钛微合金化HRB400E钢筋组织性能及强化机理

为系统研究含钛钢连续冷却相转变和强化机理,利用热模拟试验机、高分辨透射电镜及金相显微镜等设备进行试验。结果表明,低冷速下(0.5~1 ℃/s),组织主要为铁素体和珠光体;冷速逐步增加(1~5 ℃/s),贝氏体组织出现,且贝氏体比例逐渐增加;高冷速后(5~10 ℃/s),组织以贝氏体为主。含钛试验钢强化机制为析出强化和细晶强化。晶粒内部弥散析出10~20 nm的TiN。优化冷速为(1.5±0.5) ℃/s开展20 mm HRB400E钢筋工业试制,屈服强度不小于430 MPa,断后伸长率不小于20%,最大力总伸长率不小于15%,强屈比不小于1.4。

Microstructure and strengthening mechanisms of Ti microalloyed HRB400E rebar

Continues cooling phase transformation behavior and strengthening mechanisms of the Ti-containing steel were systematically studied by thermal simulation testing machine, high-resolution transmission electron microscope and metallographic microscope. The result showed that the microstructure was mainly composed of ferrite and pearlite at the low cooling rate (0.5-1 ℃/s). When the cooling rate was gradually increased (1-5 ℃/s), the bainite structure appeared and the ratio of bainite increased. And the microstructure mainly consisted of bainite at the high cooling rate (5-10 ℃/s). The strengthening mechanisms of the Ti-containing steel were precipitation strengthening and fine-grain strengthening. TiN mainly precipitated as fine particles dispersing and its size was 10-20 nm. The optimized cooling rate was (1.5±0.5) ℃/s for the 20 mm HRB400E steel industry trial production, the yield strength was above 430 MPa, the elongation after fracture was above 20%, the maximum gross elongation was above 15%, and the ratio of tensile strength and yield strength was above 1.4.