正火预处理对高速犁用28MnB5钢组织及力学性能的影响

为解决现有国产高速犁入土部件存在强韧性不足的问题，研究了正火-淬火-回火(N-Q-T)工艺对28MnB5钢微观组织与力学性能的影响机制，并与现有淬火-回火(Q-T)工艺生产的高速犁入土部件进行了对比。结果表明，N-Q-T态和Q-T态28MnB5钢的组织均以板条马氏体为主，N-Q-T态的马氏体板条平均宽度(0.9μm)显著低于Q-T态(1.5μm),且N-Q-T态的强度和韧性均显著高于Q-T态。基于Hall-Petch关系进一步分析可知，板条马氏体细化是导致N-Q-T态28MnB5钢强度提升的主要原因。同时，N-Q-T态28MnB5钢的板条马氏体细化也导致其大角度晶界占比(34.9%)显著高于Q-T态(25.1%),有助于产生更多的残留奥氏体来抑制裂纹的扩展，从而间接地提高韧性。

Effect of normalizing pretreatment on microstructure and mechanical properties of 28MnB5 steel for high-speed plough

Aiming at solving the problem of insufficient strength and toughness of domestic soil-engaging components,the influence mechanism of normalizing-quenching-tempering (N-Q-T) process on microstructure and mechanical properties of 28MnB5 steel was studied, and compared with the high-speed ploughing parts produced by quenching-tempering (Q-T) process.The results indicate that the microstructure of N-Q-T and Q-T 28MnB5 steel is mainly comprised of lath martensite. However, the average width of lath martensite of N-Q-T 28MnB5 steel(0.9 μm) is significantly lower than that of Q-T 28MnB5 steel(1.5 μm), and the strength and toughness of N-Q-T 28MnB5 steel are significantly higher than that of Q-T 28MnB5 steel. A further analysis based on the Hall-Petch relationship reveals that the strength improvement of N-Q-T 28MnB5 steel is related to the refinement of lath martensite. At the same time, due to the refinement of lath martensite,the high angle grain boundaries ratio of N-Q-T 28MnB5 steel (34.9%) is higher than that of Q-T 28MnB5 steel (25.1%), which is beneficial for generating more retained austenite to inhibit the crack propagation and indirectly improve toughness.