非鉄クラッド鋼の接合境界部における相互拡散に関する研究 Ｉ アルミ青銅クラッド鋼におけるαバンドおよびβ′相の生成について

Abstract

Copper alloy clad steels have been produced by the hot rolling process with insert metal to prevent the interfaces to be bonded from the oxidation. Nickel is most popular for the insert of copper alloyc lad steel.But in the case of aluminum bronze clad steel, an intermetallic compound forms necessarily by the interdiffusion between alumium bronze and nickel when nickel insert is used.This intermetallic compound sometimes gives rise to the separation of clad steel during rolling, or the reduction of bond strength even if the separation does not occur.Therefore, it is necessary to avoid the formation of intermetallic compound in order to produce the clad steel. A counteract for this compound is to insrt a copper layer between the two metals.Investigation on the diffusion phenomena at the bonded region of clad steel, especially, on the formation and growth process of intermetallic compound was carried out using aluminum bronze nickel and aluminum bronze/copper/nickel diffusion couples.The following are result of this investigation.1) The intermetallic compounds formed by interdiffusion between alumnum bronze and nickel are β' phase and α' phase which are respectively NiAl and Ni3Al type compounds both containing Cu and Fe. The β' phase is very hard and brittle.2) Incubation time of the formation of β' ophase becomes linearly longer with a square root of the thickness of copper layer.3) A banded α phase formed by diffusion becomes thicker with a thickness of copper just as much as the thickness of copper layer before diffusion.4) Thickness of the α band at the incubation time of β' phase is independent of diffusion temperature but depends on the thickness of copper. Linear relationship is existing between the thicknesses of α band and copper layer.Above result will be available to the industrial production of aluminum bronze clad steel.