一、前言低碳奥氏体本质晶粒度的测定,在现行的YB27-77与ISOR43推荐标准中规定有网状铁素体法。由于标准对此法适用的钢种及热处理工艺规定不明确,因而在生产检验中难以执行。为适应生产的需要,对C≤0.22％的3C船板钢应用相变原理和回归分析方法,摸索出简便易行的临界淬火法,并可依据此钢的化学成分,由回归方程求得在奥氏体晶界析出网状铁素体的临界淬火温度。二、原理概述奥氏体冷却时,在铁素体的形成方面就热力学而言是不稳定的,转变时先析出先共析铁素体。它是完全扩散型转变的产物,且常 I. Preface The determination of the intrinsic grain size of low-carbon austenite provides for the reticular ferrite method in the current YB27-77 and ISOR43 recommendations. As the standard for the law applicable to the type of steel and heat treatment process is not clear, and therefore difficult to implement in the production test. In order to meet the need of production, the principle of phase transformation and regression analysis was applied to 3C ship steel with C≤0.22%. The critical quenching method was explored. Based on the chemical composition of the steel, the regression equation was obtained Austenite grain boundary precipitation of reticular ferrite critical quenching temperature. Second, the principle outlined austenite cooling, the formation of ferrite in terms of thermodynamics is unstable, the first precipitation of proeutectoid ferrite transformation. It is the product of a completely diffusion-type shift, often