• Journal of Welding and Joining
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• 제33권5호
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• pp.14-19
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• 2015

This study has been performed to investigate the adhesive slag at GTAW weld zone after FCAW multi-pass welding. The cause of adhesive slag formation was examined using optical microscope, field emission scanning electron microscope(FE-SEM) and XRD analysis. The results obtained in this experiment are summarized as follows. Slag of GTAW weld zone surface during welding were formed by mixing the presence of slag in FCAW weld zone. While the slag cools, Cr-spinel phase were formed due to reactions in slag/metal interface. Also, a Cr moves form the weld metal to the slag to strong affinity between oxide atoms and Cr atoms. Hence, detachability of slag was exacerbated by decreasing the interfacial tensions between slag and weld metal.

• Journal of Welding and Joining
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• 제25권6호
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• pp.53-58
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• 2007

The present study examined the mechanical properties of the friction welding of shaft made of SKH51 and SM45C, of which the diameter is 12mm. Friction welding was done at welding conditions of 2,000rpm, friction pressure of 104MPa, upset pressure of 134MPa, friction time of 0.5sec to 2.5sec by increasing 0.5sec, upset time of 2 seconds. Under these conditions, a tensile test, a bending test, a shear test, a hardness test and a microstructure of weld interface were studied. When the friction time was 1.0 second under the conditions, the maximum tensile strength of the friction weld observed to be 963MPa, which is 89% the tensile strength of SKH51 base metal and 101% of the tensile strength of SM45C base metal. When the friction time was 1.0 seconds under the conditions, the maximum bending strength of the friction weld happened to be 1,647MPa, which is 78% the bending strength of SKH51 base metal(2,113MPa) and 87% of the bending strength of SM45C base metal(1,889MPa). When the friction time was 1.0 seconds under conditions, the maximum shear strength of the friction weld was observed to be 755MPa, which is 92% the shear strength of SKH51 base metal and 122% of the shear strength of SM45C base metal. According to the hardness test, the hardness distribution of the weld interface varied from Hv282 to Hv327. HAZ was formed from the weld interface to 1.2mm of SKH51 and 1.6mm of SM45C. Upon examination it was found that the microstructure became finer along with increase of friction revolution radius.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 춘계학술대회 논문집
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• pp.401-404
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• 2007

Inertia welding is a solid-state welding process in which butt welds in materials are made in bar and in ring form at the joint face, and energy required for welding is obtained from a rotating flywheel. The stored energy is converted to frictional heat at the interface under axial load. The quality of the welded joint depends on many parameters, including axial force, initial revolution speed and energy, amount of upset, working time, and residual stresses in the joint. Inertia welding was conducted to make the large rotor shaft for low speed marine diesel engine, alloy steel for shaft of 140mm. Due to different material characteristics, such as, thermal conductivity and flow stress, on the two sides of the weld interface, modeling is crucial in determining the optimal weld geometry and parameters. FE simulation was performed by the commercial code DEFORM-2D. A good agreement between the predicted and actual welded shape is observed. It is expected that modeling will significantly reduce the number of experimental trials needed to determine the weld parameters.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제49권4호
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• pp.239-245
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• 2000

A copper-tungsten sintered alloy(WCu) has been friction-welded to a tough pitch copper (Cu) in order to investigate friction weldability. The maximum tensile strength of the SWu-Cu friction welded joints had cp to 96% of those of the Cu base metal under the condition of friction time 0.6sec, friction pressure 45MPa, upset pressure 125MPa and upset time 5.0sec. And it is confirmed that the tensile strength of friction welded joints are influenced highly by upset pressure rather than friction time. And it is considered that mixed layer was formed in the Cu adjacent side to the weld interface, W particles included in mixed layer induced fracture in the Cu adjacent side to the weld interface and also, thickness of mixed layer was reduced as upset pressure increase.

• 한국생산제조학회지
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• 제21권6호
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• pp.932-937
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• 2012

In the presented study, SM45C carbon steel parts were joined by friction welding. The welding process was carried out under optimized conditions using statistical approach. The study of SM45C is conducted with various combinations of process parameters. Parameter optimization, microstructure and mechanical property correlation are the major contribution of the study. The welded joints were produced by varying spindle revolution speed, friction pressure, upset pressure and burn-off length. Tension tests were applied to welded parts to obtain the strength of the joints. Fracturs properties were additionally obtained experimentally under fluctuated tensile loads. Microstructures using microphotographs were examined in the weld interface and weld region and heat affected zone and base metal and flash zone of welded parts. Finally, Hardness variations in welding zone and base metal were also obtained. Through these tests, the optimum conditions of parameters for ${\phi}20$ SM45C in friction welding were obtained when the friction spindle revolution was 1,950 rpm, the friction pressures was 30 MPs, upset pressures was 50 MPs.

