• Journal of Welding and Joining
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• v.35 no.2
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• pp.43-51
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• 2017

The automatic welding systems, have received much attention in recent years, because they are highly suitable not only to increase the quality and productivity, but also to decrease manufacturing time and cost for a given product. Automatic welding work in semiconductor or space industry to be carried out in pipe line and butt joint mostly and plasma arc welding(PAW) is actively applied. To get the desired quality welds in automated welding system is challenging, a mathematical model is needed that has complete control over the relevant process parameters in order to obtain the required mechanical properties. However, In various industries the welding process mathematical model is not fully formulated for the process parameter and on the welding conditions, therefore only partial variables can be predicted. Therefore, this paper investigates the interaction between the welding parameters and mechanical properties for predicting the weld bead geometry by analyzing the S/N ratio.

• Journal of Welding and Joining
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• v.27 no.5
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• pp.62-67
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• 2009

Welding deformation during the assembly process is affected by not only local shrinkage due to rapid heating and cooling, but also root gap and misalignment between parts to be welded. Therefore, the prediction and control of welding deformation have become of critical importance. In this study, it was focused on the development of the 3-axis apparatus for real-time measurement of the welded deformation. To achieve the objective, a D-H algorithm has been carried out to check the behavioral and performance evaluation for the developed robot. The sequence experiments were taken the base materials of $400{\times}200{\times}4.5mm$ plate for butt welding. The real-time experimental measurements are in good agreement with the measured results.

• Journal of Welding and Joining
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• v.32 no.1
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• pp.28-33
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• 2014

In this paper, I-butt welding with 6mm thickness using Plasma-GMA welding was carried out. And weld characteristics of the Al-5083 aluminium alloy for Plasma-GMA hybrid welding was evaluated. The orthogonal experimental design was used to investigate the influence of plasma-MIG welding parameters such as plasma current, wire feeding rate, MIG-welding voltage and welding speed on the weld bead geometry and tensile strength using the ANOVA(Analysis of Variation). Then we conducted evaluation of contribution for process parameters. ANOVA results show that bead dimensions are affected by wire feeding speed, welding voltage and welding speed and tensile strength is mainly affected by welding speed and plasma arc current. Tensile strength was decreased by rise in plasma welding current because GMA welding current was decreased by plasma arc.

• Journal of Welding and Joining
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• v.7 no.4
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• pp.30-37
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• 1989

Effect of heat treatment on mechanical properties of an overlay weldment was investigated. Over welding was carried out on the structural C-Mn mild steel substrate to take required test specimens. Shielded metal arc welding process with 13Cr-0.2Ni stick electrode was applied. The heat treatment temperatures and holding times were $450{\circ}C., 550{\circ}C., 650{\circ}C., 750{\circ}C., 850{\circ}C.$ and 0.5hr, 2hr, 10hr, respectively. Mechanical tests and microscopic inspection were also carried out to investigate welds soundness. Test results indicated that carbon migration was dominant near bonded zone. At temperature of around 650.deg. C, carburized layer and decarburized layer were formed remarkably along overlay welds region and C-Mn mild steel region, respectively. The wideth of these layers became wider with increasing heat treatment temperature and/or holding time at the elevated temperature, and this relationship agreed with Larson-Miller parameter. Side bending test results demonstrated that the crack free region of overlay welds could be deduced from the relationship between temperature and holding time.

• Journal of Welding and Joining
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• v.31 no.6
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• pp.8-16
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• 2013

As the energy consumption increases rapidly, power generation needs the high energy efficiency continuously. To achieve the high efficiency of power generation, the materials used have to endure the higher temperature and pressure. The 9-12%Cr steels possess good mechanical properties, corrosion resistance, and creep strength in high temperature due to high Cr contents. Therefore, the 9-12%Cr steels are widely used for the high-temperature components in power plants. Even though the steels usually have a fully martensitic microstructure, they are susceptible to the formation of ${\delta}$-ferrite specifically during the welding process. The formation of ${\delta}$-ferrite has several detrimental effects on creep, ductility and toughness. Therefore, it is necessary to avoid its formation. As the volume fraction of ${\delta}$-ferrite is less than 2% in microstructure, it has the isolated island morphology and causes no significant degradation on mechanical properties. For ${\delta}$-ferrite above 2%, it has a polygonal shape affecting the detrimental influence on the mechanical properties. The formation of ${\delta}$-ferrite is affected by two factors: a chemical composition and a welding heat input. The most effective ways to get a fully martensite microstructure are to reduce the chromium equivalent less than 13.5, to keep the difference between the chromium and nickel equivalent less than 8, and to reduce the welding heat input.

