자동차용 강판의 점용접성에 관한 연구

배석천,민준기 啓明大學校 産業技術硏究所 1997 産業技術硏究所 論文報告集 Vol.20 No.-

The resistance spot welding is widely used for automotive assembling, electric manufacture and airplane industry. Parametric studies, welding current, welding time, and electrode forec, has been madeto to investigate spot weldability, microstructure of welding zone, TSS and CTS of SPC, HPC, SPC Zn and SPC Zn-Fe. Some of important results derived in this study are followed : - In spot welding, weldability is moved into the lower welding current area as the tensile strength of sheet metal increases, and for the optimum welding condition the electroplated steel sheet requires higher current comparing with uncoated steel plate. - The electrode force and welding time obviously affects the TSS, CTS, but the critical range of representing ultimate welding strength is observed - Indentation formed by over welding current causes a decrease in the welding strength. - CTS and ductility ratio of HPC are increased by the tempering treatment. The improvement of these mechanical properties is marked for the higher strengthened base metal among HPC.

Inconel 600 접합용 적정용가재 성분계 설정에 관한 연구

배석천 啓明大學校 産業技術硏究所 1997 産業技術硏究所 論文報告集 Vol.19 No.2

The main objective of this study is to develope the insert metal foil for joining Ni-base heat-resistant alloys. As the purpose of the project, joining the materials such as Inconel 600, a studied by using commercial brazing insert metals. The brazed interface was analyzed and the effect of alloying elements on spreadability and strength was investigated. The suitable components of insert metals for joining Inconel 600 were selected by evaluating these properties. These properties including microstructures were compared with the developing insert metals of Ni-Zr-Cr for Inconel 600 and which were produced experimentally in the laboratory.

Ti 함유 저탄소강의 재결정거동에 관한 연구

배석천,이상우 啓明大學校 産業技術硏究所 1998 産業技術硏究所 論文報告集 Vol.21 No.2

AH강의 재결정거동을 조사한 결과, AH강의 재결정속도는 Ti-V강에서 보고된 것에 비해 훨씬 빠르며, C-Mn강의 속도와 유사하였다. 반면 재가열입도 및 재결정입도는 Ti-V강에서 예측되는 것보다는 조대하지만, C-Mn강의 경우보다는 미세하였고, 재결정립성장속도도 Ti-V강에서와 같이 성장이 억제되지는 않지만 C-Mn강의 경우보다는 다소 늦은 속도를 보였다. 이상의 결과에서 AH강 내의 TiN 입자는 재결정속도에는 영향을 미치지 못한다고 추론되며, 결정립의 크기에는 어느정도 영향을 미친다고 판단된다. 즉, TiN의 크기는 Roberts등이 제시한 임계크기(5-20nm)보다는 커서 결정립성장 억제 효과가 크지 못하지만, 이들 TiN이 재결정립의 크기나, 결정립의 성장등을 지연시키는 효과가 상당히 있는 것으로 평가된다. 이상의 재결정거동을 고려할 때, AH강을 압연한 후의 오스테나이트 입도는 Ti-V강에서 예측되는 만큼 미세하지는 못하지만, Ti가 첨가되지는 않은 단순 C-Mn강에서 얻어지는 입도보다는 미세하고, 압연이력을 조절하면 보다 효과적인 Austenite condition을 얻을 수 있을 것으로 사료된다. Recrystallization behavior of Ti-bearing low carbon steel(AH grade steel) was studied to investigate the effect of deformation on the recrystallization kinetics and grain size of austenite during recrystallization controlled rolling process. Using hot deformation simulator, the reheated grain size, recrystallization kinetics, recrystallized austenite grain size and grain growth were investigated. And the prediction equations were suggesred by regression of experimental results. Ti-added AH32 steel showed faster recrystallization kinetics than that reported by other researchers in Ti-V steel. Recrystallization kinetics of AH steel was almost the same as that of Ti-free C-Mn steels. Although the recrystallized austenite grain was smaller than that predicted in C-Mn steel, it was larger than that predicted by other researchers in Ti-V steel. Growth rate of recrystallized austenite of AH steel was slower than that of C-Mn steel, but was a little faster than that reported by other researchers in Ti-V steel. From the results, it could be known that TiN particles in AH steel did not remarkably affected the recrystallization kinetics of deformed austenite and played a little role in retarding the grain growth. These results seemed to occur because the size of TiN in AH slab was not fine enough to restrict the recrystallization effectively. Considering the recrystallization behavior of AH steel, however, the effective austenite condition after recrystallization controlled rolling could be obtained by delicate control of rolling schedule.

Ni base계 초내열 합금 접합용 극박 Insert Metal 개발

배석천 啓明大學校 産業技術硏究所 1997 産業技術硏究所 論文報告集 Vol.19 No.2

The purpose of this study is to develop new brazing insert metals for Ni-base superalloy 14 kinds of insert metals based on Ni-Zr-Cr system for Ni-base superalloy brazing were newly designed, manufactured by melt spinning process and tested on wettability, brazing conditions, microstructure of bonded area and bonding strength at high temperatures. Main results are as follows. For the brazing of Ni-base superalloys such as Inconel 718 and Rene' 41, insert metal of Ni-6Cr-3B-1Zr-1Al composition was newly developed and exhibited excellent brazeability. The bonding strength of Inconel 718 brazed joint was 98.6kgf/mm²at room temperature and 80-62 kgf /mm²at elevated temperature of 540-760℃, which were higher values than those of commercially producted insert metals. Another insert metal of Ni-11P-6Cr-1Zr-1Al compositions which has relatively low melting point was also manufactured under the form of amorphous foil. Two kinds of above insert metals represented good brazeability not only for Inconel alloy but for Rene' 41. The brazing temperature of Ni base superalloy with developed insert metals was 1150℃ for Rene' 41 alloy and 1120℃, for Inconel 718 alloy. However, the brazing temperature could be lower when the insert metal of amorphous structure applied. Some of developed insert metals possess better brazeability than commercially producted insert metals.

