Brazing between cemented carbides and steel for tool investigated by copper alloy brazing filler. Copper alloy filler was high liquidus temperature($990^{\circ}C$), therefor the shank(steel) occurred softening. Because brazing sample was necessary to heat treatment after brazing process. This experiment, influence of austenite time and purge temperature on heat treatment were investigated. As a result, these treatments obtained to high deflective strength In case of austenite time was short and purge temperature was low. Especially, nitride precipitated brazing layers was strongly influenced by the deflective strength.

레이저 아크 하이브리드 용접에서 보호가스로 헬륨을 사용하였을 때 레이저에 의해 발생하는 금속 증기가 아크 플라즈마의 거동에 미치는 영향에 관하여 시뮬레이션 하였다. 해석에 필요한 기본적인 물성치들은 헬륨과 금속 증기의 부분압에 따라 비율로서 결정하였고 아르곤을 사용하였을 때와 비교하여 헬륨 플라즈마의 특성을 파악하였다. 또한 보호가스의 종류에 따라 레이저 빔의 흡수율을 계산하여 고옥의 플라즈마가 발생할 때 헬륨 보호가스가 적당함을 보였다.

In the field of welding the behavior of a welded structure under consideration may be predicted via heat transfer and residual stress analysis. In order to facilitate the industrial applications of welding, numerical modeling of heat transfer and residual stress in weldment has been carried out applying Finite Element Method (FEM) and the analysis with the external load including this residual stress due to welding has been done. The present work includes the specialized finite element codes for the calculation of nonlinear heat transfer details and residual stress redistributed along with the external load in the welded structures. A basic interface, which allows models, built in commercial preprocessing package access to the data necessary to build standard input decks for these specialized FEM codes, which are not supported by commercial package. The results from the FEM codes are imported back into commercial package for visualization. In addition the residual stress values are exported to commercial package (such as ANSYS, PATRAN etc.) for further analysis with the external loads, which make the FEM codes fully applicable to the industrial purpose.

Recently many research works are going on in the field of application of Laser-Arc hybrid welding for superstructures such as shipstructures. However, the study on heat distribution and welding residual stress of hybrid weld by numerical simulation loaves much to be desired. Therefore in this study an optimized welding condition and numerical simulation for hybrid welding by using Previous numerical analysis which was used to calculate the kent source for hybrid welding has been analyzed.

The fuel assemblies as the nuclear fuel for the pressurized water reactor(PWR) are loaded in the reactor core throughout the residence time of three to five years. The spacer grid assembly, which is an interconnected array of slotted grid straps and is welded at the intersections to form an egg crate structure, is one of the main structural components of the fuel assembly. The spacer grid assembly is structurally required to have enough buckling strength under various kinds of lateral load acting on the fuel assembly so as to keep the fuel assembly straight. To meet the requirement, integrity on the spacer grid welding parts should be carefully checked. In this study, welding quality of the spacer grid assembly welded by several welding companies are examined and compared.

The purpose of this study is to optimize Nd:YAG laser welding parameters to seaz a Rf source into a Ti micro capsule. Ti tube ends can be sealed as some length of ぉbe end is melted and coalesced. The exact control of the melted length is the most important to get sound sealing. The Nozzle type, tube rotating speed, tilt angle, focal position, pumping voltage, pulse frequency and pulse width were selected as the Nd:YAG laser welding Parameters. These Parameters were optimized by the Taguchi experimental method using 115 orthogonal array. Appearance and cross section of the seated tube ends were examined by SEM.

The phenomenon of weld shrinkage mainly occurs owing to residual stress by heating, which largely effects on welding quality, Actually as the shrinkage rate depends on the weld deposit amount, so it is desired that the sectional area of weld joint shall be reduced. In this respect the Electron beam welding has more profitable position compare to Narrow-gap TIG welding which is even superior to other arc welding processes. In case of thick austenitic stainless steel the shrinkage rate of Electron beam welding has about $10\%$ of Narrow-gap TIG welding's, which means that residual stress is a lot less than that of Narrow-gap TIG welding. And heat input and welded section area also indicate large difference between two processes.

In this study EB(Electron Beam) welder was modified to apply Ef welder to micro-joining for soldering and micro-brazing. The power and beam current of EB welder is 6kW, 100mA(60kV) and the minimum current was 1mA. The minimum current of EB welder was modified to decrease the amount of beam current to 0.0lmA and the monitoring system to observe materials was made up. The system is developed including teaching function for generating patterns. The control system and CAD/CAM software for EB direct writing was developed and the deflection beam was controlled without moving workpieces. the possibility of applying EB welder to micro-joining for soldering and brazing was studied through this experiments.

