钒微合金化异型坯S355ML的高温热塑性

High Temperature Thermoplasticity of Vanadium Microalloyed Beam Blank S355ML

对钒微合金化异型坯S355ML进行高温拉伸实验,采用激光共聚焦显微镜、热场发射环境扫描电镜等分析异型坯翼缘裂纹处组织及脆性温度区的断口形貌,研究异型坯断面收缩率、抗拉强度等高温性能及断口处组织比例与断面收缩率间的关系。结果表明:在1×10^(-3)s-1应变速率下,第Ⅲ脆性区间为700~900℃,随断口处α铁素体组织比例的增加,铸坯塑性先减小后增大,850℃时断口处α铁素体体积分数为1.97%,断面收缩率为24.66%;850℃以下,断面收缩率随α铁素体组织比例的增加而增加,700℃时,α铁素体体积分数为64.51%,断面收缩率增至59.42%;根据拉伸试样的断口形貌和断面收缩率,异型坯最佳矫直温度区间为900~1200℃。

The high temperature tensile test of vanadium microalloyed beam blank S355ML was carried out.The microstructure at flange crack and fracture morphology at brittle temperature zone of the beam blank were analyzed by laser confocalujm microscopy,thermal field emission environmental scanning electron microscopy and scanning electron microscopy.The high temperature properties of the beam blank such as area reduction,tensile strength and the relationship between the microstructure proportion at fracture and area reduction were studied.The results show that at the strain rate of 1×10^(-3)s-1,the third brittle region is 700-900℃,and the plasticity decreases first and then increases with the increase ofα-ferrite at fracture.When the test temperature is 850℃,the volume fraction ofα-ferrite at fracture is 1.97%,and the reduction of area is 24.66%;When the test temperature is below 850℃,the reduction of area increases with the increase ofα-ferrite.When the test temperature is 700℃,the volume fraction ofα-ferrite is 64.51%,and the reduction of area also increases to 59.42%.According to the fracture morphology and reduction of area of tensile specimen,the best straightening temperature range of beam blank is 900-1200℃.