车轮钢中氧化物夹杂的疲劳法评估

Evaluation of oxide inclusions in wheel steel by fatigue test method

提出了疲劳法评估车轮钢中氧化物夹杂的形状、尺寸和成分,设计了一套表面强化处理和疲劳试验相结合的车轮钢夹杂物分析方法。分别在CL60车轮轮辋中超声波探伤发现密集型缺陷区域和单点缺陷区域处取样,通过该方法对车轮钢中缺陷的尺寸、形状和成分进行了分析。结果表明:单点缺陷对应毫米级宏观夹杂物,密集型缺陷对应微米级微观夹杂物。宏观夹杂主要含Ca、Si、Mg,微观夹杂主要含Al、Ca,两种夹杂物均近似呈细长椭圆状。使用统计极值法推测的一个轮辋中可能引起浅层剥离的最大夹杂物尺寸在95%置信区间内为[752μm,1 168μm]。

In this study,a method was proposed to evaluate the shape,the size and the chemical compositions of oxide inclusions in railway wheel steel.The evaluation method which consists the surface strengthening process and the fatigue test was carefully designed.The ultrasonic inspection was first conducted to CL60 wheel to identity the regions which contains densely-distributed defects and single defect,respectively.The samples were taken from both of the identified regions,and then the shape,the size and the chemical compositions of the defect within the wheel steel were evaluated using the proposed method.The evaluation results show that the single defect is the macro-inclusion with millimeter scale,while the densely-distributed defect is the micro-inclusion with micrometer scale.The macro-inclusion mainly contains Ca,Si and Mg,while the micro-inclusion mainly contains of Al and Ca.Both of the inclusions are in a shape of slender ellipse.According to extreme values method,the largest micro-inclusion which can induces subsurface-initiated fatigue was predicted to be[752μm,1 168μm]within 95%confidence intervals in a wheel.