Metall. Res. Technol.
Volume 119, Number 1, 2022
|Number of page(s)||13|
|Published online||16 February 2022|
Characterization of nanoscale precipitates and enhanced mechanical properties of high strength weld metals containing Cu additions after PWHT
School of Materials Science and Engineering, Tianjin University, Tianjin 300350, China
2 Tianjin Key Laboratory of Advanced Joining Technology, Tianjin 300350, China
* e-mail: firstname.lastname@example.org
Accepted: 14 January 2022
In order to match rapidly development of high strength low alloy steels, the new metal cored wire contained copper was designed. The multi-pass weld metals were obtained by gas metal arc welding. Results show that microstructure of weld metals is bainite with M-A constituents, and there are nano-9RCu precipitates after PWHT. The weld metal as welded achieves 737 MPa of yield strength (YS) and 1097 MPa of ultimate tensile strength (UTS), with an elongation 8%. After PWHT, the YS and UTS are 725 MPa and 968 MPa, respectively, and elongation increases to 16%. The lower dislocations density and reduction of Cu element at solid solution state hence for the decrease of YS. As well, the nano-Cu precipitates and reduction of effective grain size make it increase. The combined effect of these factors makes YS decrease by only 12 MPa after PWHT. Besides, a good impact performance (46.6 J) can be obtained after PWHT, while it is only 27.7 J of weld metals as welded. The improved toughness of weld metals after PWHT is obtained by the contributions of finer effective grain size, soft bainite, and dispersed nano-9RCu precipitation. The nano-Cu precipitates can improve strength without damage to toughness of weld metal after PWHT.
Key words: weld metal / bainite / nano-Cu precipitation / yield strength / toughness
© EDP Sciences, 2022
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