• Journal of the Korean Society for Precision Engineering
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• v.20 no.5
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• pp.73-81
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• 2003

In case of hollow cylinder extrusion using porthole die, the effects of extrusion parameters-temperature, the speed of extrusion, the shape of the die and mandrel-on metal flow in porthole die extrusion of aluminum have been investigated. However, there have been few studies about condenser tube extruded by porthole die. Original metal flow of condenser tube by porthole die extrusion is similar to hollow cylinder extrusion but the estimation of metal flow for extrusion parameters is different. For example, variation of chamber length in hollow extrusion only affects the welding pressure, however, the welding chamber length in condenser tube extrusion influences to the welding pressure as well as the deflection of mandrel. This study was designed to evaluate metal flow, welding pressure, extrusion load, tendency of mandrel deflection according to angular variation in the bottom of chamber in porthole die. Estimation was carried out using finite element method in as non-steady state. Analytical results can provide useful information the optimal design of porthole die.

• Journal of the Korean Vacuum Society
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• v.2 no.3
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• pp.275-281
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• 1993

본 논문은 포항가속기에서 건설 중인 진공 chamger의 용접에 관한 것이다. 저장링에 전자빔을 5시간 이상 저장하기 위하여 10-10torr 이하로 진공도를 유지하도록 설계되어 있기 때문에 초고진공에 적합한 TIG 용접(tungsten inert gas welding)을 하였다. 진공 chamber는 Al 5083-H321이며 flange의 재질은 Al 2219-T852이다. Sector chamber I, II의 총 용접 길이는 각각 27m, 37m이며 진공에 유해한 균열과 virtual leak가 생기지 않도록 하는 용접조건 등을 선정하였다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.427-430
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• 2008

Electroforming is one of the key technologies for the regenerative thrust chamber of the rocket engine. To use nickel electroforming method for the thrust chamber, direct electroforming of nickel on cupper and the welding method between different materials are needed. Minimizing the internal stress is one of the important factor for making thick electroforming,. Also minimizing contamination(ex. Sulfur containing compound) is another important factor for the stability of quality. This paper includes advanced methods for thick nickel electroforming, those of strength test results and EDS/EPMA inspection results. Advanced for electroforming process makes the achievement of Electro-beam welding between Inconel718(Manifold) and Nickel Electroforming. This paper also includes the influence of the electroforming precipitation angle on strength. Thus advanced electroforming improvement processes and the test results make achievement for manufacturing of the regenerative thrust chamber with direct nickel thick electroforming on cupper materials.

• Journal of Welding and Joining
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• v.11 no.4
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• pp.36-43
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• 1993

1)sector chamber II에서 가장 우려되었던 J5, J8의 변형량이 $28\mu\textrm{m}$,$36\mu\textrm{m}$ 이었으므로 목표 값 $50\mu\textrm{m}$을 충분히 보증할 수 있다. 2) Helicoflex gasket type으로 제작된 초도품 챔버에서는 140.deg.C bake-out후 이온 펌프만 으로 20시간 진공배기한 후의 진공도는 2*$10^{-9}$ Torr에 도달하였으며, 용접 type으로 제 작된 챔버에서는 2*$10^{-10}$ Torr에 도달하여서 진공도도 우수하였다. 3)표면조도에 민감한 Helicoflex gasket를 사용하지 않고 알루미늄 플랜지를 용접하여 AI gasketc 를 이용할 수 있기 때문에 초도품챔버에서와 같이 알루미늄 챔버와 스텐레스 스틸 부품을 연결하 는 stainless spool piece가 필요하지 않게 된다. 4)고가의 helicoflex gasket을 쓰지 않으므로 가격절감을 할 수 있다.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.11a
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• pp.33-41
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• 2002

