Papers by Author: Junsuke Fujiwara

Abstract: Titanium alloys have high strength to weight ratio, corrosion resistance, retention of strength at elevated temperatures and low thermal conductivity. In cutting of the titanium alloy, these characteristics have bad influence on tool wear. Therefore, the titanium alloy is generally machined in the milling at low cutting speed. Recently, the demand of the titanium industrial products is increasing and the high speed milling of the titanium alloy is desired. In this study, the Ti-6Al-4V alloy was machined at high cutting speed, and the tool wear progress and the cutting mechanics were experimentally investigated in order to clarify an effective tool material and cooling method for the cutting of the titanium alloy. The results obtained are as follows: In the cutting with a cemented carbide tool and coated cemented carbide tools of TiAlN, TiCN, DLC at the cutting speed 200 m/min, the wear progress of the coated tools were slower than that of the cemented carbide tool. The titanium alloy was cut in the dry and mist methods in order to avoid the thermal effect of the inserts, the wear progress in mist cutting was longer than that in dry cutting.

Abstract: Drilling experiments of CFRP/Ti6Al4V laminated stack board were carried out use of a TiAlN-coated cemented carbide drill and a TiAlCr/TiSi-coated cemented carbide drill. In the experimental conditions described herein, tool life is longer for lowered feed speed, and a TiAlCr/TiSi-coated cemented carbide drill has longer life than the other. Additionally, the cooling performance between dry process and water-mist-cooling were compared. Regarding water-mist-cooling, although the thrust is smaller, chips are much harder. They also adhere to the drill margin and impart damage to the CFRP wall of the hole. For a number of holes less than 50, water-mist-cooling reduces tool abrasion. However, the abrasion increases suddenly for hole numbers greater than 50. Accordingly, for the number of holes drilled well over 50, tool life is longer in dry processing than in water-mist-cooling.

Abstract: In this study, turning of the cemented carbides that their WC particle size was standardized were carried out with the PCD and the cBN tools. The WC particle diameter of cemented carbides was about 2µm and the Co contents were 10, 15, 20 and 25%, respectively. The influence of the WC particle size and Co contents was investigated. Summary of results are shown as follows: (1) In turning with the PCD tool, the more the Co contents increase, the more the tool wear increases. (2) In turning with the cBN tools, the more the Co contents of the work material increase, the more the tool wear decreases. (3) In turning of the cemented carbides contained the larger quantity of Co, the cBN tools are more effective than the PCD tool.

Abstract: Leaded free-machining steel is used in production industry. However the use of the leaded free-machining steel is limited from an environmental problem. So sulfurized free-machining steel, not include lead, has been researched widely. In order to improve the machining performance of the sulfurized free-machining steel, it is necessary to find out the behavior of inclusion. The experiment was carried out to find out the mechanism of the surfurized inclusion on the machinability, using some kinds of materials which were changed the size of the inclusion. In orthogonal cutting, the deformation behaviors of the sulfurized inclusion in the work materials were observed in the vicinity of tool face. Cutting forces were also measured and finished surfaces were observed. Besides, low speed orthogonal cutting in Scanning Electron Microscope (SEM) which was mounted a small cutting device was carried out in order to observe the deformation behavior more microscopically. As a result, it is clear that some inclusions creates voids around them and some broke to several pieces depending on their conditions. Moreover, in order to investigate the formation and growth of BUE, a quick stop experiment was done during turning. As a result, it is clear that the larger inclusions can reduce the formation of BUE.

Abstract: One of the surface modification methods is proposed in this report to improve the wear resistance of light metal such as aluminum alloys. At first alumite layer is formed on the surface of aluminum alloy JIS A6061 which was used as the substrate with anodic oxidation treatment method. Then thin layer of CrN is coated with sputtering method, and diamond like carbon (DLC) layer is finally coated with ion plating method. The influence of the thickness of the alumite layer on wear-resistance is experimentally investigated. The critical load of the coated aluminum alloy in scratch test is measured with the surface property tester, and the wear amount of the coated aluminum alloy is measured with the SUGA abrasion tester. The main results obtained are as follows: (1) The critical load of coated aluminum alloy with the alumite layer in the scratch test is higher than that without the alumite layer. (2) The wear amount of the coated aluminum alloy increased with the increase of the thickness of the alumite layer. (3) This combined surface treatment method can become new surface modification method because this method provided excellent adhesive strength and good wear-resistance.