This study was investigated on the impact toughness and microstructure of welded metal and heat affected zone for B grade steel. With welding procedures, welding heat inputs applied were 30, 79 and 264 kJ/cm, Prior austenite grain size in coarse zone has increased with increasing welding heat input for B grade steel. The toughness of fusion line zone of Bgrade steel has decreased with increasing welding heat input while the toughness fusion line +3 and +5 mm zone increased contrarily.

20 vol.$\%$ SiC를 포함한 두 층간의 $Si_{3}N_{4}/SiC$ 나노 복합재료는$\alpha$ $-Si_3N_4$,13 nm 크기의 나노탄소 분말 그리고 $5\;wt$\%\;Y_2O_3$의 분말로 두 단계 소결을 통하여 제작된다. $Si_3N_4$ 입계 사이의 결합은 소결 후 변하지 않고 남은 compact와 $51\~62\%$의 기공으로 얻어진 표면적 사이의 반응에 의해 생성된다. 이 연구에서는 Ti 합금을 SiC 층에 브레이징을 이용하여 제작하고 기계적 특성을 연구하였다. 다양한 변형율과 결합물의 강도, 변형율 증가에 따른 층간 변화를 연구하였다. 층간 파괴 형태는 금속과 브레이징 합금 사이의 파괴, 세라믹과 브레이징 합금 사이의 파괴, 그리고 세라믹 내부에서의 파괴를 보였다.

Recently 9Cr-1Mo azzoy is used in the Nuclear power plant due to its special properties. This material has the merit of high-strength resistance and corrosion resistance. Therefore the demand for this alloy is dramatically increased in the Nuclear power, petro-chemical complex etc. Re various research has been conducted to improve the material properties of this alloy. In spite of this circumstance, detail research in the area of welding process of this alloy is yet to be expanded In this study the numerical non-linear heat transfer analysis of laser welding which may possibly replace the conventional SMAW fabrication of 9Cr-1Mo steel has been carried out.

This study was investigated on the impact toughness and microstructure of welded metal and heat affected zone for Hi Nitrogen TiN Steel. With welding procedures, welding heat input applied were 30, 79 and 264 kJ/cm. TiN steel has shown very small prior austenite grain size for all the welding heat input applied, which was considered to result from the effect of TiN particles. In case of single SAW and EGW welding, the dilution rate of base metal into the weld was not high, resulting that there were no significant effects of base metal chemical composition on the mechanical properties of welds. However, TSAW with double Ypreparation carried very high dilution rate so that TiN steel has impaired the toughness of weld metal because N content in the weld was increased through the dilution of base metal.

석출물의 용해 온도보다 낮은 온도에서의 석출물의 야금학적인 거동을 예측하였다. 평균 사이즈 석출물의 지속적인 성장만을 고려하는 기존의 모델과 달리, 본 연구에서 제안된 모델의 경우에는, Gibbs-Thomson equation으로부터 유도되는 critical particle size를 고려하였다. 제안된 모델을 이용해서 TiN석출물의 거동을 예측하였으며, 이를 실험 결과 및 기존의 모델에 의한 예측 값과 비교하였다. 석출물들의 분포는 전형적인 log-normal 분포를 따르는 것으로 관찰되었으며, 본 연구에서 제안된 모델이 기존의 모델에 비해서 실험결과와 잘 일치함을 확인할 수 있었다.

The experimental simulation welds using 3kinds of 70ksi titania based flux-cored consumables were performed on 24 inches 24.6-thick API 5L Gr. B pipe with relatively high current, over 300A and four different Post Weld Heat Treaonent(PWHT) conditions at $625^{circ}C$ were applied to each consumable test coupon. It is well known that, in common welding processes such as Submerged Arc Welding(SAW) or Flux Cored A.c Welding(FCAW), the cooling rates in as-deposited weld bead are normally so ,apid that actual precipitation of microalloy carbonitrides, Nb(C,N) or V(C,N) is not likely to occur in the as-welded weld metal, however, during stress relief or PWHT the operation of precipitation can reduce the impact properties of the weld metal. As results of mechanical testing, it is concluded that PWHT at $625^{circ}C$ is detrimental to weld metal impact toughness of Ti-B type flux- cored (FC) welding consumables regardless of the amount of Nb and V, but two optima were exhibited, one at 800ppm Ti, 75ppm 5 and another 360ppm Ti, 54ppm 5.

This study was aimed at evaluation of residual stress of steel pipe structures. The production process of pipes was complex (at first bending was done by roll forming or press forming and welding was final process of making of steel pipes). So there could be effected high residual stresses in steel pipes. In order to evaluate the changes of residual stress the locations of measurement were selected carefully. Measurements of residual stress were done for various kinds of pipes (shapes in circular and square). For the evaluation of residual stress, hole-drilling method (ASTM E837 was applied. The results showed that along the weld Eine high tensile stress were measured as effected, and high tensile stresses were measured where large plastic deformation developed. Through these efforts, experimental results could be more effectively assisted by numerical method.

