【作者】 李超；

【导师】 王立君；

【作者基本信息】 天津大学 ， 材料加工工程， 2010， 硕士

【摘要】 随着地下燃气管道的广泛使用,实际工程中不可避免地应用到在役燃气管道带压改线技术。目前我国带压管道改线技术只是基于过去积累的经验,缺乏对整个改造工程科学、量化的数据支持。因此,本课题将对天津市某带压燃气管道改线工程进行系统的研究与校验,主要考察焊接过程中燃气管道内壁的温度和焊接力学行为。本课题首先针对带压管道改线中的环焊缝制定合理的焊接工艺参数,包括:焊接方法,焊接材料的选择、焊接接头的尺寸及热处理方法等。主要用到的试验方法为拉伸试验、刻槽试验、宏微观金相试验和硬度测试。焊接工艺确定后,应用有限元软件ANSYS对这种方式下的带压管道改线焊接过程进行模拟。焊接过程包含了热学和力学两种问题,所以选择有限元数值模拟方法的热-应力耦合法对改线问题进行模拟。同时,又由于焊接过程是一个不均匀的瞬态非线性热输入问题,为了得到精确模拟结果,本文选择了间接耦合方法分别对3MPa,4MPa和5MPa管道内压情况下的模型进行热学数值计算,对3MPa和4MPa内压下的模型进行了力学数值计算,其中对焊接过程应用了“生死单元”这个功能。在热学与力学耦合部分,为了协调二者网格疏密程度不一致问题,本文应用了ANSYS的BFINT功能对体载荷进行插值运算。最终发现三种内压下进行的带压改线焊接,对于所采用的手工电弧焊接工艺,燃气管道内壁的最高温度为755℃,低于Battelle的982℃,即施工过程中不会发生烧穿现象。同时,由于管道的对流系数会随着管道压力的升高而升高,因此燃气管道的内壁温度随之降低。通过分别对3MPa管道内压进行模拟发现,焊接过程中的最大等效应力为327MPa,小于母材的屈服强度360MPa。改线焊接结束后,管道恢复供压时的4MPa时,管道的最大等效应力提高到337MPa,依然符合安全要求。另一方面,两种内压下,管道发生的最大位移均小于1mm界限,也符合安全经验标准。因此,针对本文研究的管道结构,在3MPa下进行带压燃气管道的改线施工是一种安全合理的选择。更多还原

【Abstract】 With the wide usage of the buried gas pipeline,people have paid more and more attention on in-service welding of gas pipelines. At present, China’s such technology is only based on previous experience which lacks scientific and quantitative data. Therefore, this paper will do research on modification welding of gas pipelines whose topic is supplied from Tianjin Gas Group CO.LTD. It is mainly about the temperature of pipe inside wall and the strength of the welding joint.Firstly, the paper found proper technics parameters for the modification welding of gas pipelines, which includes: welding method, the choice for base metal and welding filler, the size of welding joint the heat treatment method and so on. In order to get these parameters, it needs a few experiments: tensile test, groove test and so on. After confirming the welding technics, the paper used the finite element software, ANSYS, to simulate the modification welding process of gas pipelines. Since the welding process contains two parts, thermal issue and stress issue, the paper chose the thermal-stress coupling method of finite element numerical simulation. Meanwhile, because the welding process is a quite unstable and asymmetric issue for inputting heat, the paper choice indirect coupling method to get the accurate solution. There are three kinds of internal press (3MPa, 4MPa and 5MPa) condition for simulation. In the simulation, the paper utilized the important function of "birth-death element". In the thermal-stress coupling section, in order to coordinate the different element density between thermal part and stress part, the paper harnessed the BFINT function to activate the body force interpolation operation which is the highlight of this research.At last, it is found that under three internal press condition, the temperature of the gas pipeline’s inside wall is all less than 982℃. It means it would not burn through during the welding process. At the same, with the increased internal press, the coefficient of thermal transfer is also raised, so the temperature of the gas pipeline’s inside wall is reduced. However, raising the internal press leads to the increase of stress and displacement. Therefore, the 3MPa is a proper and safe press for the modification welding of gas pipelines.更多还原