Online edition:ISSN 2188-0921
Print edition:ISSN 0913-4794

No. 39  Nov. 2021

≪ All Articles ≫
<Feature-Ⅰ>Energy and Environment
1 Demonstration of Hydrogen Refueling Station Using Renewable Energy for Fuel Cell Vehicles
Dr. Akitoshi FUJISAWA, Shigeru KINOSHITA, Dr. Shin-ichi MIURA,
Sueki NAKAO, Fumiaki SUZUKI, Kazuhiro YAMASHITA 
To significantly reduce CO2 emissions during the production of hydrogen for hydrogen refueling stations, it is effective to use water-electrolysis hydrogen generated with renewable electricity. Kobe Steel has devised a configuration to add a hydrogen generator using a solid-polymer-electrolyte water electrolyzer (20 Nm3/h) and equipment for storing generated hydrogen at a high pressure (45 MPa) to a standard hydrogen refueling station (hydrogen supply capacity 300 Nm3/h) and has designed and built a demonstration plant. The demonstration included the operation of the water-electrolysis hydrogen generator for about 780 hours with the variable power source without any problems with followability and durability. In addition, the function of the entire system designed was verified by the operation linked with the hydrogen refueling station. In the future, further cost reduction and efficiency improvement will be considered. It is necessary to set a social value for hydrogen, which emits less CO2.
6 Utilization of Cold Energy in Intermediate Fluid-type Vaporizer (IFV) for LNG Receiving Terminals
Tomohiro SUZUKI, Shinji EGASHIRA, Yuji SUMIDA 
Intermediate fluid-type vaporizers (IFVs), a type of LNG vaporizers, have been used as vaporizers that enable the utilization of the cold energy of LNG in, for example, cryogenic power generation. Recently, there is an increasing number of cold energy utilization projects using chilled water from an IFV for, e.g., the intake air cooling of gas turbines. This paper introduces the latest trends in LNG receiving terminals including offshore receiving terminals, the features of IFVs as LNG vaporizers for cold energy utilization, and examples of cold energy utilization using IFV including gas-turbine-intake air cooling.
13 Expanding Application of Micro Channel Equipment (Diffusion Bonded Compact Heat Exchanger; DCHE™)
Yasutake MIWA, Masataka AZUMA, Dr. Koji NOISHIKI 
The demand for microchannel heat exchangers, a type of compact heat exchanger, is expected to increase as they are used in applications requiring light weight and compactness and as apparatuses for offshore equipment. Above all, their demand has been increasing in recent years for use in the fuel supply systems of offshore equipment that uses liquefied natural gas (LNG) and small-capacity LNG vaporizers for satellite bases.
These applications require, not only pressure tightness and compactness, but also measures to be taken against the freezing of the fluid serving as the heat medium. In the case of diffusion bonded compact heat exchangers (DCHE™s), concepts having to do with the suppression of freezing have been incorporated into their design, and tests were conducted using liquid nitrogen and LNG, to establish the design guidelines for the range of vaporization performance and icing. This report introduces the effort to apply a DCHE™ to LNG vaporizer applications.
20 Large Capacity Reactor, Stacked Multi-Channel Reactor (SMCR™) for Flow Chemistry
Nobumasa ICHIHASHI, Tomohiro OZONO, Akira MATSUOKA 
The stacked multi-channel reactor (SMCR™) is a (continuous) flow chemical reactor that replaces the conventional stirred bed reactors and has been developed as a reactor capable of large-capacity processing. As an effort after the development, an SMCR™ made of metal has been added to the lineup and, furthermore, a ceramic SMCR™ with high corrosion resistance has been developed to expand the applications, for which verification tests have been conducted against thermal shock. Moreover, basic tests and bench scale testing equipment have been actively commissioned and implemented with the aim of promoting the commercialization of SMCR™ in addition to equipment supply. As for bench scale testing, a bench scale testing apparatus installed in Kobe Steel performs verification tests to verify the usefulness of SMCR™ units.
27 Compressed Air Energy Storage System
Hiroki SARUTA, Dr. Takashi SATO, Masatake TOSHIMA, Yohei KUBO 
Large-scale power storage equipment for leveling the unstable output of renewable energy has been expected to spread in order to reduce CO2 emissions. The compressed air energy storage system described in this paper is suitable for storing large amounts of energy for extended periods of time. Particularly, in North America, China and other areas, where rock salt layers are widely distributed, using underground spaces formed in the rock salt layers to store compressed air can reduce the unit kWh cost of equipment. The equipment's responsiveness was obtained on the basis of the data for large-scale demonstration equipment of 1 MW class, verifying that the equipment can respond to commands within seconds. This paper further describes the future development of the compressed air energy storage system.
