CSP流程铁素体轧制对低碳钢组织性能的影响

Effect of ferrite rolling on microstructure and properties of low carbon steel in CSP process

通过光学显微组织观察、扫描电镜形貌观察、透射电镜形貌观察和力学性能检验,对比研究了CSP流程奥氏体轧制和铁素体轧制工艺下获得的低碳钢热轧板,以及其后续冷轧+罩式退火、冷轧+连续式退火产品的组织及性能。结果表明:采用奥氏体轧制工艺的热轧板平均晶粒尺寸为10.3μm,珠光体或渗碳体主要分布在三角晶界处,而采用铁素体轧制工艺的热轧板平均晶粒尺寸达到23.4μm,珠光体或渗碳体不仅分布在晶界上,还分布在铁素体晶粒内,并且位错密度有所降低。在后续的罩式退火板和连续式退火板中,铁素体轧制工艺的晶粒尺寸仍略粗一些。采用铁素体轧制工艺以后,各板的规定塑性延伸强度和抗拉强度均降低,其降低值分别可达到102 MPa和66 MPa。晶粒粗大是铁素体轧制强度降低的主要原因。

Microstructure and properties of low carbon steel hot rolled plate obtained by austenitic rolling and ferritic rolling in CSP process and its subsequent cold rolling+batch annealing,cold rolling+continuous annealing products were compared and studied by means of optical microscope,scanning electron microscope(SEM),transmission electron microscope(TEM)and mechanical properties test.The results show that the average grain size of the hot rolled plate by austenite rolling process is 10.3μm,with pearlite or cementite mainly distributing at triple grain boundary junctions.The average grain size of the hot rolled plate by ferrite rolling process reaches 23.4μm,with the pearlite or cementite distributing not only at the grain boundary,but also inside the ferrite grain.The dislocation density also decreases in ferrite rolling hot rolled plates.The grain size of the ferrite rolling steel plates is still slightly larger after both the batch annealing and the continuous annealing.After the ferrite rolling process,the proof strength and tensile strength of the plates are reduced,the reduced value can reach 102 MPa and 66 MPa respectively.Grain coarsening is the main reason of such strength decrease.