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通过Gleeble-2000试验机研究了Q345C钢连铸坯的高温热塑性。利用扫描电镜、金相显微镜、透射电镜观察了第Ⅰ、Ⅲ脆性温度区内拉伸试样断口部位的显微组织及形貌,分析了动态再结晶、相变、析出物等对微合金化钢高温延塑性的影响。结果表明:在1×10-3/s应变速率下,Q345C钢存在两个脆性温度区,即第Ⅰ脆性区(1 200～1 300℃)和第Ⅲ脆性区(600～875℃),无第Ⅱ脆性区出现;最高塑性出现在1 050℃左右,断面收缩率(Z)达到85.8%;在第Ⅲ脆性区,沿奥氏体晶界析出膜状铁素体抗拉能力较低,晶界处存在夹杂物以及微合金元素的析出物,是钢的热塑性降低的主要原因。
The high temperature thermoplasticity of Q345C steel continuous casting slab was studied by Gleeble-2000 testing machine. The microstructures and morphologies of the fractured parts of the tensile specimens in the first and the third brittle temperature zones were observed by scanning electron microscopy, optical microscope and transmission electron microscopy. The effects of dynamic recrystallization, phase transformation and precipitation on the micro-alloying Effect of high temperature ductility on steel. The results show that there are two brittle temperature zones in the Q345C steel at the strain rate of 1 × 10-3 / s, namely, the first brittle zone (1 200 ~ 1 300 ℃) and the third brittle zone (600 ~ 875 ℃) The second brittle zone appeared; the highest plasticity appeared at about 1 050 ℃, and the reduction of area (Z) reached 85.8%; in the third brittle zone, the tensile strength of the film ferrite was lower along the austenite grain boundary, The presence of inclusions and precipitates of microalloy elements is the main reason for the decrease of the thermoplasticity of steel.