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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。
The effects of heat treatment, heat treatment, transmission electron microscopy, electrolytic phase extraction and electron diffraction on Nb in Nb-containing steel were investigated. It is found that two-thirds of the trace Nb exists in the form of Nb (C, N) in the residual heat-treated Nb-containing reinforcing bar and the rest is in solid solution. The solid solution of austenite and the precipitation of austenite by Nb (C, N) strongly prevents the recrystallization of deformed austenite, thereby refining the deformed austenite and the transformed structure. The ferrite Or the very fine Nb (C, N) precipitated from the phase boundary exhibit a precipitation strengthening effect. The combination of grain refinement and precipitation hardening reduces the weld zone strength.