• Journal of Welding and Joining
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• v.27 no.3
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• pp.60-66
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• 2009

The structures distorted by welding have to be corrected. Since the correcting work needs a lot of costs and time, it is very important to minimize the buckling distortion due to welding of thin plate structure. Therefore the aim of this study is to investigate the effect of single bead on plate welding and fillet welding on the buckling distortion. In the single bead on plate welding, it was found that the welding speed and welding sequence were the most dominant factors on distortion. In the fillet welding, there were four typical buckling modes observed, and the welding sequence was the most influential factor on the buckling distortion. However typical distortion measuring method is not considered for the distortion correcting process costs of each buckling modes, therefore, in this study, the measuring method is developed to classify the buckling modes for torsion of specimen and buckling distortion depend on nodal point for the bead on plate welding specimen and fillet welds.

• International Journal of Korean Welding Society
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• v.1 no.2
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• pp.30-35
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• 2001

Nowadays, repair welding on in-service natural gas pipeline is a matter of primary concern of gas company. The main purpose of this study is to investigate the effects of welding conditions on the allowable heat input for crack-free welds and welds without burn-through onto in-service natural gas pipeline. First of all, single pass weld bead on plates of the various thickness was deposited to evaluate the penetration of weld metal, the depth of heat affected zone and the hardness of repair weld under various welding conditions. Also, finite element analysis has been conducted to validate experimental results of bead-on plate welds and to develop appropriate model for repair welding. The welding experiments of bead-on-plate weld confirmed the influence of plate thickness, heat input and welding process on safety. And, the finite element model was demonstrated by comparing experimental results. The agreement between the computed and measured values was shown to be generally good. Therefore, It is possible to predict the safety of repair welding under various welding conditions with experimental results and finite element analysis model.

• Journal of Welding and Joining
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• v.15 no.3
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• pp.118-127
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• 1997

With the trend towards welding automation and robotization, mathematical models for studying the influence of various variables on the weld bead geometry in gas metal arc (GMA) welding process are required. Partial penetration, single-pass bead-on-plate welds using the GMA welding process were fabricated in 12mm mild steel plates employed four different process variables. Experimental results has been designed to investigate the analytical and empirical formulae, and develop mathematical equations for understanding the relationship between process variables and weld bead geometry. The relationships can be usefully employed not only for open loop process control, but also for adaptive control provided that dynamic sensing of process output is performed.

• Journal of Welding and Joining
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• v.14 no.4
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• pp.33-42
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• 1996

In recent years there has been a significant growth in the use of the automated and/or robotic welding system, carried out as a means of improving productivity and quality, reducing product costs and removing the operator from tedious and potentially hazardous environments. One of the major difficulties with the automated and/or robotic welding process is the inherent lack of mathematical models for determination of suitable welding process parameters. Partial-penetration, single-pass bead-on-plate welds were fabricated in 12mm AS 1204 mild steel flats employing five different welding process parameters. The experimental results were used to develop three empirical equations: curvilinear; polynomial; and linear equations. The results were also employed to find the best mathematical equation under weld bend width to assist in the process control algorithms for the Gas Metal Arc Welding(GMAW) process and to correlate welding process parameters with weld bead width of bead-on-plates deposited. With the help of a standard statistical package program. SAS, multipe regression analysis was undertaken for investigating and modeling the GMAW process, and significance test techniques were applied for the interpretation of the experimental data.

• Journal of Welding and Joining
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• v.26 no.2
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• pp.50-54
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• 2008

The wearplate with Cr-C has been used in condition of severe abrasion. Recently, the demand of wearplate made by hardfacing with Cr-C has increased in the world, but it is lack of supply and expensive due to low productivity. CMAW (Compound Metal Arc Welding) is very useful process of several welding methods to make wearplate. In this paper, twin torch CMAW to use twin torch at the same time was developed to improve productivity and to ensure quality of wear plate. When the distance between two touches was smaller than 30mm, arc blow was occurred. However when the distance was larger than 35mm, there was no arc blow any more. If the oscillation path of each torch was overlapped together, the melt through at the overlapped zone was occurred due to concentrated heat input in substrate. On the other hand, the turning point of each torch was open more than 5mm, separated bead was generated. Therefore twin torch CMAW which has adequate conditions was able to make wearplate having flatter surface at the bead connection than single torch.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.661-667
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• 2002

