【作者】 张建军；

【导师】 李午申；

【作者基本信息】 天津大学 ， 材料加工工程， 2011， 博士

【摘要】 随着世界石化工业的飞速发展,乙烯的产需量不断提高。目前,乙烯球罐向着高参数、大型化发展的趋势日益明显,这种发展趋势对乙烯球罐用钢及其焊接性提出了更高的要求。另外,由于焊接残余应力的存在严重威胁着乙烯球罐的使用安全,并直接影响着其运行寿命,因此研究焊接工艺与残余应力之间的关系对于控制乙烯球罐焊后残余应力有着十分重要的意义。本研究以国产低温压力容器用钢07MnNiCrMoVDR为研究对象,利用物理模拟和数值模拟的方法对其焊接热影响区的组织和性能以及焊接接头的残余应力分布进行了系统的研究。研究过程中,采用一次回归正交试验的方法,分别考察了热输入和预热温度对07MnNiCrMoVDR钢焊接热影响区组织和性能的影响。测定了不同工艺参数下焊接热影响区的热循环曲线,利用SYSWELD有限元分析软件,采用双椭球焊接热源模型,分析了07MnNiCrMoVDR钢的焊接温度场的变化,并给出了工艺参数与t_8/5和t_H的关系模型;采用热模拟试验的方法对07MnNiCrMoVDR钢的焊接热影响区的组织和性能进行了研究,并利用线性回归的方法给出了性能的预测模型。以低温韧性作为目标函数优化了焊接工艺参数。经过优化和试验证明,最佳焊接工艺参数配比为:小线能量（10KJ/cm）和高预热温度（180℃）。通过对不同焊接工艺参数下焊接热应力的数值模拟,定量分析了焊后残余应力的分布和大小,以及热输入和预热温度对焊接残余应力的影响规律,为乙烯球罐在生产中的实际应用提供理论依据。考察了焊后热处理对07MnNiCrMoVDR钢焊接接头组织、性能以及应力分布情况的影响规律,研究发现热处理后的等效峰值应力可以降低到200MPa左右;经热处理后,粗晶区的板条马氏体转变为回火索氏体,并有大颗粒碳化物不均匀析出,碳化物的不均匀析出显著降低了粗晶热影响区的低温韧性。更多还原

【Abstract】 With the rapid development of the world’s petrochemical industry, the amount of ethylene production and demand rising. At present, the ethylene sphere towards high parameters and large-scale development is increasingly clear that this trend of ethylene tank and weldability of steel made a higher demand. In addition, because of the existence of welding residual stresses, a serious threat to the ethylene spherical tank’s service life and even might result in severe security disaster, therefore it is very important to control the welding residual stress by study the relationship of welding parameters and residual stress. In this paper, the low-temperature pressure vessel steel of 07MnNiCrMoVDR was made as a research object, the physical modeling and numerical simulation were used to investigate the heat-affected zone of welded joints and the performance and the residual stress distribution in systemic.Taking into account the influence of heat input and preheat temperature, using a regression orthogonal experiment and welding thermal simulation technology, 07MnNiCrMoVDR steel HAZ microstructure and properties in different welding parameters were studied. The thermal cycle for different condition were measured. The Sysweld software with double ellipsoid heat source model was used to analysis the change of welding temperature field and the relationship modeling between welding parameters and t_H, t_8/5 were given. Linear regression method was used to establish the forecast formula of performance, and also utilize the MATLAB to optimize the welding procedure by the low temperature toughness optimal solution as the objective function. The small linear energy （10KJ/cm） and the high preheating temperature（180℃） is the best craft parameter.The thermal stress with different welding parameters was simulated by numerical method. The distribution and size of welding residual stress and the rules affected by heat input and preheat temperature were analyzed quantitatively.The application of ethylene spherical tanks in practical manufacturing will be theoretically based on such an examination. Finally, the change of microstructure and performance after the heat treatment also was inspected in this paper. From this we find the 07MnNiCrMoVDR steel has reheat brittleness in coarse grain zone, this phenomenon maybe relative with the alloying elements separated out in the crystal boundary.更多还原