고온 연강 유동특성을 상사하는 모델재료 개발에 관한 연구

이종헌,김영호,배원병,이원화 대한기계학회 1993 대한기계학회논문집 Vol.17 No.5

본 연구에서는 모델실험을 통해 실제재료에 관한 정량적인 정보를 얻기 위하 여 모델재료인 플리스티신에 라놀린(lanolin), 레진(resin)등을 첨가하여 새로운 유 동특성을 갖는 혼합 플라스티신을 개발하고자 하였다. 개발된 모델재료와 기존의 플라스티신을 MTS(Material Testing System)을 이용하여 링 압축실험과 실린더 압축 실험으로 온도와 변형률속도 변화에 따라 재료에 혼합된 첨가제가 모델재료의 마찰 특성과 기계적 성질에 미치는 영향을 조사하고 비교 검토하고자 한다. 또한 실제 재료의 다양한 가공공정을 시뮬레이션하기 위한 모델재료의 상사실험에서 다이와 소재 의 분리가 비교적 용이한 윤활제로 실링 페이퍼(sealing paper), 바셀린(vaseline)을 바른 실링페이퍼, 파우다(talc powder)의 마찰특성에 대해서도 연구되었다.그리고 조사된 모델재료들이 연강인 0.15%C강의 고온 (900.deg. C∼1100.deg. C)에서의 온도변화에 따 른 상사재료로 사용될 수 있는지의 타당성을 검토하고자 한다. Model materials are developed to achieve similarity of flow patterns for mild steels in forming processes at high temperatures. The model materials consist of pure plasticine and one or two additives such as resin and lanolin. To verify the similarity of flow patterns between physical modeling and compression of mild steels at high temperatures, ring and compression tests have been carried out with the developed-model materials at various strain rates, temperatures and lubricants. The test results are in good agreement with the flow patterns obtained from upsetting of a mild steel at high temperatures.

아크 용접에서 자화 디자인에 따른 물성 변화

이정현(Lee, Jung Hyun),이우람(Lee, Wooram) 한국전시산업융합연구원 2013 한국과학예술융합학회 Vol.13 No.-

본 연구는 자동차 및 조선 산업에서 널리 사용되는 연강으로 용접 공정 시 자화 영향에 따라 용접부 품질 및 기계적 성질을 평가하는 목적을 가지고 있다. 피복금속 아크 용접 공정 시 주로 이용되는 연강 재료를 사용하였다. 또한, 레이저 유도 분광기법(LIBS)을 이용하여 용접부 원소의 생성 및 감소 여부를 평가하였다. 특히 자계를 정량적으로 상승 시켜 자기력 변화에 따른 원소 별 파장, 성분 분석 및 미세 조직을 통하여 정량적인 변화를 규명하였다. 분석 결과에 따라 용접부 결함을 저감 시킬 수 있는 자기력을 제시하고 용접공정 시 최적의 조건을 도출하였다. 또한, 레이저 유도플라즈마 분광 기법을 통하여 용접 공정 후 동일한 위치의 성분을 분석하여 자계 영향에 따른 변화를 규명하였다. This study is concerned to the characterization of magnetic fields in a weld metal consisted of the mild steel, which are widely used in the automobile and shipbuilding industry. The sheets are used in these applications, which is mainly fabricated by arc welding. It also reports an interesting application of LIBS(Laser Induced Breakdown Spectroscopy) in order to determine the elemental composition diffusion of mild steel. In particular, the mechanical properties of the joint is influenced by not only geometrical and mechanical factors but also the welding conditions for the arc welded joint. Therefore, the mechanical properties and performance are evaluated by performing a physicochemical component analysis, which increases in mail steel content and microstructure. As results, appropriate range for magnetic fields could be achieved. Therefore, the effect of magnetic force in a butt weld of mild steel plates was investigated by comparing to the measured data.

