Effect of tempering temperature on microstructure and mechanical properties of 2 300 MPa grade low alloy ultra-high strength steel
The increase of strength of ultra-high strength steels is very effective in realizing lightweight of components.At present,the strength of ultra-high strength steel plates is generally not higher than 2 000 MPa.SEM,TEM and extraction phase analysis method were carried out to study the effect of tempering temperature on the microstructure and mechanical properties of 2 300 MPa grade low alloy ultra-high strength steel.The results show that the microstructure of the experimental steel is slatted martensitic and ε-carbide after tempering treatment at different temperatures of 140-230 ℃,and the content of ε-carbide increases from 0.196 wt.％to 0.718 wt.％with the increase of tempering temperature.When the tempering temperature increases from 140 ℃ to 230 ℃,the tensile strength of the experimental steel decreases from 2 441 MPa to 2 169 MPa,the yield strength decreases from 1 720 MPa to 1 825 MPa,and the impact absorption work fluctuates up and down 19 J/cm2.The increase in yield strength of experimental steel is due to the increase of ε-carbide precipitation strengthening,while the decrease in tensile strength is due to the decrease of dissolved carbon content in martensite.
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