超声速法评价低碳钢的石墨化

Ultrasonic velocity method evaluating graphitization in low-carbon steel

低碳钢的石墨化是导致材料高温性能劣化的原因之一.试验选择石墨化程度不同的20#钢作为研究对象,通过测量超声波在其中的传播速度,考察声速法评价低碳钢石墨化的可行性.研究结果表明:随着石墨化程度的加剧,超声波速度随时效时间按照指数规律递减.声速降低的根本原因在于石墨化削弱了原子间结合力,割断了基体的连续性.依据弹性模量与原子间的相关性判断,这将导致弹性模量的降低.

The graphitization in low-carbon steel is one of the causes that lead to the worse material mechanical performance at high temperature. The ultrasonic velocity in 20~# steel graphitized specimens is measured in order to determine the possibility of ultrasonic evaluating graphitization in low-carbon steel. The results show that there is definite relationship between velocity and aging time. With the graphitization increasing, the velocity is decreasing according to the index law. The further analysis indicates that the main reason resulting in the decreasing velocity is that graphitization weakens the inter-atomic bonding force and cuts off the continuity of the body. Based on the relationship between inter-atomic bonding force and elasticity modulus, it will cause the reduction of elasticity modulus.