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Wei L.,Hokkaido University | Wei L.,Nippon Metal Industry Co. | Ohsasa K.,Akita University
ISIJ International | Year: 2010

Supercooling and subsequent solidification behavior of phase change materials (PCM) of sodium acetate trihydrate (SAT) and erythritol were studied by using a thermal analysis technique. A molten SAT specimen easily supercooled below 0°C and the observed maximum degree of supercoolimg was 89°C. Three changes due to phase transformation were observed in the cooling curve of the SAT. First change corresponds to the precipitation of sodium acetate (CH3COONa), and second change is the recalescence due to the solidification of supercooled SAT. It was considered that third change corresponds to the solid state transformation of SAT. From the maximum degree of the supercooling of SAT the solid/liquid interfacial energy of SAT was evaluated as 5.56× 10-2J/m2. The observed maximum degree of the supercooling of erythritol was 91°C. An experiment to induce the nucleation in supercooled liquid of SAT was carried out and the effectiveness of the combination of the ultrasonic irradiation and the addition of nucleation catalysts was demonstrated. © 2010 ISIJ. Source


Saida T.,Nippon Metal Industry Co. | Nakai S.,Nagoya University | Sato K.,Nippon Metal Industry Co. | Kuroda K.,EcoTopia Science Institute | Okido M.,EcoTopia Science Institute
Zairyo to Kankyo/ Corrosion Engineering | Year: 2013

In order to clarify the influence of sulfur content on the pitting corrosion behavior of surface, L-section longitudinal sectionand T-sectiontransverse sectionof stainless steel plate, cyclic corrosion testCCT and anodic polarization measurement in 0.85 M NaCl aqueous solution have conducted. Thick plate specimens t 25 mmof type 304 stainless steels containing 7, 29 and 57 ppm S were subjected to these tests. In CCT, rusting was more significant over T-section than surface and L-section. However, the number of initial rust spots over the T-section decreased with a reduction of S content. In pH 7 solution, the pitting potentialEpitfor 57 ppm S specimen was less noble at T-section than surface and L-section. But Epit at the T-section was shifted toward noble side with a reduction of S content. On the other hand, in pH 1 solution, Epit was low value regardless of S content. Furthermore, the cross-sectional shape of pits originated from MnS inclusion at the T-section was investigated. The MnS inclusion stretched into the steel matrix along the rolling direction and the growth of pitting corrosion along the MnS inclusion were observed. Source


Saida T.,Nippon Metal Industry Co. | Yamamoto T.,Nippon Metal Industry Co. | Sato K.,Nippon Metal Industry Co. | Nakamura S.,Nippon Metal Industry Co. | Okido M.,Nagoya University
Zairyo to Kankyo/ Corrosion Engineering | Year: 2012

The cut edge surface of the stainless steel sheet is susceptible to corrosion compared with the surface of the sheet. At the cut edge surface, red rust easily tends to occur by the attack of chloride ion. However, there are still a lot of points not clear about the cause of the cut edge corrosion. The salt spray test and the immersion test using NaCl solutions were conducted to evaluate corrosion resistance for the shear cut edge of SUS304 (18Cr-8Ni) and SUSXM7 (18Cr-9Ni-3Cu) cold rolled strips. It was found that transverse section (T section) corroded easier than longitudinal section (L section). In addition, the rust at the machined edge was less than shear cut edge. The difference of the corrosion behavior in each section, L and T, was investigated by the electrochemical method. In anodic polarization curves at T section, the current density rose gradually at the less-noble potential than the L section. By the SEM observation and EPMA elemental mappings after anodic polarization measurement, it was considered that non-metallic inclusions (MnS etc.) extended along the metal flow of rolling direction influenced on the initiation and the growth of pitting corrosion. Source


Saida T.,Nippon Metal Industry Co. | Sato K.,Nippon Metal Industry Co. | Kuroda K.,EcoTopia Science Institute | Okido M.,EcoTopia Science Institute
Zairyo to Kankyo/ Corrosion Engineering | Year: 2013

The combined addition of Si and Cu is effective in order to improve the stress corrosion cracking(SCC) resistance in hot water environment, and SUS315J1(18Cr-10Ni-1.5Si-1Mo-3Cu)has been developed and put in practical use. But, the preset temperature of equipments for supplying hot water in recent years has tended to become high(near 100°C). Moreover, the influence of anion-species included in hot water on SCC has not been confirmed yet. The SCC resistance of various stainless steels was examined by the immersion test using spot-welded specimens in 200 mg/L Cl- solution at 60, 95 and 125°C. The materials used were SUS304, SUS315J1, SUS316 and SUS444 cold-rolled steel. SUS315J1 showed the good SCC resistance compared with SUS304 and SUS316 at a temperature under 95°C. The influence of various anion-species(NO3 -, SO4 2-, CO 3 2- and HCO3-) on SCC was considered by the immersion test or electrochemical measurement in 200 mgL -1 Cl- solution. These anion-species that generally act as a corrosion inhibitor performed as accelerator on SCC initiation in addition of a small amount of anions. However, SCC tended not to occur in SUS315J1 in these solutions. Source

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