精轧开轧温度对超高强度厚板心部性能的影响

Effects of Finish Rolling Start Temperature on Mechanical Properties at the Center of Ultra High Strength Heavy Plate

利用SEM、EBSD、冲击试验、落锤试验等方法,针对控轧控冷(TMCP)工艺下精轧开轧温度对超高强度厚板心部显微组织和力学性能的影响展开研究。结果表明,低的精轧开轧温度760℃使得钢板原奥氏体晶粒内部缺陷密度更大,增加了铁素体相变的形核位置,最终使相变后的显微组织细小均匀;精轧开轧温度的降低提高了钢板-60℃冲击功,同时降低了无塑性转变温度;42.9%较高比例的大角度晶界、23.5°较大的平均取向差、较高强度的{112}<110>和{332}<113>织构及64.3%较高含量的{110}滑移面是提高超高强度厚钢低温韧性的关键。

By means of SEM,EBSD,impact test and DWTT,the effects of finish rolling start temperature on microstructure and mechanical properties of ultra high strength heavy plate at the center under TMCP conditions are studied.The results show the lower finish rolling start temperature of 760 ℃ leads to higher density defects inside prior austenite grain,which increases the nucleation positions of ferrite transformation and finally enables the formation of refined microstructure after phase transformation.The lower finish rolling start temperature increases the impact value at-60 ℃,but decreases the nil-ductility transition temperature.High proportion of large angle grain boundary at 42.9%,large average misorientation difference at 23.5°,high strength texture of {112}<110> and{332}<113> and high volume fracture of {110} slip planes at 64.3% are the key factors to improve the low temperature toughness of ultra high strength steel plate.