【作者】 罗征志；

【导师】 曾京；

【作者基本信息】 西南交通大学 ， 车辆工程， 2013， 博士

【摘要】 铁路罐车罐体结构零部件是罐车关键承载零部件,其制造加工质量直接关系到罐车运行安全和可靠性。罐车罐体主要包括封头和筒节两大关键零件。罐体制造加工工艺主要包含封头冲压成形、筒节滚压成形等塑性加工成形过程,以及坯料制备过程中的对接焊接和罐体组装过程中的焊接加工工艺过程。目前,由于铁路罐车罐体尺寸大、材料厚度较厚,制造企业对罐体封头冲压、筒节滚压及其相关焊接工艺规程的制定基本还是依靠传统模式进行,即根据经验和实验试制调整工艺参数来开展新产品的开发和研制。该方法极大的提高了产品研制的成本,且生产效率极为低下。而且传统罐体制造工艺方法对罐体制造过程中可能出现的质量缺陷及其对罐体后期运行中的安全影响无法进行预测和控制。因此,在罐体制造加工中引入并使用先进的成形工艺研究手段十分必要。本文采用以罐体成形理论分析为基础,使用有限元数值模拟和实验相结合的方法,对罐体制造加工工艺过程展开系统而深入的研究。本文主要研究内容和研究结论如下：(1)进行罐体材质Q345R材料性能研究。Q345R材料是罐车罐体常用材料,其也是压力容器专用钢板。采用试验的方法对Q345R母材试样和对接焊试样材料进行拉伸试验、弯曲试验和冲击试验。试验表明,Q345R材料有良好的塑性成形性能。(2)试验对比研究罐体封头成形工艺。铁路罐车封头由于尺寸大、材料厚,其塑性成形加工难度大。为保证既能顺利成形封头,又能保证良好的产品性能和质量,采用试验的方法,分别使用冷冲压工艺、热冲压工艺和旋压工艺进行封头塑性成形加工。试验表明,热冲压封头成形方便,但成形后产品形状尺寸变化大,且需要加热等附属设备；旋压封头成形表面质量较差,成形效率较低,仅适合单件试制；冷冲压封头尺寸稳定,产品质量好,但成形载荷大。综合比较分析表明,采用冷压工艺进行铁路罐车封头加工能更好的保证罐车的加工质量和运行安全,因此采用冷拉延成形工艺进行罐车封头大批量制造。(3)对封头冷拉延成形过程进行有限元模拟分析。大型封头的冷拉延成形过程中,型面回弹和起皱是其主要成形缺陷,而拉延筋是控制其成形缺陷的重要工艺措施。根据椭圆形封头成形特性和要求,设计了圆形筋、矩形筋展开拉延成形分析,并和无拉延筋的成形工艺进行比较。对比分析表明,矩形拉延筋能更有效的保证封头成形质量。(4)展开封头拉延成形重要工艺参数,如摩擦系数、压边力、凸凹模间隙等对成形过程的影响进行了研究。封头成形工艺参数要既能保证产品成形质量,又能节约设备吨位,降低能耗。研究表明,压边力和模具间隙对成形载荷和成形质量影响明显。过小间隙使得成形载荷急剧上升,但成形后回弹较小,产品无明显起皱和鼓包成形缺陷；压边力过小则造成起皱明显,材料无法顺利转移到模内,亦使得成形载荷急剧上升。根据研究结果,得到封头成形时合理的压边力、凸凹模间隙等成形工艺参数。(5)筒节滚弯成形数值模拟分析。使用有限元法对筒节滚弯渐进塑性变形过程进行研究。研究表明,筒节成形过程中摩擦系数等工艺参数对成形有重要影响。(6)封头拉延模具磨损分析。封头拉延成形过程中,模具成形表面,尤其是小圆角型面的磨损是影响模具寿命的主要因素。对拉延模具成形过程中的模具受力及磨损的模拟分析表明,合理设置模具工艺参数能延长模具寿命,进而降低产品制造成本。(7)罐体制造中的焊接分析。罐体加工时,涉及的主要焊接问题是封头坯料制备时的厚板对接焊,筒节滚弯成形后的对接焊以及筒节、封头的组装焊接。封头制备时的对接焊,直接影响封头塑性冲压加工,尤其是焊后残余应力对冲压有一定的影响。筒节对接焊残余应力也对焊后滚弯校形有一定的影响。使用焊接数值模拟技术,对厚板焊接过程进行分析。研究表明,焊接焊后高残余应力区主要在焊缝区,可通过时效处理和退火来降低焊缝区残余应力。罐体总装时高残余应力也主要集中在焊缝区,其将对焊后变形有一定的影响。通过合理的焊接顺序的设置,可适当降低焊接残余应力和变形。更多还原

