• Journal of Welding and Joining
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• 제27권3호
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• pp.67-72
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• 2009

The flux cored arc welding (FCAW) process is one of the most frequently employed and important welding process due to high productivity and excellent workability. The process is performed either as an automated process or as a semi-automatic process. In FCAW process, welding voltage has been considered as a qualitative indication of arc length. But it is necessary to let welding operators know, maintain and manage the arc length directly by estimating and displaying it. In this study, to develop arc length estimation technique, we measured a welding circuit resistance($R_sc$) and then we calculated welding circuit voltage drop($V_sc$). Also, we measured arc peak voltage($V_ap$). By subtracting $V_sc$ from $V_arc$, we can easily calculate net arc voltage drop($V_arc$). Consequently, we suggested arc length estimating equation and basic algorithm by regressive analyzing the relationship between net arc voltage drop($V_arc$) and real arc length(Larc) measured by high speed camera. Therefore, arc length can be predicted by just monitoring welding current and voltage.

• 한국기계가공학회지
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• 제10권6호
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• pp.128-133
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• 2011

In this study, the steel material for shipbuilding(LR-A class) was used, and FCAW was taken advantage of 3G attitude and they are welded by different welding ways. As a result of analyzing wave with welding monitoring system, the stable values are obtained which are the first floor(electronic current 164~182 A, voltage 24 V), the second floor(electronic current 174~190 A, voltage 22~25 V), the third floor(electronic current 158~188 A, voltage 22~25 V), and fourth floor(electronic current 172~184 A, voltage 22~25 V), at this time, the stable wave standard deviation and changing coefficient could be obtained. When the welding testing through nondestructive inspection was analyzed know defect of welding, there was no defect of welding in A, D, E, but some porosities in B, and slag conclusion near the surface in C, because the length of arc was not accurate, and the electronic current and voltage was not stable. After observing the change of heat affect zone through micro testing, each organization of floor formed as Grain Refinement, so welding part was fine, the distance of heat affect zone is getting wider up to change the values of the electronic current and voltage. As a result of degree of hardness testing, the hardness orders were the heat affect zone(HAZ), Welding Zone(WZ), and Base Metal(BM). When the distribution of degree of hardness is observed. B is the highest degree of hardness The reason why heat effect zone is higher than welding zone and base metal, welding zone is boiled over melting point($1539^{\circ}C$) and it starts to melt after the result of analysis through metal microscope, so we can know that delicate tissue is created at the welding zone. Therefore, in order to get the optimal conditions of the welding, the proper current of the welding and voltage is needed. Furthermore the precise work of welding is required.

• 한국기계가공학회지
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• 제16권1호
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• pp.112-117
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• 2017

The arc, generated by Tungsten Inert Gas(TIG) welding, is stable and provides excellent quality of the weld. Since automation is difficult, a lot of work is performed by hand. In addition, to obtain the uniform weld quality is difficult when using a base metal having a nonuniform welding line, or when welding inside a pipe. Generally, TIG welding power has the characteristic of constant-current. The welding voltage is changed in proportion to the arc length. Hence, the automatic voltage control equipment should be applied at the TIG welding system. The automatic voltage control equipment has been designed using LabVIEW software. It consists of a manufactured voltage divider circuit, and jig for moving the torch. The voltage measurements and driving of the motor were performed through the algorithm implementation in LabVIEW. Welding was conducted while increasing the arc length. In this process, it was confirmed that the automatic voltage control equipment kept the arc length constant.

• Journal of Welding and Joining
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• 제15권3호
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• pp.79-87
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• 1997

This study was performed to evaluate basic characteristics of electron beam welding process for a 9% Ni steel plate. The principal welding process parameters, such as working distance, accelerating voltage, beam current and welding speed were investigated. The AB (Arata Beam) test method was also applied to characterize beam size and energy density of the electron beam welding process. The electron beam size was found to decrease with the increase of accelerating voltage and the decrease of working distance. So, in case of high voltage (150kV), spot size and energy density of electron beam were revealed to be 0.9mm and $6.5\times10^5W/\textrm{cm}^2$ respectively. The accelerating voltage among the welding parameters was found to be the most important factor governing the penetration depth. When the accelerating voltage of electron beam was low ($\leq$90kV), beam current and welding speed did not affect on the penetration depth significantly. However, in case of high voltage ($\geq$120kV), the depth of penetration increased very sensitively with the increase of beam current and the decrease of welding speed.

