车轮钢中的白点及其断口形貌研究

RESEARCH OF FLAKING AND ITS FRACTOGRAPHY IN A WHEEL STEEL

研究了车轮钢中白点的形成过程,制备了白点(氢压裂纹)的真实断口,并与含白点试样的各种断口进行了对比．结果表明,先形成氢鼓泡,然后从鼓泡壁产生微裂纹,它们互相连接形成白点．白点断口和含白点试样的断口概念不同,前者为准解理, 与氢致滞后开裂断口相同;后者则依赖断裂方式和试样厚度．钢中白点除了产生二次裂纹外,对各种断口形貌均无影响．车轮钢的滞后断裂由原子氢引起,与白点无关．

Forming process of flaking in a wheel steel has been investigated. The cracking surface of the flaking was got using a special method, and compared to various fracture surfaces of samples containing flaking. The results show that a cavity with hydrogen, i.e. hydrogen blistering, formed and grew firstly, then microcracks initiated from the wall of the blistering, grew and connected each other resulting in formation of flaking. The cracking surface of flaking is a different idea with fracture surface of the sample containing flaking. The former is quasi-cleavage, similar to that of hydrogen-induced delayed cracking, but the later is dependent upon the failure method and the thickness of the sample. There is no effect of flaking in the steel on various fracture surface morphologies besides secondary cracks. Hydrogen-induced delayed failure is due to atomic hydrogen instead of flaking.