钒在长条钢产品中的应用

Use of Vanadium in Long Steel Products

钒已被广泛地应用于长条钢产品,诸如锻造制品、螺纹钢筋、型材、管材、钢轨、弹簧和盘条。钒在长条钢产品中是优选的添加剂,因为与铌和钛相比,它的碳氮化合物在奥氏体中的溶解度要高得多,并对碳含量的敏感性较小。钒能起到析出强化和晶粒细化的作用,从而得到强度和韧性的良好配合。通过控制氮的含量,能使析出强化最大化,氮随钒的优先析出也使氮应变时效的危险性降至很小。此外,钒还能在较低含碳量情况下得到所期望的强度,较低的含碳量对延性和焊接性有利。再者,对淬火回火钢来说,钒有利于回火抗力,并起到二次硬化作用。细小的钒碳化合物还对易扩散的氢起到有力的捕集点作用。钒的碳氮化合物相对较低的溶解温度,得以有效地利用能源和采用低的加热温度。传统的热轧或热锻,一般采用高的终加工温度,这对生产长条钢产品是不可避免的,而对钒微合金钢来说却可以用来获得所需要的力学性能和服役功能。此外,钒微合金化钢的性能对加工处理条件的变化相对地不怎么敏感。

Vanadium has been widely used in long steel products such as forging grades,reinforcing bars,sections,tubes,rails,springs and wire rods. Vanadium is the preferred addition in long steel products because of the much higher solubility of its carbonitrides in austenite and lower sensitivity to carbon level compared to niobium and titanium. Vanadium provides precipitation strengthening and grain refinement,resulting in good combinations of strength and toughness. The precipitation strengthening can be maximized by management of nitrogen level and the preferential precipitation of vanadium with nitrogen also minimizes the risk of nitrogen strain aging. In addition,vanadium enables desired strength levels to be attained at lower carbon content,which is beneficial for ductility and weldability. Furthermore,vanadium contributes to temper resistance and provides secondary hardening for quenched and tempered steels. Fine vanadium carbides also act as strong trap sites for diffusible hydrogen,leading to good delayed fracture resistance.The relatively low solution temperature of vanadium carbonitirdes permits the use of energy efficient,low reheating temperatures. Conventional hot rolling or forging with high finish working temperatures,which are inevitable for production of long steel products,can be used for vanadium microalloyed steels to achieve the required mechanical properties and service performance. In addition,the properties of vanadium microalloyed steels are relatively insensitive to changes in processing conditions.