Papers by Author: Hisaki Watari

Abstract: This paper describes direct cladding of magnesium (Mg) and aluminum (Al) alloys using a tandem horizontal twin roll caster that has three pairs of upper and lower rolls. Manufacturing conditions that are appropriate for fabricating Al/Mg and Al/Mg/Al cladded material were investigated. The surface condition of the cladded cast strip was examined. An electron probe micro analyzer was used to observe the interface between Al alloy and Mg alloy. The thickness of the mixed layer of Al and Mg alloy was 15μm, and how the materials were connected was clarified. Microscopic observation and backscattered electron analysis were used to investigate the cladding mechanisms of the Al and Mg alloy layers. Average hardness was determined using the Vickers hardness test at the Al layer and at the diffused layer between Mg and Al alloys. Cladding of Al/Mg alloy and A/Mg/Al alloy was possible using a tandem twin-roll caster. In addition, Al₃Mg₂ and Al₁₂Mg₁₇ phase precipitation at the interface of the Al and Mg alloys was confirmed during direct cladding from molten metals.

Abstract: A vertical type tandem twin roll caster equipped with a scraper for the clad strip was invented. This roll caster could cast three layers clad strip which base strip had lower melting point than that of the overlay strips. The base strip was cast by an upper twin roll caster and the overlay strips were cast by a lower twin roll caster. The scrapers were attached to the lower twin roll caster, and were innovated to cast this type of three layers of clad strip. Solidification layers those became the overlay strips were pulled from between the scraper and the roll. The melt of the alloy which was as same as the base strip was poured between the scraper and the base strip. This melt connect the overlay strip and the base strip. The base strip was not re-melted. The scraper enabled that the solidification layer of the overlay strip contact to the melt of the base strip without mixing of the melt of the base and overlay strip. In this way, the sound three layers clad strip which base strip had lower melting point than that of the overlay strip could be cast by the vertical type tandem twin roll caster equipped with a scraper.

Abstract: In recent years, global warming has become a worldwide problem. The reduction of carbon dioxide emissions is a top priority for many companies in the manufacturing industry. In the automobile industry as well, the reduction of carbon dioxide emissions is one of the most important issues. Technology to reduce the weight of automotive parts improves the fuel economy of automobiles, and is an important technology for reducing carbon dioxide. Also, even if this weight reduction technology is applied to electric automobiles rather than gasoline automobiles, reducing energy consumption remains an important issue. Plastic processing of hollow pipes is one important technology for realizing the weight reduction of automotive parts. Ohashi et al. [1-2] present an example of research on pipe formation in which a process was carried out to enlarge a pipe diameter using a lost core, achieving the suppression of wall thickness reduction and greater pipe expansion than hydroforming. In this study, we investigated a method to increase the wall thickness of a pipe through pipe compression using planetary rolls. The establishment of a technology whereby the wall thickness of a pipe can be controlled without buckling the pipe is an important technology for the weight reduction of products. Using the finite element analysis method, we predicted that it would be possible to increase the compression of an aluminum pipe with a 3mm wall thickness by approximately 20%, and wall thickness by approximately 20% by pressing the hollow pipe with planetary rolls.

Abstract: A growing demand for lightweight products has been brought about by the rapid development of new automobiles in order to reduce fuel consumption, since the global environment conservation meeting at Kyoto. One of the keys to reduced fuel consumption is to utilize high-strength, light materials like stainless-steel, high-tensile strength steels and magnesium alloys, which are difficult to form due to their material characteristics compared to normal steel tubes. The purpose of this paper discuses the development of our new pressing technology that forms a relatively high-strength and light weight stainless-steel tube which is SUS436 with surface screw threads. Our new press-forming process was tested in order to obtain accurate screw threads on stainless-steel tubes. Finite element simulation and a 3-D digitizer were used to measure the accuracy of tubes manufactured by the proposed pressing method. It was proved from FEM simulation and a 3-D digitizer measurement that the proposed press-forming method decrease tube thickness more effectively than conventional roll-forming technology. As a result, the maximum decrease in material thickness produced by conventional roll-forming process was 40%, but the maximum decrease in material thickness produced by our press-forming process was 20%. Especially the processing by four outer dies and two inner dies is better as for material thickness than the processing by six outer dies and three inner dies.

