温度参数对铌微合金高强度结构钢组织性能的影响

通过控轧控冷试验,力学性能检验和组织的光学显微观察,研究了温度参数对铌微合金钢组织性能的影响。结果表明:两阶段控轧及控冷所获晶粒尺寸明显小于常规轧制+快速冷却的晶粒尺寸;随冷却速率的增大或终冷温度的降低或精轧开轧温度的降低,试验钢晶粒细化,混晶程度加重,强度增大,塑性降低;精轧低温开轧利于韧性提高;铁素体混晶可能源于因铸坯中Nb(C,N)的不均匀分布造成的原始奥氏体混晶,粗轧大压缩比轧制可以消除这种混晶现象。

Effect of Temperature Parameters on Microstructure and Mechanical Properties of Nb Micro-Alloyed High Strength Structural Steel

Effect of TMCP temperature parameters on the microstructure and mechanical properties of Nb-microalloyed steel was investigated. The following results be obtained. The finer grain can be obtained by two-stage controlled rolling and cooling compared with conventional rolling and rapid cooling. With increasing the cooling rate (10 to 23℃/s), or decreasing the start temperature of finish rolling (780 to 605℃) or lowering the final cooling temperature (930 to 850℃), the grains size are refined, content of the mixed grains is aggravated, the strength increased and the plasticity decreased. The lower rolling temperature of finish rolling is helpful to improve the low temperature toughness. The mixed ferrite grains arise from mixed austenite grains which is due to inhomogeneous distribution of Nb(C,N) precipitates. Rolling with larger compression ratio (3.67) of coarse rolling can eliminate the mixed grains. The inheritance and aberrance of the mixed original austenite grains are significantly affected by the following temperature parameters. Applying these results to industrial production of high strength low alloyed structural steels for Hebei Puyang Iron & Steel Co., Ltd., making reasonable control rolling and control cooling process, the product properties meet the national standard requirement of GB/T 1591-94.