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420J2 마르텐사이트계 스테인레스강의 오스테나이트화 온도가 기계적 성질에 미치는 영향
김용길,김영주,김기돈,성장현 ( Y . G . Kim,Y . J . Kim,G . D . Kim,J . H . Sung ) 한국열처리공학회 1992 熱處理工學會誌 Vol.5 No.2
For the purpose of investigating the effect of austenitizing temperatures on the mechanical properties of 0.23%C-13.6%Cr martensitic stainless steel, tensile properties, hardness, impact value and carbide extraction were examined after changing the austenitizing temperatures and tempering temperatures. The results obtained are summerized as follows. The carbide laminations formed from hot rolling before austenitization could not be eliminated after austenitizing at 950℃. With increasing austenitizing temperature, hardness increased and showed maximum value at 1050℃ and then slightly decreased. With increasing tempering temperature up to 500℃, impact value and elongation appeard to be decreased but hardness showed nearly unchanged at austenitizing temperature of 1150℃ due to the fine M_7C₃carbides precipitation. The abrupt increase in impact value, hardness and elongation above the tempering temperature of 500℃ appeared to change in carbide structure from fine M_7C₃to coarse M_(23)C_6.
김효겸(Hyo-Gyeum Kim),김현수(Hyun-Su Kim),성장현(Jang-Hyun Seong),박준홍(Joon-Hong Park),김형준(Hyoung-jun Kim),이재섭(Jae-Seob Lee) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
Cooling tower is a kind of heat exchanger that be widely used in plant or air conditioning apparatus of a large size building. It is fixed above the concrete structure by H-beam support part. Cooling tower support part is designed by according to the spot experience without design plan. In this study, strength evaluation of cooling tower support part is used to finite element analysis. Design factor is selected cross section dimension of beam. It investigated the propriety of the analysis result which uses the solid element and the beam element. Therefore, various cross section dimension of beams show that the volume and the stress decreases.
김형준(Hyung Jun Kim),박준홍(Joon Hong Park),성장현(Jang Hyun Sung),김현수(Hyun Su Kim),전언찬(Eun Chan Jeon),박영철(Young Chul Park) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
Hardness is most likely to mean the resistance to indentation, and to the design engineer it often means an easily measured and specified quantity which indicates something about the strength and heat treatment of the metal. Especially, Vickers hardness is one of the most widely useful methods to obtain mechanical properties of a product. Firstly, in this study, a method to estimate hardness will be presented using FE simulations of Vickers hardness tests from the viewpoint that hardness indicates resistance to plastic deformation. To verify our method, the results of the simulations for several materials such as commercial aluminum alloy and steel will be compared with those of Vickers hardness tests for the materials. Most conventional cutting-tools are made from high-speed steel (HSS). Efficiency of machining of metals and non-metals and economy of whole processing lines is often controlled by selection of suitable materials among numerous groups of tool materials. In those cases where good machinability in annealed condition is required, high speed steel cutting tools retain their dominating position. High speed steels are used for multiple edge tools and other complex heavy duty tools. Although the volume of their production is relatively low, their importance in controlling output, efficiency, and reliability in many branches of industry cannot be underestimated. Secondly in this study, prediction of the relation between effective strain and hardness for high speed steel was performed.
열처리공학회지,제27권 제1호(2014) -고온 가스질화 된 STS 430 스트인리스강의 냉간 가공성에 미치는 항온변태 열처리 시간 변화의 영향
김정민 ( J. M. Kim ),현양기 ( Y. K. Hyun ),송상우 ( S. W. Song ),김기동 ( G. D. Kim ),손영호 ( Y. H. Son ),성장현 ( J. H. Sung ) 한국열처리공학회 2014 熱處理工學會誌 Vol.27 No.1
This study is to investigate the phase changes and cold workability after isothermal transformation at l800C by using the high temperature gas nitrided (HTGN) STS 430 ferritic stainless steel specimens. The phase diagram of STS 430 steel obtained by calculation showed that the phase appeared at 11 OO°C showed as α + г →г+ Cr₂N →г+ Cr₂N + CrN with increasing nitrogen concentration. Also. the transformation of г→ Cr₂N during heat treatment isothermally at 780°C, nitrogen pearlite with lamellar type was fully formed at the nitrogen permated surface layer for 10 hrs. However. this transformation was not completed for 1 hr, resulting nitrogen pearlite plus martensite. The cold rolled specimen of isothermally transformed at l80°C for 10 hrs after high temperature gas nitriding decreased the layer thickness of nitrogen pearlite inducing the deformation of hard Cr₂N phase. the dissolution rate of Cr₂N phase increased rapidly with increasing cold rolling ratio. Specimens with the microstructure of nitrogen pearlite (isothermally transformed at l80°C for 10 hrs) were possible to cold rolling without crack formation. However, the mixed structures of nitrogen pearlite + martensite (isothermally transformed at 780°C for 1 hr) were impossible to cold deformation without cracking.
김형준(H. J. Kim),박준홍(J. H. Park),김현수(H. S. Kim),성장현(J. H. Sung),김효겸(H. G. Kim),이재섭(J. S. Lee) 한국생산제조학회 2006 한국생산제조시스템학회 학술발표대회 논문집 Vol.2006 No.5
In this study, it is attempted to find out the optimal shape of U-type bellows using the finite element method. The effective factors, mountain height, length, thickness, and number of convolutions are considered and the proper values are chosen for the simulation. The results shows that if the number of convolutions are reduced, the volume decreases while the stress increases. However, the number of convolutions are increased, the volume increases above the standard volume and the stress obviously increases. In addition, the effect of the thickness of bellows on the stress is very large. Both of the volume and stress are decreasing at a certain lower value region.
경도와 변형률 관계 예측을 위한 유한요소해석에 관한 연구
박준홍(J. H. Park),김형준(H. J. Kim),김효겸(H. G. Kim),이재섭(J. S. Lee),김현수(H. S. Kim),전언찬(E. C. Jeon),김영희(Y. H. Kim),성장현(J. H. Sung) 한국생산제조학회 2006 한국생산제조시스템학회 학술발표대회 논문집 Vol.2006 No.5
Vickers hardness is one of the most widely useful methods to obtain mechanical properties of a product. The hardness number of a cold-forged product is in close relation with its effective strain. However, few attempts to obtain the relation not by empirical results but by only simulation have been made for the Vickers hardness test. This paper presents the method to predict the relation between effective strains and the hardness by using FE-simulation of the hardness test without time-killing experiments. The results of FE-simulation for the materials are compared with those of experiments and also compared with those of experiments of the previous study to show the feasibility of the proposed method.