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[論文] 연강의 결정학적 경계가 기계적 성질에 미치는 영향
임병수(Byeong Soo Lim),이창훈(Chang Hoon Lee) 한국자동차공학회 1984 오토저널 Vol.6 No.4
The experimental investigation has been made to determine the effect of crystallographic boundaries and chemical composition on the strength and hardness using mild steels of SAE 1016 and 1022.<br/> Through heat treatments and quantitative analysis, different microstructures varying in grain size from 4.4㎛ to 23.2㎛ and in Fe₃C particle spacing from 0.56㎛ to 2.46㎛ were obtained.<br/> Mechanical properties of yield strength, tensile strength and micro vickers hardness were measured and the relationship between these properties and microstructures were obtained.<br/> Some of the conclusions are as follows; When mild steels are strengthened by both grain size hardening and Fe₃C precipitation hardening mechanisms;<br/> (1) the yield strength, σ_y, can be expressed in kg/mm²as σ_y=σ_t+2.35d^-½+0.0022λ^-1<br/> where σ_t: constant, d: grain size(mm), λ:Fe₃C particle spacing(mm).<br/> (2) the micro vickers hardness, MVH, can bc cxprcssed as <br/> MVH(P=500g)=H_o+5.29d^-½+0.0132λ^-1(SAE 1016)<br/> MVH(P=500g)=H_o+3.32d^-½+0.0111λ^-1(SAE 1022)<br/> where H_o is constant.<br/> (3) the tensile strength, σ_t,s. can be expressed in kg/mm² as<br/> σ_t,s^mix σ_o+1.72d^-½<br/> where σ_o is constant.<br/>
플라즈마 침탄 공정을 이용한 SCM415강의 표면 경화 특성
김대욱,김동원,임병수,김석범,Kim, Dae-Wook,Kim, Dong-Won,Lim, Byeong-Soo,Kim, Seuk-Buom 한국재료학회 1998 한국재료학회지 Vol.8 No.8
현재 자동차용 소재 및 기계부품에 폭넓게 이용되는 SCM415강의 플라즈마 침탄 특성을 연구하기 위해 가스조성, 압력, 전류밀도, 온도 및 시간을 변수로 사용하였다. 가스조성의 경우 저합금강에서는 수소 가스 효과보다 메탄가스에 의해 주로 침탄특성이 좌우되며 메탄가스 100%일 때 시편 내의 모든 방향에서 경화층 분포가 일정하고, 최대의 유효경화깊이를 얻을 수 있었다. 가스압력이나 플라즈마 전압이 상승할 때 전류밀도가 상승하게 되는데, 이에 따라 최표면의 탄소농도가 증가되어 강의 유효경화깊이는 증대되었다. 침탄 온도일 경우 적어도 85$0^{\circ}C$이상되어야 유효경화깊이를 얻을 수 있었고, 온도가 상승할수록 유효경화깊이의 증가를 나타내어 침탄 효과가 우수하였다. 탄소의 확산 깊이는 침탄 시간의 제곱근에 비례하는 것으로 나타났다. 플라즈마 치탄한 강의 피로강도를 평가한 결과 열처리하지 않은 시편이나 재가열처리한 시편에 비해 높은 피로강도를 나타내었다. The influence of plasma carburizing process on the surface hardness of SCM415 low-alloy steel (0.15% C) was investigated under the various process conditions of gas composition. gas pressure, plasma current density. temperature and time. The effective case depth was found to depend on the amount of methan gas containing carbon. thus the deepest case depth and the uniform hardeness were obtained with the 100% methan gas. The case depth increased with the plasma current density. The effective plasma carburizing temperature of SCM415 steel was found to be higher than 85$0^{\circ}C$, and the case depth was proportional to the square root of carburizing time under the same current density. The bending fatigue strength of the plasma carburized specimen is' higher than those of as- received specimen or reheat-quenched specimen.
