大厚度高强钢焊接接头CTOD允许值的研究

STUDY ON CRITICAL CTOD OF BIG-THICKNESS AND HIGH-STRENGTH STEELS

CTOD作为焊接构件韧性的评定标准之一,已经应用于各个领域,但是,国内CTOD准则的理论基础相对比较薄弱,对于大厚度高强度钢板焊接接头CTOD允许值的讨论已成热点,基于英国标准BS 7910-1999《金属结构中缺陷验收评定方法导则》的评定技术路线,将60 mm厚EQ70高强钢CTOD试样的单边疲劳预裂纹作为缺陷,结合焊接接头的CTOD试验结果,对其焊接接头热影响区进行失效评定。同时采用扫描电镜对EQ70焊接接头粗晶区微观组织进行分析。结果表明,焊接接头热影响区的CTOD试验值都在可接受缺陷范围内,且其热影响区存在有利于韧性的良性组织,为高强钢CTOD的允许值取值提供了思路。

As one of the essential criteria of assessment to welding toughness, CTOD（Crack tip opening displacement） is widely applied in engineering. The research on critical CTOD of big thickness and high strength steels has been a hot issue, therefore the theoretical research in China lags behind its overseas. The present paper takes the single edge fatigue precrack of CTOD specimen as a flaw based on the technical route of the British Standard 7910-2005, which is ＂Guide to methods for assessing the acceptability of flaws in metallic structures＂. In the meanwhile, make the grading assessments of the HAZ of the 60mm thick EQT0 steel welded joints, combining the results of the CTOD tests. The CGHAZ microstructures of EQ70 steel welded joints has been analyzed by SEM. The assessments on welded joints of EQ70 show that the CTOD values are in the acceptable range. And there are some fine microstructures good for the toughness of the welded joint. This method provides a useful guidance in researches of critical CTOD.