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使用微机控制相变内耗仪测量了18CrNiWA钢连续冷却和等温淬火过程中的内耗.连续冷却测量表明,在400—430℃和320℃(M_s点附近)各出现一个内耗峰.试样经湿氢脱碳后内耗峰移向600℃。它们的峰温与频率无关,而峰高均随频率的降低而升高。等温淬火测量表明,无论试样脱碳与否,初期的内耗值总是最高,随着时间的延长逐渐降到背景值。实验结果显示,贝氏体与马氏体相变内耗峰有相同的频率效应;在贝氏体孕育期内存在预相变的实质是贝氏体自身的形核,而与碳的扩散与否无关,孕育期的最初阶段贝氏体即开始大量形核,通常测到过冷奥氏体的孕育期长短只不过是在特定实验条件下贝氏体长大到可以被察觉的时间。
The internal friction of 18CrNiWA steel during continuous cooling and isothermal quenching was measured by using a controlled phase transformation internal friction instrument.The results of continuous cooling showed that there was one internal friction peak at 400-430 ℃ and 320 ℃ (near M_s point) After decarburization internal friction peak to 600 ℃. Their peak temperature has nothing to do with the frequency, and the peak height increases with decreasing frequency. Isothermal quenching measurements show that regardless of the decarburization of the sample or not, the initial internal friction value is always the highest, with the time gradually decreased to the background value. The experimental results show that the internal friction peaks of bainite and martensitic transformation have the same frequency effect. In the bainite incubation period, the essence of pre-phase transformation is the nucleation of bainite itself, but not with the diffusion of carbon It does not matter that bainite begins to nucleate extensively in the initial stages of the incubation period. It is usually measured that the duration of the undercooled austenite is merely the time it takes for the bainite to grow to be detectable under the specific experimental conditions.