Vol.3 No.4 2011

57/72

Research paper : New material development by the integration of cast technology and powder metallurgy technology (K. Kobayashi et al.)−298−Synthesiology - English edition Vol.3 No.4 (2011) decades to Fig. 7 to emphasize that long time was needed for the material development.4 Selection of elemental technologies for practical utilizationComment (Hisao Ichijo, Tsukuba Center, Inc.)This is a description of a series of processes from the need of R&D, the material synthesis, the evaluation of properties, and the development of new hard material through fusion research. The process of selection and integration of the elemental technologies is important in Type 2 Basic Research, and I think it will help the understanding if you explain the selection process.Answer (Keizo Kobayashi)As you indicated, I added a brief explanation of the selection of the elemental technologies. For the topics for the material and the process of considering its use as the mold material, I got the idea from hearing the comments of the private companies at the academic conferences.In high-tech manufacturing, we focused on the medium to high-temperature mold as an outlet. Using the WC-FeAl hard material, for which we have been evaluating the basic properties (mechanical properties, oxidation resistance, wear test, etc.), we conducted experiments for creating material of significant size to fabricate a mold that can be used industrially, for the usability of conventional cemented carbide processing to evaluate the machining cost, and for the evaluation of cracks and oxidation by repeated heating and cooling. These items were selected by talking to the companies that showed interest in this material at academic conferences (Japan Society of Powder and Powder Metallurgy). I added and modified the text to clarify the background.5 Effect of pulsed current sinteringQuestion (Norimitsu Murayama)Please tell us the effect of the pulse current sintering. If the process involves forming at low temperature range of 660 ºC and combustive synthesis reaction that is followed by sintering, isn’t it possible to fabricate the target hard material by ordinary pressure sintering?Answer (Keizo Kobayashi)Using the basic idea in this process (forming by molten aluminum, combustive synthesis reaction, and sintering), I think for small compacts, it can be done by a process in which heating and pressing can be done simultaneously, as in the hot press. However, for large compacts, external heating using a heater as in a hot press causes temperature differences between the area near the heater and the central part of the compact. This causes a time lag in the production of the liquid phase of aluminum and the following combustive synthesis reaction, and it would be difficult to fabricate an even sintered compact. This is a finding that we made during semi-solid forming; in pulsed current sintering, the current goes inside the compact allowing Joule heating between the powders, and this controls the occurrence of temperature difference compared to the external heating method. As a result, I believe we were able to fabricate a sintered compact without cracks, as the Al liquid phase acted evenly as a forming additive in the fabrication of the large WC-FeAl sintered compact.

※このページを正しく表示するにはFlashPlayer9以上が必要です