【作者】 张中平；

【导师】 王国栋； 杜林秀；

【作者基本信息】 东北大学 ， 材料加工工程， 2007， 博士

【摘要】 汽车工业的快速发展和激烈的市场竞争对汽车用钢提出了越来越高的要求,高强度汽车梁用钢在汽车制造上得到越来越广泛的应用。本着低成本、高性能的减量化钢材生产原则,结合攀钢特有的资源优势,本文对V、Ti微合金化高强度汽车大梁钢轧制过程组织变化规律及控轧控冷工艺(TMCP-Thermic Machine Control Process)进行研究。通过实验室热模拟实验,研究含钒、钛高强度再结晶行为及工艺参数对显微组织的影响规律,在此基础上进行实验室热轧实验和现场工业实验。通过单轴拉伸试验、低温系列冲击试验和弯曲试验研究高强度汽车大梁板的力学性能,确定轧制工艺参数对力学性能的影响规律,并在攀钢热轧生产线进行了工业化生产。论文的主要内容包括：1)通过双道次压缩实验研究了含V、含Ti微合金钢奥氏体静态再结晶规律,结果表明,V和Ti在较低的温度范围内(850-900℃)对奥氏体静态再结晶过程具有较为明显的抑制作用,所以在相对较低的轧制温度下,钢中添加V和Ti有利于未再结晶区控制轧制。2)利用热模拟实验和热轧实验研究了含V微合金钢的析出行为,结果表明,含钒钢950℃以下会发生一定程度的V(CN)在奥氏体中的形变诱导析出；620-660℃范围内铁素体中V(CN)析出量较大,600℃以下析出量较小。3)利用热模拟实验研究了V、Ti对轧后冷却过程相变的影响,结果表明,与Nb的作用不同,低碳钢中随着含V量的增加,获得铁素体的冷却速度范围扩大,即对铁素体相变有促进作用,含V量较大时,变形对铁素体相变和珠光体相变的促进作用增大；Ti的作用与V类似,变形对铁素体相变和珠光体相变具有明显的促进作用。4)通过热轧试验研究了变形工艺参数对组织性能的影响,结果表明,降低终轧温度对铁素体晶粒有明显的细化作用,降低卷取温度在细化晶粒的同时,也可以获得一定的相变强化的效果。但卷取温度降低时,不利于发挥V、Ti合金元素沉淀强化的效果。5)通过工业实验确定了攀钢利用低成本P510L的化学成分生产P590L的减量化轧制工艺,即合理控制终轧温度和卷取温度,充分利用细晶强化和沉淀强化的强化机制,以达到提高材料强韧性的目的。组织性能分析结果表明,低成本P590L具有良好的综合力学性能、冷成形性及焊接性。更多还原

【Abstract】 High strength steels for automotive frame have been widely applied because of the strict requirements which were ordered by the rapid development and drastic competition of the Motor Industry. According to the principle of reduced steel rolling technology, the works of this dissertation were carried out integrating with the resource advantages in Panzhihua Iron and Steel Company, and the evolving rule of the microstructure combining with TMCP(TMCP-Thermic Machine Control Process) for high strength microalloyed steels with vanadium or titanium for automotive beam were investigated. Utilizing thermal simulation experiments, the effects of recrystallization behavior and processing parameters on microstructure were investigated; based on which the experimental and commercial tests were preceded. In order to obtain the effects of rolling processing parameters on the mechanical properties of the products, series of tests were adopted including uniaxial tensile test, low temperature impact test and bending test. Finally, the industrial production was attained in the hot rolling production line of Panzhihua Iron and Steel Company.The main works involved as follows:1)The austenite static recrystallization behaviors of V/Ti microalloyed steels were investigated using double-hit hot compression test. The results indicate that control rolling in the non-recrystallization zone could be easily implemented in the relatively low rolling temperature with addition of vanadium and titanium.2) Precipitation behaviors of V-microalloyed steel were studied through the thermal simulation experiment and hot rolling test. The results shows that deformation induced precipitation of V(CN) occurred in austenite at the temperature below 950℃;the amount of vanadium carbonitride precipitated in ferrite at the temperature between 620-660℃was relatively more than the temperature below 600℃.3) The effect of vanadium and titanium on phase transformation in cooling stage was investigated. The results show that the ferrite transformation was accelerated with increasing of vanadium content. Both ferrite and pearlite transformations could be promoted when the vanadium content goes to a high level. The effect of titanium is similar with vanadium on the transformation.4) Effects of deformation processing parameters on the microstructure and property were discovered through hot rolling experiment. The results indicate that ferrite grains could be effectively refined by decreasing the finish rolling temperature, while both refinement of grains and transformation strengthening were obtained with lowering the coiling temperature. But the problem is that lowering the coiling temperature is unbeneficial to the precipitation strengthening of vanadium and titanium.5) Reduced rolling processing for the production of P590L was determined utilizing the commercial tests, that is appropriate controlling of finish rolling temperature and coiling temperature, and full utilization of grain refinement strengthening and precipitation strengthening in order to improve the strength and toughness. The analysis of microstructure and property shows that the low-cost P590L has possessed well combination property, cold formability and weldability.更多还原