高性能低成本FB510L热轧带钢的开发

Development of high performance and low cost FB510L hot rolled strip

针对汽车底盘用冲压高强钢510L成形过程中容易出现局部开裂的问题,对高性能低成本Ti微合金化FB510L热轧带钢进行了开发。采用510L钢(Nb+Ti复合强化)和FB510L钢(单Ti强化)为试验钢,采用不同的控轧控冷工艺,对热轧后带钢微观组织、析出物、力学性能、扩孔性能、抗疲劳性能及其应用情况进行了对比研究。结果表明:Ti微合金化FB510L带钢中存在大尺寸和小尺寸的TiC析出物,呈长方形,弥散分布在铁素体基体中;510L钢中由于存在Nb-Ti微合金化成分,观察到纳米级呈不规则椭圆形的(Ti,Nb)C。Ti微合金化FB510L钢充分利用了析出物在加热、轧制、冷却过程中抑制奥氏体、铁素体晶粒长大的作用,同时通过控轧控冷工艺的优化设计,获得了均匀的铁素体+贝氏体双相组织,大幅提高了其扩孔性能,扩孔率达80%以上,解决了510L带钢冲压翻边成形开裂的问题。FB510L钢较510L钢具有更好的扩孔成形性能和抗疲劳性能,同时由于节省了Nb合金的添加,吨钢节约合金成本84.45元,实现了汽车底盘用冲压高强钢高性能低成本生产。

The high performance and low cost Ti microalloyed FB510L hot rolled strip was developed to solve the problem of local cracking during the forming process of high strength stamping steel 510L for automobile chassis.Using 510L steel(Nb+Ti compound strengthening)and FB510L steel(single Ti strengthening)as tested steel,adopting different controlled rolling and controlled cooling process,the microstructure,precipitates,mechanical properties,reaming properties,fatigue resistance and application of the hot rolled strips were studied.The results show that there are large and small TiC precipitates in Ti microalloyed FB510L strip,which are rectangular in shape and dispersed in ferrite matrix.Due to the presence of Nb-Ti microalloy composition in 510L steel,the nanoscale irregular elliptical(Ti,Nb)C was observed.Ti microalloyed FB510L steel takes full advantage of the effect of precipitates on the growth of austenite and ferrite grains during heating,rolling and cooling,by optimizing the design of controlled rolling and controlled cooling,the uniform F+B dual-phase microstructure was obtained,and the hole expansion property was improved greatly,the hole expansion ratio was more than 80%,and the cracking problem of 510L strip during stamping flanging was solved.Compared with510L steel,the FB510L steel has better hole expansion formability and fatigue resistance.At the same time,because of saving Nb alloy,84.45 yuan alloy cost per ton of steel was saved,and the production of high performance and low cost stamping high strength steel for automobile chassis was successfully realized.