Abstract

The wear behavior of two steels for tread-braked wheels (ER7⁺ and CLASS B⁺) against the same brake block cast iron was studied through pin-on-disc tests to understand the phenomena at the interface and compare the steels. The contact stress (0.61 MPa) and sliding speeds (0.52 and 0.62 m/s) were set considering the UIC 510-5 (E) for technical approval of monobloc wheels. The friction coefficient, weight loss of both the steel pin and cast iron disc, and pin hardness were correlated with the damage of the pin. In addition, a preliminary thermal finite element model was proposed to predict the temperature of the pin contact surface. The experiments showed that material transfer from the cast iron disc to the steel pin and the subsequent detachment of the adhesion joints caused high friction coefficient fluctuations. The removal of the adhesion joints probably promoted the detachment of steel particles from the pin, which could explain the high weight loss and remarkable delamination of the pin in some of the studied conditions. In contrast, small friction coefficient fluctuations and red oxide formation due to the temperature increase were detected when the material transfer was very limited. ER7⁺ steel showed lower weight loss and less damage than CLASS B⁺ at the lowest sliding speed, in contrast to what was observed at the highest sliding speed. Finally, the simulation showed that the maximum temperature of the pin contact surface varies between 61 and 97 °C, which is consistent with the presence of red oxide.

摘要

两种用于胎面制动车轮的钢材（ER7 ⁺和 CLASS B ^{+ ）的磨损行为}) 通过销盘试验研究了对同一制动块铸铁的研究，以了解界面处的现象并比较钢。接触应力 (0.61 MPa) 和滑动速度 (0.52 和 0.62 m/s) 的设置考虑了 UIC 510-5 (E) 的整体车轮技术批准。钢销和铸铁盘的摩擦系数、重量损失和销硬度与销的损坏相关。此外，提出了一个初步的热有限元模型来预测销接触表面的温度。实验表明，从铸铁圆盘到钢销的材料转移以及随后的粘合接头分离会导致高摩擦系数波动。粘合接头的去除可能促进了钢颗粒从销上的分离，这可以解释在某些研究条件下销的高重量损失和显着分层。相反，当材料转移非常有限时，由于温度升高而检测到小的摩擦系数波动和红色氧化物的形成。ER7^{+钢在最低滑动速度下比 CLASS B +}表现出更低的重量损失和更少的损坏，与在最高滑动速度下观察到的情况形成对比。最后，仿真表明引脚接触面的最高温度在 61 到 97 ℃之间变化，这与红色氧化物的存在是一致的。