冷却速度对SAE 9254V弹簧钢相变规律的影响

Influence of cooling rate on phase transformation of spring steel SAE 9254V

利用热膨胀仪、显微硬度计以及光学显微镜,对SAE 9254V钢相变点温度、硬度及组织进行了测定和观察,绘制出不同冷速下的CCT曲线。结果表明:0. 05℃/s加热时,SAE 9254V的临界转变温度Ac1为745℃,Ac3为765℃。以9. 0 mm规格的SAE9254V材质圆钢丝为参考,奥氏体化后当冷速大于2℃/s时,开始出现贝氏体转变,冷速大于4℃/s时,完全转变为马氏体,Ms为261℃,Mf为118℃。随着冷速的增大,显微硬度逐渐升高,由281 HV0. 3增大至874 HV0. 3。

By using of dilatometer,mierohardness instrument and optical microscope,the temperature of Ac1 and Ac3 of SAE 9254V steel were tested and the mierohardness of the sample was calculated,and the static CCT curves were plotted according to the temperature- dilatometrie curves under different cooling rates.The results show that the Ac1 point is 745℃,and the Ac3point is 765℃.When the eooling rate is greater than 2℃/s,bainite begins to appear;when the cooling rate is greater than 4℃/s,the austenite is completely transformed into martensite,with the Ms and Mf being 261℃ and 118℃ respectively.With the increase of cooling rate,the mierohardness of the steel after transformation also gradually increases,from 281HV0.3to 874HV0.3.