Dlouhy Jaromir, Podany Pavel, Dzugan Jan
COMTES FHT a.s., Prumyslova 995, 334-41 Dobrany, Czech Republic.
Materials (Basel). 2021 Apr 14;14(8):1962. doi: 10.3390/ma14081962.
Bainitic steels were the focus of this study. These steels have the potential to obtain a good combination of strength, ductility, and edge stretchability, which is a very desirable characteristic in the automotive industry. Cu precipitation potential was investigated during prolonged isothermal bainitization treatment. Precipitation strengthening and ductility were measured using a tensile test, and edge stretchability was measured using a hole expansion test. The microstructure was characterized by high-resolution scanning electron microscopy and an electron backscattered diffraction. Lower bainite was obtained by austenitization treatment and subsequent immersion into a salt bath at 400 °C. Cu precipitation occurred after 120 min of holding in the bath and enhanced the yield stress of the Cu-alloyed steel by 120 MPa as compared with a reference steel without Cu. The strengthening did not affect ductility and decreased the edge stretchability by 10%. Steels with different Mn contents were examined. It was found that the enhancement of Mn content from 1 to 2 wt.% did not boost Cu strengthening ability. This result showed that the presence of Mn did not cause an Mn-Cu precipitation strengthening synergy, observed previously during martensite tempering procedure.
贝氏体钢是本研究的重点。这些钢有可能获得强度、延展性和边缘拉伸性的良好组合，这在汽车工业中是非常理想的特性。在长时间等温贝氏体化处理过程中研究了铜的析出潜力。使用拉伸试验测量析出强化和延展性，使用扩孔试验测量边缘拉伸性。通过高分辨率扫描电子显微镜和电子背散射衍射对微观结构进行表征。通过奥氏体化处理并随后浸入400°C的盐浴中获得下贝氏体。在盐浴中保温120分钟后发生铜析出，与不含铜的参考钢相比，铜合金化钢的屈服应力提高了120MPa。强化不影响延展性，但边缘拉伸性降低了10%。研究了不同锰含量的钢。发现锰含量从1wt.%提高到2wt.%并没有提高铜的强化能力。该结果表明，锰的存在并未导致在马氏体回火过程中观察到的锰-铜析出强化协同作用。
