회주철의 마찰용접 특성에 관한 연구 - 입열량 이론식을 중심으로 -

정호신,방국수,Jeong, Ho-Shin,Bang, Kook-Soo 대한용접접합학회 2014 대한용접·접합학회지 Vol.32 No.3

Joining of grey cast iron by fusion welding has much difficulties for its extremely low ductility and low toughness because of the flake form of the graphite. And the brittle microstructure, i.e. ledeburite may be formed during fusion welding by its rapid cooling rates. By these kinds of welding problem, preheat and post heat treatment temperature must be increased to avoid weld crack or welding problems. In order to avoid these fusion welding problem, friction welding of cast iron was carried out for improving joint soundness, establishing friction welding variables. There is no factor for evaluating friction weldability in continuous drive type friction welding. In this point of view, this study proposed the parameters for calculating friction weld heat input. The results obtained are as follows ; 1. There was a close relationship between tensile strength and flash appearance of friction welded joint. 2. Tensile strength was decreased and flash was severely oxidized as increasing frictional heating time. 3. As increased forging pressure $P_2$, flash had a large crack and tensile strength was decreased. 4. As powdered graphite by rotational frictional force induced flat surface and hindered plastic flow of metal, tensile strength of welded joint was decreased. 5. Heat input for continuous drive type friction welding could be calculated by the factors of $P_1$, $P_2$ and upset distance(${\delta}$).

벌크 비정질 금속의 마찰접합에 미치는 접합계면 온도의 영향

박정수(Jung-Soo Park),정윤철(Yoon-Chul Jung),신형섭(Hyung-Seop Shin) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5

This study aims to investigate the how the temperature distribution at the joining interface influence on the weld characteristic of dissimilar friction welding of bulk metallic glasses(BMG) to crystalline metals. An infrared thermal imager (FLIR-ThermaCam SC-2000) was used to measure the temperature distribution at joining interface of the specimens during friction welding. Understanding the temperature distribution on the joining interface is important, because not only it determines whether the friction welding will be implemented successfully or not, but also it influences the residual stress, the crystallization of amorphous phase, and the eventually strength of the welds. A successful welding is achieved by using a friction welding apparatus which incorporates a pneumatic actuator and gripper to give a precise control of the friction time and pressure. The shape of the protrusion formed at the weld interface were examined. A Zr??Cu₄?Al₁? bulk metallic glasses and crystalline metals of Ti-alloys and Al-alloys were adopted as samples. In order to characterize the friction welded interface, the micrographic observation and the X-ray diffraction analysis on the weld cross-section were carried out. The obtained results were disussed based on the temperature distribution measured at the weld interface A successful joining of the bulk metallic glasses(BMG) to crystalline metals could be obtained for certain pairs of the material combination through the precise control of friction conditions. The residual strength after welding was evaluated by the four-point bending test and compared with the cases of friction welding to similar materials.

수치해석을 활용한 마찰교반용접 공정의 온도 특성 분석 연구

김무선 한국산학기술학회 2019 한국산학기술학회논문지 Vol.20 No.12

Friction Stir Welding is a welding technique for metal materials that utilizes the heat generated by friction between the material to be welded and the welding tool that rotates at high speed. In this study, a numerical analysis method was used to analyze the change in the internal temperature of the welded material during friction stir welding. As the welding target material, AZ31 magnesium alloy was applied and the welding phenomenon was considered a flow characteristic, in which a melting-pool was formed. FLUENT was used as the numerical tool to perform the flow analysis. For flow analysis of the welding process, the welding material was assumed to be a high viscosity Newtonian fluid, and the boundary condition of the welding tool and the material was considered to be the condition that friction and slippage occur simultaneously. Analyses were carried out for various rotational speeds and the translational moving speed of the welding tool as variables. The analysis results showed that the higher the rotational speed of the welding tool and the slower the welding tool movement speed, the higher the maximum temperature in the material increases. Moreover, the difference in the rotational speed of the welding tool has a greater effect on the temperature change. 마찰교반용접(Friction Stir Welding) 기술은 금속 소재를 대상으로 하는 용접기술 중의 하나로 용접대상이 되는 소재와 고속으로 회전하는 용접툴 사이의 마찰로 인한 열을 활용하여 소재의 융점 이하 온도에서 접합하는 기술이다. 이번 연구에서는 마찰교반용접을 진행할 때, 용접 대상물의 내부 온도 변화를 분석하기 위한 방법으로 수치해석기법을 사용하였다. 용접소재로는 마그네슘 합금인 AZ31을 고려하였으며, 용접현상을 멜팅풀(melting-pool)이 생성되는 유동특성으로 간주하고 유동해석을 수행하기 위해 유동특성 수치해석 툴인 FLUENT를 이용하였다. 용접과정의 유동해석을 진행하기 위해 용접소재는 고점도 뉴턴 유체로 가정하였고, 용접툴과 용접대상 소재의 경계면은 마찰 및 미끄러짐이 동시에 발생하는 조건으로 경계조건을 선정하였다. 그리고 용접툴의 회전속도 및 용접속도를 변수로 하여 다양한 해석을 진행하였다. 해석 결과로부터 용접툴의 회전속도가 높을수록, 용접속도가 느릴수록 소재 내 최고온도가 증가함을 확인할 수 있었으며, 그 중 용접툴의 회전속도 차이가 온도 변화에 더 큰 영향을 보임을 확인하였다.

