Joining and Welding Research Institute

Ōsaka, Japan

Joining and Welding Research Institute

Ōsaka, Japan

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Imai H.,Joining and Welding Research Institute | Imai H.,Xi'an University of Technology | Li S.,Xi'an University of Technology | Kondoh K.,Joining and Welding Research Institute | And 5 more authors.
Materials Transactions | Year: 2014

In this study, the microstructure and mechanical properties of Cu40Zn brass alloy with 0.5 mass% Cr additives produced by powder metallurgy (P/M) process were investigated. Cu40Zn0.5Cr and Cu40Zn brass powders were made by water-atomization process, and used as raw materials. These powders were consolidated by hot extrusion at various temperatures by considering the precipitation behavior of phase and Cr. Yield stress of Cu40Zn0.5Cr extruded at 773K was 514.6 MPa, while that of the monolithic Cu40Zn extruded at the same temperature was 332.6 MPa. Solid solution of chromium in the Cu40Zn0.5Cr brass alloy extruded at 773K was about twice as that of the same brass alloy extruded at 873 K. The strength impact of Cr solid solution was much effective compared to Cr precipitation strengthening. The ratio of solid solution strengthening by chromium additive was 130 MPa/mass%[Cr]. The grain size of extruded materials increased with increasing the extrusion temperature. © 2013 The Japan Institute of Metals and Materials.


Song K.H.,Korea Institute of Industrial Technology | Chung Y.D.,Joining and Welding Research Institute | Nakata K.,Joining and Welding Research Institute
Metals and Materials International | Year: 2013

This study was conducted to investigate the microstructure and mechanical properties of friction stir lap joints. Monel 400 and Inconel 600 were selected as the experimental materials, and friction stir welding was carried out at a tool rotation speed of 200 rpm and welding speed of 100 mm/min. The application of friction stir welding to Monel 400 effectively reduced the grain size in the stir zone; the average grain size of Monel 400 was reduced from 11.9 μm in the base material to 4.2 μm in the stir zone, which resulted in an improvement in the mechanical properties of the stir zone. The joint interface between Monel 400 and Inconel 600 showed a relatively sound weld without grooves or cracks, and only a small amount of voids with a size of 0.5 μm; however, no intermetallic compounds were observed in the lap jointed interface. Moreover, the hook on the advancing side of Monel 400 was formed from Inconel 600, which contributed to maintenance of the tensile strength. The evolution of microstructures and mechanical properties of friction stir lap jointed Monel 400 and Inconel 600 are also discussed herein. © 2013 The Korean Institute of Metals and Materials and Springer Science+Business Media Dordrecht.


Takada A.,Joining and Welding Research Institute | Terasaki H.,Joining and Welding Research Institute | Komizo Y.,Joining and Welding Research Institute
Science and Technology of Welding and Joining | Year: 2013

This paper describes the effect of Al content on the formation of acicular ferrite in low carbon steel welds. Inclusions and the microstructures of welds with three levels of Al content were analysed. Acicular ferrite was formed in the low and medium Al content samples, but not in the high Al content sample. In the low and medium Al samples, a TiO layer, which encourages acicular ferrite nucleation, was formed around the inclusions. Grain boundary ferrite was formed only in the low Al content sample. Inclusions in the low Al sample were predominantly composed of the amorphous phase, whereas those in the medium Al sample were composed of spinel structures. It was confirmed by electron energy loss spectroscopy analysis that boron existed in the amorphous phase. The formation of the amorphous phase enhances grain boundary transformation by absorbing boron, which stabilises austenite grain boundary, whereas the formation of spinel structures enhances intragranular transformation by suppressing the boron absorption. © 2013 Institute of Materials, Minerals and Mining.


