【作者】 刘燕；

【导师】 王威强； 范志超；

【作者基本信息】 山东大学 ， 化工过程机械， 2009， 硕士

【摘要】 尿素合成塔是尿素合成装置的关键设备。但是焊接残余应力、制造缺陷、应力腐蚀等因素的存在致使尿塔层板开裂,严重的甚至导致爆破事故。尿塔无疑成了一个存在严重安全隐患的设备。为杜绝事故再次发生,对尿塔材料行为的测试研究十分必要。作者从山东峄山某报废尿塔取样,进行了层板材料15MnVR的室温拉伸、中温拉伸、室温摆锤冲击试验。并与齐鲁一化尿塔、平阴尿塔的材料性能进行了对比分析。结果表明,材料的下屈服强度等各项力学性能指标均在标准要求范围之内。邹城尿塔材料的室温拉伸、中温拉伸以及室温摆锤冲击性能均与齐鲁一化尿塔相当;其室温拉伸性能优于平阴尿塔,抗脆断性能不如平阴尿塔。采用带有预裂纹的C（T）试样进行了中温疲劳裂纹扩展试验。利用试验机自带的电炉加热和保温,并由柔度法反算裂纹长度。分别用Paris公式、Forman公式以及王泓公式对试验数据进行了描述,获得了Paris公式和Forman公式的指数和系数。结果表明,Paris公式对稳定扩展区的裂纹扩展速率进行了很好的描述,但部分Forman公式拟合数据的相关系数不高。服役后材料的裂纹扩展速率未见明显升高,且与取样位置关系不大。它随平均应力的增加而增加,但在裂纹稳定扩展区的影响不明显。而王泓公式对试验数据的估算值与试验数据差别较大,不适宜用来分析本试验数据。按标准推荐的多试样法、采用带有整体刀口的SE（B）试样进行了裂纹尖端张开位移试验。获得了室温下材料的裂纹扩展阻力曲线,确定了CTOD特征值δ_0.05=0.088mm,δ_i=0.191mm。验证了厚度B≥5mm即可获得稳定临界CTOD值这一结论。并以汽轮机材料20Cr3MoWV钢的断裂韧度与温度的关系作为参照,给出了180℃时15MnVR钢的断裂韧度估算值。在补充、积累层板包扎高压容器材料的疲劳裂纹扩展及断裂韧度性能数据的同时,也为评价层板包扎高压容器的剩余寿命提供了基础数据和理论基础。更多还原

【Abstract】 Urea reactors are the key equipments of urea synthesis devices. However, cracking of layers was induced because of residual welding stress, manufacturing defect and stress corrosion. Series cracking may lead to serious urea reactor blasting accidents. Urea reactors are equipments with security risks definitely. It’s necessary to test and study the mechanics behavior of the urea reactor layers.The author took samples in a disabled urea reactor from a factory of Shandong Province. Tensile tests were carried out under room temperature and medium temperature, as well as impact test under room temperature. The material properties are compared with other urea reactors. The results indicate that, the material properties including tensile strength and toughness still satisfy the standard after service. They are quite close to the value of urea reactor from Qilu. The tensile strength is higher than urea reactor from Pingyin, but the toughness is lower.Fatigue crack propagation test under 180℃was carried out by using compact tension specimens. The crack length was caculated by compliance measurement method. The test data are described by Paris formula, Forman formula and Wang’s formula separately. The parameters of Paris formula and Forman formula are got from the test. The results reveal that the data are described quite well by Paris formula. The fatigue crack propagation rate hasn’t increased obviously after srevice. And it is independent of the position where the specimens taken. The average stress doesn’t affect the crack propagation rate much in the stable crack growth area. But data estimated by Wang’s formula are marked different from the test results.CTOD test was carried out according to resistance curve method by using SE(B) specimens. The resistance curves of the material are obtained by the test, as well as CTOD characteristic value. The results validate the conclusion that steadyδ_c can be obtained when the thickness of specimens is bigger than 5mm. Referring to the relationship between fracture toughness and temperature of 20Cr3MoWV steel, the fracture toughness of 15MnVR under 180℃is also discussed in the paper. The fatigue crack propagation data of urea reator material are supplied by the test. The fracture toughness data are accumulated at the same time. Basic data for estimating the residual life of urea reators are also provided here.更多还原