夹杂物对15MnB钢冲击性能的影响

15MnB钢的化学成分和生产工艺决定了材料中极易出现MnS和TiN这两种夹杂物,研究了15MnB钢中S、Ti两种元素对夹杂物的产生及冲击性能的影响。设计不同S元素、Ti元素含量的15MnB钢,采用相同锻造、轧制及热处理工艺处理后,检测其冲击性能。采用光学显微镜观察试样的显微组织和夹杂物形貌,并用扫描电镜及能谱仪对夹杂物的化学成分进行检测。结果表明:S元素含量≤0.0029%,Ti元素含量≤0.03%时,15MnB钢的冲击性能最优;S元素含量≤0.0029%时,材料中形成的夹杂物数量少且尺寸小,15MnB钢的冲击性能稳定性随其含量减少而增强;Ti元素含量≥0.06%时,材料中会形成大量尺寸较大的TiN导致15MnB钢冲击性能大幅度降低。为了获得良好且稳定的冲击性能,建议企业在生产15MnB钢时严格控制夹杂物种类和等级,具体要求:D类(细系)≤1.0级、TiN≤0.5级,不应存在其他类型的夹杂物。

Effect of inclusions on impact performance of 15MnB steel

Under the influence of chemical composition and production process, MnS and TiN inclusions are easy to appear in 15MnB steel. The influence of S and Ti elements on the generation of inclusions and the impact performance of the 15MnB steel were studied through testing the steel with different S and Ti element content and with the same forging, rolling and heat treatment processes. The microstructure and inclusions of the specimen were analyzed by using optical microscope, and the chemical composition in different types inclusions was identified by using SEM and EDS. The results show that the impact performance of the 15MnB steel is the best when the S element content ≤0.0029% and the Ti element content ≤0.03%. The number and size of inclusions formed in the steel are both small, and the stability of impact performance of the steel increases with the decrease of its content when the S element content ≤0.0029%. A large amount of TiN with large size forms in the steel resulting in a significant reduction in the impact performance of the steel when the Ti element content ≥0.06%. In order to obtain good and stable impact performance, it is suggested that the species and grade of inclusions should be strictly controlled in the industrial production of 15MnB steel: inclusions of class D (thin series) ≤ grade 1.0, TiN inclusion ≤ grade 0.5, and no other types of inclusions.