연강의 습식 수중 아크 용접 특성에 관한 연구

곽희환(H. H. Kwak),김창규(C. G. Kim) 한국동력기계공학회 2007 동력시스템공학회지 Vol.11 No.1

연강의 습식 수중 아크 용접 특성에 관한 연구

곽희환(H. H. Kwak),김창규(C. G. Kim),김민남(M. N. Kim) 한국동력기계공학회 2004 한국동력기계공학회 학술대회 논문집 Vol.- No.-

Underwater wet arc welds were experimentally performed on 11mm thick SS400 mild steel plate as base metal by using six different types of flux coated electrodes of 4.0mm diameter; KSKR, KSKT, USBL, JPUW, UWEA, and UWES. As results, the developed flux coated underwater electrode had a good weldability compared with other domestic terrestrial electrodes. By rapid cooling rate, the hardness value of HAZ were increased by quenching effects. Mechanical properties for the multi-pass butt-welding specimen are also tested experimentally. The feasibility of the developed underwater electrode was experimentally studied and the results achieved in this wet arc welds have shown that the developed wet welding electrode UWEB can have a degree of integrity.

熱變形이 軟鋼의 破壞靭性에 미치는 影響

朴昌彦,金洙鏞 조선대학교 생산기술연구소 1982 生産技術硏究 Vol.1982 No.-

It is one of the most important cause of brittle fracture that hot strain embrittlement occurred in welding sructure during welding. It is known that hot strain deteriorates fracture toughness, and embrittlement by hot strain depends on strain-amount and straining temperature. But these relations are not known quantitatively and, also, the relation between fracture toughness and plastic deformation behavior at notch tip is not known. In this study, COD fracture toughness test has been applied to investigate the relation between hot strain and fracture toughness quantitatively. In addition, micro hardness survey and measuring of the plastic zone size by recrystallization technique were conducted to verify above mentioned relations. The results are summarized as follows; 1) Critical COD value, δc, of the specimens strained at 250℃ in mild steel is 'considerably decreased in comparison with the case of other conditions such as; 150℃, 200℃, 300℃, 350℃. 2) In each case of accumulated COD, ∑δt, is 0.2㎜ and 0.6㎜ at 250℃, transition temperature move toward high temperature region about 20℃ and 25℃ respectively. 3) In the specimen strained at 250℃, the maximum hardness value at notch tip is the highest and this value is increased with hot strain-amount. 4) The plastic zone size at notch tip of the specimen strained at 250℃ is the smallest. 5) Deterioration of fracture toughness of material due to hot strain depends upon the plastic zone size and maximum hardness value at notch tip. And that, because of the most significant effect of hot strain embrittlement caused at 250℃, this would be the most effective temperature of hot strain embrittlement in mild steel.

적외선 카메라에 의한 연강의 비파괴 평가에 대한 연구

한정섭(JEONG-SEB HAN),박진환(JIN-HWAN PARK) 한국해양공학회 2008 韓國海洋工學會誌 Vol.22 No.2

The application of infrared thermography for detecting defects under the surface of a material was studied. Defects in a specimen were made by back-drilled circular holes. To get alarge temperature difference at the surface, a halogen lamp was used for surface heating. We confirmed that the defect location had a good relationship with the maximum temperature difference. The sizes of the defects could be calculated by means of the FWHM. The value of the FWHM of a temperature difference decreased with time. Therefore in an extremely short time after the heating, the true defect size could be measured.

FEM을 이용한 자동차 타이어용 알류미늄 합금 금형의 열변형 특성에 관한 연구

오율권,서동표,양호동,박근욱,김용범 朝鮮大學校 機械技術硏究所 2006 機械技術硏究 Vol.9 No.1

대부분의 타이어 제조를 위한 금형생산 공정은 실험적인 결과에 바탕을 두어 거의 경험치에 의존하고 있다. 이러한 방법은 금형제품을 생산하는데 있어 비효율적이고 비경제적인 측면이 많다. 따라서, 정밀도를 향상시키고 품질이 좋은 타이어를 제조하기 위해 금형의 제조공정은 재평가가 이루어져야 한다. 본 연구에서는 자동차 타이어용 알루미늄 합금 금형의열변형 및 특성을 조사하기 위해 유한요소법을 이용하여 수치해석적으로 연구를 수행하고자 하였다. 알루미늄 합금의 금형의 열변형 및 특성에 관해 조사하기 위해, 알루미늄 합금 금형 내부에서 발생되는 온도분포, 수축량, 응력 그리고 변형량을 수치해석적으로 계산하는연구를 수행하였다. 뿐만 아니라, 정밀도를 향상시키고 좋은 품질의 금형을 얻기 위해, 알루미늄 합금과 연강의 수치해석 결과를 비교하였다. 결국, 수치해석을 통해 얻은 결과들은향후 효과적이고 최상의 금형 제품을 제작하는데 도움을 줄 수 있으리라 본다. Most the mold product process is based on a experimental results and is almost dependent on experiments for tire manufacturing. This method produced the mold product is not only the ineffectiveness but also the bad economy. So, the product process of metal mold should be revaluated to produce the improved precision and good quality of tires. In this study, numerical analysis applied a finite element method (FEM) was used to predict the thermal strain characteristics of Aluminum (AI) alloy mold for automobile tire. To investigate the thermal strain and characteristics of Al alloy mold, it was performed that the temperature distribution. the contraction rates, the stress and the strain occurred on the inside of Al alloy mold was calculated by numerical works. Moreover, numerical analysis results of Al alloy mold were compared with those of mild steel mold in order to obtain the improved precision and good quality of mold. So, the numerical results of this study will be presented to help to make the effective and the best mold products.

