日本金属学会誌

J. Japan Inst. Metals, Vol. 61, No. 6 (1997),
pp. 553-560

Effects of Impurity Sulfur and Oxygen on Soft Magnetic Properties ofFe-38 mass%Ni-8 mass%Cr Alloys

Takuji Hara1, Tomoharu Shigetomi1,Takuji Okiyama2 and Toshihiko Takemoto1

1Steel & Technology Development Lab., Nisshin Steel Co., Ltd., Shinnanyo 746
2Marketing & Products Development Dept., Nisshin Steel Co., Ltd., Chiyoda-ku, Tokyo 100

Abstract:

Soft magnetic properties of Fe-38 mass%Ni-8 mass%Cr alloys are extremely influenced by a small amount of sulfur(S) and oxygen(O) in the alloys. In the cases of low S(≤q9 ppm) and low O(≤q24 ppm), the soft magnetic properties are as high as those of Fe-78 mass%Ni alloys. When the S content is more than 9 ppm or the O content is more than 24 ppm, however, they are substantially deteriorated. In this paper, the effects of a small amount of S and O on the soft magnetic properties of Fe-38 mass%Ni-8 mass%Cr alloys have been examined from a practical point of view. The results obtained are summarized as follows: After annealing at 1100°C in a dry hydrogen atmosphere (dew point: -45°C), the soft magnetic properties of an alloy containing high S(S=23 ppm) and an alloy containing high O(O=38 ppm) are inferior to those of a pure alloy (S=8 ppm, O=18 ppm). In the alloy containing high S, many MnS particles whose sizes are mainly smaller than 0.5 μm are precipitated. In the alloy containing high O, many oxide inclusions whose sizes are mainly 0.26{~}0.75 μm exist. It is considered that in the alloy containing high S, the MnS precipitates whose sizes are smaller than 0.5 μm little interfere with domain wall displacement, while they interfere with grain growth. Thus, the alloy containing high S is inferior to the pure alloy in the soft magnetic properties. On the contrary, it is considered that in the alloy containing high O, the oxide inclusions whose sizes are larger than 0.5 μm interfere both with domain wall displacement and with grain growth. Therefore, the alloy containing high O is much inferior to the pure alloy in the soft magnetic properties. The results may indicate that the domain wall thickness of Fe-38 mass%Ni-8 mass%Cr alloys is about 0.5{~}1 μm.


(Received February 17, 1997)

Keywords:

iron-nickel-chromium alloy, magnetic property, sulfur, oxygen, texture, precipitate, inclusion, grain size, domain wall displacement, grain growth


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