33 This paper was originally written in January 2020
MIDREX® Process: Bridge to Ultra-low CO2 Ironmaking
Midrex Technologies Inc. - a wholly owned subsidiary of Kobe Steel since 1983 - has been the market leader in direct reduction of iron for nearly 45 years. This success is based on a simple and efficient process, years of continuous innovations and improvements, the excellence of plant operators, and the support from Kobe Steel.
With the emphasis on reducing greenhouse gas emissions following the ratification of the Paris Agreement, direct reduction is the only commercially-proven process that can achieve significant reduction in CO2 emissions for the iron and steel industry today, using natural gas or liquified natural gas (LNG). The MIDREX H2™ is an evolution of the MIDREX® Process that can produce iron with almost no CO2 emissions; but it requires amounts of hydrogen that are not currently available from renewable sources today. This article describes the MIDREX® Process and significant improvements made over the last 50 years and offers a vision of ultra-low carbon ironmaking that can be realized in the hydrogen economy.
41 Destruction of Old or Abandoned Chemical Weapons by Controlled Detonation
While a large part of the world's stockpile of chemical weapons has been destroyed already, the destruction of non-stockpiled chemical weapons will continue in the future. Dismantling non-stockpiled chemical munitions such as old/abandoned chemical weapons is a very difficult task and involves a high risk of accidents. Controlled detonation is suitable for old/abandoned chemical weapons, since it can destroy chemical munitions without prior dismantling. In controlled detonation, the shells of chemical munitions are fragmented, and the chemical agents and explosives filling the shells are destroyed by the shock wave, as well as by the high-pressure and high-temperature environment produced by the detonation of the donor charge. A detonation chamber and a controlled detonation system, whose main component is the detonation chamber, have been developed and used in destroying many old/abandoned chemical weapons in and out of Japan since 2004. The controlled detonation system and destruction of chemical weapons are outlined in this report.
47 Design of Detonation Chamber for Destructing Chemical Warfare Materials
A detonation chamber is a device for destroying chemical warfare materials by detonation, using tens of kilograms of explosives in the process. Special structural features are required to satisfy fragment resistance, operability and leak tightness. The normal design code for static pressure vessels cannot be applied to the basic structural design of the robust detonation chamber because the detonation shock wave causes instantaneous dynamic pressure. Hence, the Code Case "Impulsively loaded pressure vessels," published recently by the American Society of Mechanical Engineers (ASME), was used as the design guideline. It requires dynamic pressure analysis and dynamic stress and strain analysis, which are used for the evaluation of each mode of failure such as fatigue damage and local strain limit, to allow detailed design. This paper introduces the design features with examples.
<Feature-Ⅱ> Advanced Materials Business
54 Strengthening of Aluminum Alloy Forgings for Automotive Suspension by Two-step Aging
Masayuki HORI, Kenichi HIRUKAWA, Masashi NAKANO,
Masakazu TANAKA, Yohei OKAFUJI 
In order to improve the fuel efficiency of automobiles, it is important to reduce the weight of vehicle bodies. The weight of suspensions is also being reduced, by applying Al-Mg-Si aluminum alloy forgings, for example. Further reducing the weight of suspensions will require additional strengthening of the material, and Kobe Steel has conducted a study to increase the strength by two-step aging. As a result, a two-step aging process combining pre-aging at 160℃ and high-temperature aging at 190℃ has achieved a peak proof stress of 390 MPa in a short time period of only 8 hours. Obtaining the same peak proof stress by single-step aging at 160℃ requires 56 hours. This is attributed to the fact that β″ phase, having a size of 3 to 4 nm, which is greater than the critical size for non-reversion, precipitates with a high number density during the pre-aging and grows at the high temperature to increase the strength. This technology has enabled a weight reduction of 3% over that of the conventional technology and is expected to contribute to improving fuel efficiency and reducing the carbon dioxide emissions of automobiles.
