U75V钢轨白点失效分析

Flakes failure analysis of U75V steel rail

对U75V失效钢轨的化学成分、力学性能、显微组织和断口形貌进行了分析。结果表明,钢中溶解过量的氢聚集后造成局部应力集中,形成内部微裂纹,形成白点;基体中硫化物夹杂的存在降低了钢的塑性和韧性,并加剧裂纹扩展;钢轨表面局部形成马氏体组织,其氢致裂纹敏感性高,产生极高的相变应力和热应力引起氢致开裂。

Chemical composition, mechanical properties, microstructure and fracture features of failed U75V steel rail were analyzed. The results show that excess hydrogen dissolved in steel and aggregates lead to the local stress concentration and form the inner crack, namely flakes. Sulfide inclusions in matrix decrease the plasticity and toughness of the steel, which also spurs the crack propagation and stretch. Martensite formed in the rail surface with high hydrogen induced crack sensitivity will produce high phase transformation stress concentration and thermal stress that lead to hydrogen induced cracking.