Song K.H.,Korea Institute of Industrial Technology | Nakata K.,Joining and Welding Research Institute
Korean Journal of Materials Research | Year: 2011

This study was carried out to evaluate the microstructures and mechanical properties of a friction stir welded Ni based alloy. Inconel 600 (single phase type) alloy was selected as an experimental material. For this material, friction stir welding (FSW) was performed at a constant tool rotation speed of 400 rpm and a welding speed of 150~200 mm/min by a FSW machine, and argon shielding gas was utilized to prevent surface oxidation of the weld material. At all conditions, sound friction stir welds without any weld defects were obtained. The electron back-scattered diffraction (EBSD) method was used to analyze the grain boundary character distributions (GBCDs) of the welds. As a result, dynamic recrystallization was observed at all conditions. In addition, grain refinement was achieved in the stir zone, gradually accelerating from 19 μm in average grain size of the base material to 5.5 μm (150 mm/min) and 4.1 μm (200 mm/min) in the stir zone with increasing welding speed. Grain refinement also led to enhancement of the mechanical properties: the 200 mm/min friction stir welded zone showed 25% higher microhardness and 15% higher tensile strength relative to the base material.


Imai H.,Joining and Welding Research Institute | Li S.,Joining and Welding Research Institute | Kosaka Y.,SAN ETSU Metals Co. | Kojima A.,SAN ETSU Metals Co. | And 2 more authors.
Materials Science Forum | Year: 2010

Copper-40mass%zinc (Cu-40Zn) brass alloy powder containing 1.0 mass% Cr was prepared by the water atomization. Graphite particles, having a mean particle size of 5 μm, were added to the as-atomized powders by the ball milling equipment for 4h under 120 rpm. Spark plasma sintering process was used to consolidate the above elemental mixed powders (sintered material). Sintered materials were heat-treated for the precipitation of much Cr (HT material). The machinability of Cu-40Zn brass alloys was evaluated by a drilling test using a drill tool under dry conditions. The matrix hardness of sintered material was higher than that of HT material. On the other hand, the machinability of sintering material was higher than that of HT material. There is no trade-off relationship between the matrix hardness and machinability of the brass alloys. SEM-EDS observation indicated that Cr content dissolved in the brass matrix of sintered material and HT one was 0.42 mass% and 0.19 mass%, respectively. As the reason why machinability of HT material lowered, the precipitation of the hard Cr particle or generation of Cr-C compound caused to inhibit the machinability. © (2010) Trans Tech Publications.


Shigeta M.,Joining and Welding Research Institute | Miyake M.,Joining and Welding Research Institute | Tanaka M.,Joining and Welding Research Institute
Yosetsu Gakkai Ronbunshu/Quarterly Journal of the Japan Welding Society | Year: 2015

This study clarifies the collective growth processes and size distributions of fume primary particles generated around an arc plasma in welding by numerical analysis using a model which can treat growth through homogeneous nucleation, heterogeneous condensation and coagulation among particles with any size distribution ranging from sub-nanometers to a few hundreds nanometers. In a representative case, almost all iron vapor is converted into iron particles in a very short time of 218 μs after nucleation starts. The particles grow mainly by nucleation and condensation in an early period, whereas coagulation becomes dominant after vapor consumption. The vapor consumption rate of condensation exhibits approximately 400 times as high as that of nucleation at their maxima. Homogeneous nucleation rate is high when both the temperature and the cooling rate are also high. In a region closer to the base metal, a fewer particles are generated because the cooling rate is lower and the vapor concentration is higher, which cause a lower homogeneous nucleation rate. As a result, heterogeneous condensation becomes more effective. Furthermore, the particles take longer time to reach their melting points. In consequence, the particles generated in the vicinity of the base metal have larger sizes.


Wahba M.,Central Metallurgical Research and Development Institute | Wahba M.,Osaka University | Wahba M.,Joining and Welding Research Institute | Kawahito Y.,Osaka University | Katayama S.,Osaka University
Journal of Materials Processing Technology | Year: 2011

Lap joints between AZ91D thixomolded Mg alloy and amorphous polyethylene terephthalate (PET) were produced by direct irradiation of high power diode laser beam from either plastic or metal side. Joints with strength higher than that of PET could be successfully produced. Joining mechanism involves the generation of gas bubbles in a narrow region inside PET specimen adjacent to the interface. The pressure induced by expansion of these bubbles secures tight bonding in the micro size between AZ91D and PET specimens. Discrete bubbles morphology associated with metal-side laser-irradiation promoted higher joint strength in comparison with networked wormhole morphology in the case of plastic-side laser-irradiation. The presence of pre-made pits on the AZ91D specimen surface proved to be effective to the improvement in the performance of plastic-side laser-irradiated joints. © 2011 Elsevier B.V. All rights reserved.