• 한국산업정보학회논문지
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• 제21권2호
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• pp.39-44
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• 2016

본 연구에서는 용접전류 및 용접전압 신호처리에 의한 용접 상태 검출에 있어 용접 와이어의 직경이 미치는 영향에 관하여 연구하였다. 실험을 위하여 인위적으로 모재의 간격을 용접 와이어보다 작은 경우와 큰 경우에 대하여 분석하였다. 사용된 용접 와이어의 직경은 1.2 mm이었으며 인위적으로 형성한 용접 모재 사이의 간격은 1.0 mm와 2.0 mm 두 종류를 사용하였다. 실험결과 용접 와이어의 직경보다 큰 용접 결함 요인에 대하여서는 용접전류 및 용접전압의 변화를 감지할 수 있으나 직경보다 작은 용접 결함 요인에 대하여서는 용접전류 및 용접전압의 변화를 감지할 수 없었다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1999년도 특별강연 및 추계학술발표대회 개요집
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• pp.47-50
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• 1999

The term adaptive control is often used to describe recent advances in welding process control but strictly this only applies to system which are able to cope with dynamic changes in system performance. In welding applications, the term adaptive control may not imply the conventional control theory definition but may be used in the more descriptive sense to explain the need for the process to adapt to the changing welding conditions. This paper proposed a methodology for obtaining a good bead appearance based on multi-torches welding system with the vision system in SAW. The methodologies for adaptive filling control used the welding current/voltage, arc voltage/welding current/wire feed speed combination and welding speed by using the vision sensor. It was shown that the algorithm for the welding current/voltage combination and welding speed revealed the sound weld bead appearance compared with that of the voltage/current combination.

• 한국산업정보학회논문지
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• 제19권6호
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• pp.25-31
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• 2014

GMAW(Gas metal arc welding) 방법은 높은 용착률과 낮은 비용으로 인해 제조 산업분야에서 폭넓게 사용되고 있다. 이 용접방법은 제조 산업분야에서 높은 생산력을 유지하는데 바탕이 되고, 자동화 설비 또는 로봇을 이용한 용접에 적합하다. 용접전압과 전류는 용접비드에 많은 영향을 미친다. 그럼에도 불구하고 용접 전압과 전류는 용접 조건과 사용자 환경에 따라 그 변화가 심하고 예측이 불가능하다. 이 값들을 직접 용접 상태 검출에 사용할 수 없기 때문에 적절한 데이터 분석 기법이 사용되어야 한다. 본 논문에서는 용접 중에 측정된 전압과 전류 데이터에 대하여 이동평균필터를 적용하였다. 그 결과 정상용접 상태의 전압 및 전류의 신호특성과 비정상용접 상태의 전압 및 전류 신호의 특성을 구분할 수 있었으며 이를 통해 용접 상태 검출이 가능하게 되었다.

• Journal of Welding and Joining
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• 제17권6호
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• pp.90-99
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• 1999

Significant portion of the total manufacturing time for a pipe fabrication process is spent on the welding following primary machining and fit-up processes. To achieve a reliable weld bead appearance, automatic seam tracking and adaptive control to fill the groove are urgently needed. For the seam tracking in welding processes, the vision sensors have been successfully applied. However, the adaptive filling control of the multi-torches system for the appropriate welded area has not been implemented in the area of SAW(submerged arc welding) by now. The term adaptive control is often used to describe recent advances in welding process control by strictly this only applies to a system which is able to cope with dynamic changes in system performance. In welding applications, the term adaptive control may not imply the conventional control theory definition but may be used in the more descriptive sense to explain the need for the process to adapt to the changing welding conditions. This paper proposed various types of methodologies for obtaining a good bead appearance based on multi-torches welding system with the vision system in SAW. The methodologies for adaptive filling control used welding current/voltage, arc voltage/welding current/wire feed speed combination and welding speed by using vision sensor. It was shown that the algorithm for welding current/voltage combination and welding speed revealed sound weld bead appearance compared with that of voltage/current combination.

• Journal of Welding and Joining
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• 제30권5호
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• pp.46-50
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• 2012

This study was carried out to investigate the effect of welding parameters such as shielding gas compositions welding voltage and welding current on the pore formation in the weld beads of galvanized steel pipes produced with gas metal arc welding. The porosity was evaluated and rated by metallography and radiographic test in terms of weight percentage, number and distribution of pores in weld beads. The porosity increased with increasing welding voltage and current, in which Ar gas produced the most porosity while $Ar+5%O_2$ generated the least porosity. It was found that the porosity could be reduced by selection of the proper gas mixture composition such as $Ar+5%O_2$ and $Ar+10%CO_2$ and by using current (130~150A) and voltage(16~20V).

• 전력전자학회논문지
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• 제21권4호
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• pp.351-355
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• 2016

Welding machines are high-capacity systems used in a low-frequency range using IGBT. As their system is similar to a large transformer, most welding machines suffer a great loss because of hard switching and vast leakage inductance. A voltage-balancing circuit is designed to overcome these shortcomings. This circuit can reduce the transformer size by making it into a high frequency and reducing the input voltage by half and by adopting a serial structure that connects two full-bridges in a series to use a MOSFET with a good property at high frequency. In addition, a Schottky diode is used in the primary rectifier to overcome the low efficiency of most welding machines. To use the Schottky diode with a reliably relatively low withstanding voltage, an active snubber is adopted to effectively limit the ringing voltage of the diode cut-off voltage.