• 소성∙가공
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• 제16권4호
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• pp.266-270
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• 2007

Inertia welding is a solid-state welding process in which butt welds in materials are made in bar and in ring form at the joint face, and energy required for welding is obtained from a rotating flywheel. The stored energy is converted to frictional heat at the interface under axial load. The quality of the welded joint depends on many parameters, including axial force, initial revolution speed and energy, amount of upset, working time, and residual stresses in the joint. Inertia welding was conducted to make the large rotor shaft for low speed marine diesel engine, alloy steel for shaft of 140mm. Due to material characteristics, such as, thermal conductivity and high temperature flow stress, on the two sides of the weld interface, modeling is crucial in determining the optimal weld parameters. FE simulation is performed by the commercial code DEFORM-2D. A good agreement between the predicted and actual welded shape is observed. It is expected that modeling will significantly reduce the number of experimental trials needed to determine the weld parameters.

• 한국공작기계학회논문집
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• 제16권6호
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• pp.29-36
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• 2007

The present study examined the mechanical properties of the friction welding of Ni-Cr-Mo to SM45C. Friction welding was conducted at welding conditions of 2,000 rpm, friction pressure of 100MPa, friction time of 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0 seconds, upset pressure of 150MPa, and upset time of 3.0 seconds. When the friction time was 1.6 seconds, the maximum tensile strength of the friction weld happened to be 1,020MPa, which is 120% of the base material's tensile strength(850MPa). At the same condition, the maximum shear strength was 438MPa, which is equivalent to 103% of the base material's shear strength(425MPa). At the same condition, the maximum vickers hardness was Hv490 at Ni-Cr-Mo nearby weld interface, which is higher Hv40 than condition of the friction time 0.8 seconds, and the maximum vickers hardness was Hv305 from weld interface of SM45C, which is higher Hv12 than condition of the friction time 0.8 seconds. The results of microstructure analysis show that the structures of two base materials have fined and rearranged along a column due to heating and axial force during friction, which has affected in raising hardness and tensile strength.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 D
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• pp.1934-1937
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• 1999

A copper-tungsten sintered alloy(Cu-W) has been friction-welded to a tough pitch copper (Cu) in order to investigate friction weldability. The tensile strength of the friction welded joint was increased up to 87% of the Cu base metal under the condition of friction time 1.0 see, friction pressure 40MPa and upset pressure 100MPa, upset time 5.0 sec. And it is related to upset pressure rather than friction time. Mixed layer was formed in the Cu adjacent weld interface and W particles which were included in mixed layer could induce fracture in the Cu adjacent to the weld interface. Thickness of mixed layer was reduced as upset pressure increase.

• Journal of Welding and Joining
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• 제1권2호
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• pp.45-52
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• 1983

Many pressure vessels for the hot H$\sub$2//H$\sub$2/S service are made of 2+1/4Cr-1Mo steel with austenitic stainless steel overlay to combat agressive corrosion due to hydrogen sulfide. Hydrogen dissolves in to materials during operation, and sometimes gives rise to unfore-seeable damages. Appropriate precautions must, therefore, be taken to avoid the hydrogen induced damages in the design, fabrication and operation stage of such reactor vessels. Recently, hydrogeninduced cracking (or Disbonding) was found at the interface between base metal and stainless weld overlay of a desulfurizing reactor. Since the stainless steel overlay weld metal is subjected to thermal and internal-pressure loads in reactor operation, it is desirable for the overlay weld metal to have high strength and ductility from the stand point of structural safety. In section III of ASME Boiler and Pressure Vessel Code, Post-Weld Heat Treatment(PWHT) of more than one hour per inch at over 1100.deg. F(593.deg. C) is required for the weld joints of low alloy pressure vessel steels. This heat treatment to relieve stresses in the welded joint during construction of the pressure vessel is considered to cause sensitization of the overlay weld metal. The present study was carried out to make clear the diffusion of carbon migration by PWHT in dissimilar metal welded joint. The main conclusion reached from this study are as follows: 1) The theoretical analysis for diffusion of carbon in stainless steel overlay weld metal does not agree with Fick's 2nd law but the general law of molecular diffusion phenomenon by thermodynamic chemical potential. 2) In the stainless steel overlay welded joint, the PWHT at 720.deg. C for 10 hours causes a diffusion of carbon atoms from ferritic steel into austenitic steel according to the theoretical analysis for carbon migration and its experiment. 3) In case of PWHT at 720.deg. C for 10 hours, the micro-hardness of stainless steel weld metal in bonded zone increase very highly in the carburized layer with remarkable hardening than that of weld metal.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2000년도 특별강연 및 추계학술발표대회 개요집
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• pp.314-316
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• 2000