Achievement of ultra-high strength in 45Si2MnCr2Mo steel via efficient and low-energy tempering

Abstract

In this study, 45Si2MnCr2Mo steel was fabricated by casting, hot rolling, and normalizing, followed by tempering at different temperatures from 180 to 520 °C for 2 h. Special attention was paid to the effects of tempering on the microstructure and mechanical properties of the steel. The results indicate that microstructure of tempered steel consists of bainite, martensite, and retained austenite (RA), and it is not sensitive to tempering at temperatures below 320 °C. However, after tempering at temperatures of 420 and 520 ℃, bainitic ferrite plates merged and their lath boundaries became vague. In turn, RA decomposed, whereas carbide particles appeared and then coarsened. With increasing tempering temperature, the volume fraction of RA achieved its peak value at 320 °C and carbon concentration within RA attained its peak value at 420 °C. The optimal balance of ultimate tensile strength of 2306 MPa and total elongation of 8.24% in the steel were achieved after being normalized at 950 °C for 0.5 h and subsequent tempering at 220 °C for 2 h. These values are found to exceed those of air-cooled and isothermal bainitic steels. Finally, the correlation between microstructure and mechanical properties of the steel under consideration was discussed.

Study on the effect of tempering on the impact abrasive wear performance of 45Si2MnCr2Mo ultra-high strength steel

“…The steel plates were fabricated and then normalized by holding them at 930 °C for 15 min, and the heat treatment plate was tempered at 150 °C, 220 °C, 290 °C and 360 °C for 120 min. The detailed preparation process of the steel plates is described in the literature [16] . The prepared samples were etched in 4% nitric acid in an ethanol solution and scanned using Zeiss-Auriga scanning electron microscope.…”

“…The impact test by a pendulum impact tester (ZBC2452-B) with the size of the open U-notch is 5 × 10 × 55 mm at room temperature. XRD calculated the residual austenite phase volume fraction (Vγ) in the studied steels [16] .…”

“…There are many studies on the influence of thermal treatment on the wear performance of ultra-high strength steel [11][12][13][14] . Still, there are few studies [6,15,16] on the influence of tempering thermal treatment on the impact of abrasive wear resistance of UHSS [15] . Therefore, it is necessary to study further the influence of tempering temperature on the three-body impact abrasive wear performance of new UHSS.…”

“…In this article, three-body abrasive wear experiments of 45Si2MnCr2Mo new UHSS [16] after different tempering temperatures were carried out, the wear performance of UHSS was studied, and the wear analysis method of ultra-high strength steel was put forward, which provided a basis for the design of wear-resistant ultra-high strength steel.…”