Influence of hot rolling\u2009+\u2009heat treatment on microstructure and mechanical properties of NM500/Q345/NM500 composite plate

Abstract

The NM500/Q345/NM500 composite plates were subjected to different hot rolling and heat treatment processes in this paper. The influence of hot rolling and heat treatment on the microstructure, element distribution and defect composition of the bonding interface of the as-rolled clad plates was studied by using optical microscope, scanning electron microscope, electron backscattered diffraction and transmission electron microscope. Meanwhile, the mechanical properties of wear-resistant steel were analyzed by microhardness and tensile tests. It was revealed that the increase in rolling reduction promoted the metallurgical bonding between NM500 and Q345 steels. The composite texture components of {112}\u2009~\u2009{113}\u2009<\u2009110\u2009>\u2009, {332}\u2009<\u2009113\u2009>\u2009, {223}\u2009<\u2009110\u2009>\u2009, {554}\u2009<\u2009225\u2009>\u2009and\u2009<\u2009110\u2009>\u2009∥RD were formed in the tissue when the reduction rate was 70%. γ/α phase transformation reinforced the texture components and thus increased {332}\u2009<\u2009113\u2009>\u2009and {554}\u2009<\u2009225\u2009>\u2009after quenching treatment. Typical lath martensites were present in the structure, and there were high-density dislocations and substructures between the laths. Tempering treatment at 200 °C facilitated the deposition of some needle-like or rod-like ε precipitates in the martensite. The best tensile strength (1432.28 MPa) and elongation (22.68%) in the composite plate could be achieved by post-rolling treatment of quenching at 900 °C and tempering at 200 °C.