盾构机轴承套圈用钢变形与热处理组织性能研究
发布时间：2019-05-27 08:31
【摘要】：盾构机作为一种常用的大型挖掘设备,广泛应用在国家大型基础设施建设之中。对于盾构机主要部件的主轴承,目前国内的盾构机生产厂家完全从国外进口。开发盾构机主轴承用钢,尤其是轴承套圈直径在3m以上的轴承套圈用钢,是打破垄断实现盾构机主轴承国产化的前提。本文根据盾构机的直径3m以上轴承套圈用钢的性能要求,对影响变形和热处理组织性能的几个关键科学问题进行研究,并基于直径小于3m轴承套圈用钢42CrMo的研究,开发出直径3m以上轴承套圈用钢,从而实现大型盾构机轴承套圈用钢的综合质量控制。大尺寸锻件是生产轴承套圈的主要材料,用来生产直径3m以上轴承套圈的锻件,吨位将达到17t以上,不可避免带来严重的冶金缺陷。本文通过动态再结晶规律研究,以及镦粗和拔长工艺数值模拟研究,明确了17t以上大尺寸锻件变形过程中的空洞闭合规律,给出了简化的空洞闭合判定条件,得到了锻造过程的工艺参数对锻件内部应力应变和空洞闭合的影响主次。提出了更利于大尺寸锻件内部组织均匀化和精细化的锻造工艺：镦粗时,压下量50%、变形温度1200℃、变形速率0.05s-1、高径比1.7、砧子倾角0°；拔长压方时,大压下且保证砧宽比在0.43以上,同时难变形区尽量采用满砧压下,生产出了满足组织均匀性和探伤要求的锻件。感应淬火是轴承套圈生产的必要工序,是实现轴承套圈表面高硬度的重要手段。感应加热过程中的奥氏体长大行为研究,是实现淬火后组织精确控制的关键。本文首次建立了考虑连续加热过程中的奥氏体晶粒尺寸的等温加热和连续加热奥氏体晶粒长大的精确模型,通过实验验证了模型的准确性。利用模型预测和实验研究,得出在实验钢容许感应淬火温度范围内,快速加热后的奥氏体晶粒尺寸对淬火原始室温组织的粗细十分敏感,而对不同原始组织状态(淬火态、调质态和退火态)敏感较弱。淬火态得到的初始晶粒最细,调质态次之,退火态最粗,当加热温度在1000℃以下,对加热后奥氏体晶粒尺寸影响较大。为了获得较细的淬火组织,以获得良好的强韧性匹配,应细化原始室温组织。目前常用于盾构机的直径小于3m轴承套圈的钢种主要为42CrMo钢,而由于直径3m以上轴承套圈尺寸较大,综合性能控制难度更大,所需钢的成分控制也必然存在特殊性。本文通过对42CrMo钢的组织性能研究,得到该实验钢的最佳热处理工艺参数下获得的冲击功为145.5J,回火硬度为269HB。调质后的实验钢在快速加热短时间保温后冷却的硬度可以达到56.5HRC以上。获得的各项性能,不能满足盾构机的直径3m以上轴承套圈用钢的综合性能要求。而通过系统研究合金元素C、Mn和Ni元素对于钢的组织和性能的影响,提出了满足直径3m以上轴承套圈用钢性能要求的主要元素成分为(wt%):C:0.43、Si:0.23、Mn:0.60、Cr:1.08、 Mo:0.22和Ni：0.60。通过新开发盾构机的直径3m以上轴承套圈用钢的实验研究,讨论了Ni元素对于调质后冲击韧性和硬度的影响,以及Ni元素和冷却速度对于快速加热短时间保温冷却后组织和硬度的影响机理。结果表明实验钢在最佳调质热处理工艺下,能够保证基体具有良好的韧性(最高Akv为107.2J)和合适的硬度；套圈表面在快速加热短时间保温后冷却时,冷速为50℃/s以上时,钢的硬度达到58HRC以上,给出较宽的冷却工艺控制窗口。生产出满足直径3m以上轴承套圈综合性能要求的材料。
[Abstract]:As a common large-scale mining equipment, the shield machine is widely used in the construction of large-scale national infrastructure. For the main bearing of the main components of the shield machine, the domestic shield machine manufacturers are imported from abroad. The development of the steel for the main bearing of the shield, in particular for the bearing ring with the diameter of more than 3 m, is the premise to break the monopoly to realize the localization of the main bearing of the shield. According to the performance requirement of steel for bearing ring with diameter of more than 3m, this paper studies several key scientific problems that affect the performance of deformation and heat treatment, and develops the steel for bearing ring with diameter of more than 3m based on the research of steel 42CrMo with diameter less than 3m bearing ring. So as to realize the comprehensive quality control of the steel for the bearing ring of the large-scale shield machine. The large-size forging is the main material for producing the bearing ring, which is used to produce the forgings with the diameter of 3 m or more, and the tonnage will reach above 17t, which will inevitably lead to serious metallurgical defects. In this paper, through the study of the law of dynamic recrystallization and the numerical simulation of the rough and long process, the void closure law in the deformation process of the large-sized forgings above 17t is defined, and the simplified void closure determination condition is given. The influence of the process parameters of the forging process on the internal stress strain and the void closure of the forging is obtained. The forging process which is more beneficial to the homogenization and refinement of the inner tissue of the large-size forging is proposed. When the forging process is rough, the reduction amount is 50%, the deformation temperature is 1200 DEG C, the deformation rate is 0.05 s-1, the high-diameter ratio is 1.7, the angle of the anvil is 0 DEG, and when the long-pressing square is pulled out, the high pressure is reduced and the aspect ratio of the anvil is ensured to be more than 0.43, At the same time, the hard deformation area is pressed by the full-anvil as much as possible, and the forging which meets the requirements of tissue uniformity and flaw detection is produced. Induction quenching is a necessary step in the production of bearing ring, which is an important means to realize the high hardness of bearing ring surface. The study of the growth behavior of the austenite in the induction heating process is the key to the precise control of