High strength steel (600–900 MPa) deposited metals: microstructure and mechanical properties

Abstract

The microstructure and mechanical properties of the deposited metals of five metal cored wires for welding 600–900 MPa ultralow carbon bainitic steels were investigated. It was found that lowering the C content and optimising the Mn, Ni, Mo and Cr contents of the deposited metal significantly improved the strength and toughness. At the lowest strength level (627 MPa), ferrite dominated, mainly acicular ferrite and proeutectoid ferrite. However, at the highest strength level (>800 MPa), bainite dominated, mainly degenerate upper bainite and granular bainite. Good strength toughness match was achieved by a deposited metal having an interlaced multiphase microstructure with degenerate upper bainite and martensite acting as main strengthening phases, and granular bainite and acicular ferrite acting as toughening phases.

Keywords:

• Ultralow carbon bainitic steels
• Metal cored wires
• Deposited metals
• Microstructure
• Mechanical properties

Acknowledgements

The authors would like to acknowledge the financial support of the Beijing Natural Science Foundation of China (grant no. 2152008), the National Natural Science Foundation of China (grant no. 51275008) and the China Scholarship Council (grant no. 201406250040).