304L不锈钢热变形过程微观组织演变机制的研究
发布时间：2018-11-28 12:29
【摘要】：304L奥氏体不锈钢是核电大锻件的主要材料之一。核电不锈钢大锻件不仅体积大,而且要求材料纯净、锻件组织性能均匀。由自由锻引起的温度、材料流线和变形不均匀性导致锻造过程中大锻件实际生产中存在着热锻开裂、晶粒粗大且不均匀技术问题。解决以上问题的关键在于锻件内部晶粒细化和均匀,其技术的核心就是锻造过程中大锻件内部晶粒度的有效控制。然而目前国内对于该钢的基础研究还远不能满足实际生产要求,进而影响大锻件热变形工艺的进一步优化。 本文采用GLEEBLEl500D热模拟实验机对锻态304L不锈钢进行了单道次热压缩实验,在不同应变速率、变形温度下得到了304L不锈钢的应力-应变曲线,研究了304L不锈钢热变形过程初始晶粒尺寸、变形温度、变形量、应变速率等变形参数对奥氏体动态再结晶和流变应力的影响规律。建立了304L不锈钢动态再结晶的动力学模型、运动学模型、流变应力模型、再结晶晶粒尺寸模型以及位错密度模型。通过金相试验、透射电镜(TEM)实验得到动态再结晶后304L不锈钢的再结晶晶粒尺寸、位错组态以及密度分布。 采用ANSYS有限元软件模拟了热模拟试验的变形过程,分析了304L不锈钢试样的不同变形区域在热变形过程中的等效应变、应力以及温度场的分布情况。并参照金相图,分析了非均匀应变对奥氏体动态再结晶及晶粒尺寸的影响。结果表明,在试样的不同区域,等效应变和应力分布相差很大;温度分布也有差异,剪应变对动态再结晶程度的影响比等效应变大。在试验所设定的最大变形量下,等效应变对晶粒细化的影响存在一个临界值,而随着剪应变的增加,奥氏体晶粒不断细化,可见剪应变对奥氏体晶粒尺寸的影响更大。仿真结果与实验结果较为一致,这表明该模型能用来准确描述304L不锈钢热变形过程。 通过的热模拟试验和数值模拟,探究热变形下晶粒尺寸、分布情况,引起的原因和微观机理,建立与变形量、变形温度、保温时间、应力状态等宏观变形参数之间的关系。研究成果可为核电奥氏体不锈钢大锻件生产中的塑性加工质量预报和控制技术提供可靠的科学依据。
[Abstract]:304L austenitic stainless steel is one of the main materials for nuclear power forgings. Nuclear stainless steel forgings are not only large in volume, but also pure in material, uniform in structure and properties. The temperature, material streamline and deformation inhomogeneity caused by free forging lead to hot forging cracking, coarse grain size and inhomogeneous technical problems in the actual production of large forgings. The key to solve the above problems lies in the grain refinement and uniformity in the forging. The core of the technology is the effective control of the internal grain size in the forging process. However, at present, the basic research on the steel in China is far from meeting the actual production requirements, which will affect the further optimization of the hot deformation process of large forgings. In this paper, the single pass thermal compression test of forged 304L stainless steel was carried out with GLEEBLEl500D thermal simulation machine. The stress-strain curves of 304L stainless steel were obtained at different strain rates and deformation temperatures. The effect of deformation parameters such as initial grain size, deformation temperature, deformation amount and strain rate on dynamic recrystallization and rheological stress of austenite during hot deformation of 304L stainless steel were studied. The dynamic model, kinematics model, rheological stress model, recrystallization grain size model and dislocation density model of 304L stainless steel were established. The recrystallization grain size, dislocation configuration and density distribution of 304L stainless steel after dynamic recrystallization were obtained by metallographic test and transmission electron microscope (TEM) test. The deformation process of thermal simulation test was simulated by ANSYS finite element software, and the distribution of equivalent strain, stress and temperature field in different deformation regions of 304L stainless steel specimen was analyzed. The effect of inhomogeneous strain on the dynamic recrystallization and grain size of austenite was analyzed by referring to the metallographic diagram. The results show that the distribution of equivalent strain and stress varies greatly in different regions of the specimen, and the temperature distribution is different, and the effect of shear strain on dynamic recrystallization degree is greater than that of equivalent strain. There is a critical value of the effect of equivalent strain on grain refinement under the maximum deformation set in the experiment. However, with the increase of shear strain, austenite grain is refined continuously, and the effect of shear strain on austenite grain size is greater. The simulation results are in good agreement with the experimental results, which indicates that the model can accurately describe the hot deformation process of 304L stainless steel. Through the thermal simulation test and numerical simulation, this paper explores the grain size, distribution, causes and microscopic mechanism of hot deformation, and establishes the relationship between deformation amount, deformation temperature, holding time, stress state and other macroscopic deformation parameters. The research results can provide a reliable scientific basis for the prediction and control of plastic working quality in the production of austenitic stainless steel forgings.