• Journal of the Korean Society for Heat Treatment
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• v.32 no.3
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• pp.124-130
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• 2019

Friction stir welding is one of the interesting welding methods for titanium and its alloy which proceeds with plastic flow due to thermo-mechanical stirring and friction heat. Solid-state welding can solve severe problems such as high-temperature oxidation, interstitial oxygen diffusion and grain coarsening by liquid-state welding. Dynamic recrystallization and grain refinement can vary significantly with the plunging load and rotational speed of tool during friction stir welding, and suitable process conditions must be optimized to obtain microstructure and better mechanical characteristics. Suitable FSW conditions were 1000 kg of plunging load and 200 rpm of rotational speed and it showed YS 270 MPa, UTS 332.1 MPa, and El 17.3%, which were very similar to those of wrought titanium sheet.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.96-101
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• 2004

Conventionally, SMAW process was applied to join pipes of RCL, which caused lot of loss in time and cost due to excessive heat input and defects in joining section. Recently, narrow-gap welding(NGW) process was introduced to overcome the disadvantages of SMAW. However, the application of NGW to nuclear power plant is not yet common because safety of NGW process is not proven. In present paper, the welded coupons are made of carbon steel. They are manufactured under different processes; general welding(GW), post-weld heat treatment(PWHT) after GW, repair welding after GW and PWHT with repair welding after GW in carbon steel. Performed are various mechanical tests investigation of microstructure, hardness test, tensile test at room and high temperature, bending test, impact test and J-R test. It is verified that the mechanical properties of carbon steel are greatly changed after repair welding process due to applied heat flux, and that the effect of PWHT is beneficial.

• Journal of Welding and Joining
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• v.34 no.6
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• pp.28-34
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• 2016

Galvannealed(GA) steels are now generally used in car body manufacturing for corrosion resistance. In this study, the weldability and joint mechanical behavior of a newly developed 1.2GPa grade GA ultra high strength TRIP(transformation induced plasticity) steel was investigated for three joining processes, such as adhesive bonding, resistance spot welding and weldbonding. Under both shear and peel stress conditions, the failure mode of the adhesive joints were the mixture of the adhesive cohesive failure, adhesive interface failure and coating layer failure. It means that the adhesion strength of GA coating onto the base metal was similar to that of adhesive bonding onto the GA coating. Under the shear stress condition, the weldbonding exerted to expand the optimal spot welding condition of 1.2GPa GA TRIP steel because the strength of adhesive bond overwhelmed that of the resistance spot weld. Under the peel stress condition, the weldbonding also exerted to expand the optimal spot welding condition of 1.2GPa GA TRIP steel by inducing the tear fracture mode rather than the partial plug fracture mode.

• Journal of Welding and Joining
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• v.32 no.2
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• pp.29-36
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• 2014

Recently, in order to enhance the function and usefulness of products, cladding of dissimilar materials that maximizes the performance of the material is being widely used in all areas of industry as an important process. Clad steel plate, produced by cladding stainless steel plate, an anticorrosive material, on carbon steel plate, is being used to produce pressure vessels. Stainless steel plate has good corrosion resistance, and carbon steel plate has good rigidity and strength; clad steel can satisfy all of these qualities at once. This study aims to find the ${\delta}$-ferrite behavior, mechanical properties, structure change, integrity and reliability of clad steel weld on hot rolled steel plates. For this purpose, multi-layer welding, repair welding and post weld heat treatment were implemented according to welding procedure specifications (WPS). In order to observe the mechanical properties and toughness of clad steel weld zone, post weld heat treatment was carried out according to ASME Sec. VIII Div.1 UW-40 procedure for post weld heat treatment. With heat treatment at $625^{\circ}C$, the hold time was used as the process variable, increased by intervals that were doubled each time, from 80 to 1,280 min. The structure of weld part was typical cast structure; localized primary austenite areas appeared near central vermicular ferrite and fusion line. The heat affected zone showed rough austenite structure created by the weld heat input. Due to annealing effects of heat treatment, the mechanical properties (tensile strength, hardness, impact value) of the heat affected area tended to decrease. From the results of this study, it is possible to conclude the integrity of clad steel welds is not affected much in field welding, repair welding, multi-layer welding, post weld heat treatment, etc.

• Journal of Welding and Joining
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• v.23 no.6
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• pp.37-42
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• 2005

Most of the welding steel plate structures have complicated mechanical problems such as rolling directional characteristics and residual stresses caused by manufacturing process. For the enhancement of reliability and safety in those structures, therefore, a systematic investigation is required. SS400 steel plate used for common structures was selected and welded by FCAW butt-welding process for this study, and then it was studied experimently about characteristics of fatigue crack propagations with respect to rolling direction and welding residual stress of welded steel plates. When the angles between rolling direction and tensile loading direction in base material are increased, their ultimate strength not show a significant difference, but yielding strength are increased and elongations are decreased uniformly. It is also shown that fatigue crack growth rate can be increased from those results. When the angles between welding bead direction and loading direction in welded material are increase, fatigue crack growth rate of them are decreased and influenced uniformly according to the conditions of residual stress distribution. In these results, it is shown that the welded steel plate structures are needed to harmonize distributed welding residual stress, rolling direction and loading direction fur the improvement of safety and endurance in manufacture of their structures.