Correlation of martensite-austenite constituent and cleavage crack initiation in welding heat affected zone of low carbon bainitic steel

The relationship between martensite-austenite (MA) constituent and cleavage crack initiation in the heat affected zone of a low carbon bainitic steel was investigated according to welding simulation and instrumental Charpy impact testings. The results showed that with increasing heat input, the toughness of the specimen deteriorates and the MA constituent size increases gradually. The MA constituent can assist the formation of microcrack by interface debonding mechanism. According to the classical Griffith theory, the calculation size of Griffith crack is consistent with the width size of the MA constituent under most circumstances, indicating that the decrease in the crack initiation absorbed energy is mainly attributed to coarse MA constituent. (C) 2014 Elsevier B.V. All rights reserved.