Imai H.,Joining and Welding Research Institute | Li S.,Joining and Welding Research Institute | Kondoh K.,Joining and Welding Research Institute | Kosaka Y.,SAN ETSU METALS Co. | And 3 more authors.
Materials Transactions | Year: 2011

The machinability of high strength lead-free brass was investigated in this study. Copper-40 mass% zinc (Cu-40Zn) brass powder with chromium was prepared by the water atomization. Chromium was used for strengthening of brass matrix. Graphite particles as machinable element were added to the as-atomized powders by conventional mixing process. Spark plasma sintering process was used to consolidate the above elemental mixed powder (X K SPSed material) at 873 K and 1053 K. The sintered materials at 1053 K were heat-treated for the precipitation of much Cr (HT material) at 1053 K for 12 h in Ar atmosphere. The machinability was evaluated by a drilling test using a drill tool under dry conditions. The matrix hardness of sintered material was higher than that of HT material. On the other hand, the machinability of sintering material was higher than that of HT material. The trade-off relationship between the matrix hardness and machinability of the brass alloys was not established. The solution of chromium content dissolved in the brass matrix of sintered material at 873 K, 1053 K and HT material was 0.55 mass%, 0.42 mass% and 0.19 mass%, respectively in SEM-EDS observation. The chromium carbide increased with decreasing chromium solution in the brass matrix. The generation of hard chromium carbide and decrease in the relative graphite particle caused to inhibit the machinability of HT material. © 2011 The Japan Institute of Metals.


Song K.H.,Korea Institute of Industrial Technology | Kim W.Y.,Korea Institute of Industrial Technology | Nakata K.,Joining and Welding Research Institute
Materials and Design | Year: 2012

The microstructures and mechanical properties of friction stir welded Inconel 600 and SS 400 lap joints were evaluated in this study. Friction stir welding was carried out at a tool rotation speed of 200. rpm and a welding speed of 100. mm/min. Application of friction stir welding was notably effective in reducing the grain size of the stir zone, as a result, the average grain size of Inconel 600 was reduced from 20 μm in the base material to 8.5 μm in the stir zone. The joint interface between Inconel 600 and SS 400 was soundly welded without voids and cracks, and MC carbides with a size of 50. nm were partially formed in the region of the lap joint interface in Inconel 600. In addition, a hook from SS 400 was formed on the advancing side of the Inconel 600 alloy, which directly affected an increase in the peel strength of the weld. In this study, we systematically discussed the effect of friction stir welding on the evolution of the microstructures and mechanical properties of friction stir lap jointed Inconel 600 and SS 400. © 2011 Elsevier Ltd.


Song K.-H.,Korea Institute of Industrial Technology | Nakata K.,Joining and Welding Research Institute
Korean Journal of Materials Research | Year: 2012

The microstructures and mechanical properties of friction stir welded lap joints of Inconel 600 and SS 400 were evaluated; friction stir welding was carried out at a tool rotation speed of 200 rpm and welding speed of 100 mm/min. Electron back-scattering diffraction and transmission electron microscopy were introduced to analyze the grain boundary characteristics and the precipitates, respectively. Application of friction stir welding was notably effective at reducing the grain size of the stir zone. As a result, the reduced average grain size of Inconel 600 ranged from 20μm in the base material to 8.5μm in the stir zone. The joint interface between Inconel 600 and SS 400 showed a sound weld without voids and cracks, and MC carbides with a size of around 50 nm were partially formed at the Inconel 600 area of lap joint interface. However, the intermetallic compounds that lead to mechanical property degradation of the welds were not formed at the joint interface. Also, a hook, along the Inconel 600 alloy from SS 400, was formed at the advancing side, which directly brought about an increase in the peel strength. In this study, we systematically discussed the evolution of microstructures and mechanical properties of the friction stir lap joint between Inconel 600 and SS 400.

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