两相区热轧对20钢组织和力学性能的影响

The Effect of Hot-rolling in Two-phase Zone on Microstructures and Mechanical Properties of 20 Steel

利用Gleeble-3500热模拟试验机对20钢(α+γ)两相区内进行热压缩试验,获得不同变形条件下的真应力-真应变曲线。结果表明,当变形温度相同时,流变应力随着应变速率的增大而增大;当应变速率相同时,流变应力随着变形温度升高而减小,但在850℃时略有增大现象。采用光学显微镜(OM)和场发射扫描电镜(FG-SEM)技术分析了变形温度为750~850℃、应变速率为1s-1时的20钢微观组织变化,并得出结论:20钢在两相区轧制时,在750~820℃范围内,温度是影响力学性能的主要因素;在820~850℃范围内,(α+γ)相变是影响力学性能的主要因素。

This paper presents the results of investigations of the microstructure and mechanical properties of 20 steel by Gleeble-3500 thermal simulation testing machine after different deformation conditions.With the deformation temperature range of750—850 ℃ and the strain rate range of 1—10 s-1,the experiment was performed inα＋γtwo-phase zone.The true stress-strain curves under different deformation conditions were obtained,and the microstructure of 20 steel was studied by the optical microscope（OM）and field emission scanning electron microscopy（FE-SEM）.It was noticed that at a constant temperature,the flow stress increased with increasing strain rate,and the flow stress decreased with the increase of deformation temperature at a constant strain rate,but an abnormal increase on flow stress was observed at 820—850 ℃.From the point of view of the phase transition,higher temperature led to a lower volume fraction ofα-phase which is an important factor to reduce the intensity of the microstructure of 20 steel.It could be concluded that temperature was a key factor to determine the mechanical properties in the temperature range of750—820 ℃,and（α＋γ）phase transition worked in 820—850 ℃.