Study Of The Properties Of 40T And 44T Spring Steel

With the developed of fast-speed and heavy-carried trains, the designed stress of the bogie spring steel needed to be improved urgently. It is expected that the new spring steels 40Tand 44T have a higher strength, toughness and plasticity than the new spring steel 60Si₂CrVA. This article, we make a further research on the mechanic properties, fatigue performance and microstructure of the newly-developed super-high-strength spring steel 40T and 44T. It have been showed, by the study on the heat treatment process and mechanical properties, that for the steel 40T,quenched at 880℃and then tempered in the range of temperature of 380℃,its mechanical properties are σ_0.2=1750 MPa,σ_b=1950 MPa,ψ=44%,δ₅=10%,Ak=30 J/cm² ;respectively for the steel 44T ,quenched at 900℃,and then tempered in the rage of temperature of 900℃, its mechanical properties are: σ_0.2=1820 MPa,σ_b=1970 MPa,ψ=40%,δ₅=10%,Ak=29 J/cm² ,respectively. Through analysis on the microstructure, it has been showed that, at quenched state the microstructures of the new kinds of high strength spring steels are both lath matensite, there are high density of dislocations, and some twin matensite. Temepered retueen 380℃-450℃in the quenched specimens the microstructures still keep the appearance of the lath matensite, but due to the change of the dislocation configuration, the matensite laths have been divided into little areas, the sub-grains formed in the lath, and recrystallization centers have been formed, the second phase...