X-선을 이용한 열교환기 브레이징 접합부 결함 검출

김진영,서상우,Kim, Jin-Young,Seo, Sang-Woo 제어로봇시스템학회 2011 제어·로봇·시스템학회 논문지 Vol.17 No.10

The quality of brazing joints is one of the most important factors that have an effect on the performance of the brazing joint-based heat exchangers with the growing use in industry recently. Therefore, it is necessary to inspect the brazing joints in order to guarantee the performance of the heat exchangers. This paper presents a non-destructive method to inspect the brazing joints of the heat exchangers using X-ray. Firstly, X-ray cross-sectional images of the brazing joints are obtained by using CT (Computerized Tomography) technology. Cross-sectional image from CT is more useful to detect the inner defects than the traditional transmitted X-ray image. Secondly, the acquired images are processed by an algorithm proposed for the defect detection of brazing joint. Finally, two types of brazing joint are examined in a series of experiments to detect the defects in brazing joints. The experimental results show that the proposed algorithm is effective for defect detection of the brazing joints in heat exchangers.

브레이징 접합공정 조건이 SiN₄/S.S. 316 접합체의 기계적 특성 및 신뢰도에 미치는 영향

장희석,박상환,최성철,Chang, Hwi-Souck,Park, Sang-Whan,Choi, Sung-Churl 한국세라믹학회 2002 한국세라믹학회지 Vol.39 No.10

활성 금속 브레이징법의 공정변수인 브레이징 온도 및 시간의 변화가 Cu buffer layer를 사용한 $Si_3N_4$Stainless steel 316 접합체의 기계적 특성 및 신뢰도에 미치는 영향을 규명하기 위하여 브레이징 조건 변화에 따른 접합계면 미세구조 변화를 조사하였다. 900${\circ}C$ 이상의 온도에서 브레이징 된 접합체에서는 Cu buffer layer가 브레이징 합금에 용해되어 연속 Cu층을 유지하지 못하였으며, $Si_3N_4$/brazing alloy 계면에서 계면 반응물 층의 두계도 급격히 증가하였다. 950${\circ}C$에서 브레이징된 Cu buffer layer를 사용한 $Si_3N_4$/Stainless steel 316 접합체의 파괴강도는 접합체 내 잔류응력의 증가로 급격히 감소하였다. 950${\circ}C$ 이하의 온도에서 브레이징 시간의 변화는 Cu buffer layer를 사용한 $Si_3N_4$/Stainless steel 316 접합체의 파괴강도 및 파괴경로에 큰 영향을 미치지 못하였다. The microstructure change of brazed $Si_3N_4$/Stainless steel 316 joint with Cu buffer layer were examined to clarify the effects of brazing process conditions such as brazing time and temperature on the mechanical properties and reliability of brazed joints. For the brazed joint above 900${\circ}C$, the Cu buffer layer was completely dissolved into brazing alloy and the thickness of reaction product formed at $Si_3N_4$/brazing alloy joint interface was abruptly increased, which could increase the amounts of residual stress developed in the joint. The fracture strength of brazed $Si_3N_4$/Stainless steel 316 joint with Cu buffer layer at 950${\circ}C$ was much reduced comparing to those of joints brazed at the lower temperature. But, it was found that the effects of brazing time was not critical on the mechanical properties as well as the reliability of $Si_3N_4$/Stainless steel 316 joint with Cu buffer layer brazed at the temperature below 900${\circ}C$.

