摘要
采用热模拟、透射电镜、电解萃取相分析及电子衍射等手段对余热处理含Nb钢筋中Nb的作用进行了考查。发现经余热处理的含Nb钢筋中,微量Nb的2/3以Nb(C,N)的形式存在,其余为固溶态。固溶于奥氏体和由奥氏体析出的Nb(C,N),强烈阻止了形变奥氏体的再结晶,从而细化了形变奥氏体及相变后的组织,由铁素体或从相界析出的极细Nb(C,N)发挥了析出强化作用。细晶强化及析出强化的共同作用减少了焊区强度降。
Effects of niobium on Nb-containing reinforced bars during postrolling waste heat treatment were systematically investigated by means of heat simulation,transmission electron microscope,electroextraction and electron diffraction. It was found that in such bars about 2/3 of the trace Nb content added occurs in the form of compound Nb(C, N) and the rest in solid solution. Being solved in and precipitated from austenites Nb (C, N) plays a strong role in inhibiting the recrystallization of deformed austenites so as to refine further the deformed austenites and the structures after transformation. Then, the extraordinary fine Nb (C, N) precipitated form ferrites or phase boundaries will serve the function of precipitation hardening. It is proved that the strength drop in welding zone will be reduced by the joint effect of grain refining together with such a precipitation hardening.
关键词
钢筋
余热处理
碳氮化铌
含铌
postrolling waste heat treatment, Nb-containing reinforced bar, niobium carbonitrides, precipitation,grain refining, dynamic recry-stallization.
