钢脱碳对零部件疲劳寿命影响研究

Study on the Effect of Steel Decarburization on its Fatigue Life

摘要:

钢质部件热处理时，若发生脱碳会导致其硬度降低，而准确建立硬度与疲劳寿命的定量关系对材料应用具有重要意义。基于金属材料硬度与抗拉强度的关系及零部件的结构设计参数，采用修正Miner法得到S-N曲线，从而获得各类钢质部件的疲劳极限。依据累积损伤理论，采用零部件服役应力谱，以45钢和ZG230-450钢部件脱碳引起的疲劳失效为应用实例，进行了疲劳寿命评价的验证。结果表明：脱碳会导致部件表面硬度的降低，其主要是通过降低裂纹萌生寿命而影响零部件疲劳寿命；通过理论模型计算得到的疲劳寿命结果与应用实例的结果进行对比分析，发现表面硬度影响零部件疲劳寿命的评价方法具有适用性，有助于零部件表面发生脱碳后进行疲劳寿命的定量分析。

Abstract:

Decarburization during heat treatment could induce surface hardness decrease for steel components. An approach of demonstrating structure fatigue strength according to material hardness has been performed with the demand of structural reliability assessment. In this paper， the fatigue limit range and S-N curves for steel structural components have been achieved based on the tensile strength deduced by hardness and design parameters. Furthermore， the effect of decarburization on the fatigue life has been explored for 45 steel and ZG230-450 according to modified Mine’s linear cumulative damage and stress spectrum. The experimental results show that decarburization-induced surface hardness decrease could significantly affect the crack initiation， thus decreasing the fatigue life of the steel structures. In addition， an application case comparison with the result of evaluation results based on cumulative damage model indicates the feasibility of the presented approach and highlights the quantitative analysis relationship between the hardness decrease and fatigue life deteriorate.