With the increasing demand of users for weathering steel,higher requirements are put forward for its properties Loow C,low Si,low Ni design was used,by increasing the content of strengthening and toughening elements such as Mn,Nb,Ti,and controlling the con-tent of corrosion resistant alloy elements such as Si,Cr,Ni,Cu and the proportion of Cu and Ni content,while reasonably designing the rolling process,Q460NHE weather-resistant structural steel was successfully developed.The mechanical properties,microstructure,charac-teristics of primary oxide film and corrosion resistance of the tested steel were also studied.The results show that the microstructure of tested steel is mainly composed of ferrite,bainite,and a small amount of pearlite.The precipitated phases are mainly TiC and Nb-Ti carbonitrides,in which the ferrite grain shape is equiaxed.The characteristic of the microstructure ensures the superior mechanical and low-temperature im-pact properties of the tested steel.Its yield strength can reach more than 490 MPa,the tensile strength can reach more than 610 MPa,and the impact toughness can reach more than 80 J at-40 ℃.The thickness of the primary oxide film of the tested steel is less than 10 μm,its density and flat property are good,and it is closely bound to the matrix.There are different degrees of enrichment of Cr,Si,Ni,Cu and other corrosion resistant elements,among which Cr and Si are the most obvious enrichment.The characteristics of the oxide film are conducive to inhibiting the diffusion of corrosive media.The corrosion resistance index I of the tested steel is 6.76,and the corrosion rate is only 58％com-pared with Q345B steel.After corrosion,the surface morphology of the rust layer is relatively flat and dense,and part of the rust layer appears flocculent,which is conducive to preventing the penetration of corrosive media.The stable phase α-FeOOH content in the rust layer is relatively high and α/γ-FeOOH(mass fraction)is greater than 2,indicating that the rust layer has reached a stable state.The mechanical properties,low-temperature impact properties,and corrosion resistance of the developed Q460NHE weathering structural steel meet the standard requirements.
维普
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