| 摘要 |
PROBLEM TO BE SOLVED: To provide a stable vacuum valve that is excellent in contact resistance and cut-off characteristics. SOLUTION: The contact material of a vacuum valve comprises a high conductivity constituent cupper or the like and an arc resistant constituent consisting of Cr, in which particles having a diameter in the range of 1-150μm occupy at least 90 vol.%, and the ratio of the difference between the thermal expansion coefficientα900 at 900 deg.C, and the thermal expansion coefficientα50 at 50 deg.C, to the thermal expansion coefficientα900 at 900 deg.C of the contact material, [(α900 -α50 )×100/(α900 )] should be not less than 0.8% and not more than 12%. Thereby, the formation of a groove produced in the interface between a Cr particle and a Cu matrix after undergoing a brazing process is suppressed so that the stabilization of the static withstand voltage, contact resistance and cutoff characteristics can be realized.
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