In isothermal spheroidizing process,the spheroidization and growth of the carbide formed in hot-deformed high-carbon chromium cast steel at high temperature were investigated.The results showed that the spheroidizing ...In isothermal spheroidizing process,the spheroidization and growth of the carbide formed in hot-deformed high-carbon chromium cast steel at high temperature were investigated.The results showed that the spheroidizing growth of carbide proceeds in such a way that the bigger carbide particles swallow the smaller ones,and the short rhabdoid carbides dissolve and are spheroidized by itself.When the samples were held at 720℃ for more than 3 h,the spheroidization is not obvious.The feature of the process is the size increment and the amount decrement of carbide particles.The empirical equation for growth rate of carbides was obtained.The volume fraction of carbides keeps constant.The growth process agrees well with Ostwald Ripening Law.展开更多
The Ostwald ripening of carbide particles occurs during the process of subcritical annealing in SCM435 steel, and the degree of ripening influences the microstructure and mechanical properties of the steel. The effect...The Ostwald ripening of carbide particles occurs during the process of subcritical annealing in SCM435 steel, and the degree of ripening influences the microstructure and mechanical properties of the steel. The effects of Ostwald ripening were studied by simulating different soaking time at 680 ~C using SCM435 steel. The spheroidized specimens were analysed by conducting microstructure and mechanical tests. After increasing the soaking time from 2 to 6 h at 680 ~C during subcritical annealing, the number of carbide particles and the spheroidization ratio increased gradually, and the formability was improved. When the soaking time ranged from 6 to 8 h, the spheroidization ratio was similar; however, the number of carbide particles decreased, and the formability gradually worsened. Therefore, by comprehensively comparing the microstructures and mechanical properties, the optimum soaking time was determined to be 6 h at 680 ~C during subcritical annealing to obtain preferable cold heading. In addition, the carbide particles gradually coarsened when the soaking time was extended from 2 to 8 h. A formula was presented to quantitatively characterize the progress of Ostwald ripening of the carbide particles during the subcritical annealing of SCM435 steel, and the relative error was less than 8.02%.展开更多
在实验室绝缘油中溶解气体分析(dissolved gas analysis,DGA)过程中,顶空取气法作为一种常规油样脱气方法,其准确性主要取决于计算时所采用的平衡分配系数或Ostwald系数Ki的准确性。首先根据油中溶解气体组分浓度的不同表征方式,分别通...在实验室绝缘油中溶解气体分析(dissolved gas analysis,DGA)过程中,顶空取气法作为一种常规油样脱气方法,其准确性主要取决于计算时所采用的平衡分配系数或Ostwald系数Ki的准确性。首先根据油中溶解气体组分浓度的不同表征方式,分别通过理论推导和实验探究两种方式,研究并分析了气压因素对Ostwald系数的影响。然后基于所得结论,针对Ostwald系数定义所采用的油中溶解气体浓度表征方式以及测定时存在的问题加以讨论分析。通过该研究和对相关问题的探讨,有助于加深对溶解平衡过程和平衡分配系数Ki的理解和认知,从而避免在测定和使用Ki值时因引入额外误差而影响测定结果以及绝缘油DGA分析的准确性。另外,该研究也为相关文献和标准的修正提供了参考。展开更多
基金National Natural Science Foundation of China(51301027,51571038)the Natural Science Foundation of Jiangsu Higher Education Institutions of China(14KJB430002)the Natural Science Foundation of Jiangsu Province(BK20151188)
基金Item Sponsored by Guiding Programme of Science and Technology Research of Hebei of China(94122123)
文摘In isothermal spheroidizing process,the spheroidization and growth of the carbide formed in hot-deformed high-carbon chromium cast steel at high temperature were investigated.The results showed that the spheroidizing growth of carbide proceeds in such a way that the bigger carbide particles swallow the smaller ones,and the short rhabdoid carbides dissolve and are spheroidized by itself.When the samples were held at 720℃ for more than 3 h,the spheroidization is not obvious.The feature of the process is the size increment and the amount decrement of carbide particles.The empirical equation for growth rate of carbides was obtained.The volume fraction of carbides keeps constant.The growth process agrees well with Ostwald Ripening Law.
文摘The Ostwald ripening of carbide particles occurs during the process of subcritical annealing in SCM435 steel, and the degree of ripening influences the microstructure and mechanical properties of the steel. The effects of Ostwald ripening were studied by simulating different soaking time at 680 ~C using SCM435 steel. The spheroidized specimens were analysed by conducting microstructure and mechanical tests. After increasing the soaking time from 2 to 6 h at 680 ~C during subcritical annealing, the number of carbide particles and the spheroidization ratio increased gradually, and the formability was improved. When the soaking time ranged from 6 to 8 h, the spheroidization ratio was similar; however, the number of carbide particles decreased, and the formability gradually worsened. Therefore, by comprehensively comparing the microstructures and mechanical properties, the optimum soaking time was determined to be 6 h at 680 ~C during subcritical annealing to obtain preferable cold heading. In addition, the carbide particles gradually coarsened when the soaking time was extended from 2 to 8 h. A formula was presented to quantitatively characterize the progress of Ostwald ripening of the carbide particles during the subcritical annealing of SCM435 steel, and the relative error was less than 8.02%.
文摘在实验室绝缘油中溶解气体分析(dissolved gas analysis,DGA)过程中,顶空取气法作为一种常规油样脱气方法,其准确性主要取决于计算时所采用的平衡分配系数或Ostwald系数Ki的准确性。首先根据油中溶解气体组分浓度的不同表征方式,分别通过理论推导和实验探究两种方式,研究并分析了气压因素对Ostwald系数的影响。然后基于所得结论,针对Ostwald系数定义所采用的油中溶解气体浓度表征方式以及测定时存在的问题加以讨论分析。通过该研究和对相关问题的探讨,有助于加深对溶解平衡过程和平衡分配系数Ki的理解和认知,从而避免在测定和使用Ki值时因引入额外误差而影响测定结果以及绝缘油DGA分析的准确性。另外,该研究也为相关文献和标准的修正提供了参考。