단조재와 파이프의 이종 마찰용접에 대한 음향방출법의 평가

김동규,공유식,이진경 한국비파괴검사학회 2018 한국비파괴검사학회지 Vol.38 No.6

In this paper, the main parameters (such as tensile strength) of tube-to-bar friction welding for piping materials, were examined visually in order to increase the quality of friction welding. The specimens were tested as-welded. The tensile strength of the friction welded steels has increased up to 100% compared to the A105 base metal, under the condition of all time heating. An acoustic emission (AE) technique was applied to evaluate the optimal friction welding conditions nondestructively. For this purpose, we analyzed the signals generated during friction welding by evaluating parameters such as accumulative count, amplitude, waveform and frequency. During the heating time, mainly the continuous type AE occurs, while burst type AE occurs in the upset time and accumulative count has become a useful parameter for estimating the optimal friction welding conditions. 본 논문에서는 각종 배관재의 이종 마찰용접을 시행하여 플랜트산업 등에 적용 가능성을 제안하고 마찰용접 변수의 기계적 특성을 분석하여 최적화 조건을 결정하고자 하였다. 최적 용접조건에서 용접부의 이음효율이 100 %이상으로 나타났다. 그리고 음향방출 기법을 이용하여 최적의 마찰용접조건을 도출하고자 하였으며 이를 위해 AE 계수와 진폭 등의 파라미터와 파형과 주파수 스펙트럼의 분석을 통하여 마찰용접시 발생하는 신호를 분석하였다. 가열시간에서는 연속형 AE가 주로 발생하며 업셋시간에서는 돌발형 AE가 발생하는 특성을 나타내었으며, 마찰용접 시험편의 음향방출 특성과 강도분석을 통하여 마찰용접의 최적 용접 조건을 추정하는데 유용한 AE 파라미터는 누적계수임을 확인하였다.

경량 피스톤 로드를 위한 마찰용접 적용연구(SM45C/SM45C-Pipe 사용)

민병훈,임형택,민택기,Min, Byung-Hoon,Lim, Hyung-Taek,Min, Taeg-Ki 대한용접접합학회 2008 대한용접·접합학회지 Vol.26 No.2

Various research to reduce weight of a car is achieving. This research is tendencious to manufacture solid piston rod of shock absorber as hollow piston rod using friction welding. This study deals with the friction welding of SM45C to SM45C-Pipe that is used in car shock absorber, The friction time was variable conditions under the conditions of spindle revolution of 2,000rpm, friction pressure of 55MPa, upset pressure of 75MPa, and upset time of 2.0seconds. Under these conditions, the microstructure of weld interface, tensile fracture surface and mechanical tests were studied of friction weld, and so the results were as follows. 1. In tensile strength, the hole processing is better than non-hole processing. 2. When the friction time was 1.5seconds under the conditions, the maximum tensile strength of the friction weld happened to be 869MPa, which is 103% of SM45C's tensile strength and 91% of SM45C's Pipe. 3. When the friction time was 2.0seconds under the conditions, the maximum bending strength of the friction weld happened to be 1599MPa, which is 80% of SM45C's bending strength and 118% of SM45C's Pipe.

마찰교반점접합한 5454-O 알루미늄합금 판재의 접합부 거시조직 및 기계적 특성에 미치는 접합인자의 영향

최원호,권용재,윤성욱,강명수,임창용,서종덕,홍성태,박동환,이광학,Choi, Won-Ho,Kwon, Yong-Jai,Yoon, Sung-Ook,Kang, Myoung-Soo,Lim, Chang-Yong,Seo, Jong-Dock,Hong, Sung-Tae,Park, Dong-Hwan,Lee, Kwang-Hak 대한용접접합학회 2011 대한용접·접합학회지 Vol.29 No.6

Friction stir spot welding between 5454 aluminum alloy sheets with the different thicknesses of 1.4 and 1.0 mm was performed. In the welding process, the tool for welding was rotated ranging from 500 to 2500, and plunged to the depth of 1.8 mm under a constant tool plunge speed of 100 mm/min. And then, the rotating tool was maintained at the plunge depth during the dwell time ranging from 0 to 7 sec. The pull-out speed of the rotating tool was 100 mm/min. The increase of tool rotation speed resulted in the change of the macrostructure of friction-stir-spot-welded zone, especially the geometry of welding interface. The results of the tensile shear test showed that the total displacement and toughness of the welds were increased with the increase of the tool rotation speed, although the maximum tensile shear load was decreased. However, the change in the dwell time at the plunge depth of the tool did not produce the remarkable variation in the macrostructure and mechanical properties of the welds. In all cases, the average hardness in friction-stir-spot-welded zone was higher than that of the base metal zone. By the friction stir spot welding technique, the welds with the excellent mechanical properties than the mechanically-clinched joints could be obtained.

