盾构机用大断面高碳铬轴承钢组织性能控制研究

发布时间：2018-05-30 04:14

本文选题：轴承钢 + 网状碳化物　；参考：《北京科技大学》2015年博士论文

【摘要】：随着我国盾构施工领域的快速发展,盾构机的生产和制造行业迅速发展。但是,由于我国高品质轴承钢材料的生产技术落后,盾构机的核心部件——主轴轴承还未能实现国产化,而是100%采用了进口产品,这大大增加了盾构机的生产成本,严重制约了我国大型盾构机行业的进一步发展。本文以轴承钢GCr1SSiMn为研究对象,开展了6米以上直径的大型盾构机主轴承滚动体材料的组织演变机理和性能控制研究,实现了国内大型盾构机用轴承滚动体材料质量控制的新突破,为大型盾构机轴承滚动体制造的国产化提供了材料保障；以轴承钢GCr15为研究对象,系统开展高碳铬轴承钢的Nb微合金化研究,阐述Nb对高碳铬轴承钢显微组织的影响规律和作用机理。对轴承钢GCr15SiMn的热变形行为和晶粒长大行为进行了研究。确立了变形温度和变形量与动态再结晶状态的关系,为轴承钢生产过程中的轧制工艺设计提供了理论基础；利用动态再结晶的动力学模型,实现了对轴承钢GCr15SiMn动态再结晶体积分数的准确预测；确定了加热温度和保温时间与奥氏体晶粒尺寸的定量关系,并建立奥氏体晶粒长大动力学模型,实现了对轴承钢GCr15SiMn奥氏体晶粒尺寸的准确预测。研究了变形量、变形温度和冷却速度与网状碳化物状态的变化规律。明确了控制轴承钢GCr15SiMn网状碳化物的临界冷却条件；通过研究共析转变过程中网状碳化物的析出规律,阐述了轧后冷却过程中网状碳化物的析出机理以及控制策略。确定当精轧累积变形量为50%-60%,终轧温度为850-900℃,轧后以大于3℃/s的冷却速度冷却到620℃等温相变时,可以有效地抑制二次网状碳化物的形成与析出,获得具有良好索氏体组织状态的轧材。通过对大断面轴承钢GCr15SiMn热处理过程中碳化物遗传性及演变机理的研究,提出了轧材网状碳化物厚度与最终热处理产品网状碳化物级别的定量关系,确定了可以经热处理完全消除的临界网状碳化物尺寸为0.29μm,为控制轧材产品中的网状碳化物状态提供了新的思路和方法。系统研究了大断面轴承滚动体材料GCr15SiMn的强韧化机制,获得了硬度、强度和韧性具有良好的匹配高品质轴承钢材料,实现了国内大型盾构机用高品质轴承钢滚动体材料质量控制的新突破。确定了大断面轴承钢GCr15SiMn的最佳热处理工艺为：815～830℃淬火,淬火保温1h,165-180℃回火,回火4-6h；明确了最佳显微组织,即细小板条束的马氏体基体上分布着均匀、细小的颗粒状碳化物,马氏体板条间分布厚度约为20nm的薄膜状残余奥氏体,体积分数在12.8%～17.7%之间。通过在轴承钢GCr15中添加了不同含量(0%,0.018%和0.040%)的Nb元素,系统开展了高碳铬轴承钢的Nb微合金化研究。阐明了随着Nb含量增加,网状碳化物厚度和碳化物网尺寸减小,珠光体片层间距变薄的规律；提出了Nb促进轴承钢球化退火的两个机制,即未溶碳化物核心增多和奥氏体中C浓度的不均匀增大；揭示了Nb在高碳铬轴承钢碳化物演变过程中的作用机理。
[Abstract]:With the rapid development of the field of shield construction in China, the production and manufacturing industry of the shield machine has developed rapidly. However, because of the backward production technology of high quality bearing steel materials in our country, the core component of the shield machine, the spindle bearing, has not been made domestically, but 100% of the imported products have been adopted, which greatly increases the production cost of the shield machine. This paper seriously restricts the further development of large shield machine industry in China. This paper, taking bearing steel GCr1SSiMn as the research object, carried out the research on the mechanism and performance control of the material of the main bearing rolling body of large shield machine with 6 meters in diameter, and realized a new breakthrough in the quality control of the large shield machine. The localization of the bearing roller of type shield machine provides material support. Taking the bearing steel GCr15 as the research object, the study of Nb microalloying of high carbon chromium bearing steel is carried out systematically, and the influence rule and action mechanism of Nb on the microstructure of high carbon chromium bearing steel are expounded.
The thermal deformation behavior and grain growth behavior of bearing steel GCr15SiMn were studied. The relationship between the deformation temperature and the deformation amount and the dynamic recrystallization state was established, which provided the theoretical basis for the rolling process design in the bearing steel production process, and the dynamic re junction of the bearing steel GCr15SiMn was realized by dynamic recrystallization dynamic model. The accurate prediction of the crystal volume fraction, the quantitative relation between the heating temperature and the holding time and the austenite grain size was determined, and the dynamic model of austenite grain growth was established, and the accurate prediction of the grain size of the bearing steel GCr15SiMn austenite was realized.
The changing laws of deformation, deformation temperature, cooling rate and network carbide state are studied. The critical cooling conditions for controlling GCr15SiMn network carbide in bearing steel are clarified, and the precipitation mechanism of net carbide in the process of cooling and control strategy in the process of cooling process is expounded. It is determined that the formation and precipitation of two reticulate carbide can be effectively suppressed when the cumulative deformation of the finishing rolling is 50%-60%, the final rolling temperature is 850-900 C, and the cooling rate of 3 degrees centigrade is more than 3 C, and the rolling material with good Soxhlet structure can be obtained.
Through the study of the carbides heredity and evolution mechanism during the heat treatment process of large section bearing steel GCr15SiMn, the quantitative relationship between the thickness of the mesh carbide and the net carbide level of the final heat treatment product was put forward. The critical mesh size of the reticular carbides, which can be completely eliminated by heat treatment, was determined to be 0.29 mu m, which was used to control the rolled products. The network carbide state provides new ideas and methods.
The strong and toughening mechanism of the rolling material GCr15SiMn of large section bearing is studied systematically. The hardness, strength and toughness are well matched with high quality bearing steel material. The new breakthrough in quality control of the high quality bearing steel roller material used in large shield machine is realized. The best heat treatment worker of large section bearing steel GCr15SiMn is determined. The art is: quenching at 815~830 C, quenching and holding heat for 1h, tempering at 165-180 C and tempering 4-6h, it is clear that the best microstructure, that is, the martensitic matrix of the martensitic matrix of the thin strip beam is distributed evenly, fine granular carbides, and the thin film like retained austenite with a thickness of about 20nm between martensitic plates, and the volume fraction is between 12.8% and 17.7%.
By adding Nb elements with different content (0%, 0.018% and 0.040%) in the bearing steel GCr15, the study of Nb microalloying of high carbon chromium bearing steel was carried out systematically. The law of the thickness of network carbide and the size of carbide net decreased with the increase of Nb content, and the two of Nb to promote the spheroidization of bearing steel by Nb was put forward. The mechanism, that is, the increase of the undissolved carbide core and the inhomogeneous increase of the C concentration in the austenite, reveals the mechanism of Nb in the evolution of carbides in high carbon chromium bearing steel.
【学位授予单位】：北京科技大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TG142.1

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