50CrVA弹簧钢的奥氏体连续冷却相变研究

Study on austenite continuous cooling phase transformation of 50CrVA spring steel

采用膨胀法并结合金相-显微硬度法,在Gleeble-3500热模拟试验机上测定了弹簧钢50CrVA的相变临界点Ac1、Ac3、Ar1、Ar3;测定了该钢在不同冷却速度时的膨胀曲线,绘制了该钢的连续转变曲线(CCT曲线)。结果表明,随着冷却速度的增加,其显微硬度增加;当冷却速度小于5℃/s时,转变产物为多边形铁素体、珠光体和少量贝氏体的混合组织,当冷却速度在5～10℃/s之间时,转变产物为铁素体、珠光体和少量贝氏体;当冷却速度大于10℃/s,得到马氏体组织。

The phase transition critical points Ac1,Ac3,Ar1 and Ar3 of spring steel 50CrVA have been measured by use of the expansion method and the metallographic-microhardness method on the Gleeble-3500 thermal simulator.The expansion curve of the steel at different cooling rates has been measured and the continuous transition curve (CCT curve) has been drawn.The results show that the micro-hardness increases with the increase of cooling rate;when the cooling rate is less than 5 ℃/s,the transformation product is a mixture of polygonal ferrite,pearlite and a small amount of bainite;when the cooling rate is 5-10℃/s,the transformation product is a mixture of ferrite,pearlite and a small amount of bainite;when the cooling rate is greater than 10℃/s,a martensite structure has been obtained.