반용융 성형가공한 SiCp / AZ91HP Mg 복합재료의 피로 및 내마모 특성
하홍수,김명균,안선규,임병수,김영직 ( Hong Soo Ha,Myoung Gyun Kim,Sun Kyu Ahn,Byeong Soo Lim,Young Jig Kim ) 한국주조공학회 1997 한국주조공학회지 Vol.17 No.5
N/A The effect of size and mass fraction of SiC particulate on the fatigue and wear have been investigated for semi-liquid formed SiCp/AZ91HP Mg composites. In the study, different particulate sizes of 7, 20, 50 ㎛ were prepared with various mass fraction for sample preparation. By tension-tension fatigue tests, whose procedures are standardized in ASTM standard 647E-93, the da/dN vs. ΔK curves were obtained. Also, the crack propagation paths were observed by optical microscope. As a result of wear test, specific wear loss is decreased with increasing mass fraction and particulate size. Specific wear loss of 30 mass% 50 ㎛ SiC reinforced Mg composite is compared to SKD11. (Received July 21, 1997)
소형 펀치 시험법을 이용한 열화된 P92강의 크리프 거동 특성 평가
기동현(Dogn-hyun Ki),임병수(byeong-soo Lim) 한국자동차공학회 2004 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Recently, the number of high temperature components that are being used under high pressure and temperature, is increasing and for better thermal efficiency, new high temperature materials are being developed. Such effort required development of nod· high temperature materials, which have better high temperature properties and as the result, P92 steel is developed as a piping material.<br/> In this study, the creep behavior of P92 is observed by Small punch creep test method at 600℃ and characteristics were investigated using Base metal, weld metal, heat affected zone of P92 steel that has been exposed to the welding process.
G91강 저주파 피로균열 성장에 미치는 온도와 응력비의 영향
김종범 ( Jong Bum Kim ),황수경 ( Soo Kyung Hwang ),김범준 ( Bum Joon Kim ),이종훈 ( Jong Hoon Lee ),박창규 ( Chang Gyu Park ),이형연 ( Hyeong Yeon Lee ),김문기 ( Moon Ki Kim ),임병수 ( Byeong Soo Lim ) 대한금속재료학회 ( 구 대한금속학회 ) 2012 대한금속·재료학회지 Vol.50 No.4
9-12% Cr steels have been used in thermal power plants which repeat start and stop operations. Major factors of fatigue life are temperature, frequency, stress ratio, holding time, microstructure, and environment. Normally, fatigue life decreases at high temperature, low frequency, high stress ratio, and long holding time conditions. A Mod.9Cr-1Mo steel, called G91, was developed at ORNL (Oak Ridge National Laboratory, USA) and was adopted as a high-temperature structural material in the ASME Code in 2004. However, its low-cycle fatigue and fatigue crack growth characteristics have been rarely studied. In this work, we have investigated the low-cycle fatigue crack growth behaviors of G91 steel under various test conditions in terms of temperature and stress ratio. As temperature and stress ratio increase, the crack growth rate becomes faster and striation distance also increases. On the other hand, the number of branch cracks decreases.
[재료부문] 사다리꼴 하중 파형의 크리프-피로 균열성장에 미치는 cavity의 영향
김범준(Bumjoon Kim),정찬서(Chanseo Jeong),임병수(Byeong Soo Lim) 한국자동차공학회 2001 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2001 No.11_2
Most of the high temperature components are subjected to both creep and fatigue damage due to their cyclic loading condition.<br/> In this study, the crack growth behavior in P92 steel(9%Cr-2%W) was investigated at 600℃ under trapezoidal waveshape with various loading and unloading time. Also, the relationship between the crack growth rate and the size and density of cavity that was generated by creep effect was studied. As the result, the crack growth rate increased with increase in total amount of time per cycle and under same total amount of time, the crack growth rate was found out to be the same. However, the crack growth rate in P92 steel(weld metal) was higher than P92 steel(as received) under same waveshape. This behavior is believed to be due to the cavity growth in weld metal. In weld metal, the crack growth rate increased with the increase in cavity size and density under the waveshape of 500sec. loading time-5sec. tensile hold time-l sec. unloading time due to reduced fatigue life.<br/>