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70.残余奥氏体的功过淬火时不能完全转变为马氏体而被保留下来的奥氏体叫做残余奥氏体(γ_R)。钢的M_s点出现在常温以下时,γ_R的数量随着钢含C的百分比、淬火温度,冷却速度等而变化。含C的百分比越高、淬火温度越高,γ_R量就越多。此外、油冷与水冷相比,γ_R量增多。残余奥氏体数量大致为10～30％。实际上,γ_R中包括不稳定的残余奥氏体和稳定的残余奥氏体。不稳定的残余奥氏体具有因外力作用而易于转变为马氏体的性质;但是,稳定的残余奥氏体是非常稳固的,不发生丝毫的变化。
70. The residual austenite, which can not be completely transformed into martensite by the hardening of retained austenite, is called retained austenite (γ_R). When the M_s point of steel occurs below room temperature, the amount of γ_R varies with the percentage of steel containing C, the quenching temperature, the cooling rate, and the like. The higher the percentage of C, the higher the quenching temperature, the greater the amount of γ_R. In addition, oil-cooled and water-cooled, γ_R increased. The amount of retained austenite is approximately 10 to 30%. In fact, γ_R includes unstable retained austenite and stable retained austenite. Unstable retained austenite has the property of being easily transformed to martensite by an external force; however, stable retained austenite is very stable without any change.