• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.665-668
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• 2002

Joining thin aluminum alloy is difficult using most wilding techniques. Many of problems associated burn-through by the high heat input Common welding techniques are TIG, MIG, and MIG-PULSE welding. The VP-GMAW provides more control of the heat balance in the voiding arc by taking advantage of the different arc characteristics obtained with each of the two polarities. In this paper, we proposed new VP_GMA Welding method by control DSP 320C32, and the characteristic and experiment result-voltage, current, welding bead. penentraion by this method are presented

• Journal of Welding and Joining
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• v.12 no.3
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• pp.56-62
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• 1994

The spot weldability of high strength steel sheet and two stories galvannealed high strength steel sheet has been studied. 1) Tensile shear strength decreased inversely as welding current increased over 12KA in the case of two stories galvannealed high strength steel sheet. 2) When heat flux input over 12KA, hardening region become narrow in case of two stories galvannealed high strength steel sheet. 3) The size of hardening region affect the strength of nuggets.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.4
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• pp.1-12
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• 2007

S45C steel has been widely used in industrial applications, such as crank shafts, gears, main spindles of machine tools, connecting rods, etc., because of its distinguished mechanical property. In the convention arc welding of S45C plates without heat treatments, it is possible for welding defects to take place, such as a void or a hot-crack, due to a high carbon composition of S45C. 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, single-pass thick section capability, and small distortion after welding. The objective of this research works is to investigate the influence of the process parameters, such as power of laser and welding speed, on the characteristics of laser welding for the case of nickel coated and nickel uncoated S45C steel. As the result of the experiment, in case of butt welding, nickel coated S45C steel has a uniform formation of welding zone and it was judged that the welding nature was better as inner defects and the quantity of spatter were formed relatively fewer than nickel uncoated S45C steel.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.8
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• pp.681-685
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• 2015

Hastelloy C-276 composed of Cr, Mo, and Ni is a versatile, corrosion-resistant alloy with numerous industrial applications including its use in nuclear reactors, general chemical plants, and as a superconducting base material. Of especial significance, it can be used as a thin-sheet type whereby lap-joint welding is occasionally necessary. The main welding problems for thin-sheet metals are deformation and burn-through from an excessive heat input. Laser welding can minimize these problems because it has a high energy density and low heat effect on the base material. In this study, the laser-welding characteristics of lap-joint Hastelloy C-276 sheet metal were determined. The criteria of the laser-welding variables were chosen using a heat-conduction analysis, and the optimal welding parameters were selected by experimenting with an Nd:YAG laser.

• Journal of the Korean Society for Heat Treatment
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• v.19 no.3
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• pp.156-162
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• 2006

The aim of this study is to investigate the full annealing parameter for A3003 Al alloy welded tubes. The A3003 Al alloy tubes with 34 mm in external diameter and 1.3 mm in thickness for OPC drum were manufactured by high frequency induction welding with the V shaped convergence angle $6.7^{\circ}$ and power input 50 kW. The tensile and yield strength decreased with increasing the annealing temperature and time remarkably, but elongation increased remarkably. Vickers hardness in welds and base metal decreased with increasing the annealing temperature and time remarkably. In a certain experimental condition, the welds line in A3003 alloys disappeared at $520^{\circ}C$ for 4hr because of the same mechanical properties and structures between welds and base metal.

• Journal of Welding and Joining
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• v.32 no.4
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• pp.26-33
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• 2014

The metallurgical and mechanical characteristics, toughness and corrosion resistance of dissimilar welds between super duplex stainless steel UNS S32750 and carbon steel ASTM A516Gr.70 have been evaluated. Three heat inputs of 21.12, 24.00, 26.88kJ/cm were employed to make joints of dissimilar metals with flux cored arc welding(FCAW). Based on microstructural examination, vermicular ferrite was formed in the first layer of weld at low heat input(21.12kJ/cm) and $Cr_{eq}/Ni_{eq}$ of 1.61 while acicular ferrite was formed in last layer of weld at high heat input(26.88kJ/cm) and $Cr_{eq}/Ni_{eq}$ of 1.72. Ferrite percentage in dissimilar welds was lowest in the first layer of weld regardless of heat inputs and it gradually increased in the second and third layers of weld. Heat affected zone showed higher hardness than the weld metal although reheated zone showed lower hardness than weld metal due to the formation of secondary austenite. Tensile strengths of dissimilar welds increased with heat input and there was 100MPa difference. The corrosion test by ferric chloride solution showed that carbon steel had poor corrosion resistance and pitting corrosion occurred in the first layer(root pass) of weld due to the presence of reheated zone where secondary austenite was formed. The salt spray test of carbon steel showed that the surface only corroded but the amount of weight loss was extremely low.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.10
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• pp.1078-1088
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• 2012

In this paper, we present research experimental results about the different thickness T-joint welding of the high power continuous wave(CW) Nd:YAG laser for the secondary battery of a vehicle. Although the conventional method used for the secondary battery is a argon TIG welding, we utilize a laser welding to improve Tungsten Inert Gas(TIG) welding's weakness. The laser, which has a couple of advantage such as aspect ratio, low Heat Affected Zone(HAZ), good welding quality and fast productivity utilized in this work is a CW Nd:YAG laser. In order to observe laser welding sections, we used a optical microscope. Through the analysis of the metallographic, hardness, aspect ratio, and heat input, we obtained the desired data in condition of 1800 W laser beam power and 1.8 m/min and 2.0 m/min laser beam travel speeds. In order to compare electric resistances of the argon TIG welding and laser welding, we made an actual battery and the electric resistance of the laser welding is reduced by 40~45% comparing with the argon TIG welding.

• International Journal of Korean Welding Society
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• v.2 no.1
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• pp.25-28
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• 2002

In the coarse grain HAZ adjacent to the fusion line, most of the TiN particles in conventional Ti added steel are dissolved and austenite grain growth is easily occurred during welding process. To avoid this difficulty, thermal stability of TiN particle is improved by increasing the nitrogen content in steel. In this study, the effect of hlgh nitrogen TiN particle on preventing austenite grain growth in HAZ was investigated. Increased thermal stability of TiN particle is helpful for preventing the austenite grain growth by pinning effect. High nitrogen TiN particle in simulated HAZ were not dissolved even at high temperature such as 1400'E and prevented the austenite grain growth in simulated HAZ. Owing to small austenite grain size in HAZ the width of coarse grain HAZ in high nitrogen TiN steel was decreased to 1/10 of conventional TiN steel. Even high heat input welding, the microstructure of coarse grain HAZ consisted of fine polygonal ferrite and pearlite and toughness of coarse grain HAZ was significantly improved.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.670-677
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• 2003

Although Gas Tungsten Arc Welding (GTAW or TIG welding) is considered as high quality and precision welding process, it also has demerit of low melting rate. Narrow-gap TIG welding which has narrow joint width reduces the groove volume remarkably, so it could be shorten the welding time and decrease the overall shrinkage in heavy wall pipe welding. Generally Narrow-gap TIG welding is used as orbital welding process, it is important to select the optimum conditions for the automatic control welding This paper looks at the application and metallurgical properties on Narrow-gap TIG welding joint of heavy wall large austenitic stainless steel pipe to determine the deposition efficiency, the resultant shrinkage and fracture toughness. The fracture toughness depends slightly on the welding heat input.

• 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.