【作者】 袁立方；

【导师】 陈荐；

【作者基本信息】 长沙理工大学 ， 动力机械及工程， 2007， 硕士

【摘要】 汽轮机转子由于长期承受温度载荷和应力载荷的作用,发生蠕变损伤,导致材料性能劣化,加剧转子的寿命消耗。因此,准确预测转子部件的损伤和蠕变剩余寿命,对防止非计划停车、拟订合理的维护和检修计划、保证生产和设备安全具有重要的实际意义。目前已发展的转子蠕变寿命的研究方法主要有解析和数值分析方法、有损评价方法和无损评价方法。解析和数值分析方法由于所需数据比较多,计算难度大,限制了其在工程上的应用;有损评价方法由于所需时间较长、要从转子上切割试样而受到限制;无损评价方法可在较短时间内,对较多部位进行寿命诊断,而且计算简单,在工程上得到了应用与发展。电阻法是基于损伤过程中电阻值的变化来预测损伤和剩余寿命的一种无损诊断新方法,具有操作简单、能较为直观反映材料的内部损伤的优点。本文结合电阻法等分析方法,对国产汽轮机转子钢30Cr1Mo1V时效老化损伤、常温拉伸损伤及蠕变寿命消耗进行了研究。开展的主要工作和研究结果如下:1、在630℃下进行了30Cr1Mo1V钢200h、500h、800h、1000h及1200h的高温时效实验,利用电阻法、硬度法、金属夏比冲击断口测定方法,结合微观组织分析对时效过程中材料电阻率、硬度、脆性转变温度及微观组织进行了研究。研究结果表明,电阻率随时效时间的增加而减小,材料硬度与电阻率变化以及脆性转变温度与电阻率变化具有线性关系,碳化物沿晶界析出和聚集、基体合金元素的贫化以及金属碳化物相结构变化导致材料电阻率、硬度及脆性转变温度发生变化。2、在常温下进行了30Cr1Mo1V转子钢200MPa、500MPa、630MPa、680MPa及730MPa的短时拉伸试验,利用电阻法测量了材料在拉伸过程中的损伤变化,结果表明材料在拉伸过程中的损伤量与电阻变化呈线性关系。3、在538℃、300MPa下进行30Cr1Mo1V转子钢100h、300h、400h、450h、500h及试样断裂时的蠕变试验,对蠕变试样的硬度、电阻及微观组织变化进行了研究。结合538℃下30Cr1Mo1V转子钢的蠕变断裂特性参数及Kachanov常数,对转子钢电阻变化与蠕变寿命消耗之间的关系进行了描述,得出了蠕变寿命分数与标准电阻的关系曲线。微观组织分析表明,在538℃下,蠕变裂纹呈穿晶和沿晶混合模式,蠕变过程中微观孔洞的形成与发展是材料电阻发生变化的原因。更多还原

【Abstract】 After a long term service at elevated temperatures and high pressure, creep damage occurs in turbine rotor, which results the degradation of properties and loss of life. Therefore, accurate and reliable prediction of damage and creep remaining life provides a basis for timely, safe, and economic replacement or repair of rotor, which helps to eliminate unnecessary replacements and reduce costly unscheduled outages caused by in-service failures.At present, the methods to study the creep life of turbine rotor can be seem as three kinds: analytic and numerical methods, destructive methods and nondestructive methods. The analytic and numerical methods need a lot of data and are very difficult to calculate, so they are not easy to be applied in engineering. The destructive methods are time-consuming and need to take samples from turbine rotor. The nondestructive methods can diagnose more parts in short time, and have the merit of simplification in calculation, so they are easy to be applied in engineering. Electrical resistance method is a novel one of the nondestructive methods. Based on the change of electrical resistance, damage and life can be valued simply and quickly. The high temperature aging damage, room temperature tensile damage and creep life expenditure of 30Cr1Mo1V rotor steel were studied with electrical resistance method and other methods in the dissertation. The main results are listed as follows:1. Aging experiments were performed at 630℃from 200h to 1200h. Electrical resistivity, Vickers hardness, fracture appearance transition temperature and microstructure of 30Cr1Mo1V rotor steel were studied with electrical resistance test, hardness test, metallic materials Charpy notch impact test and micro-structure test. The results indicate that electrical resistivity decreases with the aging time increasing and there are some linear relations between Vickers hardness and electrical resistivity, fracture appearance transition temperature and electrical resistivity. The changes of these parameters may be caused by the change of micro-structure due to the precipitation of carbide and the dissolution of solid element within matrix.2. Room temperature tensile experiments on 30Cr1Mo1V rotor steel were performed at the stress of 200MPa, 500MPa, 630MPa, 680MPa and 730MPa, and the tensile damage was studied via electrical resistance method. The results show that there is some linear relation between the resistance and tensile damage.3. Creep experiments of 30Cr1Mo1V rotor steel were carried out at 538℃and 300MPa for different time. The Vickers hardness, electrical resistance and micro-structure of creep samples were studied. The relationship between creep life and electrical resistance was described with the characteristic parameters of creep rupture and the constant of Kachanov. And the relation curve between creep life fraction and normal resistance was obtained. The study of micro-structure indicates that the crack propagation is of inter-granular and trans-granular mixture mode at 538℃and the change of electrical resistance is caused by the propagation and development of creep cavities.更多还原