【摘要】：盾構(gòu)機作為一種常用的大型挖掘設(shè)備,廣泛應用在國家大型基礎(chǔ)設(shè)施建設(shè)之中。對于盾構(gòu)機主要部件的主軸承,目前國內(nèi)的盾構(gòu)機生產(chǎn)廠家完全從國外進口。開發(fā)盾構(gòu)機主軸承用鋼,尤其是軸承套圈直徑在3m以上的軸承套圈用鋼,是打破壟斷實現(xiàn)盾構(gòu)機主軸承國產(chǎn)化的前提。本文根據(jù)盾構(gòu)機的直徑3m以上軸承套圈用鋼的性能要求,對影響變形和熱處理組織性能的幾個關(guān)鍵科學問題進行研究,并基于直徑小于3m軸承套圈用鋼42CrMo的研究,開發(fā)出直徑3m以上軸承套圈用鋼,從而實現(xiàn)大型盾構(gòu)機軸承套圈用鋼的綜合質(zhì)量控制。大尺寸鍛件是生產(chǎn)軸承套圈的主要材料,用來生產(chǎn)直徑3m以上軸承套圈的鍛件,噸位將達到17t以上,不可避免帶來嚴重的冶金缺陷。本文通過動態(tài)再結(jié)晶規(guī)律研究,以及鐓粗和拔長工藝數(shù)值模擬研究,明確了17t以上大尺寸鍛件變形過程中的空洞閉合規(guī)律,給出了簡化的空洞閉合判定條件,得到了鍛造過程的工藝參數(shù)對鍛件內(nèi)部應力應變和空洞閉合的影響主次。提出了更利于大尺寸鍛件內(nèi)部組織均勻化和精細化的鍛造工藝：鐓粗時,壓下量50%、變形溫度1200℃、變形速率0.05s-1、高徑比1.7、砧子傾角0°；拔長壓方時,大壓下且保證砧寬比在0.43以上,同時難變形區(qū)盡量采用滿砧壓下,生產(chǎn)出了滿足組織均勻性和探傷要求的鍛件。感應淬火是軸承套圈生產(chǎn)的必要工序,是實現(xiàn)軸承套圈表面高硬度的重要手段。感應加熱過程中的奧氏體長大行為研究,是實現(xiàn)淬火后組織精確控制的關(guān)鍵。本文首次建立了考慮連續(xù)加熱過程中的奧氏體晶粒尺寸的等溫加熱和連續(xù)加熱奧氏體晶粒長大的精確模型,通過實驗驗證了模型的準確性。利用模型預測和實驗研究,得出在實驗鋼容許感應淬火溫度范圍內(nèi),快速加熱后的奧氏體晶粒尺寸對淬火原始室溫組織的粗細十分敏感,而對不同原始組織狀態(tài)(淬火態(tài)、調(diào)質(zhì)態(tài)和退火態(tài))敏感較弱。淬火態(tài)得到的初始晶粒最細,調(diào)質(zhì)態(tài)次之,退火態(tài)最粗,當加熱溫度在1000℃以下,對加熱后奧氏體晶粒尺寸影響較大。為了獲得較細的淬火組織,以獲得良好的強韌性匹配,應細化原始室溫組織。目前常用于盾構(gòu)機的直徑小于3m軸承套圈的鋼種主要為42CrMo鋼,而由于直徑3m以上軸承套圈尺寸較大,綜合性能控制難度更大,所需鋼的成分控制也必然存在特殊性。本文通過對42CrMo鋼的組織性能研究,得到該實驗鋼的最佳熱處理工藝參數(shù)下獲得的沖擊功為145.5J,回火硬度為269HB。調(diào)質(zhì)后的實驗鋼在快速加熱短時間保溫后冷卻的硬度可以達到56.5HRC以上。獲得的各項性能,不能滿足盾構(gòu)機的直徑3m以上軸承套圈用鋼的綜合性能要求。而通過系統(tǒng)研究合金元素C、Mn和Ni元素對于鋼的組織和性能的影響,提出了滿足直徑3m以上軸承套圈用鋼性能要求的主要元素成分為(wt%):C:0.43、Si:0.23、Mn:0.60、Cr:1.08、 Mo:0.22和Ni：0.60。通過新開發(fā)盾構(gòu)機的直徑3m以上軸承套圈用鋼的實驗研究,討論了Ni元素對于調(diào)質(zhì)后沖擊韌性和硬度的影響,以及Ni元素和冷卻速度對于快速加熱短時間保溫冷卻后組織和硬度的影響機理。結(jié)果表明實驗鋼在最佳調(diào)質(zhì)熱處理工藝下,能夠保證基體具有良好的韌性(最高Akv為107.2J)和合適的硬度；套圈表面在快速加熱短時間保溫后冷卻時,冷速為50℃/s以上時,鋼的硬度達到58HRC以上,給出較寬的冷卻工藝控制窗口。生產(chǎn)出滿足直徑3m以上軸承套圈綜合性能要求的材料。
[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，

本文編號：2486007