【Abstract】 The structure parts of tank body for railway tank car are the key load bearing components, the quality of manufacturing of the parts directly affects the running safety and reliability of the tank car. The heads and shell sections are the two main impoertant parts of the tank. The manufacturing of the tank body mainly includes the plastic forming process such as the head stamping and shell section rolling, and the welding process in blank preparation and tank body assembly. Because of the large size and thickness of the tank body, the traditional manufacturing crafts that according to the experience and experiments are adopted for the forming of the heads and shell sections, and tank body welding. The traditional process leads to the high cost and inefficiency of the prduct development. And the tank body defects and the influence on operation safty can not been forecast and controlled using the traditional crafts. Therefore, it is very necessary to apply the advanced research methods to tank body manufacturing process. Based on the theoretic analysis of tank body forming, a systematical and profound study on tank body manufacturing process is undertaken using the combine method of the finite element simulations and experiments. The main research contents and conclusions are listed as follows.(1) The material properties of Q345R that used for tank body were studied. The Q345R is the material commonly used for tank car body and also is the special steel for pressure vessel. The experiments including tension test, bending test and impact test were implemented for the material property of Q345R. The experiments indicated that the Q345R material has good stamping formability.(2) The contrast experiments were implemented to study the stamping process for the ellipsoidal heads of tank car. Because of the large profile dimension and large thickness, it has some difficulties on the stamping process of tank body heads. In order to ensure the heads stamping quality, the forming experiments include cold stamping process, hot stamping process and spinning process were implemented. The experiments indicated that the heads can be conveniently formed with the hot stamping process, but the heads shape changed greatly after stamping, and heating equipment were needed for this process. The experiment also showed that the heads which formed with spinning process had poor surface quality and formed inefficiently. Thus the spinning process is only suitable to trial-producing of single head. The heads formed with cold stamping process had good dimensional stability and excellent product quality, but the stamping load was higher. The experiments and analysis indicated that cold stamping process can assure the quality and safety of the tank car, therefore, the cold stamping process was applied to heads stamping.(3) The cold stamping process of ellipsoidal heads was simulated with the finite element method. The spring-back of ellipsoid surface and crinkles are the main forming defects during the large heads drawing processing. While the draw-bead is the important and effective technical measures to avoid the forming defects. Thus the round draw-bead and rectangular draw-bead were designed based on the shape of the ellipsoidal heads, and the simulations were carried out for this drawing process. Then these simulation results were compared with the simulation results of no bead stamping process, which indicated that the rectangular draw-bead can effectively assure the stamping quality of the heads.(4) The main process parameters of drawing forming have great influence on the heads stamping process. The influences of process parameters have been studied. The process parameters consist of frictional coefficient, blank holding force, clearance between punch and die, and so on. The process parameters should ensure product quality and reduce forging equipment and energy usage. The study shows that the blank holding force and the clearance have significant effect on product quality. The small clearance can cause the forming load rising up rapidly, while the defects of wrinkles and blowups do not appear. The small blank holder force can cause wrinkles appearing and the forming load rising up rapidly because the material can not flow easily. According to the study results, the reasonable blank holding force and the clearance have been drafted for heads stamping.(5) The shell sections rolling process have been analyzed by using the numerical simulation method. The incremental forming process of the shell sections rolling was studied using the finite element method. The study shows that the frictional coefficient has great effect on the shell section rolling process.(6) The wear analysis of the drawing die was conducted. The wear at the die surface, especially at the little round surface is the main factor affecting the tools life. The stresses and the wear of tools were analyzed. The study indicates that the reasonable process parameters can prolong tools’life and reduce the product processing cost.(7) The welding process of tank body manufacturing was analyzed. The welding process during the tank body manufacturing includes the butt welding of thick blank plate, the butt welding of shell sections after rolling and the butt welding between shell sections and heads. The butt welding of heads blank, especially welding residual stresses directly affect the subsequent stamping process. The butt welding of shell sections after rolling also has some effects on its’adjustment process. Hence, the welding process was analyzed with numerical simulation technology. The study indicates that the high residual stress zone is distributed at the weld metal zone and the residual stress can be reduced by the aging treatment and annealing. The high welding residual stress of tank body assembly is also distributed at the weld metal zone and which has some influence on the distortion after welding. Therefore, the reasonable welding sequence could be drafted to reduce the welding residual stress and distortion.更多还原