the microstructure after quenching. In this paper, the exact model of isothermal heating and continuous heating of the austenite grain growth in the continuous heating process is established for the first time, and the accuracy of the model is verified by the experiment. Using the model prediction and experimental study, it is concluded that the austenite grain size after the rapid heating is very sensitive to the thickness of the original room temperature tissue in the range of the allowable induction quenching temperature of the experimental steel, and the sensitivity of the austenite grain size to the different original tissue states (the quenching state, the quenching state and the annealing state) is weak. The initial crystal grain obtained in the quenching state is the most fine, the tempering state is the second, the annealing state is the most coarse, and when the heating temperature is below 1000 DEG C, the size of the austenite grain after the heating is greatly affected. In order to obtain a finer quenching structure, the original room temperature tissue should be refined to obtain a good strong toughness match. At present, the steel grade of the bearing ring of less than 3m in diameter of the shield machine is mainly 42CrMo steel, and because the size of the bearing ring with the diameter of more than 3m is larger, the comprehensive performance control is more difficult, and the component control of the required steel also has the special characteristics. Based on the study of the microstructure of the 42CrMo steel, the impact energy obtained under the optimum heat treatment process parameters of the experimental steel is 145.5J, and the tempering hardness is 269 HB. The hardness of the quenched and tempered test steel after rapid heating for a short period of time can reach a hardness of 56.5 HRC or more. And the obtained performance can not meet the comprehensive performance requirement of the steel for bearing rings with the diameter of more than 3m in the shield machine. The effects of alloying elements C, Mn and Ni on the microstructure and properties of the steel are studied by the system. The main elements of the steel properties of the bearing ring with the diameter of 3 m or more are (wt%): C: 0.43, Si: 0.23, Mn: 0.60, Cr: 1.08, Mo: 0.22 and Ni: 0.60. The effect of Ni element on impact toughness and hardness after quenching and tempering, and the influence mechanism of Ni element and cooling rate on microstructure and hardness after rapid heating for short time are discussed. The results show that the steel has good toughness (maximum Akv is 107.2J) and suitable hardness, and the hardness of the steel reaches more than 58HRC when the cooling rate is above 50 鈩，
本文编号：2486007
[Abstract]:As a common large-scale mining equipment, the shield machine is widely used in the construction of large-scale national infrastructure. For the main bearing of the main components of the shield machine, the domestic shield machine manufacturers are imported from abroad. The development of the steel for the main bearing of the shield, in particular for the bearing ring with the diameter of more than 3 m, is the premise to break the monopoly to realize the localization of the main bearing of the shield. According to the performance requirement of steel for bearing ring with diameter of more than 3m, this paper studies several key scientific problems that affect the performance of deformation and heat treatment, and develops the steel for bearing ring with diameter of more than 3m based on the research of steel 42CrMo with diameter less than 3m bearing ring. So as to realize the comprehensive quality control of the steel for the bearing ring of the large-scale shield machine. The large-size forging is the main material for producing the bearing ring, which is used to produce the forgings with the diameter of 3 m or more, and the tonnage will reach above 17t, which will inevitably lead to serious metallurgical defects. In this paper, through the study of the law of dynamic recrystallization and the numerical simulation of