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DEVELOPMENT OF ANTI-DARK SPOT RAILWAY RAILS

防暗点铁路钢轨的研制

基本信息

批准号：
10555054
负责人：
KANETA Motohiro
金额：
$ 8.26万
依托单位：
KYUSHU INSTITUTE OF TECHNOLOGY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-10555054/
关键词：
Dark spot Cracking Pearlitic steel Bainitic steel Railroad Rolling contact fatigue Vickers hardness Tribology レール

项目摘要

As traffic speed on railroads increases, various kinds of defects have been produced in rail systems. One of them is the rail dark spot defect or rail shelling. The dark spot defect is characterised by a principal crack, which initiates at the contact surface and propagates at an acute angle to the rail surface in the direction of traffic, and a second crack, which grows more slowly from almost the same point on the surface, in the opposite direction to traffic and at a slightly less shallow angle. The principal crack has many sub-cracks and at some stage one of these may extend transversely across the railhead leading to a catastrophic tensile failure of the rail. Thus, this defect is a very dangerous rail failure. The authors have found the mechanism for the dark spot cracking. Furthermore, they have made a bainitic steel, which seems to be effective for the occurrence of rolling contact fatigue failures. The purpose of this study is to establish the design instruction for the develo … More pment of anti-dark spot defect railway rails on the basis of the mechanism for dark spot cracking. The main results obtained are summarised as follows :1. Cracking is produced by a high traction force due to a local direct contact. The crack initiated propagates by a hydraulic pressure effect due to water penetrated into the crack in a period of wet running.2. Under conditions where the mean traction force is rather low, the dark spot resistance of bainitic steel is much higher than that of conventional pearlitic steel.3. Under conditions where the mean traction force is rather high, surface damages due to the plastic deformation are produced. The increase in hardness of steels is effective for the enhancement of such damages.4. The bainitic steel is much worse than the pearlitic steel in the wear resistance. However, the wear resistance of bainitic steel can be improved by increasing the hardness and the carbon content.5. Although a common opinion that the higher wear rate prevents the crack initiation is believed, the fact is somewhat different.6. The welded parts of bainitic steel rails are almost the same joint performance as those of conventional pearlitic steel rails.7. Presently, the rolling contact fatigue resistance test of bainitic steel railroads (HB=250-350) is in progress using actual railways. It has been found that the dark spot defect resistance of bainitic steel rails is much higher than that of conventional pearlitic steel rails.Considering above results, the chemical composition of bainitic steel is under investigation now for application of bainitic steel rails so as to satisfy JIS standard on pearlitic rail steel strength and the electrical resistance standard established by the Japan Rail companies. Less

随着铁路运输速度的提高，铁路系统产生了各种各样的缺陷。其中之一是钢轨黑点缺陷或钢轨剥落。暗点缺陷的特征是主裂纹和第二裂纹，主裂纹始于接触面，并在交通方向上与钢轨表面成锐角扩展，第二裂纹从表面上几乎相同的点在与交通相反的方向上以稍微浅一些的角度扩展得更慢。主裂纹有许多子裂纹，在某个阶段，其中一个子裂纹可能横跨钢轨头部，导致钢轨灾难性的拉伸失效。因此，这种缺陷是一种非常危险的钢轨故障。作者已经找到了黑斑破裂的机理。此外，他们还制造了贝氏体钢，这似乎对滚动接触疲劳失效的发生是有效的。本研究的目的是建立开发…的设计指南。在分析钢轨黑斑开裂机理的基础上，提出了更多的抗黑斑缺陷钢轨。主要研究结果如下：1.裂纹是由局部直接接触产生的高牵引力引起的。在湿运行期间，由于水渗入裂缝而产生的水压效应导致裂缝萌生扩展。在平均牵引力较小的条件下，贝氏体钢的黑斑电阻远高于常规珠光体钢。在平均牵引力较大的情况下，会产生塑性变形引起的表面损伤。钢材硬度的提高对这种损伤的强化是有效的。贝氏体钢的耐磨性远不如珠光体钢。但是，提高贝氏体钢的硬度和含碳量可以提高其耐磨性。虽然普遍认为较高的磨损率可以防止裂纹萌生，但事实有所不同。贝氏体钢轨焊接件的接头性能与常规珠光体钢轨基本相同。目前，贝氏体钢轨道(HB=250-350)的滚动接触疲劳抗力试验正在进行中。结果表明，贝氏体钢轨的黑点缺陷抗力远高于常规珠光体钢轨，因此，为满足JIS珠光体钢轨强度标准和日本铁道公司制定的电阻标准，目前正在研究贝氏体钢的化学成分，以便应用于贝氏体钢轨。较少