氮含量对正火型钒微合金化钢强化效果和显微组织的影响

 利用V-N微合金化技术，在Q345钢基础上进行V-N微合金化，将通用型正火容器用钢的强度水平由345 MPa升级至400 MPa。考察了不同N含量对正火型V-N钢组织和强化效果的影响。结果表明，随着N含量增加，正火态V微合金化试验钢的屈服强度明显提高；每加入50×10-6的N，屈服强度提高18 MPa左右，同时屈强比上升。随着N含量提高，V微合金化钢产生明显的晶粒细化效果，试验钢的铁素体晶粒尺寸由13.36 μm逐渐细化至7.89 μm。对比热轧态试验钢和正火态试验钢的强化效果，发现正火态试验钢的析出强化作用相对较弱，而细晶强化作用相对显著。

Effect of N Content on Microstructure and Strengthening Effect in Normalized V-N Microalloyed Steel

Based on the chemical composition of the Q345 C-Mn steel, 400 MPa-grade pressure vessel steel which was increased from 345 MPa was designed by the V-N microalloyed technology. Gradually increasing N content was added in the experimental steels in order to investigate the influence of N content on the microstructure and strengthening?effect. The results show that the yield strength as well as yield ratio is improved significantly with the addition of N content. Every 50×10-6 N content will result in a 18 MPa yield strength increase in normalized experimental steels. With increasing N content, the average size of ferrite is refined from 13.36 μm to 7.89 μm. Compared with the hot-rolled experimental steels, the normalized steels have a better refine-grain strengthening effect but a weakening of precipitation strengthening effect.