前驱体对含Cu低碳钢I&Q&P处理后组织性能的影响

采用IQP工艺和EPMA、SEM和XRD等手段,研究了3种前驱体对含Cu低碳钢残余奥氏体含量及力学性能的影响。结果表明,双相区保温初期试验钢奥氏体长大由C配分控制,后期由合金元素Mn、Cu配分控制;双相区保温奥氏体化后,双相区配分后形成弥散分布的局部高浓度Mn、Cu区域仍保留富集效果,在随后的淬火-碳配分阶段易于形成残余奥氏体。经IQP处理后,前驱体为P+F的钢室温组织中马氏体板条较粗,原始奥氏体晶界并不明显;前驱体为F+M钢得到的马氏体板条有序细密;前驱体为M的钢室温组织中马氏体板条更加细密。其中,前驱体组织为M的钢中残余奥氏体量最高,延伸率为24.1%,强塑积可达25 338 MPa·%,综合性能最好。

Influence of Precursor on Microstructure and Mechanical Property of a Cu Bearing Low-carbon Steel by I&Q&P Treatment

Effect of different precursor microstructure on retained austenite and mechanical properties of a Cu bearing low-carbon steel was studied by means of scanning electron microscopy (SEM),electron microprobe analysis (EPMA) and X-ray diffraction (XRD). The results showed that austenite nucleation and growth were controlled by C partition in initial stages and Mn, Cu partition in the later stages of intercritical annealing. The effect of Mn, Cu enrichment formed in the intercritical partitioning was retained after austenitizing. The rigion could form retained austenite easily in the quenching and C partitioning stages subsequent. After I&Q&P heat treatment, the steel with ferrite + pearlite (P+F) precursor could obtain the coarser martensite lath, but the original austenite grain boundary was not obvious. The steel with ferrite + martensite (P+M) precursor could obtain the orderd martensite lath and the lath was fine; While the martensite (M) precursor steel could obtain a microstructure of more refined martensite lath. After I&Q&P heat treatment, the steel with M precursor had the most volume fraction of retained austenite. The elongation of this kind of steel was up to 24.1%, and thus the product of strength and elongation was 25 338 MPa·%, the mechanical properties was the best.