In case of hollow cylinder extrusion using porthole die, the effects of extrusion parameters-temperature, the speed of extrusion, the shape of the die and mandrel-on metal flow in porthole die extrusion of aluminum have been investigated. However, there have been few studies about condenser tube extruded by porthole die. This study was designed to evaluate metal flow, welding pressure, extrusion load, tendency of mandrel deflection according to variation of chamber length. in porthole die. Estimation was carried out using finite element method. Porthole die is analyzed in as non-steady state. Analytical results provide useful information the optimal design of porthole die.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.9 no.2
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• pp.90-99
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• 1999

Fume extracting welding gun is one of the promising options for reducing the welder's fume exposure. The performance of the gun was assessed on the basis of capture efficiency. Capture efficiencies were measured in a test chamber recommended by American Welding Society. The overall capture efficiency was turned out to be above 95%. But it did not include the effect of crossdraft existing in the real work environment because all experiments were conducted in a closed chamber. It thus needs more work in the future. In addition, the future directions for improving the pres ent commercial techniques of the gun were discussed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.515-519
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• 2011

Structural tests for the mixing head of a 75tonf class thrust chamber were performed to verify structural stability. The mixing head of a thrust chamber is loaded by high pressure with regeneratively cooled fuel and cryogenic liquid oxygen(LOx) as well as it transfers thrust load generated by liquid rocket engine. Therefore structural stability of mixing head is a very important factor to work without any plastic deformation or structural failure. In this study, two mixing heads were manufactured using different welding methods, Tungsten Inert Gas(TIG) welding and Electron Beam Welding(EBW) and evaluated a structural stability. The results of structural tests showed that the mixing head assembled by EBW can withstand the applied design load without any structural failures and be structurally more stable than that of TIG welding.

• Journal of Welding and Joining
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• v.13 no.1
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• pp.73-77
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• 1995

이 글에서는 챔버의 용접에 대해서 기술하였다. 전자빔용접에 의하여 누설률이 1*$10^{-10}$ torr.1/sec 이하로 목표값을 만족하기 때문에 초고진공에 적합한 용접법이다. 챔버는 용접부에 trench 구조를 가져야 진공용접을 하는데 보다 효과적이다. 이것은 지금까지 전자빔 용접에서 시험되지 않은 것이기 때문에 향후 보다 많은 연구가 있으리라고 본다.

• Journal of the Korean Society of Safety
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• v.13 no.2
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• pp.65-75
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• 1998

The cases of welders illness by welding fume generated during arc welding are recently reported, which makes the legal regulation in the welding work place. Also, this situation makes the employers and welders be concerned about the welding fume seriously. At this point of time it is necessary that a standard testing method is developed as a fundamental tool for the evaluation of Fume Generation Rate(FGR) required for making progress in the development of low fume electrodes and welding process technology and also constructing the ventilation system in welding area. However, the current standard(KS D 0062) is only applicable to the manual covered electrode arc welding. In this study the evaluation procedure for the FGR is established by developing the fume collection chamber which can be applicable to semiautomatic and automatic arc welding as well as manual arc welding. This evaluation system and procedure can be used as a tool not only to develop the low fume welding electrode and welding process technology but also to construct the equipment controlling the welding workshop atmosphere.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.5
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• pp.99-104
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• 2017

Friction stir welding is a solid-state joining process and is useful for joining dissimilar metal sheets. In this study, the experimental conditions of the friction stir welding were determined by the two-way factorial design to evaluate the characteristics of the dissimilar friction stir welding of AZ31 and AZ61 magnesium alloys. The levels of rotation speed and welding speed, which are welding variables, were 1000, 2000, 3000 rpm and 100, 200, 300 mm/min, respectively. From the results, the greater the rotation speed and the lower the welding speed of the tool were, the greater the tensile strength of the welded part was. The contribution of the welding speed of the tool is larger than that of the rotation speed of the tool. In addition, the optimal conditions for tensile strength in the dissimilar friction stir joint were predicted to be the rotation speed of 3000 rpm and welding speed of 100 mm/min, and the tensile strength under the optimal conditions was estimated to be $214{\pm}6.57Mpa$ with 99% reliability.