U75V热处理钢轨滚动接触疲劳裂纹和磨耗试验

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

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.

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 that there were 3 main periods during the fatigue crack growth., crack initiation and rapid propagation, co-existence of crack and wear, and growth and wear control crack. The crack at the gauge corner propagated into the railhead with the angle of 10.8° to 29.4° with respect to the rail longitudinal surface. When the hardness of the heat-treated layer was 340 to 360 HB and above, the wear growth rate was less than 0. 015 mm · Mt^-1 with rapid fatigue crack growh. The rail pre-grinding from new rail installation to 5 to 10 Mt and preventive grinding with an interval of 30 to 60 Mt were recommended to balance the crack and wear. The thickness of the heat-treated layer with 340 to 360 HB and above should be over 10 mm.