目的 研究建筑结构用高强度钢材低温下脆性断裂的力学性能特征.方法 利用实验室的CSS - 2220电子万能试验机和高低温环境保温箱全套低温设备对14 mm厚的高强度钢材Q460C进行了低温下垂直轧制平面的拉伸试验研究.结果 温度的降低使得钢材的抗拉强度、屈服强度以及屈强比均升高,断后伸长率与断面收缩率均减小；扫描电镜分析表明,-40℃下的试件断口呈现出从韧性向脆性断裂过渡的微观形貌,-60℃下的断口则表现出显著的脆性断裂特征.结论 低温使得Q460C钢材的塑性和韧性变差；温度≤-40℃时,Q460C钢材倾向于脆性破坏,应加强低温防脆断措施.%The paper is to research the rule of the brittle fracture of high-strength construction-structure steel at low temperature. The main mechanical properties of the steel are precondition and foundation for its toughness study. In this paper,uniaxial tensile test of Q460C( 14mm thickness), the high-strength construction-structure steel was tested at the low temperature to obtain the intensity index (including yield strength, tensile strength) ,the plastic index(including elongation at break, reduction of area) ,and the relations of these indexes along with the temperature changing;as well as calculate the Q460C steel's temperature sensitive coefficient, which may be used to forecast the intensity index of Q460C at low temperature; furthermore, analyze the scanning electronic microscope of the tensile specimen fracture surfaces. The experimental data show that the yield ratio of the Q460C was found to increase with the elongation at break,and the reduction of area decrease while the plasticity and toughness decrease as the testing temperature drops. In addition , the fracture surface takes on the transition from toughness to brittle fracture whose abruption occurs at -40℃. Moreover the significant feature of brittle morphology is shown on the tension fracture which takes place at - 60℃. The result indicates that the Q460C steel is inclined to low temperature brittle fracture, so brittle fracture prevention measures should be strengthened.
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