Papers by Author: Shinji Kumai

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Authors: Ryoji Nakamura, T. Asai, Hisaki Watari, Shinji Kumai
Abstract: Rheo-casting of 4045 aluminum alloy bar was operated using an unequal diameter twin roll caster and a cooling slope. The semisolid slurry was made by the cooling slope. The thickness of the bar was 12 mm and width was 100mm. The casting speed was 1m/min. Quantity of the melt poured on the cooling slope was important to make sound bar. The primary crystal became spherical, and its size was about 40μm.
295
Authors: Ryoji Nakamura, Ryoji Nakamura, Shinji Kumai, Hisaki Watari
Abstract: A vertical type tandem twin roll caster which can cast clad strip was devised and assembled. The casting of the clad strip was tried. The three layers clad strip could be cast by a vertical type tandem twin roll caster at only one process. The clad strip was connected directly from AA8079 and AA6022 at roll speed of 30m/min. The diffusion area between the strips was very narrow. The interface between the strips was clear and flat. The strips were bonded firmly.
1053
Authors: Ryoji Nakamura, Toshio Haga, Kenta Takahashi, Shinji Kumai, Hisaki Watari
Abstract: The net-inserted metal matrix composite strip could be cast by a twin roll caster at only one process. The net could be inserted in the strip or lower surface of the aluminium alloy strip. The matrix was Al-12mass%Si, and inserted net was made from SUS304 stainless steel. The diameter of the wire of the net was 0.29mm, and distance between the wires was 0.98mm (#20). The roll speed was 30m/min. The net was not reacted with the matrix, and there was not gap between the matrix and the net. The mechanical property of the net-inserted composite strip was affected by the direction of the wire of the net. When the angle of the wire against the tensile direction was 45 degrees, elongation of the composite became better than that of the matrix from 14% up to 23%. This reason was improvement of the local contraction of the composite strip. The net-inserted composite strip could be cold rolled. The reduction of the net was smaller than that of the strip. The reduction of the wire at rolling direction was larger than that of the wire at lateral direction.
1899
Authors: Toshio Haga, Kenta Takahashi, Shinji Kumai, Hisaki Warari
Abstract: Effect of Si content of Al-Si matrix on roll cast wire inserted strip was investigated in this paper. 99.5%Al, Al-4%Si , Al-12%Si and Al-18%Si were used as matrix. Slit depth of the nozzle, superheat of melt, wire-diameter and roll speed was chosen as the casting parameters, too. Addition of the Si was useful to prevent the reaction between the matrix and the wire. A downward melt drag twin roll caster could cast the wire inserted strip of the Al-Si matrix of which Si content was ranging up to18%. Composite strip, which matrix was hyper eutectic Al-18%Si, could be cast at the speeds up to 20m/min. The gap between the wire and matrix became thin when the superheat was high. When the slit depth of the nozzle was too shallow, the wire could not be inserted in the strip. The thickness of the wire inserted strip became thinner as the roll speed became higher.
979
Authors: Ryoji Nakamura, Masaki Ikawa, Shinji Kumai, Hisaki Watari
Abstract: Fe was added to 6016 aluminum alloy as the impurity, and this alloy was used as the model of the recycled 6016 aluminum alloy. The content of the Fe was from 0.18 mass% up to 1.0 mass%. 6016 including impurity-Fe was cast into the strip using a high speed twin roll caster at speed of 60 m/min. The increase of the content of impurity-Fe makes castability better rather than worse. The formability was investigated by tension test and 180 degrees bending test. The increase of Fe did not have influence on the bending test. There was no crack at outer surface of T4-heat treated strip after 180 degrees bending. The formability of 6016 strip including impurity-Fe cast by the high speed twin roll caster was enough for hem forming. The ductility of Fe added 6016 was improved by the high speed twin roll caster. It is thought that Al-Si-Fe impurity became fine by the effect of the rapid solidification, and deterioration could be improved.
605
Authors: T. Masuya, N. Yoneyama, Shinji Kumai, Akikazu Sato
267
Authors: Ryoji Nakamura, Hisaki Watari, Shinji Kumai
Abstract: Two kinds of roll casters, which were suitable for high speed roll casting, were devised. One was a vertical type twin roll caster, and the other was an unequal diameter twin roll caster. The semisolid roll casting using a cooling slope was adopted to these roll casters. The solid fraction was smaller than 5%. 3 mm thickness of 6111 strip was cast at 60 m/min by the vertical type twin roll caster, and 5 mm thickness of 6111 strip was cast at 30 m/min by the unequal diameter twin roll caster. The microstructure of the as-cast strip was equiaxed and spherical, not columnar. The mechanical properties of the strip rolled from roll-cast strip were almost as same as that of the strip made from cast ingot.
343
Authors: Ryoji Nakamura, Yusuke Shiotsu, Kosuke Komeda, Shinji Kumai, Hisaki Warari
Abstract: Porosity occurred in the 5182 aluminum alloy strip cast by a vertical type high speed twin roll caster. The porosity was caused by high-roll-speed and low-roll-load. Improvement of the porosity was tried by a scraper. The scraper was mounted on the roll, and the scraper was moveable depend on the thickness of the solidified layer on the roll. The scraper scribed the semisolid layer to improve the porosity. The scraper was useful to decrease the porosity of roll cast 5182 aluminum alloy strip.
1108
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