CSP工艺热轧低碳钢板的强化机制

Strengthening mechanism of hot strip of low carbon steel produced by CSP

采用金相显微镜、H—800透射电镜和正电子湮没方法分析了CSP热轧低碳钢板金相组织、析出物形貌、尺寸、分布及位错密度。结果表明:CSP工艺热轧低碳钢板的晶粒较为细小,约为5.3μm;当累积变形量较小、变形温度较高时,析出物主要在晶界上,数量少见比较粗大,其尺寸大多大于150nm;当累积变形量较大、变形温度较低时,析出物主要在晶内,细小、弥散且数量较多,其尺寸大多为20～100nm,析出物主要为Al_2O_3、MnS或Cu_7S_4;随着累积变形量的增加,位错密度明显增加,终轧后轧件的位错密度约为6.35×10^(14)m^(-2)。晶粒细化、析出物弥散分布及位错密度增加是CSP工艺热轧低碳钢板强度高的决定因素。

The microstructures, precipitates of thin foil and dislocations density of hot strip of low carbon steel produced by CSP were observed using optical microscope, H-800 transmission electron microscopy and positron annihilation technology (PAT). The average grain size of 2.0 mm sheet of finished product is about 5.3 μm. In the front pass, because of light cumulative deformation and high temperature, a few of precipitates with average dimension about 150 nanometer, mainly located in grain boundaries, were observed. With heavy deformation and temperature decreasing, many of fine and dispersive particles with dimension about 20-100 nm were in grains. The composition of precipitates mainly was Al2O3, MnS and Cu7S4. At the same time, dislocations density increased with increasing the cumulative reduction. The dislocation density is about 6.35×1014m-2 calculated after finishing pass.