曲线尖轨踏面伤损原因分析

Analysis on Causes of Tread Damage of Curved Switch Rail

为了研究伤损曲线尖轨轨头宽15 mm断面处踏面连续掉块的原因,对其进行断口宏观形貌观察、金相分析、非金属夹杂物检测、化学成分分析、淬火层形貌观察及硬度分布检测。结果表明:在距轨顶面约3.5~6.0 mm处存在较粗大夹杂物是引起尖轨内部起裂的主要原因;曲线尖轨使用过程中,在轮轨接触应力的作用下,在踏面次表层粗大夹杂物处萌生纵向疲劳裂纹,降低了尖轨的承载能力,最终导致尖轨连续掉块。为防止该类伤损发生,应提高钢轨钢的纯净度,加强钢轨钢冶金质量的控制和检验,减小钢中非金属夹杂物的数量和尺寸,尤其应控制道岔尖轨小尺寸断面的冶金质量。

In order to study the reasons for the continuous spalling of the tread at the section with the width of 15 mm at the rail head of the damage curve switch rail,the macro morphology observation,metallographic analysis,non-metallic inclusion detection,chemical composition detection,quenching layer morphology observation and hardness distribution detection were carried out. The results show that the existence of coarse inclusions about 3.5~6.0 mm from the top of the rail is the main reason for the internal crack of the switch rail. During the use of curved switch rail,under the action of wheel rail contact stress,longitudinal fatigue cracks are initiated at the coarse inclusions on the sub surface of the tread,which reduces the bearing capacity of the switch rail and finally leads to continuous spalling of the switch rail. In order to prevent this kind of damage,we should improve the purity of rail steel,strengthen the control and inspection of metallurgical quality of rail steel,reduce the number and size of non-metallic inclusions in steel,and control the metallurgical quality of small-size section of turnout switch rail.