용융 아연 도금 강판의 Braze-Welding 기술 개발에 관한 연구

배석천 啓明大學校 産業技術硏究所 1996 産業技術硏究所 論文報告集 Vol.19 No.1

The final results of the study on applicability of braze-welding process to improve the characteristics of brazed joints of galvanized steel plate are summarized as follows; -At the Ar 96% and CO₂4% of gas mixture ratio for the most appropriate brazed joint formation of galvanized steel plate, the most ideal brazed seam was formed. -Also for the smooth outgasing of melted pool, the lower welding speed in a low current, compared to the welding condition in general, is required. -In case of applying MIG and TIG process, of the filler metal used, the Cusi₂Mn produced the excellent metallurgical trait of brazed joint. When CuAl8 filler metal was used, the formation of Fe-rich phase of FeAl system due to the familiarity between Fe and Al harmed the trait of brazed joint. However, in case of applying the optimal brazing condition for the two processes, the formation of Zn coating free zone between the brazed joint and the base material, coming out of the existing welding process using Oxygen-Acetilen and CO₂, was restrained, and at the same time, the brazed joint of good quality was obtained due to the low brazed temperature formed by the melting temperature of applied filler metal lower than the base material Fe.

저탄소 후판 제조공정에서의 상변태 및 기계적성질 예측모델에 관한 연구

배석천,이상우 啓明大學校 産業技術硏究所 1998 産業技術硏究所 論文報告集 Vol.21 No.2

To develop a structure property prediction and control(SPPC) model for manufacturing process of steel plates, the prediction models for phase transformation and mechanical properties for manufacturing process of low carbon steel plates was studied. First of all, the SPPC model for hot strip steel was theoretically reviewed. The difference in processing parameters of hot strip mill and plate mill was analyzed in details. The austenite conditioning model of hot strip mill was adopted "as is", and the transformation model and mechanical model were revised based on the data obtained from experiment. The incubation time and reaction coefficient for ferrite transformation were changed in according to the experimental results. And banite transformation start temperature was also changed. As to the mechanical property model, the equational from was revised and coefficient of each term was determined by multiple regression of actual data. Relationship between predicted mechanical property and calculated one using newly developed SPPC model was improved. For elongation prediction, more research has to be carried out to increase the predictability.

7022계 합금의 Plasma Arc 용접성에 관한 연구

배석천 啓明大學校 産業技術硏究所 1997 産業技術硏究所 論文報告集 Vol.20 No.-

Recently the advanced material such as the high-strength plastic once widely used loses its advantages in respect of material recycling and nature conservation, which are hot issues in all industrial fields. Therefore, the high-strengthened 7022 AI alloy is highly recommanded as a replaceable material. High density welding process utilizing heat source such as Plasma Arc should be developed to reduce pore and hot cracking, which are usually accompanied by Metal Inert Gas and Tungsten Inert Gas welding processes. According to results in plasma arc weldments, the weld edge with a lot of pores, which has resulted from the hydrogen and other impurity on the base metal and filler metal surface during the welding process, was the source of fracture of weldments but hot cracks were not observed.

열교환기용 AIMgSi1.0 합금의 접합부 강도 특성 개선에 관한 연구

배석천 啓明大學校 産業技術硏究所 1996 産業技術硏究所 論文報告集 Vol.19 No.1

The application of aluminum alloy has been gradually increased as the variety of industrial structures, anti-pollution, low fuel cost and recycling of used material are required to modern society. Especially, the application of the brazing process as a new joining technology has been increasing in the case of a complicated product like heat exchange facility. To serve the need, this investigation introduces the comparison of torch brazing process was furnace brazing process where AlSil2, ZnAl5 filler metal and flux(F600), flux(F400M) were applied to the base material, AlMgSil.0. The result of the experiment showed that the specimen in which furnace brazing process was applied with AlSil2 filler metal and flux(F600) had more excellent mechanical and metallurgical properties. According to our result, the most important factor of brazed seam characteristics of AlMgSi1.0 alloy was the effect of flux. The ZnAl5 filler metal, when compared to AlSi12, had an excellent strength property which was as strong as AlSi12 filler metal at 200℃. However, the application problem has occurred due to the low fatigue strength.

Ni-base계 초내열합금 접합용 적정용가재 성분계 설정에 관한 연구

배석천 啓明大學校 産業技術硏究所 1997 産業技術硏究所 論文報告集 Vol.19 No.2

This study is the second part of on-going project scheduled, of which the main objective is to develop the new insert metal foils for joining Ni-base heat resistant alloys. In this study, seven kinds of newly designed insert metal for Ni-base alloy were manufactured in laboratory and tested in wettability, brazability and bonding strength in comparison with the commercial insert metals.

수동 미세각막절삭기를 이용한 라식 근시교정술후 유발된 난시의 변화

이종석(Jong Seok Lee),배선량(Sun Ryang Bae),주천기(Choun Ki Joo) 대한안과학회 2000 대한안과학회지 Vol.41 No.2