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ISM에 의한 摩擦熔接材(SUH3-SUH35)의 高溫 크리프 壽命豫測에 관한 연구
오세규(Sae-Kyoo Oh),이원석(Won-Suk Lee) 한국해양공학회 1997 韓國海洋工學會誌 Vol.11 No.4
There are many research results as individual uni-axial tension creep test of heat-resisting materials. However, there are very few about the study on the high temperature creep test for the Initial Strain Method, and especially any study on it about the friction welded joints of SUH3 to SUH35.<br/> One of the important concerns is a reliable method of evaluating static creep properties. No reliable method seems available at present to evaluate or predict static creep properties. So, the reliable method to evaluate and predict them by the ISM and AE techniques was made.
오세규(Sae-Kyoo Oh),김연호(Yeon-Ho Kim),이상국(Sang-Guk Lee),이종두(Jong-Doo Lee) 한국해양공학회 1989 韓國海洋工學會誌 Vol.3 No.2
It has been very important in various industry fields to improve the fatigue strength characteristics of bearings such as bearing life, fatigue limit, etc., because such poor properties could result in shortening the machinery life as well as in decreasing the accuracy. However, no successful heat treatment criterion seems to be available at present.<br/> In this study, the effect of the 170℃×120min tempering cycles repeated after 830℃×30min oil quenching for 800℃ spheroidizing-annealed bearing steel (STB2) as base metal on the 120℃ high temperature rotary bending fatigue strength characteristics were investigated, including the effects on hardness, Charpy impact value and micro-structure, in order to seek for the best heat treatment condition finally. The important results obtained are as follows :<br/> 1) The optimal cycle of tempering so that the fatigue strength σ could become the highest was the 4th cycle. And it is confirmed that this σF is about 6 times more increased than that of base metal, and about 1.3 times more increased than the case of the 1 cycle tempered.<br/> 2) As a result of the investigation for the effects of tempering cycles on hardness, the hardness at the tempering number of 2 thru 5 cycles was not decreased severely ; only about 10% decrease from those of the quenched and 1 cycle tempered case. Such hardness is equivalent to HRC61~62 with no bad effect on anti-abrasion of bearing steel.<br/> 3) In the case of 2 thru 5 cycle tempering as well as 1 cycle tempering, the impact value was not so improved comparing with the case of quenching, but an increase of 5 to 10% could be expected at least.<br/> 4) It was experimentally confirmed that the control of the mechanical properties improvement such as fatigue strength and fatigue life for bearing steels could be possible by the number of tempering cycles.
마찰용접에 의한 드릴 생산에서의 AE에 의한 실시간 품질평가에 관한 연구
오세규(Sae-kyoo Oh),윤인진(In-jin Yoon),오정환(Jung-hwan Oh),오명석(Myeong-seok Oh) 한국해양공학회 1993 韓國海洋工學會誌 Vol.7 No.2
A study off riction welding of high speed steel(SKH 51) bar for blade side to carbon steel (STC 3) bar for shank side was carried out experimentally through tensile test, hardness test, microstructure, and acoustic emission(AE) test.<br/> So, this paper deals with optimizing the welding conditions and the real-time quality (strength) evaluation of friction welded joints by acoustic emission technique.<br/> The results obtained are summarized as follows :<br/> (1) For friction welded joints of SKH 51 to STC 3 steel bars, the total upset (U) increases linearly with an increase of heating time (t₁).<br/> (2) The determined optimum welding conditions are heating time (t₁) 7~9 sec, upsetting time (t₂) 5 sec, heating pressure(P₁) 12 ㎏<SUB>f</SUB>/㎟, upsetting pressure(P₂) 15 ㎏<SUB>f</SUB>/㎟ and rotating speed(n) 2,000 rpm, resulting in a computed relationship between the tensile strength of the joint σ (㎏<SUB>f</SUB>/㎟) and the heating time t₁ (sec) as the following : σ=2.39t₁<SUP>1.382</SUP><br/> (3) The quantitative relationship equation between AE cumulative counts(N) and the tensile strength(a) of the welded joints friction-welded under the obove optimal condition is computed as the following : σ=0.07N<SUP>0.61</SUP><br/> (4) From the quantitative relationship between the accumulated AE total count and the welding strength, it was confirmed that the nondestructive real-time evaluation of welding quality(strength) could be possible.
유공압 밸브 스풀용 강재의 봉대봉 이종재 마찰용접 최적화와 용접강도 특성 및 AE 평가
오세규(Sae-Kyoo Oh),유인종(In-Jong Yoo),오정환(Jung-Hwan Oh),박형동(Hyung-Dong Park),이연탁(Yeon-Tack Lee) 한국해양공학회 1996 韓國海洋工學會誌 Vol.10 No.3
Up to now, most of studies on mechanical properties in friction welded components are about tensile and bending strength. However the fatigue studies on the friction-welded components subjected to repeated stress are not available. The purposes of this study are the development of fundamental design and manufacturing technique of hydraulic valve spool by optimizing of friction welding, and the development of in-process real-time weld quality evaluation technique by acoustic emission for the bar-to-bar dissimilar friction welding of hydraulic valve spool steels.
摩擦熔接에 의한 超硬工具材와 金屬間의 壓接技術開發과 AE에 의한 品質評價
오세규(Sae-Kyoo Oh),전태언(Tae-Eun Jeon),박일동(Il-Dong Park),오명석(Myeong-Suk Oh),이주석(Joo-Suk Lee) 한국해양공학회 1996 韓國海洋工學會誌 Vol.10 No.1
This paper deals with determinig the proper friction welding condition and analyzing various mechanical properties of friction welded joints of sintered carbide tool materials(K20, P25 and SKDX5 for the blade part of drill or press punch) to alloy steel (SKH4, SCM440 for the shank part of drill or press punch), the alloy steel to aluminum(A6061 for the interlayer material between the blade part and the shank) and sintered carbide tool materials to aluminum. And also acoustic emission test will be carried out during fiction welding to evaluate the weld quality.