Ōsaka, Japan
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Arimoto K.,Arimotech Ltd. | Ikuta F.,Neturen Co. | Yokota H.,Nippon Oil Corporation
Materials Performance and Characterization | Year: 2014

Quenchants should be maintained based on their cooling characteristics, measured on a daily basis at every worksite for keeping their performance. A test system for this purpose is required to be compact, convenient, and reasonable. A rotary-arm type measurement apparatus using a small ball probe, which was reported by Tawara in 1941, is recognized as a compact one with an automatic device to specify a circular motion of the probe for its transfer from furnace to quenchant as well as a subsequent cooling process. In this study, the concept of Tawara's method was assessed by producing its prototype based on current heating and rotation devices, and also measurement and control systems. Trends obtained from limited results of the prototype were consistent with those of Tawara. Reasonable repeatability in measured cooling characteristics of polymer solutions was verified by systematical tests. Relative flow that occurs steadily around the probe by its circular motion is a unique point of this apparatus to enhance its accuracy and repeatability. After reviewing test methods using rotary-arm and ball probes, and standards for cooling characteristics of quenchants critically, contents, results, and outlooks on the prototype were described. © 2014 by ASTM International.


Arimoto K.,Arimotech Ltd. | Ikuta F.,NETUREN Co. | Yamanaka S.,Maruemu Works Co.
International Journal of Microstructure and Materials Properties | Year: 2012

Gas nitriding is well established as a suitable process for realisinglow distortion in precision parts under optimal conditions. However, efforts for optimising the distortions by trial and error, which are not avoidable, have been repeated over many years. A software tool based on the finite element method is developed by use of the latest models of nitriding for resolving the problems, which was applied to the nitrided austenitic stainless steels specimens. In this study, distortions in nitrided steel cylinders, which were measured systematically in 1930s, were investigated using the tool for understanding their tendencies derived from different conditions. The fruits will be used for enhancing the tool by additional verifications, and applying finally to distortion problems in practical parts. Copyright © 2012 Inderscience Enterprises Ltd.


Horino T.,Neturen Co. | Ikuta F.,Neturen Co. | Arimoto K.,Arimotech Ltd. | Jin C.,ITOCHU Techno Solutions Corporation | Tamura S.,ITOCHU Techno Solutions Corporation
ASTM Special Technical Publication | Year: 2010

Explanation of the distortion mechanism is important for realizing the low-distortion and distortion-adapted induction hardening processes. Two of our authors applied computer simulation to examine distortions of ring specimens induction hardened on their outer side and also tempered. Simulated deformations agreed well with the experimental results. In this study, a simulation for the same experiment was carried out by the more enhanced modeling techniques. The possibility of explaining the origin of distortion in induction hardened ring specimens was shown clearly from simulated distribution changes of temperature, metallic structures, stresses, and strains. Copyright © 2009 by ASTM International.


Arimoto K.,Arimotech Ltd. | Ikuta F.,NETUREN Co. | Yamanaka S.,Maruemu Works Co. | Funatani K.,IMST Institute
International Journal of Microstructure and Materials Properties | Year: 2010

By the use of computational simulation techniques for nitriding processes, diffusion and nitride precipitation phenomena in compound layers and diffusion zones have been predicted in low alloy steels, Fe-Cr alloys, and so on. They have been also applied to examining formations of the expanded austenite in nitrided austenitic stainless steels. However, the application of the simulation approach was so far limited to the one-dimensional problems along the depth direction in simple shape specimens, since it is built on the finite difference method. In order to innovate the simulation, the software tool based on the finite element method has been expanded for studying on arbitrary-shaped parts by using the latest models for nitriding. The tool, having the function to analyse stress and strain, contributes not only to resolving various practical problems but also to explaining the unsettled mechanisms of distortion and residual stress generations caused by nitriding. Furthermore, the models are also expected to be enhanced by considering stress and strain effects precisely. In this paper, some verification examples on distortions and residual stresses relating to the expanded austenite formation in nitrided austenite stainless steels are described after clarifying the theory and implementation of the expanded simulation tool. Copyright © 2010 Inderscience Enterprises Ltd.


Arimoto K.,Arimotech Ltd. | Yamanaka S.,Maruemu Works Co. | Funatani K.,IMST Institute
ASTM Special Technical Publication | Year: 2010

Case carburizing is recognized as a suitable process for realizing low distortion and high compressive stresses near the surfaces under optimal conditions. Patterns of distortion and residual stresses in carburized cylinders and rings under different conditions have been identified from measurements performed for many years. Some pioneers of the heat treatment simulation compared their simulated results of carburized and quenched parts with experimental data for verifying their programs. However, these early researchers did not sufficiently explain their distortion and stress generation mechanism using their simulated results. Although one of the authors tried to illuminate their mechanism of a carburized and quenched ring, the work has not been finished because the purpose was limited in examining the role of transformation plasticity in the process. In this paper, the same simulated results were analyzed more comprehensively for explaining the origin of distortion and residual stress in the ring based on a concrete strategy newly developed. Copyright © 2008 by ASTM International.


Arimoto K.,Arimotech Ltd.
International Journal of Microstructure and Materials Properties | Year: 2015

Efforts for reducing the quench distortions induced from case hardening processes have been repeated over many years. For solving the problem, the heat treatment simulation has been recently used as a tool. Its enhancement requires to improve models and to collect proper characteristic data by repeating comparisons with experiments. For example, tests by steel plate specimens carburised on a single side and oil quenched have been used to examine their distortion characteristics. In this study, their tests were newly simulated for comparing with the measured and past simulated results. The generation mechanism of plate distortions during the processes was explained to examine a discrepancy in the results. A theoretical calculation to study the plate bending in a furnace was added for clarifying expansion effects due to diffused carbon atoms. These studies revealed that the verification using the steel plate tests is useful to enhance models and material properties for simulating the case hardening. © 2015 Inderscience Enterprises Ltd.


Arimoto K.,Arimotech Ltd.
International Journal of Microstructure and Materials Properties | Year: 2016

The appearance of lower hardness at the surface than at the core in steels after through hardening is known as 'inverse quench-hardening'. Pioneering work was performed in the 1970s by devising a simple test method where cylindrical specimens were cooled by air and sodium chloride solution sequentially. The hardening mechanism in the same specimens as the pioneering work was examined using a finite element simulation method. However, it has not been completed for lack of experimental quenching cooling curves for the comparisons. In this study, the same experiments as those of the pioneering work were conducted to explain the origin of the phenomenon thoroughly. Experimental cooling curves showed a temperature rise due to recalescence as predicted by the simulation. The inverse quench-hardening phenomenon was also found in the measured and simulated hardness distributions of the specimens. Finally, the origin of the phenomenon was discussed based on results obtained from this study and literature. © 2016 Inderscience Enterprises Ltd.

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