논문 : 용접 및 접합 ; Al-Si-Mg-Cu-Ge 필러합금에 의한 6061알루미늄합금의 진공브레이징

이태원 ( Tae Won Lee ),이지환 ( Chi Hwan Lee ),이두면 ( Doo Myun Lee ),김종훈 ( Jong Hoon Kim ) 대한금속재료학회 ( 구 대한금속학회 ) 1998 대한금속·재료학회지 Vol.36 No.6

The vacuum brazing of 6061 aluminium alloy with Al-12Si-1Mg-5Cu-xGe(x=0, 10, 20wt.%) braze alloy has been conducted at temperatures ranged 530~570℃ for 60min under brazing pressure of 1MPa to investigate the braze joint microstructure. the joint strength and the wettability of braze alloy. The liquidus temperatures of braze alloys with Ge=0, 10, 20wt.% were 572℃, 558℃ and 541℃, respectively. The wettability of braze alloy was found to be improved with increasing the brazing temperature. Braze joint microstructure was varied with the brazing temperature. Under low brazing temperatures(≤550℃, the silicon and germanium, which are expected to be the elements present in the braze alloy, are observed at the braze joint. On the other hand, these elements were not detected under the brazing temperature of 570℃. This may be due to the diffusion of the elements into 6061 aluminium alloy. The joint strength was found to be increased with increasing the brazing temperature. The maximum joint strength was obtained at 570℃ brazing temperature and its value was 73% of tensile strength of the base metal.

구리-알루미늄 이종재료의 브레이징 특성 향상에 관한 연구

정호신(HO-SHIN JEONG),배동수(DONG SU BAE),고성우(SUNG WOO KO) 한국해양공학회 2001 韓國海洋工學會誌 Vol.15 No.3

One of the most important considerations to braze Cu-Al dissimilar materials is control of brittle metallic compound which makes it difficult to obtain a sound brazed joint. Nowdays, several attempts were made to control the metallic compound. But effective method for controlling metallic compound was not established. In this point of view, commercially pure aluminum and copper were used as base metal and Al-Si-X and Zn-Al-X alloy systems were developed as filler metal. Brazing was carried out to find optimum conditions for Cu-Al dissilmilar joint.<br/> The results obtained in this study were summarized as follows:<br/> 1) The joint brazed by Al-Si-X filler metal showed good brazeability and mechanical properties. The tensile strength of the joint brazed over solidus temperature was more than 90% of Al base metal. Especially, the joint brazed at liquidus temperature was fractured in the Al base metal.<br/> 2) Fluorides fluxes(a mixture of potassium fluoro-aluminates) were used to improve surface cleanliness of base metal and wettability of Al-Si-X filler metal. It was melted at the temperature about 10℃ lower than that of the filler metal, and made appropriate brazing environment. Therefore, it could be a proper selection as flux.

브레이징 접합부의 고장원인 및 강도 특성 평가

강기원(Ki-Weon Kang),이병재(Byung-Jei Lee),장경영(Kyung-Young Jang),김정규(Jung-Kyu Kim) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5

In order to understand failure cause and stress analysis, strength evaluation of joints and non-destructive test were done for brazing joint of copper pipe in household air conditioner. Strength of brazing joint was evaluated by shear test and test specimens were used by standard single lap form and actual form of brazing joint in copper pipe. In order to evaluate the effect where the temperature has an influenced on the joint during this brazing joint processing, micro vickers hardness is measured. Also, three dimensional X-ray non-destructive test was used to know defect existence of brazing joint. Internal pressure breaking tester was designed and was performed to make higher oil pressure by specific ratio within the interval of time.

마그네슘합금과 철강 이종소재의 레이저 브레이징 특성에 미치는 도금층의 영향

Lee, Mok-Young,Kim, Sook-Whan,Nasiri, Ali M.,Zhou, Norman Y. 대한용접접합학회 2013 대한용접·접합학회지 Vol.31 No.4

The dissimilar welding between magnesium alloy and steel sheet was required in automobile industry to increase the strength of the dissimilar joints. Laser brazing is one of the good joining processes for Mgsteel dissimilar joint. In this study, the effect of coating materials was evaluated on the laser brazing for the dissimilar joint between AZ31 and coated steels such as Zn, Sn and Ni. Diode direct laser was used to braze the lap-edge joint with Mg600 filler wire and Superior #21 flux. The wettability was best on Zn coated steel. The interlayer was formed at the interface between brazement and steel for all coating materials. The strengths of brazed specimen were 146.5N/mm, 204.6N/mm and 101.6N/mm for Zn, Sn and Ni coated steel respectively.