【学位授予单位】：太原科技大学
【学位级别】：硕士
【学位授予年份】：2011
【分类号】：TG142.15
[Abstract]:304L austenitic stainless steel is one of the main materials for nuclear power forgings. Nuclear stainless steel forgings are not only large in volume, but also pure in material, uniform in structure and properties. The temperature, material streamline and deformation inhomogeneity caused by free forging lead to hot forging cracking, coarse grain size and inhomogeneous technical problems in the actual production of large forgings. The key to solve the above problems lies in the grain refinement and uniformity in the forging. The core of the technology is the effective control of the internal grain size in the forging process. However, at present, the basic research on the steel in China is far from meeting the actual production requirements, which will affect the further optimization of the hot deformation process of large forgings. In this paper, the single pass thermal compression test of forged 304L stainless steel was carried out with GLEEBLEl500D thermal simulation machine. The stress-strain curves of 304L stainless steel were obtained at different strain rates and deformation temperatures. The effect of deformation parameters such as initial grain size, deformation temperature, deformation amount and strain rate on dynamic recrystallization and rheological stress of austenite during hot deformation of 304L stainless steel were studied. The dynamic model, kinematics model, rheological stress model, recrystallization grain size model and dislocation density model of 304L stainless steel were established. The recrystallization grain size, dislocation configuration and density distribution of 304L stainless steel after dynamic recrystallization were obtained by metallographic test and transmission electron microscope (TEM) test. The deformation process of thermal simulation test was simulated by ANSYS finite element software, and the distribution of equivalent strain, stress and temperature field in different deformation regions of 304L stainless steel specimen was analyzed. The effect of inhomogeneous strain on the dynamic recrystallization and grain size of austenite was analyzed by referring to the metallographic diagram. The results show that the distribution of equivalent strain and stress varies greatly in different regions of the specimen, and the temperature distribution is different, and the effect of shear strain on dynamic recrystallization degree is greater than that of equivalent strain. There is a critical value of the effect of equivalent strain on grain refinement under the maximum deformation set in the experiment. However, with the increase of shear strain, austenite grain is refined continuously, and the effect of shear strain on austenite grain size is greater. The simulation results are in good agreement with the experimental results, which indicates that the model can accurately describe the hot deformation process of 304L stainless steel. Through the thermal simulation test and numerical simulation, this paper explores the grain size, distribution, causes and microscopic mechanism of hot deformation, and establishes the relationship between deformation amount, deformation temperature, holding time, stress state and other macroscopic deformation parameters. The research results can provide a reliable scientific basis for the prediction and control of plastic working quality in the production of austenitic stainless steel forgings.
【学位授予单位】：太原科技大学
【学位级别】：硕士
【学位授予年份】：2011
【分类号】：TG142.15
【参考文献】
相关期刊论文 前10条
1 魏季和;舒杰辉;朱宏利;史国敏;江庆元;池和冰;;不锈钢AOD转炉侧顶复吹精炼过程数学模拟初探[J];包头钢铁学院学报;2006年02期
2 李红;罗海文;杨才福;方旭东;;奥氏体不锈钢热轧加工性能的数学模型研究[J];材料导报;2006年10期
3 李红梅,蔡s，
本文编号：2362815
本文链接：https://www.wllwen.com/kejilunwen/jixiegongcheng/2362815.html
