钒微合金钢的工艺、显微组织和性能(下)

Processes,Microstructure and Properties of Vanadium Microalloyed Steels

钒元素最早作为一个重要的钢的合金元素,源自于钒钢回火后所得到的性能。由于透射电子显微镜的分辨率达到了~1 nm,以及选区电子衍射技术的进步,提升了对钒钢显微组织进行研究的兴趣。第二项及时的技术进步是控制轧制,特别是板、带产品控轧技术的开发。本概述的内容包括以下几方面的历史背景,即淬火回火钒钢,等温时效时、常规控轧时和薄板坯直接装炉时的析出,以及提高钒微合金钢强韧性的进展。介绍钒钢显微组织的特征,特别是析出物化学成分的分析方法及技术的进步,由于20世纪70年代X-光能谱分析的运用,电子能损失谱的运用使得钒微合金钢中碳和氮的定量分析得以实现。当今,关于钒钢还存在许多矛盾的课题。这些课题包括：钒碳化物均匀析出物的形核次序,这类形核是否是共格形核,钒析出物的化学成分,相间析出的形核机制,奥氏体中钒的碳氮化物形变诱导析出的重要性,相间析出和铁素体中的无序析出对屈服强度的贡献,以及工艺过程参数对性能的影响。对这些课题进行讨论,并将结合其它合金的长期研究,集中讨论热轧钒微合金钢。

Vanadium as an important alloying element in steels was initially associated with the properties achieved following tempering.Interest in the microstructure was stimulated by the advent of transmission electron microscopes with a resolution of y1 nm together with selected area electron diffraction techniques.A second timely development was that of controlled rolling,particularly of plate and sheet products.The scope of this review will include the historical background on quenched and tempered vanadium steels,precipitation during isothermal aging,conventional controlled rolling and during thin slab direct charging and the development of strength and toughness in vanadium microalloyed steels.The characterisation of microstructure,in particular the methods for the analysis of the chemical composition of precipitates has progressed since the availability of X-ray energy dispersive analysis in the 1970 s,and the role played by electron energy loss spectroscopy in providing quantitative analysis of carbon and nitrogen in vanadium microalloyed steels will be presented.There are still many topics involving vanadium microalloyed steels that are controversial.These include the nucleation sequence of homogeneous precipitates of vanadium carbonitride and whether this occurs coherently,the composition of the vanadium precipitates,the nucleation mechanism for interphase precipitation,the importance of strain induced precipitation in austenite of vanadium carbonitride,the contributions of both interphase precipitation and random precipitation in ferrite to the yield strength,and the role of the process route parameters in developing properties.These topics will be considered in this paper which concentrates on hot rolled vanadium microalloyed steels placed in the context of pertinent research on other alloys.