Vibration occurs due to the wind and vehicles, etc., in the field welded joints of steel bridges. However, the effect of vibration on the fatigue strength of field welded joints in steel bridge are not yet clearly understood. In this paper, the effect of vibration on the fatigue strength of welded joints was elucidated in order to improve reliability in the field welded joints of steel bridge. The base material used in this investigation was SM 490A steel of weldable grade. Flux Cored Arc Welding(FCAW) process was used to fabricate the doubte 'V' butt joints. Welding was performed on the steel under the mechanical vibration of given frequency. The applied frequency was resonant frequency. Also, weldments formed under no vibration were fabricated. Fatigue tests were conducted using a servo hydraulic controlled 50ton1 capacity UTM with a frequency of 5Hz under constant amplitude loading.

The failure pressure for corroded pipeline was measured by burst testing and classified with respect to corrosion sizes and corroded regions - the body, the girth weld and the seam weld of pipe. A series of finite element analyses were performed to obtain a limit load solution for corrosion defects on the basis of burst test. As a result, the criteria for failure assessment of corrosion defect within the body, the girth weld and the seam weld of API 5L X65 gas pipeline were proposed.

Electromagnetic force is one of the most important factor that effect on metal transfer mode, short-circuit rate, spatter generation rate and mechanical properties of weld metal etc. Also, shielding gas and welding current have influence on metal transfer mode in GMAW. In this paper, different ways for external electromagnetic forces are applied by attaching cylindrically rounded conducting wire solenoid on touch tip holding. With the applied electromagnetic field, the arc transfer mode changes from normal mode to rotating mode and spatter generation decreased in electromagnetic fields(N-pole). In MIG welding, the influences of electromagnetic force on the spatter generation showed different tendency as in the $CO_2$ welding. It is possible reasons were discussed.

The duplex stainless clad vessel with 38m & over thickness shall be performed to PWHT based on the ASME code. In this case, it is well-known that precipitators such as carbides and sigma($\sigma$) phase are formed at gram boundary between ferrite and austenite phase. Therefore, a weld test for simulating this situation has been planned and performed by 3309LMo71-1 for barrier layer and E2209Tl-1 for 2nd & over layer and then carried out to investigate the overlaid weld metal. Based on the test results, it could be concluded that PWHT should be carried out after the completion of 1st(barrier) layer and then 2 & over layer should be applied.

High capacity container carrier has been considered for many decades to transport the more containers at the same time. Therefore, it is required for high capacity container ship to be applied thicker plate to accomodate a number of containers compared to that of general container ship. To maintain the same productivity of this thicker plate, new welding process should be considered. One of the process for vertical-up position is 2 electrodes EGW(Electro Gas Welding). 2 ectrodes EGW was applied and evaluated whether it can be applicable or not. The heat input used for 72mm thick plate was 520k11cm. from the mechanical test, it is considered that this process can be applicable, showing satisfaction of mechanical properties such as tensile strength, elongation and impact property.

Inconel 625 is useful in variety of industrial applications because of the resistance to attack in various corrosive media at temperatures from $200^{circ}C$ to over $1090^{circ}C$, in combination with good low- and high-temperature mechanical strength. Recently, this material is also used widely in offshore process piping in order to extend the maintenance term and improve the quality of anti-corrosion. Nowadays, the flux cored wire is developed and applied for the better productivity in several welding position including the vertical position. In this study, the weldability and weldment characteristics of inconel 625 are considered in FCAW weld associated with the several shielding gases in viewpoint of welding productivity.

The purpose of this study is to evaluate the effects of welding conditions on the shape of arc of FCAW using high speed camera system. Length and deflection of arc were evaluated from images of arc which were transformed by threshold processing. Based on the experimental results, a regression model for the length of arc was established. A major factor affecting deflection of arc was the length of arc.

국제용접학회(IIW) 및 대한용접학회(KWS)의 용접전문기술자 교육, 시험 및 검정에 대해서 기술한다. 그리고 현재까지 용접전문기술자 교육 및 검정과 관련되어 진행된 사업추진 실적에 대해서 기술하고, 이와 관련된 국내외의 환경 그리고 전망에 대해서 기술한다.

Characteristics of the wear resistance thermal sprayed coatings was investigated in order to determine proper coating process. Hardness evaluation and microstructural observation were conducted to find relationship between coating characteristics and its wear performance. It was found that HVOF process would give better properties than arc thermal process in terms of hardness and adhesion strength which resultantly determine wear performance of the coatings.