the rough and long process, the void closure law in the deformation process of the large-sized forgings above 17t is defined, and the simplified void closure determination condition is given. The influence of the process parameters of the forging process on the internal stress strain and the void closure of the forging is obtained. The forging process which is more beneficial to the homogenization and refinement of the inner tissue of the large-size forging is proposed. When the forging process is rough, the reduction amount is 50%, the deformation temperature is 1200 DEG C, the deformation rate is 0.05 s-1, the high-diameter ratio is 1.7, the angle of the anvil is 0 DEG, and when the long-pressing square is pulled out, the high pressure is reduced and the aspect ratio of the anvil is ensured to be more than 0.43, At the same time, the hard deformation area is pressed by the full-anvil as much as possible, and the forging which meets the requirements of tissue uniformity and flaw detection is produced. Induction quenching is a necessary step in the production of bearing ring, which is an important means to realize the high hardness of bearing ring surface. The study of the growth behavior of the austenite in the induction heating process is the key to the precise control of the microstructure after quenching. In this paper, the exact model of isothermal heating and continuous heating of the austenite grain growth in the continuous heating process is established for the first time, and the accuracy of the model is verified by the experiment. Using the model prediction and experimental study, it is concluded that the austenite grain size after the rapid heating is very sensitive to the thickness of the original room temperature tissue in the range of the allowable induction quenching temperature of the experimental steel, and the sensitivity of the austenite grain size to the different original tissue states (the quenching state, the quenching state and the annealing state) is weak. The initial crystal grain obtained in the quenching state is the most fine, the tempering state is the second, the annealing state is the most coarse, and when the heating temperature is below 1000 DEG C, the size of the austenite grain after the heating is greatly affected. In order to obtain a finer quenching structure, the original room temperature tissue should be refined to obtain a good strong toughness match. At present, the steel grade of the bearing ring of less than 3m in diameter of the shield machine is mainly 42CrMo steel, and because the size of the bearing ring with the diameter of more than 3m is larger, the comprehensive performance control is more difficult, and the component control of the required steel also has the special characteristics. Based on the study of the microstructure of the 42CrMo steel, the impact energy obtained under the optimum heat treatment process parameters of the experimental steel is 145.5J, and the tempering hardness is 269 HB. The hardness of the quenched and tempered test steel after rapid heating for a short period of time can reach a hardness of 56.5 HRC or more. And the obtained performance can not meet the comprehensive performance requirement of the steel for bearing rings with the diameter of more than 3m in the shield machine. The effects of alloying elements C, Mn and Ni on the microstructure and properties of the steel are studied by the system. The main elements of the steel properties of the bearing ring with the diameter of 3 m or more are (wt%): C: 0.43, Si: 0.23, Mn: 0.60, Cr: 1.08, Mo: 0.22 and Ni: 0.60. The effect of Ni element on impact toughness and hardness after quenching and tempering, and the influence mechanism of Ni element and cooling rate on microstructure and hardness after rapid heating for short time are discussed. The results show that the steel has good toughness (maximum Akv is 107.2J) and suitable hardness, and the hardness of the steel reaches more than 58HRC when the cooling rate is above 50 鈩，
本文编号：2486007
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