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Nishi-Tokyo-shi, Japan

Sakai Y.,Covalentmaterial Co. | Ohta K.,Covalentmaterial Co. | Yamazaki M.,Covalentmaterial Co. | Sakusabe H.,Covalentmaterial Co.
Zairyo/Journal of the Society of Materials Science, Japan

We have tried to apply a pressureless sintered silicon carbide radiant tube to heat treatment in a metal furnace using a high temperature over 1250K. The tube was a 2-meter single-end type radiant tube, where both outer and inner tubes were cantilevered at each flange without any other support. In this study we researched fundamental mechanical and thermal characteristics when using silicon carbide for a radiant tube. Bending strength does not decrease in temperatures less than 1580K, which is about the maximum temperature for a burner head made of metal. The safety factor calculated from the Weibll probability of failure is sufficient for use. We found no problem on either oxidation or thermal shock resistance tests through burning. On a simulation of the radiant-tube furnace, the stress that occurred because of the difference between the temperatures of the upper and lower surfaces was found to be not large enough to cause fractures; this, because of high thermal conductivities. Pressureless sintered silicon carbide radiant tubes have been in use in such industrial furnaces as carburizing furnaces for more than 10 years. The long life of radiant tubes contributes to a low running cost for customers, and has zero emissions. We recognize the practical use for pressureless sintered silicon carbide radiant tubes. © 2012 The Society of Materials Science, Japan. Source

Sakai Y.,Covalentmaterial Co. | Ono K.,Covalentmaterial Co. | Seko S.,Covalentmaterial Co. | Hyodo T.,Covalentmaterial Co. | Kondo N.,Covalentmaterial Co.
Zairyo/Journal of the Society of Materials Science, Japan

We have developed a gas-fired immersion heater tube for use with melting furnaces for the processing of molten zinc. The tubes are made out of a pressureless sintered silicon carbide. The tubes single-ended have dimensions of either ø230 x ø210 x 2300mm or ø310 x ø290 x 1000mm. In this study, we examined thermal shock resistance upon water quenching, measured the gas temperature along the tubes, and simulated their tube wall temperature strength/stress distributions. Maximum stress of tube occurs just above the ring of contact with the surface of the molten zinc, where the temperature differential is the maximum. By inserting a thermal insulation sleeve (alumina silicate cloth) within the immersion heater tube, stress is decreased from 51.5MPa to 22.5MPa. The stress on dipping slant, which occurred at mechanical fixing part of tube, were not so large. We also checked the resistance of immersion heater tubes to molten zinc corrosion within actual production furnaces. We have found that within industrial zinc furnaces, the tubes can keep to operate on good condition (i.e., corrode only partially) after 6 years of service with normal burners and 4 years of service with regenerative burners. © 2013 The Society of Materials Science, Japan. Source

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