Water jet propulsion system has high efficiency on middle to high speed, and it provides better safety than conventional screw propeller because it has not projected propeller and rudder. So many leisure boat and high-speed ferries use this propulsion system. We developed water-jet propulsion unit for small planning boat, and launched that in the boat, after that we tested water-jet unit in the lake. As a result, we certify heat dissipation at the bearing housing and reverse duct's shape for neutral position are important at the design, and alignment water-jet unit and keel line are important at the launching, and ship's resistance performance and jet's propulsion performance also are needed to consideration.

가속기의 저장링 및 빔라인에는 방사광을 차단 혹은 일부 통과 둥의 목적으로 Photon Absorber와 같은 진공 부품이 사용되고 있으며, 이는 일반적으로 구리와 스테인리스 스틸 등의 이종재료를 브레이징 공정을 이용하여 제작함으로써 부품이 구조적 건성의 확보와 더불어 진공환경 및 수밀을 유지하고 있다. 그러나, Photon Absorber는 사용 용도에 따라 구조적 형상이 서로 다르기 때문에 브레이징 공정을 적용하는 경우, 상대적으로 제품 생산가격의 상승, 유지보수 및 제작불량에 따른 공정 제어의 어려움이 나타나고 있다. 본 연구에서는 스테인리스 스틸 (STS 304)과 구리(OFHC Copper)의 이종금속에 접합에 GTAW 용접 공정 기술을 적용하여 제반 용접공정에 따른 용접부 성능 및 진공 특성 등을 검토하였다. 용접봉 (ER CuSi-A)을 직접 사용하여 이종 재료의 시험편에 GTAW 용접을 적용한 결과, 진공 누설율은 $1{\times}10^{-10}\;Torr{\cdot}l/s$ 이하를 얻을 수 있었으며, 용접 접합부의 인장강도 210 MPa로써 구리 모재와 유사한 기계적 특성을 나타내었다.

Effects of the post treatment on the fatigue strength of a bead-on-plate weldment were investigated in order to improve fatigue strength of the weldment. The post treatment applied were the grinding of weld toe and hammer peening at the weld toe. The fatigue strength of the weldment after post treatment increases. It is attributed to the decrease of the residual stress and the maximum stress at the weld toe by the post treatments. Based on the result, the principal factor controlling the fatigue strength of the weldment was identified as the toe shape of the bead-on-plate weldment.

The purpose of this study is to establish the control method of angular distortion at the weldment of the pressure hull penetration. In order to do it, comprehensive experiment and FEA were performed to evaluate the distortion behavior for the weldment of HY-100. Based on the results, a proper deposit sequence for the both sides X groove penetration weldment was established. In addition, a proper welding sequence was proposed by evaluation of bending restraint intensity with size and position of pressure hull penetration.

Fictitious notch radius approach is based on the Neuter's microstructural support hypothesis which assumes that fatigue crack is governed by highly stressed volume of the material right on the weld toe area rather than the surface stress at a pin point of weld toe area. Variety of successes have been achieved in applying this methodology to the fatigue of welded joint, hence, it became one of recommended design procedure in IIW's recommendation as well as many ship classification societies. 1mm fictitious notch radius approach was applied to the various fatigue problems of welded joints in this study covering the effect of weld size, notch stress calculation for 3D geometry and low cycle fatigue problem. It was found that fictitious notch radius approach fumed out to be very effective and accurate in dealing with fatigue strength of welded joint.

In this paper an important class of problems in welding which come under the category of phase change is considered, Solidification and melting are important process in welding field. Phase change problems are accompanied by either absorption or release of thermal energy i,e, heat transfer process. This is complicated by the release or absorption of the latent heat of fusion at the solid-liquid interface. In this study the liberation of latent heat is taken in to account using fixed grid method. The numerical simulation and the finite element codes for the heat transfer analysis including the latent heat term has been developed based on this fixed grid method.

The purpose of this study is to evaluate the effects of hammer peening on the redistribution of residual stress at the repair weldment of cast iron using FEA. The FEA results were verified by comparing with experimental results. The maximum residual stress at the repair weldment of cast iron sharply decreases by hammer peening. The effect of hammer peening on the residual stress increases with a decrease of working temperature of hammer peeing.

The purpose of this study is to identify the effects of the length of tack weldment on the rotational distortion at the one side SA butt weldment using experiment. The maximum rotational distortion at the end of the SA weldment decrease with an increase in the length of tack weld length, while the maximum rate of the distortion increases. This result indicates that the increase of the length of the tack weldment at the one-side SA butt weldment does not prevent the hot cracks.