9%Ni钢中沉淀奥氏体的形成过程及其在深冷下的表现

FORMATION OF PRECIPITATED AUSTENITE IN 9% Ni STEEL AND ITS FUNCTION AT CRYOGENIC TEMPERATURE

研究了9%Ni钢在两相区温度保温时沉淀奥氏体的析出过程及其对低温冲击韧性的影响。结果表明:在两相区保温由于C,N及Ni的重新分布,形成富Ni,Mn及C,N的奥氏体富集区及相对纯化的铁素体富集区,两者呈深浅相间的条带状组织。中温转变的奥氏体冷却到室温时部分转变成马氏体。这种第二代马氏体与奥氏体高度细化,并交织在一起形成复杂的组织。而奥氏体中高度富集C,N及Ni,它在极低温度下仍很稳定。低温冲击断口的撕裂岭都是沉淀奥氏体密集的,它们沿撕裂方向拉长。说明细碎的马氏体与奥氏体交织的组织既保持一定的强度也提高了低温韧性,这同回转奥氏体吸收杂质纯化基体密切相关。

Streaks of austenite-rich and ferrite-rich bands produce during thesoaking at α+γ region because of the re-distribution of elements. Part of the aus-tenite formed at intermediate temperatures transforms into martensite while thesteel was cooled down to room temperature. The structure which consists of finemartensite and austenite exhibits a moderate strength and high enough cryogenictoughness. One of the important cause of the excellent cryogenic properties is thatthe precipitated austenite absorbs the impurities and thus purifies the matrix of thesteel.