59 Mechanism of Attaining High Strength Sintered and Surface-rolled Gear and Merits of Its Application in Automotive Field
With the aim of expanding the application to automobiles, a study was conducted to determine the applicability of sintered parts to transmission gears that require high fatigue strength. Recent studies have reported that sintered and surface-rolled gears based on pre-alloyed steel powder can achieve fatigue strength equal to or higher than that of conventional wrought steel gears, but the mechanism that enables the former to achieve a fatigue strength higher than that of the latter has not been fully clarified. Hence, Kobe Steel has investigated the factors that may bring higher fatigue strength to sintered and surface-rolled gears in comparison with wrought steel and found that it is attributable to their highly compressive residual stress. Also studied were the advantages of applying sintered and surface-rolled gears. By optimizing the surface-rolling conditions so as to improve the tooth profile accuracy, the same contact-pressure fatigue strength as that of the ground product can be obtained without any grinding, suggesting the possibility of eliminating the grinding process.
65 Melting and Casting Technologies for Titanium Aluminide Intermetallics
Daisuke MATSUWAKA, Tomohiro NISHIMURA, Fumiaki KUDO,
Alloys based on the titanium aluminide (TiAl) intermetallic compound are lightweight and have excellent high temperature strength and oxidation resistance. Therefore, they are being increasingly used in low-pressure turbine blades of jet engines for commercial aircraft, against the backdrop of fuel consumption reduction needs and the like. Kobe Steel has been working on the development of a manufacturing technology for TiAl material with international competitiveness, devised a melt deoxidation method utilizing the phenomenon of decreased oxygen solubility when high concentration aluminum is added, and achieved an oxygen concentration of 0.03 mass% or less. The company has also realized a narrow composition range (Al content ±0.3 mass%) and improved casting yield (+25% or higher compared with the conventional method) by constructing a melting and casting process using the cold crucible induction melting (CCIM) method. This paper also details the technology for recycling titanium scrap and describes future prospects.
70 Evaluation for Morphology of Regions Having Microtexture in Ti-6Al-4V Alloy Forging Products
Dr. Yoshinori ITO, Dr. Hiroyuki TAKAMATSU, Shogo SAEKI,
Dr. Nobuhiro TSUJI 
Titanium alloys contain regions having microtexture, in which the crystallographic orientation of the alpha phase is similar. Because the regions with microtexture deteriorate mechanical properties, it is important to evaluate their morphology. In this study, ultrasonic measurement was conducted, and the results were compared with characterization results obtained by the SEM/EBSD method. It has been verified that backscattered signals by ultrasonic measurement can be used for the evaluation of the regions having microtexture.
76 An Approach to Increase Strength of Materials for Built-up Type Crankshafts
Tsukasa SHIRAFUJI, Hiroyuki TAKAOKA, Ryota YAKURA 
Recently, there is an increasing need for improving the efficiency of low-speed diesel engines for ships. In response, Kobe Steel has newly developed an inexpensive low-alloyed steel for semi-built-up type crankshafts. This steel has a high yield point and high fatigue strength while avoiding the risk of quench cracking, which often occurs in large, forged steel products. Crank throws were manufactured from multiple steel types, including the newly developed steel, and the material properties of samples of steel pieces taken from their major parts were evaluated. The results confirmed that the newly developed steel has mechanical properties and a fatigue strength superior to those of conventional steel. It is expected that this newly developed steel will be applied to next-generation engines and contribute to compliance with environmental regulations, which are expected to become increasingly stringent.
82 Automatic X-ray Stress Measurement System for Cold-rolled Fillet of Solid-type Crankshafts
Dr. Mariko MATSUDA, Hitomi ADACHI, Tatsuhiko KABUTOMORI,
Dr. Hiroyuki TAKAMATSU, Dr. Toshihiko SASAKI 
In recent years, attention has been being paid to global environmental problems, and even higher fatigue strength is required for crankshafts used in medium-speed diesel engines for onshore power generation. Surface treatment technology is drawing attention as one of the means to achieve this. In any of the surface treatment technologies, however, a tensile residual stress, which causes a decrease in fatigue strength, occurs at the boundary between the surface treated part and the untreated part, and it is necessary to understand the residual stress distribution around the surface treated part. This paper describes the evaluation of the influence of the macro-segregation peculiar to large, forged steel, and the X-ray incident angle and incident angle setting error, generated during fillet measurement, on the accuracy of X-ray stress measurement by the cos α method. Improvement measures are also described. In addition, the effectiveness of a system that can automatically and high-speed measure the residual stress in the cold rolled fillet has been demonstrated.

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