Ti对高硼钢显微组织和高温力学性能的影响

Effects of Ti on Microstructure and High Temperature Mechanical Properties of High-boron Steel

采用SEM和XRD研究了Ti对高硼钢显微组织的影响。采用冲击试验机、热力学模拟实验机、氧化增重法分析了Ti对高硼钢室温冲击及850℃高温力学、抗氧化性能的影响。结果表明,添加Ti后,基体内硼化物形态圆整、呈离散状分布,尺寸大幅减小。这种硼化物形态、分布的优化提高了高硼钢的室温冲击韧性。高硼钢中添加Ti后在基体内形成了TiC析出相,并使基体由单一奥氏体转变为奥氏体+铁素体双相组织。添加Ti元素后,B含量较低时提高B含量可以提高材料的高温力学性能;但B含量较高时,高温力学强度变化不大。B含量为0.33%(质量分数)时,材料的高温力学性能最佳。添加Ti前后高硼钢的850℃氧化测试结果均符合GB/T 13303-1991中2级"抗氧化性"标准,Ti的加入有利于提高高硼钢高温抗氧化性能。

The effects of Ti content on the microstructure of high-boron steel were investigated by SEM and XRD.The influences of Ti on impact property at room temperature,high-temperature mechanical properties and oxidation resistance at 850℃ of the steel were analyzed by impact tester,dynamic thermal-mechanical simulation testing machine and oxidation weight increase method.The results show that the boride granules which distribute in a discrete manner within the matrix exhibit a round and smooth morphology and the boride size is reduced greatly after adding Ti.The optimization of boride morphology and distribution can increase the room temperature impact toughness of the steel.TiC particles precipitate and the dual-phase with austenite and ferrite formed after adding Ti.At a low level of boron content,the high temperature mechanical properties improve with increasing of born content,while at a higher level of boron content,they change slightly.Optimum high temperature mechanical properties are obtained when boron content is 0.33 wt%.The results of the oxidation at 850℃ of the steels before and after adding Ti are all in accordance with the level 2 ＂oxidation resistance standard＂according to Chinese standard GB/T 13303-1991.The addition of Ti is conducive to the improvement of the high temperature oxidation resistance properties of high-boron steel.