마찰교반용접의 하중에 따른 구조적 편향 저감에 관한 연구

차운용,임세빈,김재원 한국기계기술학회 2023 한국기계기술학회지 Vol.25 No.6

Power converter devices require a high level of quality because they have a high direct connection with vehicle operation. Therefore, structural bonding was carried out by friction stir welding with excellent mechanical properties. Friction stir welding can cause structural deflection depending on the load of the welding tool, so it is important to control this for high quality flatness. In this study, pre-welding was performed before welding to minimize deflection generated during welding. And deflection reduction data according to the location of pre-welding were analyzed through dynamic analysis. As a result, based on computerized data rather than experimental data an optimized position of pre-welding was secured to minimize the deflection that occurs during friction stir welding. Through this, a process guide that enables high quality structural bonding was presented.

Inertia Friction Welding Process Analysis and Mechanical Properties Evaluation of Large Rotor Shaft in Marine Turbo Charger

Jeong, Ho-Seung,Cho, Jong-Rae,Oh, Jung-Seok,Kim, Euong-Nam,Choi, Sung-Gyu,Ha, Man-Young 한국정밀공학회 2010 International Journal of Precision Engineering and Vol.11 No.1

The two aims of this study are first, determining the optimal welding process parameters by using the finite element simulation and second, determining the optimal tempering temperature by evaluating the mechanical properties of friction welded part for manufacturing large rotor shaft. Inertia welding was conducted in order to make the large rotor shaft of turbo charger for low speed marine diesel engine. The rotor shaft is composed of the 310mm diameter disk and the 140mm diameter shaft. Since diameters of disk and shaft are very different, the integration using friction welding reduces manufacturing cost compared with the forming process of which a disk and shaft are forged into one body. Finite element simulation was performed, because inertial welding friction process depended on many process parameters, including axial force, initial revolution speed and energy, amount of upset, and working time. It is expected that this modeling will significantly reduce the number of experimental trials needed when determining the optimal welding parameters. Inertia welding was carried out with optimal process parameter conditions obtained from the simulation results. Welded joint part, made by friction welding, had very poor mechanical properties, and so it required heat treatment. The base material used in the investigation was SFCMV1 (SANYO special steel, high strength low alloy Cr-Mo steel) of 140mm diameter. In the study, heat treatment test carried out quenching ($950^{\circ}C$, 4hr, oil cooling) and tempering ($690-720^{\circ}C$, 6hr, air cooling) for friction welding specimens. The various tests, including microstructure observation, tensile, hardness, and fatigue tests, were conducted to evaluate the mechanical properties under various heat treatment conditions after inertia welding.

Recent Advances in Friction-stir Welding Process and Microstructural Investigation of Friction Stir Welded Pure Titanium

Jae-Deuk Kim,Eun-Geun Jin,Siva Prasad Murugan,Yeong-Do Park 대한용접·접합학회 2017 대한용접·접합학회지 Vol.35 No.4

The use of titanium and its alloys is increasing day by day, especially in aerospace, automobile, and defense fields. Friction stir welding is a prominent solid-state joining process, which produces non-melting low heat input welds with less residual stresses compared to the conventional welding process. The physical and chemical properties of Ti such as low thermal expansion and thermal conductivity, relatively high melting temperature(1668℃) and high reactivity makes the FSW a favorable joining process for Ti alloys. However, Ti friction stir welds reveal highly complexed microstructure evolution in the weld zone and exhibit several defects which can influence the mechanical properties of the weld. This paper aims at a review on the microstructural evolution and typical defects formation during the FSW of CP-Ti, with the brief review on the fundamentals of friction stir welding process and Ti and its alloys.

고탄소강 마찰용접부 미세조직 및 기계적 성질에 대한 연구

김경환,김봉준,문준오,이정원,김용현 대한용접접합학회 2023 대한용접·접합학회지 Vol.41 No.6

In this study, we aim to investigate the microstructure evolution and mechanical properties in friction welded joints of high carbon S45C steel. Thus far, S45C steel was welded with structural steel containing 0.3 wt.%C using friction welding. The microstructures in a friction welded joint were characterized by optical microscopy, scanning electron microscopy, and electron back-scattered diffraction analyses, and then compared to the microstructures of CO2 arc welded S45C welds. The mechanical properties of joints welded using friction and CO2 arc welding were evaluated through impact tests and Vickers hardness tests. The microstructural changes, based on the welding process, were analyzed carefully in terms of chemical composition and strain condition in welds. Finally, the relationship between microstructures and mechanical properties in welds was discussed.