转向架用钢成分及热处理工艺优化

发布时间：2018-04-24 09:11

  本文选题：转向架 + 铸钢　； 参考：《哈尔滨理工大学》2017年硕士论文

【摘要】：随着新时期对铁路运输提速重载新要求的提出,我国现有的转向架用钢已经不能满足铁路货车对转向架性能的要求,而现有的高性能铸钢由于合金化程度较高,导致生产成本居高不下,因此有必要研究开发一种新的转向架用钢,使之在具有高性能的同时降低生产成本。课题在北美AAR标准B+级铸钢的成分范围内,通过研究Mn、Cr、Ni和C元素含量以及正火温度对铸钢组织和性能的影响规律,成功开发出一种新铸钢并确定了新铸钢最佳正火温度,并且建立了铸钢成分、组织和性能之间的数学关系模型,使新铸钢在满足AAR标准正火C级钢性能要求的前提下,降低了生产成本。试验结果表明:随着铸钢中Mn含量的增加,铸钢中珠光体含量升高、片间距减小,铸钢的强度升高,但塑韧性降低,在Mn含量为0.9 wt.%时,铸钢的强韧性组合最佳;随着铸钢中Cr含量的升高,铸钢中珠光体含量升高,铸钢的强度升高,硬度升高,并在Cr含量为0.3 wt.%时,铸钢具有最佳的强韧性组合;铸钢中的Ni可有效细化铸钢的基体组织,提高铸钢的强韧性,但当铸钢中Ni含量超过0.3 wt%时,Ni含量的升高对铸钢性能的强化效果已经不明显;随着铸钢中C含量的升高,铸钢的强度、硬度以及珠光体含量均升高,当C含量由0.25 wt.%提高到0.31 wt.%时,铸钢的抗拉强度由545 MPa提高到616 MPa,但韧性急剧降低,延伸率由31.4%降低到了24.8%;试验最终确定的铸钢成分为:C含量为0.27 wt.%,Mo含量为0.1 wt.%,Si含量为0.4 wt.%,Mn含量为0.9 wt.%,Cr含量为0.3 wt.%,Ni含量为0.3 wt.%,此时新铸钢碳当量为0.56(CE=0.56),满足铸钢焊接性能方面的要求;对铸钢进行不同加热温度的正火热处理,结果表明:铸钢随着正火温度的升高,铸钢的强度、硬度、冲击吸收功均先升高后降低,延伸率几乎不变;在正火加热温度为900℃时,铸钢的强度最高,强韧性组合达到最佳,此时铸钢的抗拉强度为652.3 MPa,屈服强度为438.2 MPa,延伸率为24.3%,夏比V型缺口试样在-18℃的冲击吸收功为34.3 J,满足AAR标准正火C级钢的性能要求。
[Abstract]:With the raising of new requirements for railway transportation speed and heavy load in the new period, the existing bogie steel in China can no longer meet the requirements of railway freight cars for bogie performance, while the existing high performance cast steel is due to high alloying degree. Therefore, it is necessary to develop a new bogie steel to reduce the production cost while having high performance. In this paper, a new cast steel has been successfully developed and the optimum normalizing temperature has been determined by studying the influence of the contents of mn, Cr, Ni and C elements and normalizing temperature on the microstructure and properties of cast steel in the composition range of AAR class B cast steel in North America. A mathematical model of the relationship among composition, microstructure and properties of cast steel was established, which reduced the production cost of newly cast steel on the premise of satisfying the performance requirements of normalizing C grade steel of AAR standard. The experimental results show that with the increase of mn content in cast steel, the pearlite content in cast steel increases, the sheet spacing decreases, and the strength of cast steel increases, but the ductility decreases. When mn content is 0.9 wt.%, the strength and toughness combination of cast steel is the best. With the increase of Cr content in cast steel, the pearlite content in cast steel increases, the strength and hardness of cast steel increase, and when Cr content is 0.3 wt.%, cast steel has the best combination of strength and toughness, and Ni in cast steel can effectively refine the matrix structure of cast steel. The strength and toughness of cast steel were improved, but when the Ni content in cast steel exceeded 0.3 wt%, the strengthening effect of cast steel was not obvious, and the strength, hardness and pearlite content of cast steel increased with the increase of C content in cast steel. The tensile strength of cast steel increased from 545 MPa to 616 MPA when the content of C increased from 0.25 wt.% to 0.31 wt.%, but the toughness decreased sharply. The elongation of cast steel was reduced from 31.4% to 24.80.The composition of cast steel was determined to be:% C 0.27 wt.Mo 0.1wt.Si 0.4wt. mn 0.9 wt.cr 0.3 wt.Ni 0.3 wt.The carbon equivalent of newly cast steel is 0.56 CE0.56, which meets the requirements of welding properties of cast steel. The normalizing heat treatment of cast steel at different heating temperatures shows that the strength, hardness and impact absorption energy of cast steel increase first and then decrease with the increase of normalizing temperature, and the elongation of cast steel is almost unchanged when normalizing heating temperature is 900 鈩，

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