LOW THERMAL EXPANSION ALLOY

To provide a low thermal expansion alloy that is cow cost, has high oxidation resistance at high temperature and, when bonding the alloy to alumina and operating a composite member thereof with alumina in a temperature range of 20 to 600°C, hardly generates defects such as cracking and peeling due to a difference in α between the alloy and alumina in a temperature range of 20 to 600°C.SOLUTION: A low thermal expansion alloy is provided, containing in mass%, 0.05% or less of C, 0.40% or less of Si, 0.50% or less of Mn, 27.0 to 30.0% of Ni, 18.0 to 22.0% of Co, 1.0 to 2.0% of Cr, and the remainder of Fe and inevitable impurities, wherein Ni+Co×0.8-Cr×0.8 is 43.0 to 46.0%, and wherein an absolute value of a difference between an average α of the alloy and an average α of alumina in each temperature range of 20 to 100°C, 20 to 200°C,20 to 300°C, 20 to 400°C, 20 to 500°C, and 20 to 600°C is less than 2.0×10-6/°C.SELECTED DRAWING: None 【課題】低コストで、かつ高温での耐酸化性が高く、２０～６００℃の温度範囲で、アルミナと接合する際、およびアルミナとの複合部材を稼働する際に、２０～６００℃の温度範囲でアルミナとのαの差により割れや剥離等の不具合が発生し難い低熱膨張合金を提供することを課題とする。【解決手段】質量％で、Ｃ：０．０５％以下、Ｓｉ：０．４０％以下、Ｍｎ：０．５０％以下、Ｎｉ：２７．０～３０．０％、Ｃｏ：１８．０～２２．０％、Ｃｒ：１．０～２．０％、かつＮｉ＋Ｃｏ×０．８－Ｃｒ×０．８：４３．０～４６．０％であり、残部Ｆｅおよび不可避不純物からなり、２０～１００℃、２０～２００℃、２０～３００℃、２０～４００℃、２０～５００℃、２０～６００℃の各温度範囲における平均αとアルミナの平均αとの差の絶対値が２．０×１０－６／℃未満である。【選択図】 なし