Flame Braze between Aluminum Alloy 5A06 and Low Carbon Steel Q235

Nian-chun LU,Yang LIU,Guo-dong Hao,Yun-tao WANG 대한용접·접합학회 2017 대한용접·접합학회지 Vol.35 No.4

By means of the flame braze, the welding problems on Aluminum alloy(5A06)and low carbon steel Q235) were mainly researched in this paper. The welding technology adopted in this paper is that a hot-dipped Aluminum coating of ZL102 Aluminum alloy was firstly performed on the surfaces of low carbon steel, then the layer of hot-dipped aluminum and aluminum alloy were welded by the shape of the lap joint. Through the analysis of the microstructure and tensile property of welded joint after the experiment, the experimental results expressed that good welded joint can be attained by application of flame brazing. Fracture location of the joint specimens appears in the coating layer by means of tensile test. The results show that the bond strength of the coating layer was less than that of the brazing seams.

Effect of Al element in Zn-Al fillers on the corrosion resistance of Cu/Al brazed joints

Junlan Huang,Weimin Long,Sujuan Zhong 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.2

In this paper, we describe experimental torch welding 1061 aluminum alloy to T2 copper. The corrosion behavior and performance of Cu/Al brazed joints were systematically investigated. This investigation was conducted using an optical microscope (OM), scanning electron microscope (SEM), energy disperse spectroscopy (EDS) and other methodologies. The results showed that the corrosion resistance of brazed joints was closely associated with Al content in filler metal. The corrosion behavior in 3.5 % NaCl solution belonged to microelectrochemical corrosion and depended mainly on electrochemical imbalance between different phases. The excessive dissolution of Al atoms led to the occurrence of the corrosion of brazed joints and the corrosion product may be Al(OH) 3 , Zn(OH) 2 and ZnO. It can be also found that an increase of aluminum content controlled largely formation and distribution of α-Al phase and Al 2 O 3 protective film in brazing alloys, resulting in reducing the electrochemical corrosion current density and improving the corrosion resistance and shear strength of the joint.

마그네슘합금과 철강 이종소재의 레이저 브레이징 특성에 미치는 도금층의 영향

이목영,김숙환,ALI M. NASIRI,NORMAN Y. ZHOU 대한용접접합학회 2013 대한용접·접합학회지 Vol.31 No.4

The dissimilar welding between magnesium alloy and steel sheet was required in automobile industry toincrease the strength of the dissimilar joints. Laser brazing is one of the good joining processes for Mgsteeldissimilar joint. In this study, the effect of coating materials was evaluated on the laser brazing for the dissimilar jointbetween AZ31 and coated steels such as Zn, Sn and Ni. Diode direct laser was used to braze the lap-edgejoint with Mg600 filler wire and Superior #21 flux. The wettability was best on Zn coated steel. Theinterlayer was formed at the interface between brazement and steel for all coating materials. The strengthsof brazed specimen were 146.5N/mm, 204.6N/mm and 101.6N/mm for Zn, Sn and Ni coated steelrespectively.

Defect Inspection and Defect Size Measurement in a Brazing-typed Heat Exchanger

Sang-Woo Seo,Jin-Young Kim 제어로봇시스템학회 2011 제어로봇시스템학회 국제학술대회 논문집 Vol.2011 No.10

Brazing joint is one of the most critical fact in the performance of heat-exchanger. Therefore, The proper method is required for the precise inspection to detect existing defects in the brazing joints. Two types of heat exchangers were analyzed to obtain cross-sectional images by using CT(Computerized tomography) and the defects were inspected with inspection system. The detected defects were saved with their own coordinates and analyzed. With these data, the defects were three-dimensionally imaged reflecting inspection results. As a result, the type and shape of defects existing in the samples were confirmed.