【作者】 王为波；

【导师】 张敏；

【作者基本信息】 西安理工大学 ， 材料加工工程， 2006， 硕士

【摘要】 ZG-Mn13铸钢铁路辙叉在使用过程中由于受到交变载荷和大气腐蚀的联合作用，经常在其表面形成龟裂剥落甚至掉块，进而造成整个辙叉的提前失效。 从分析辙叉表面剥落失效机理出发，通过对材料表面剥落断口、化学成份、金相组织、表面硬度和力学性能等进行研究分析，确定铁路辙叉表面的脱落、掉块是腐蚀疲劳失效所致。材料组织中存在大量的疏松、气孔和夹杂物等铸造缺陷，在强烈冲击载荷和大气腐蚀的作用下，疲劳裂纹从材料缺陷处和加工硬化形成的滑移带处优先萌生。随后，表面和次表面的裂纹不断扩展并汇合，最终造成表面的剥落掉块。 为了进一步研究铁路辙叉的使用工况对其失效的影响，利用ANSYS有限元软件，分析辙叉在使用过程中复杂的受力状态。结果表明，辙叉表面接触点的最大应力值达5300MPa，应力在830MPa的作用深度达15mm，这与实际的高锰钢辙叉硬化层深度是一致的；辙叉受到摩擦力和冲击载荷的作用在水平方向的应力有2450MPa；同时受到700MPa剪应力的作用深度有1.5mm，直接加速辙叉表面的剥落。 在原高锰钢材料(ZG-Mn13)的基础上，通过降低碳元素含量、提高锰元素含量，添加适量铌、钛、钒、钼和稀土等合金元素，加入少量的铜或镍元素提高其抗腐蚀性，并选择和设计相应的铸造和水韧处理工艺，对原高锰钢进行改良。试验结果表明，改良后的高锰钢不仅保持了原有的材料耐磨性好的优点，并且材料的组织晶粒细小均匀、晶界纯净，腐蚀疲劳寿命比原高锰钢提高三倍，从而可以提高辙叉的使用寿命。更多还原

【Abstract】 ZG-Mn13 cast steel, which is used in the railway frog, forms frequently the pitting spot even spalling on the surface due to the influence of alternate load and the corrosion atmosphere, which leads to the failure of the whole component.Based on the failure mechanism analysis of frog surface spalling, through the research into the surface spalling fracture, chemical composition, microstructure, surface hardness and mechanic properties, a conclusion can be drawn that the railroad frog surface spalling and falling block is attributed to corrosion fatigue failure. Under the combined condition of the intensive impact load and the environment corrosion, fatigue cracks firstly sprout from the material flaw place and the slipping line place where the work hardening forms because there are the casting defects of shrinkage, air hole and inclusion in the material organization. When the superficial and the inferior superficial cracks unceasingly expand and converge, the surface flaking block come into being.In order to have a further study on the effect of the in-service condition of railway frog on its failure, finite element software of ANSYS is used to analyze the complex stress condition of the frog. The result indicates that the maximum stress at the superficial contact point reaches 5300MPa, and the action depth reaches 15mm with the stress 830MPa, which is consistent with the actual hardening depth of high manganese steel frog. In addition, the horizontal stress induced from friction force and impact load is 2400MPa, and the depth reaches 1.5mm with the shearing stress of 700MPa, which accelerate directly the frog surface flaking.By decreasing carbon content, increasing manganese content, adding an niobium, titanium, vanadium, molybdenum and rare-earth elements, and adding a small copper or nickel to improve its corrosive resistance, and by developing new casting and heat treatment techniques, the properties of ZG-Mn13 steel is improved based on the original high manganese steel materials. The results indicate that, materials crystal grain is homogeneous in size, crystal boundary can be purified, and corrosion fatigue life of the new ZG-Mnl3 steel exceeds that of the original high manganese steel by three times, even without lowering of abrasion resistance. Thus extends the useful life of the railway frog.更多还原