinkage defects in the cyclic mold casting process. (Received March 2, 1998)
김지준,김진수,류관호,최정길,이진형,홍준표 ( Ji Joon Kim,Jin Soo Kim,Gwan Ho Ryu,Jeong Kil Choi,Zin Hyoung Lee,Chun Pyo Hong ) 한국주조공학회 1993 한국주조공학회지 Vol.13 No.3
N/A In gravity die casting, die cooling systems are frequently employed with water cooling to remove the heat of the solidifying metal. Thermal modeling is an important technique in mold design for improving the productivity of the process. Computer simulation system which consists of pre-processor, main solidification simulator and post-processor has been developed for three dimensional solidification analysis of cyclic gravity die casting. The pre-processor is used for mesh generation in a PC system. The modified finite difference method is adopted for the main solidification simulation algorithm during all the casting cycles. The post-processor graphically presents the simulation results. Several experiments in automotive cast piston were carried out. The temperature variations in casting and mold with time are measured experimentally, and the results are compared with calculation results. The effects of cycle number on solidification pattern are also studied. Several experimental results for the prediction of shrinkage defects are compared with calculated results.