• Journal of Welding and Joining
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• 제17권3호
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• pp.79-89
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• 1999

The study was carried out to examine in more detail metallurgical and mechanical properties of brazed joints of diamond cutting wheel. In this work, shank(mild steel) and sintered bronze-base tips were brazed with three different filler materials(W-40, BAgl and BAg3S). The machine used in this work was a high frequency induction brazing equipment. The joint thickness, porosities and microstructure of brazed joints with brazing variables(brazing temperature, holding time) were evaluated with OLM, SEM, EDS and XRD. Bending(torque) test was also performed to evaluate strength of brazed joints. Further wetting test was performed in a vacuum furnace in order to evaluate the wettability of filler metals on base metals9shank and tips). The brazing temperature had a strong influence on the joint strength and the optimum brazing temperature range was about $700~850^{\circ}C$ for the bronze/steel combinations. The strength of the brazed joint was found to be influenced by the three factors : degree of reaction region, porosity content, joint thickness. The reaction region was formed in the bronze-base tip adjacent to the joint. The reaction region resulted in a bad influence on the strength due to the formation of Cu5.6Sn, CuZn4, $\beta(CuZn)$ and CdAg, etc. Porosities increased as brazing variables(brazing temperature, holding time) increased, and the brazed joints with porosities of less than about 3-5% had an optimum strength for the bronze-base tip.

• 대한기계학회논문집A
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• 제31권5호
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• pp.594-600
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• 2007

Rapid mold heating has been recent issue to enable the injection molding of thin-walled parts or micro/nano structures. Induction heating is an efficient way to heat a conductive workpiece by means of high-frequency electric current caused by electromagnetic induction. Because the induction heating is a convenient and efficient way of indirect heating, it has various applications such as heat treatment, brazing, welding, melting, and mold heating. The present study covers an experimental investigation on the rapid heating using the induction heating and rapid cooling using a vortex tube in order to eliminate an excessive cycle time increase. Experiments are performed in the case of a steel cup mold core with various heating and cooling conditions. Temperature is measured during heating and cooling time, from which appropriate mold heating and cooling conditions can be obtained.

• Journal of Welding and Joining
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• 제22권4호
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• pp.65-72
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• 2004

The aim of this study is to investigate the optimum drawing parameter for BAS111 welded tubes. The BAS111 aluminium alloy tubes with 25.4mm in external diameter and 1.5mm in thickness for heat-exchangers were manufactured by high frequency induction welding with the V shaped convergence angle 6.8$^{\circ}$ and power input 50㎾. With increasing the reduction of area (1.6, 5.8, 11.5, 14.2, 18.5, 22.5%) by drawing, tensile strength was increased and elongation was decreased. With increasing the reduction of area by drawing, hardness in weld metal increased rapidly, while that of base metal increased slowly. In the specimen with the outer diameter smaller than 22mm, hardness of weld metal was higher than that of base metal. The optimum drawing parameter of area reduction was estimated about 15% because of the work hardening of welds.

• 대한기계학회논문집A
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• 제37권12호
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• pp.1573-1579
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• 2013

핵연료의 연소성능을 시험하기 위해서는 시험 루프에 설치된 조사리그 내에 냉각수가 순환되도록 설계되어야 한다. 이때, 조사리그 내 냉각수는 $300^{\circ}C$, 15.5 MPa 의 고온 고압으로 순환시키기 때문에 냉각수의 밀봉은 핵연료 조사리그를 제작할 때 가장 중요한 공정 중 하나이다. 특히 15 개의 계장선이 조사리그의 압력경계부위를 통과하게 되는데, 이의 밀봉을 위해 일반적으로 브레이징 공정이 적용된다. 본 연구에서는 조사리그 브레이징용 진공챔버 및 고주파 유도가열기를 포함하는 유도 브레이징 시스템을 개발하고, 다양한 실험을 통해 산화막이 발생하지 않는 공정변수를 검토하였으며, 브레이징 제품의 인장시험, 단면검사, 밀봉성능검사 등을 통해 브레이징 공정의 건전성과 밀봉성능을 검증하였다.

• 한국재료학회지
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• 제14권12호
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• pp.851-856
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• 2004

The aim of this study is to investigate the optimum drawing parameter for BAS121 welded tubes. The BAS121 aluminium alloy tubes with 25 mm in external diameter and 1.3 mm in thickness for heat-exchangers were manufactured by high frequency induction welding with the V shaped convergence angle $6.5^{\circ}$ and power input 55 kW. With increasing the reduction of area ($13,\;21\%$) by drawing, tensile strength was increased and elongation was decreased. With increasing the reduction of area by drawing, hardness in weld metal increased rapidly, while that of base metal increased slowly. In the specimen with the outer diameter smaller than 22 mm, hardness of weld metal was higher than that of base metal. The optimum drawing parameter of area reduction in BAS121 alloys was estimated about $13\%$ because of the work hardening of welds.

• 한국안광학회지
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• 제12권3호
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• pp.55-58
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• 2007

티타늄과 그 합금은 경량성, 우수한 기계적 성질 그리고 우수한 내식성 때문에 주요한 안경테 소재로 사용되고 있다. 본 연구에서는 티타늄 합금 홈선에 대하여 안경테 브레이징용으로 사용되고 있는 고주파유도가열 장치를 이용한 열처리 시간의 변화에 따른 경도 및 미세조직의 변화에 대하여 조사하였다. ${\beta}-Ti$ 합금은 고주파유도가열처리 시간의 증가에 따라 경도값의 감소가 나타났으며, 이는 열처리 시간의 증가에 따른 결정립의 조대화 때문인 것으로 생각된다. Ti-325 합금의 고주파유도가열처리에서는 2초까지는 경도값이 감소하였으나, 3초에서는 급격히 증가하였다. 이는 2초까지는 결정립의 조대화에 의한 경도값의 감소가 일어나지만, 3초에서는 미세한 ${\alpha}+{\beta}$ 상의 층상조직이 발달하였기 때문으로 판단된다.