两种缺口Q420钢的低温断裂韧度

FRACTURE TOUGHNESS FOR Q420 STEEL NOTCHED PLATE AT LOW TEMPERATURE

结合工程应用背景,采用Q420桥梁用钢板,加工成W/B=2、S/W=5的非标准三点弯曲试样,通过线切割和线切割后预制疲劳裂纹两种方式得到相同长度的初始缺口,对其-30℃的低温断裂韧度进行试验研究,分析比较两种缺口试样断裂韧度测试条件值Kq和强度比Rsb,评价具有以上两种缺口时材料对脆性失稳扩展的不同抵抗能力,并求得相应的缺口修正系数;最后,从试样的P—V曲线图和断口分析其中的原因。试验分析结果为Q420钢的具体工程应用提供依据。

Based on engineering application background, the non-standard three-point bend specimens in bridge steel Q420 with the dimension of W/ B = 2, S/ W = 5 were machined. Two types of original notch with uniform length were obtained by spark machin- ing then with or without fatigue cracking afterwards respectively. Test study on this metallic material at the temperature of -30 degree was performed. Qualification value Kq of fracture toughness and strength ratio Rsb of Q420 steel plate were compared and analyzed. Different resistances against unstable brittle growth with the two types of notch were assessed and the corresponding notch correcting coefficients were calculated. Finally, the reasons why they are different were discussed through analyzing P-- V curves and fracture surfaces. The results would provide reference for further engineering usage of 0420 steel.