Abstract: Recently the growing demand for light weight products with high strength has been increased by the rapid development of automobile and aircraft technology. Also, reduction of carbon dioxide emissions is one of the most important issues also in the automobile industry. The weight reduction technology is important even if applied to electric vehicles rather than gasoline vehicles, as reduction of energy consumption is an important issue. Plastic processing of hollow pipes is an important technology for realizing weight reduction of automobile components. As an example of research into pipe forming there is the research by Ohashi et al. [1-2], who have carried out processing to enlarge pipe diameters using a lost core, which achieved suppressing reduction in wall thickness and greater pipe expansion than hydro forming. The authors investigated into a method of increasing the wall thickness of pipe by press forming. Using the finite element analysis method it was predicted that it is possible to increase the wall thickness of aluminum pipe with 2mm wall thickness by approximately 20% by hollow pipe press forming. Also, it was predicted that it is possible to increase the wall thickness by approximately 30% in places by eccentric pipe wall thickness increase. Also, the effect of the metal die which has a large effect on processing a pipe from a circular cylindrical shape to a rectangular tube shape was investigated.

Abstract: In recent years global warming has become a worldwide problem. Reduction of carbon dioxide emissions is one of the most important issues also in the automobile industry. This weight reduction technology is important even if applied to electric vehicles rather than gasoline vehicles, as reduction of energy consumption is an important issue. Plastic processing of hollow pipes is an important technology for realizing weight reduction of automobile components. As an example of research into pipe forming there is the research by Ohashi et al. [1-2], who have carried out processing to enlarge pipe diameters using a lost core, which achieved suppressing reduction in wall thickness and greater pipe expansion than hydroforming. In this research, a method of increasing the wall thickness of pipe by press forming was investigated. The establishment of technology for controlling the wall thickness of pipe without buckling the pipe is an important technology for weight reduction of products. Using the finite element analysis method it was predicted that it is possible to increase the wall thickness of aluminum pipe with 2mm wall thickness by approximately 20% by hollow pipe press forming. Also, it was predicted that it is possible to increase the wall thickness by approximately 30% in places by eccentric pipe wall thickness increase. Also, the effect of the metal die which has a large effect on processing a pipe from a circular cylindrical shape to a rectangular tube shape was investigated.

Abstract: Casting of a wire-inserted strip was tried by a downward melt drag twin roll caster. Some numbers of wires of 0.3 mm diameter were inserted. Effects of the wire-interval, matrix alloy and melt temperature on the ability of the insertion of the wire were investigated. Minimum interval of the wire, with which the insertion of the wires was able, was 1.6 mm. Insertion of the wire became easy as the roll speed becomes higher. Superheat of the melt was not important factor for the insertion of the wire.

Abstract: The approach to total weight reduction has been a key issue for car manufacturers as they cope with more and more stringent requirements for fuel economy. In sheet metal forming, local increases in product-sheet thickness effectively contribute to reducing the total product weight. Products could be designed more efficiently if a designer could predict and control the thickness distribution of formed products. This paper describes a numerical simulation and evaluation of the material flow in local thickness increments of products formed by an ironing process. In order to clarify the mechanism of the local increase in sheet thickness, a 3-D numerical simulation of deep drawing and ironing was performed using finite-element simulation. The effects of various types of finite elements that primarily affect thickness changes in original materials and thickness prediction were investigated. It was found that the sheet-thickness distribution could be predicted if the original material was relatively thick and if an appropriate type of finite element is selected.

Abstract: A 6061 aluminium alloy and an alloy with increased Fe content, representing recycled 6061 aluminium alloy were cast into strips at speed of 30m/min by an unequal diameter twin roll caster. The Fe content of 6061 aluminium alloy and the model of recycled 6061 aluminium alloy was 0.36 mass% and 0.59 mass%, respectively. Ripple marks, which are typical surface defect of roll cast strips, did not occur on the surface of both as-cast strips. Fe content did not influence the surface condition of the roll-cast-strip. The as-cast strip was cold rolled down to 1 mm, T4 heat treatment was conducted, and then subjected to180 degrees bending test. The result of 180 degrees bending test shows that roll cast 6061 aluminium alloy and 6061 aluminium alloy with increased Fe as recycled had bending ability as same as that of roll-cast 6022 aluminium alloy. In the strip cast by the twin roll caster of the present study, increased Fe content did not influence on the result of the180 degrees bending test.

Abstract: In this study, the roll casting of Al-40%Sn-1%Cu alloy was tried by an unequal diameter twin roll caster. The unequal diameter twin roll caster could continuously cast the strip. The casting load of the roll was small to prevent the flow out of the Sn. The roll-load was 0.1kN/mm(unit width). The roll casting of 400mm-width strip of 8mm-thick was tried, and it was attained. The gravity segregation of Sn did not occur. The as-cast strip could be cold rolled down to 1mm. However, this strip had much porosity. The rapid solidification was useful to prevent the porosity. The copper roll was better than steel roll to increase cooling ability. The copper roll was suitable to prevent the porosity. The temperature of solidified metal was important factor which influenced the porosity. The 4mm-thickness strip with little porosity was could be cast at the speed of 30m/min.