Cr-Niステンレス鋼における各相間の合金元素の分配とδフェライト量と磁性の関係

抄録

Properties of δferrite in Cr-Ni stainless steels and its microstructural change during aging are influenced by the composition of δ ferrite.
Therefore it is very important to examine the composition of δ ferrite in studying the effect of δ ferrite on the properties of Cr-Ni Stainless steels.
This report is concerned with an analysis of phases in Cr-Ni stainless steels using the electron probe X-ray microanalyzer. Comparison of measured values with chemically analytical values, and correction of measured values were made. Partition of alloying elements between phases and the effect of an additional element on the composition of σ phase were investigated.
The studies were also extended to an investigation of the relation between the amount of δ ferrite and the intensity of magnetization.
The following results were obtained:
i) The concentration of an austenite-former was higher in austenite than in δ ferrite.
The ratio of the concentration of an austenite-former in austenite to that in δ ferrite was the greater, the higher the potency of the austenite-former. The concentration of a ferriteformer was higher in δ ferrite than in austenite but there was no relation between the partition ratio (Cδ/Cγ) and the potency of a ferrite-former.
ii) Addition of Ti, Mo and Mn to the steels greatly promoted the formation of σ phase from δ ferrite. Mo and Ti decreased considerably the concentration of Cr in σ phase but it seemed that Mn decreased it slightly.
iii) A linear relation between the amount of δ ferrite and the intensity of magnetization was observed. The amount of martensite could be estimated from the change in the intensity of magnetization after subzero treatment of specimens with a structure consisting of austenite, martensite and δ ferrite. The amount of martensite was decreased but that of austenite was increased with an increasing temperature of solution treatment.