Welding-induced buckling distortion is one of the most problematic concerns in both design and fabrication of welded thin-plate structures. This paper deals with experimental and numerical results of the welding-induced longitudinal and/or buckling distortion occurring in welding of 6mm-thick AH36 high strength steel plates. Effects of the heat input and the plate size on the distortion were experimentally evaluated for square plates. Bead-on-plate welding was performed with the submerged arc welding process along the middle line of plate specimens. Experimental results showed that the longitudinal distortion made a single curvature in the plate, and the distortion magnitude along the weld centerline was proportional to the heat input and the plate size. The experimental results were used to examine the validity of the numerical simulation procedure for welding-induced distortion where the longitudinal distortion mode and magnitude were numerically quantified. Three-dimensional, large deformation, welding simulations were performed for selected weld models. Numerical results of the distortion mode and magnitude were in a good agreement with experimental ones. Depending on the presence of halting the distortion growth during the cooling cycle of welding, the condition discriminating buckling distortion from longitudinal distortion was established. Eigenvalue analyses were performed to check the buckling instability of tested plates with different sizes subjected to different heat inputs. The perturbation load pattern for the analysis was extracted from longitudinal inherent strain distributions. Critical buckling curve from the eigenvalue analyses revealed that the buckling instability is manifested when plate size or heat input increases.

• Journal of Welding and Joining
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• v.25 no.3
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• pp.18-27
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• 2007

Laser welding process is widely used in the industrial field due to its numerous advantages: a small heat affected zone(HAZ), deep penetration, high welding speed, ease of automation, single-pass thick section capability, enhanced design flexibility, and small distortion after welding. The objective of this research works is to investigate the influence of the process parameters, such as the welding fur metals with CW Nd:YAG lasers. The bead-on-plate and Lap welding experiments are carried out for several combinations of the experimental conditions. In order to quantitatively examine the characteristics of the welding quality of the cross section, tensile stress behavior and the hardness of the welded part are investigated in comparison of the Nickel coated and Nickel uncoated S45C steel. As a result of experiment, nickel coated S45C Steel showed more even weld zone than Nickel uncoated counterpart upon lap welding. Also, it showed relatively small amount of internal defects and spatter, and Nickel coated S45C showed better weldability than Nickel uncoated S45C steel. The optimum welding process upon lap welding of Nickel coated S45C steel is when each laser power is 1900W; focal positions is -1mm; welding speed is $0.9{\sim}1.0m/min$. The heat input was $4.178{\sim}4.36{\times}103J/cm^2$.

• Proceedings of the KWS Conference
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• 2006.05a
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• pp.286-288
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• 2006

The metallurgical and mechanical properties of fiction stir welded 304 austenitic stainless steel and AISI 1018 steel for fundamental study. Single-pass bead on plate weldments in the two steels were successfully achieved. The joints were evaluated by microscopy and hardness tests of the transverse cross section and transverse tensile tests.

• Journal of Welding and Joining
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• v.21 no.3
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• pp.51-57
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• 2003

The metal transfer in $CO_2$ welding shows the transition of transfer mode from short-circuiting to repelled transfer will the increase of welding current. While the short-circuiting mode in $CO_2$ welding has been studied very extensively relating with droplet formation and spatter generation, the repelled transfer has little been understood. In this study, high current $CO_2$ welding has been performed with bead-on-plate welds along with the waveform analyzer and high speed camera. The image of high speed camera was synchronized with its waveform so that the moment of spatter generation could be realized during drop detachment. As a results of this study, it was found that welding arc changes its location either once or three times and thus single or double pulse signals were developed in the voltage waveform. Whenever the arc moved its location, new arc was developed in a explosive way and thus it caused spatter generation. Specially severe spattering took place when the waveform showed a double-peak pattern. As a consequence of these results, new waveform control techniques could be suggested for suppressing the spatter generation in the high-current $CO_2$ welding.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.5
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• pp.70-75
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• 1999

Adaptive control in the robotic GMA(Gas Metal Arc) welding is employed to monitor the information about weld characteristics and process paramters as well as modification of those parameters to hold weld quality within the acceptable limits. Typical characteristics are the bead geometry composition micrrostructure appearance and process parameters which govern the quality of the final weld. The main objectives of this paper are to realize the mapping characteristicso f penetration through the learning. After learning the neural network can predict the pene-traition desired from the learning mapping characteristic. The design parameters of the neural network estimator(the number of hidden layers and the number of nodes in a layer) were chosen from an error analysis. partial-penetration single-pass bead-on-plate welds were fabricated in 12mm mild steel plates in order to verify the performance of the neural network estimator. The experimental results show that the proposed neural network estimator can predict the penetration with reasonable accuracy and gurarantee the uniform weld quality.