热处理工艺对高速车轮钢显微组织和断裂韧性的影响

Effect of heat-treatment on microstructure and fracture toughness of high-speed railway wheel steel

对含碳量为0.54%的高速车轮钢热处理工艺进行实验研究,得到不同晶粒尺寸和珠光体片间距的显微组织,在室温下对具有不同显微组织的紧凑拉伸(CT)试样进行断裂韧性测试。结果表明,车轮钢的平均晶粒尺寸随奥氏体化温度升高而增加;珠光体片间距随冷却速率增加而减小。车轮钢室温下的断裂模式为解理断裂,断裂韧性主要取决于晶粒尺寸的大小,晶粒尺寸越小,断裂韧性越高。珠光体片间距对断裂韧性有一定影响,粗大的珠光体片间距会降低断裂韧性,并且当晶粒尺寸较小时,珠光体片间距的影响更明显。因此,实际工程中为提高车轮钢断裂韧性,合理的奥氏体化温度是关键,同时需适当增加车轮钢奥氏体化后的冷却速率。

High-speed railway wheel steel with 0. 54% carbon was heat-treated with different austenitizing temperatures and cooling rates to achieve microstructure with various grain diameters and pearlite interlamellar spacings. Compact tension( CT) specimens with different microstructure were tested at room temperature. The results show that the average grain diameter increases with increase austenitizing temperature. The pearlite interlamellar spacing decreases with the increasing of cooling rate. The fracture mode of all the CT specimens at room temperature is cleavage. The fracture toughness of the steel increases with decrease the grain diameter and large interlamellar spacing is harmful to the fracture toughness especially when the grain size is fine. Reasonable austenitizing temperature and continuously cooling rate are important to elevate the fracture toughness of the wheel steel.