Cr-Ni ステンレス鋼の組織と諸性質におよぼす Cu, N, Mn, Al の影響

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An investigation was made into the effects of Cu, N, Mn and Al additions on structures of Cr-Ni stainless steels and of the effects of the structures on mechanical properties and corrosion resistance. Experimental results obtained were as follows : i) Specimens containing Cu were hardened by precipitation of secondary ferrite and those containing N were hardened mainly by precipitation of Cr_2N and by transformation of austenite to ferrite or martensite. Specimens containing Mn and those containing Al were hardened by formation of σ phase from δ ferrite and by precipitation of Al_3Ni respectively. ii) The grain boundary reaction which was characterized by formation of lamellar nodules occurred during aging at 750℃ with specimens containing higher N content. Granular chromium carbide precipitated within grains of δ ferrite in aging with specimens containing higher Al content. σ phase was formed more rapidly from δ ferrite in aging at 750℃ with specimens containing higher Mn content. iii) The nickel equivalence of Cu and N in their ability to extend the austenite region at high temperature was about 0.5 and 20 respectively. The Cr equivalence of Al as a ferrite former was about 4. Addition of Mn to the steels decreased the amount of δ ferrite, but on increasing the Mn to above 4% it slightly increased the amount of δ ferrite. iv) Tensile strength of specimens containing Cu and that of specimens containing Mn depended mainly upon the structural conditions. Solution-hardening by N was very large but effect of structural conditions on tensile strength was larger than that of solution-hardening at test temperature below 500℃. Tensile strength of specimens containing Al depended mainly upon the amount of AlN. v) Increase of creep-rupture strength with increasing Cu and N contents was due to both solution-hardening by Cu and N and decrement of the amount of δ ferrite with increasing Cu and N content. Creep-rupture strength of specimens containing Mn and that of specimens containing Al depended only upon the amount of δ ferrite. vi) With specimens containing N, the corrosion resistance to HNO_3 reached minimum at about 0.2% of N and that to H_2SO_4 reached maximum at the same content of N. With specimens containing the other elements, the relation between corrosion resistance to H_2SO_4 and the content of alloying elements was the same as that between creep rupture strength and the content of alloying elements.
社団法人日本鉄鋼協会の論文
1962-12-01

Cr-Ni ステンレス鋼の組織と諸性質におよぼす Cu, N, Mn, Al の影響

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