U75V热处理钢轨滚动接触疲劳裂纹和磨耗试验

对U75V热处理钢轨进行不同通过总重时的表面观测、取样、磨耗测量、实验室疲劳裂纹长度与深度显微照相以及断面硬度测量,分析钢轨的轨距角滚动接触疲劳裂纹、磨耗和硬度的关系.研究发现,轨距角疲劳裂纹的发展包括裂纹快速萌生和扩展、裂纹-磨耗共存和发展、磨耗控制裂纹三个阶段.轨距角的裂纹向钢轨内部扩展,裂纹与钢轨纵向水平线呈10.8°~29.4°.硬化层硬度在340~360 HB及以上时,磨耗发展率小于0.015mm·Mt-1,而疲劳裂纹萌生扩展较快,应考虑钢轨上道后至通过总重5~10 Mt期间实施新轨预打磨、通过总重30~60 Mt时实施预防性打磨,以平衡磨耗与裂纹的关系.同时,U75V热处理钢轨具有340~360HB及以上硬度的硬化层厚度应大于10mm.

Experiment on the Rolling Contact Fatigue Crack and Wear of U75V Heat treated Rail

The relationship among rollong contact fatigue crack at the gauge corner, wear and hardness of the U75V heat-treated rails in field curve was analyzed by surface observation, sampling, wear measurement, laboratory photomicrograp for length and depth of the crack and hardness of the rail longitudinal cross-section measurement at different traffic. The research show there were 3 main phases during the fatigue crack growth: crack initiation and propagation rapidly, crack and wear co-existence and growth and wear control crack. The crack at the gauge corner propagated into the railhead with the angle of 10.8°-29.4° with respect to the rail longitudinal surface. When the hardness of the heat-treated layer was 340-360HB and above, the wear growth rate was less than 0.015mm/MGT with fatigue crack growh rapidly. The new rail pre-grinding from new rail installation to 5-10MGT and preventive grinding with interval of 30-60MGT were recommended to balance the crack and wear. The thickness of the heat-treated layer with 340-360HB and above should be over 10mm.