• Proceedings of the KWS Conference
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• 2005.11a
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• pp.189-191
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• 2005

Dissimilar joining of AI 6013-T4 alloys and austenite stainless steel was carried out using friction stir welding technique. Microstructures near the weld zone and mechanical properties of the joint have been investigated. Microstructures in the stainless steel side and AI alloy were depended on the thermo-mechanical condition which they received. TEM micrographs revealed that the interface region was composed of the mixed layers of elongated stainless steel and ultra-fine grained AI alloy and intermetallic compound layer which was identified as the $Al_{4}Fe$ with hexagonal close packed structure. Mechanical properties were lower than those of 6013 AI alloy base metal, because tool inserting location was deviated to AI alloy from the butt line, which resulted in the lack of the stirring.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.2
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• pp.186-192
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• 2002

The fatigue crack propagation characteristics were investigated on dissimilar friction weld of two kind of heat-resisting steels (STR3 and STR35) commonly used in valve materials for vehicles. A small circular artificial defect was machined to induce fatigue crack at bonded line, heat affected zone and base metal of the weld on the surface of the specimens. From the results of the experiment, the fatigue limits of the materials STR3 and STR35 were obtained to be 429.0MPa and 409.4MPa respectably. The STR35 base metal and 1.0mm HAZ specimens showed 190% and 82% higher fatigue life than STR3 base metal. And the fatigue life of 1.0mm HAZ specimen was shown 99% on STR3 and 29% on STR35 higher than that of their base metal. But the fatigue life of weld interface specimen was shown 18% on STR3 and 72% on STR35 lower than that of their base metal because of the weld interface separation.

• Journal of Welding and Joining
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• v.16 no.4
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• pp.47-54
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• 1998

Various equipments in plants are welded with two different materials and it is required to investigate the effects of fatigue crack propagation on the neighborhood of a welded portion. The characteristics of fatigue crack growth in the base metal of carbon and stainless steel, in the carbon and stainless steel sides located in the neighborhood of welded portion (carbon/stainless steel), respectively and welded portion, are investigated. The results show that the crack growth in the welded portion (carbon/stainless steel) is an average value of the crack growths in the carbon and stainless steel respectively located in the neighborhood of the welded portion. It is found that the crack growth in the welded portion is not significantly different from those in the carbon and stainless steel sides. Hence it can be concluded that the structure welded with two different materials wold not impede the integrity based on the fatigue crack growth.

• Journal of Power System Engineering
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• v.10 no.1
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• pp.77-82
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• 2006

In this study, dissimilar friction welding were produced using 15mm diameter solid bar in chrome molybedenum steel(SCM440) to carbon steel(S45C) to investigate their mechanical properties and the relationship between the weld parameters and the nondestructive coefficients, such as AE counts and ultrasonic attenuation coefficient. The main friction welding parameters were selected to endure good quality welds on the basis of visual examination, tensile tests, Vickers hardness surveys of the bond of area and heat affected zone. The specimens were tested as-welded and post weld heat treated(PWHT). The tensile strength of the friction welded steel bars was increased up to 100％ of the S45C base metal under the condition of all heating time. The ductility of PWHT specimens is higher than as-welded.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.4 s.247
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• pp.402-408
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• 2006

Dissimilar friction welding were produced using 15(mm) diameter solid bar in chrome molybedenum steel(KS SCM440) to carbon steel(KS S45C) to investigate their mechanical properties. The main friction welding parameters were selected to endure good quality welds on the basis of visual examination, tensile tests, Vickers hardness surveys of the bond of area and H.A.Z and microstructure investigations. The specimens were tested as-welded and post-weld heat treated(PWHT). The tensile strength of the friction welded steel bars was increased up to 100% of the S45C base metal under the condition of all heating time. Optimal welding conditions were n=2,000(rpm), $P_1=60(MPa),\;P_2=100(MPa),\;t_1=4(s),\;t_2=5(s)$ when the total upset length is 5.4 and 5.7(mm), respectively. The peak of hardness distribution of the friction welded joints can be eliminated by PWHT. Two different kinds of materials are strongly mixed to show a well-combined structure of macro-particles without any molten material and particle growth or any defects.

• Journal of Korean Society of Steel Construction
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• v.11 no.1 s.38
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• pp.33-42
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• 1999

In the present study, crack initiation criteria, static failure and tensile mode fatigue behavior for a rail steel are evaluated to assure the railway vehicle's safety. The transverse fissure, which is the most critical damage in the rail, is initiated by the maximum shear stress and its location is subsurface. In addition, the possibility of transition from the shear mode to the mixed mode increases with increasing the length of subsurface crack. Because of the brittleness by the welding, the fracture toughness of the welded part is lower than of the base metal. For low ${\Delta}K$, the stage II fatigue crack growth rates of the welded part is slower than of the base metal but, for high ${\Delta}K$, this different behavior for fatigue crack growth rate is nearly diminished. These trends are more remarkable for low stress ratio, R=0.1. It is believed that this behavior is caused by the change of the microstructure which that of the welded part is coarser than of base metal.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.8
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• pp.649-656
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• 2019

Flux cored arc welding (FCAW), which is used widely in many fields, such as shipyards, bridge structures, construction machinery, and plant industry, is an alternative to shielded metal arc welding (SMAW). FCAW is used largely in the welding of carbon and alloy steel because it can be welded in all poses and obtain excellent quality in the field under a range of working conditions. In this study, the mechanical properties of welded parts were analyzed after different welding of SS400 and SM490A using FCAW. The following conclusions were drawn. The tensile test results satisfied the KS standard tensile strength in the range of 400~510 N/mm2 in all welding positions. The bending test confirmed that most of the specimens did not show surface breakage or other defects during bending and exhibited sufficient toughness, even after plastic deformation. The hardness test results were lower than the standard value of 350 Hv of KS B 0893. Similar to the hardness test, were greater than the KS reference value. The macro test revealed no internal flaws, non-metallic inclusions, bubbles or impurities on the entire cross section of the weld, and there were no concerns regarding lamination.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.2
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• pp.51-58
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• 2006

Laser welding of dissimilar metals has been widely used to improve a wear resistance and a corrosion resistance of the industrial parts. The objective of this research works is to investigate the influence of the process parameters, such as the welding for SM45C and STS304 with CW Nd:YAG lasers. The bead-on-plate welding tests are carried out for several combinations of the experimental conditions. In order to quantitatively examine the characteristics of the dissimilar welding, the welding quality of the cut section, stain-stress behavior and the hardness of the welded part are investigated. From the results of the investigation, it has been shown that the optimal welding condition without defects in the vicinity of the welded area and with a good welding qualify is 1600W of the laser power, 0.85m/min of welding speed and $4{\ell}/min$ of pressure for shielding gas.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.997-1003
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• 2005

Laser welding of dissimilar metals has been widely used to improve a wear resistance and a corrosion resistance of the industrial parts. The objective of this research works is to investigate the influence of the process parameters, such as the welding for SM45C and STS304 with CW Nd:YAG lasers. The bead-on-plate welding tests are carried out for several combinations of the experimental conditions. In order to quantitatively examine the characteristics of the dissimilar welding, the welding qualify of the cut section, stain-stress behavior and the hardness of the welded part are investigated. From the results of the investigation, it has been shown that the optimal welding condition without defects in the vicinity of the welded area and with a good welding quality is 1600W of the laser power, 0.85m/min of welding speed and 4m/min of pressure for shielding gas.

• Journal of Welding and Joining
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• v.30 no.6
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• pp.1-5
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• 2012