Cr-Ni-Mo双相不锈钢的空泡腐蚀行为

利用超声波空蚀实验装置对Cr-Ni-Mo奥氏体-铁素体不锈钢及其同质材料堆焊后的堆层金属在自来水溶液中的空蚀行为进行了研究.通过扫描电镜（SEM）、显微硬度计等检测设备研究了材料空蚀表面形貌和微观结构.结果表明：Cr-Ni-Mo双相不锈钢的抗空蚀性能明显优于经TIG（钨极惰性气体保护焊）表面堆焊后的堆层金属试样;双相不...     

Cr-Mn-N奥氏体-铁素体不锈钢的空蚀行为

利用超声振荡空蚀实验机对Cr-Mn-N奥氏体－铁素体不锈钢进行了空蚀研究。结果表明，低硬度Cr-Mn-N不锈钢的抗空蚀性能高于高硬度的0Cr13Ni5Mo不锈钢。空蚀过程中，Cr-Mo-N奥氏体－铁素体不锈钢中的铁素体优先脱落，空蚀表面的铁素体含量由19％迅速降低到6．9％后保持稳定。奥氏体易于在铁素体脱离后形成的蚀坑处开始脱落，加工硬化是该不锈钢吸收空蚀冲击能量的一个重要途径，是其硬度较低却表面出良好抗空蚀性能的重要原因。     

奥氏体不锈钢焊接接头晶间腐蚀断裂分析

核电站管道大多采用奥氏体铁素体不锈钢制成,以主管道为例,多数采用焊接方式进行连接。在现场应用之前,需要进行工艺评定的焊接和检验,以验证焊接接头是否满足高温、高压、高腐蚀的性能要求。晶间腐蚀按照标准RCCM+RCCM2000补遗中MC1312.3中B法处理后,在弯曲过程出现裂纹,对比试样也出现裂纹,难以判定是否是晶间腐蚀造成的裂纹缺陷。利用金相方法观察出现裂纹的试样,结合力学性能试验和化学成分进行分析得出,弯曲受检面产生的裂纹不是由晶间腐蚀造成的。     

A study on controlled cooling process for making bainitic ductile iron

In the present research, TTT curve of bainitic ductile iron under the condition of controlled cooling was generated. The cooling rate of grinding ball and its temperature distribution were also measured at the same time. It can be concluded that the bainitic zone of TTT curve is separated from the pearlitic zone. As compared to the water-quenching condition, more even cooling rate and temperature distribution can be achieved in the controlled cooling process. The controlled cooling can keep away from pearlitic zone in the high temperature cooling stage and produce similar results to the process of traditional isothermal cooling with a low cooling rate in the low temperature cooling stage.     

奥氏体-铁素体区循环形变对Q235钢力学性能的影响

研究开发出了一种钢材组织细化的新方法,即奥氏体-铁素体区循环形变,并采用自行设计的热模拟试样,研究了奥氏体-铁素体区循环形变对Q235钢力学性能的影响规律.结果表明:在大部分变形条件下,采用该方法所得到的Q235钢的杭拉强度大于500MPa,屈服强度大于400MPa,伸长率大于20%,     

Kinetics and microstructural modeling of isothermal austenite-to-ferrite transformation in Fe-C-Mn-Si steels

During the multi-stage processing of advanced high-strength steels, the austenite-to-ferrite transformation, generally as a precursor of the formation of other non-equilibrium or metastable structures, has a severe effect on the subsequent phase transformations. Herein, a more flexible kinetic and microstructural predictive modeling for the key austenite-to-ferrite transformation of Fe-C-Mn-Si steels was developed, in combination with the classical nucleation theory, the general mixed-mode growth model based on Gibbs energy balance, the microstructural path method and the kinetic framework for grain boundary nucleation. Adopting a bounded, extended matrix space corresponding to a single ferrite grain, both soft-impingement and hard-impingement can be naturally included in the current modeling. Accordingly, this model outputs the ferrite volume fraction, the austenite/ferrite interface area per unit volume, and the average grain size of ferrite, which will serve as the input parameters for modeling the subsequent bainite or martensite transformations. Applying the model, this work successfully predicts the experiment measurement of the isothermal austenite-to-ferrite transformation in Fe-0.17C-0.91Mn-1.03Si (wt%) steel at different temperatures and explains why the final-state average grain size of ferrite has a maximum at the moderate annealing temperature. Effectiveness and advantages of the present model are discussed arising from kinetics and thermodynamics accompanied with nucleation, growth and impingement.