軟鋼(SB41材)의 衝擊에너지와 破壞靭性에 관한 硏究

韓吉永 朝鮮大學校 動力資源硏究所 1982 動力資源硏究所誌 Vol.4 No.1

Ag-Ti계 합금을 사용한 SiC/SiC 및 SiC/연강 브레이징에서 브레이징 조건이 접합강도에 미치는 영향의 연구

이형근,이재영 대한용접접합학회 1997 대한용접·접합학회지 Vol.15 No.5

The microstructure and bond strength were investigated on the SiC/SiC and SiC/mild steel joints brazed by Ag-5at%Ti alloy. Ag-5at%Ti-2at%Fe and -5at%Fe brazing alloys were also used to see the effects of Fe addition on the bond strength of SiC/SiC brazed joints. Brazing temperature and brazing gap were selected and examined as brazing variables. The microstructure of SiC/SiC brazed joints was affected by Fe addition to the Ag-5at%Ti alloy, but the bond strength was not. Increasing brazing temperature also changed the microstructure of $Ti_5Si_3$ reaction layer and brazing alloy matrix of the SiC/SiC and SiC/mild steel joints, but not the bond strength. Brazing gap had a great effects on the bond strength. Decreasing brazing gap from 0.2 mm to 0.1 mm in SiC/SiC brazing increased the bond strength from 187 MPa to 263 MPa and, in SiC/mild steel brazing, from 189 MPa to 212 MPa. It was concluded that the most important parameter on the bond strength in SiC/SiC and SiC/mild steel brazing was the relative ratio between brazing gap and specimen size.

Ag-Ti계 합금을 사용한 SiC/SiC 및 SiC/연강 브레이징에 대한 연구

이형근,이재영 대한용접접합학회 1996 대한용접·접합학회지 Vol.14 No.4

The microstructure and bond strength are examined on the SiC/SiC and SiC/mild steel joints brazed by the Ag-Ti based alloys with different Ti contents. In the SiC/SiC brazed joints, the thickness of the reaction layers at the bond interface and the Ti particles in the brazing alloy matrices increase with Ti contents. When Ti is added up to 9 at% in the brazing alloy. $Ti_3SiC_2$ phase in addition to TiC and $Ti_5Si_3$ phase is newly created at the bond interface and TiAg phase is produced from peritectic reaction in the brazing alloy matrix. In the SiC/mild steel joints brazed with different Ti contents, the microstructure at the bond interface and in the brazing alloy matrix near SiC varies similarly to the case of SiC/SiC brazed joints. But, in the brazing alloy matrix near the mild steel, Fe-Ti intermetallic compounds are produced and increased with Ti contents. The bond strengths of the SiC/SiC and SiC/mild steel brazed joints are independent on Ti contents in the brazing alloy. There are no large differences of the bond strength between SiC/SiC and SiC/mild steel brazed joints. In the SiC/mild steel brazed joints, Fe dissolved from the mild steel does not affect on the bond strength of the joints. Thermal contraction of the mild steel has nearly no effects on the bond strength due to the wide brazing gap of specimens used in the four-point bend test. The brazed joints has the average bond strength of about 200 MPa independently on Ti contents, Fe dissolution and joint type. Fracture in four-point bend test initiates at the interface between SiC and TiC reaction layer and propagates through SiC bulk. The adhesive strength between SiC and TiC reaction layer seems to mainly control the bond strength of the brazed joints.