大直径厚壁压力气瓶热处理过程数值模拟与实验研究

发布时间：2018-01-25 02:17

本文关键词： 压力气瓶热处理 Q-P工艺 Q-P(-T)工艺　出处：《燕山大学》2015年硕士论文　论文类型：学位论文

【摘要】：大直径厚壁压力气瓶承载压力高,长期工作在“加载—卸载”的疲劳环境中。天然气钢瓶发生爆炸事故的主要原因之一就是气瓶在热处理生产过程后的残余应力水平过高。由于大直径厚壁压力气瓶具有尺寸大、质量大的特点,其热处理工艺往往十分复杂。淬火回火过程是大直径厚壁压力气瓶热处理工艺中最为重要的环节,对其最终质量和使用性能起着至关重要的作用。数值模拟技术可以准确逼真的模拟淬火回火工艺生产,预测热处理后工件质量,为大直径厚壁压力气瓶的调质工艺制定与生产工艺优化提供了一种有效研究方法。首先,本文通过查阅文献获得了30Cr Mo钢的高温力学性能以及30Cr Mo钢中不同组织在不同温度下的比热和常温密度,并给出了材料的TTT曲线和CCT曲线,为数值模拟研究提供了可靠的基础数据。接着,考虑了大直径厚壁压力气瓶在热处理过程中温度-组织-应力三者间的相互耦合关系,变物性参数、相变潜热、相变塑性等因素对调质生产过程的影响,建立了大直径厚壁压力气瓶热处理过程的数学模型。并利用CAD和CAE软件,建立了大直径厚壁压力气瓶的三维几何模型和有限元模型。进而利用有限元软件分析平台DEFORM,结合实际热处理生产工艺特点,对大直径厚壁压力气瓶的传统淬火-回火(Q-T)淬火过程,设计了“内表面间歇径向喷雾外表面连续喷水”和“内外表面同步间歇喷雾”两种淬火工艺,并进行了数值模拟计算,分析了传统淬火-回火过程中气瓶内特征节点的温度、组织和应力的变化情况。然后,针对气瓶使用过程中强度满足但韧性不足的特点,提出对大直径厚壁压力气瓶进行新型Q-P和Q-P-T热处理工艺方案,并对新型工艺下气瓶的温度和应力演变情况进行了数值模拟分析。几种工艺模的数值拟分析结果表明,四种热处理工艺淬火过程可以不同程度调节瓶体截面的温度梯度及瓶内气压,降低淬火应力,保证瓶体完全淬透,最终热处理后获得不同程度的残余应力。最后,通过拉伸试验、扫描电镜、XRD实验,验证了有限元分析模型的有效性,分析了各工艺的优缺点,并根据气瓶使用要求和各工艺参数特点确定了最佳工艺。
[Abstract]:The pressure cylinder with large diameter and thick wall has high bearing pressure. Long term work in "load-unload" In the fatigue environment, one of the main reasons for the explosion accident of natural gas cylinder is that the residual stress level of gas cylinder after heat treatment is too high. The process of quenching and tempering is the most important part in the heat treatment process of large-diameter thick-wall pressure gas cylinder. Numerical simulation technology can accurately simulate quenching and tempering process and predict the quality of workpiece after heat treatment. It provides an effective research method for the development of tempering process and optimization of production process for large-diameter thick-wall pressure cylinder. First of all. In this paper, the high temperature mechanical properties of 30CrMo steel and the specific heat and normal temperature density of different microstructure in 30CrMo steel at different temperatures were obtained. The TTT curves and CCT curves of the materials are given, which provide reliable basic data for the numerical simulation. The coupling relationship between temperature, microstructure and stress, the variable physical parameters, the latent heat of phase transformation and the plastic transformation of the large-diameter thick-wall pressure gas cylinder during heat treatment were taken into account in the process of tempering and tempering. The mathematical model of the heat treatment process of the large-diameter thick-wall pressure cylinder was established, and the software CAD and CAE were used. The three-dimensional geometry model and finite element model of the large-diameter thick-wall pressure cylinder are established, and then the finite element software platform deform is used to combine the characteristics of the actual heat treatment production process. For the traditional quenching and tempering Q-T quenching process of large-diameter thick-wall pressure cylinder, two quenching processes, "intermittent radial spray external surface continuous water spray" and "internal and external surface synchronous intermittent spray", were designed. The change of temperature, microstructure and stress of the characteristic node in the gas cylinder during the traditional quenching and tempering process is analyzed. In view of the characteristic that the strength is satisfied but the toughness is insufficient during the use of the gas cylinder, a new type of Q-P and Q-P-T heat treatment process for the large-diameter thick-wall pressure cylinder is put forward. The temperature and stress evolution of the gas cylinder under the new process are simulated and analyzed. The numerical simulation results of several process models show that. The quenching process of four heat treatment processes can adjust the temperature gradient of the bottle cross section and the air pressure in the bottle to varying degrees, reduce the quenching stress, and ensure the complete quenching of the bottle body. After the final heat treatment, different degrees of residual stress were obtained. Finally, the validity of the finite element analysis model was verified by tensile test and SEM XRD test, and the advantages and disadvantages of each process were analyzed. The optimum process is determined according to the requirements of the cylinder and the characteristics of each process parameter.
【学位授予单位】：燕山大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG161

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