化学成分和热处理对AM355不锈钢组织和力学性能的影响

Effect of Composition and Heat Treatment on Microstructure and Mechanical Property of AM355 Steels

为满足飞行器用材需求,进一步提高AM355不锈钢的强度和硬度,研究了3种成分的使用真空感应+电渣重熔工艺冶炼、经锻造成型的80mm AM355不锈钢棒。钢棒经不同温度淬火后,再进行深冷+回火处理并测试其力学性能。试验结果表明,在相近的w(Creq)/w(Nieq)下,钼含量较高的不锈钢棒容易得到较高的强度和硬度,并具有一定的塑韧性。经最佳热处理工艺(1 000℃×1h空冷+(-70℃)×8h+450℃×2h空冷+200℃×2h空冷)处理后,该AM355不锈钢棒的强度和硬度有大幅度提高,抗拉强度提高约100MPa,硬度提高约HRC5。力学性能可达到:抗拉强度1 630MPa、屈服强度1 380MPa、伸长率16%、面缩率59%、冲击值51J、硬度50HRC。对该AM355钢棒中碳化物的类型和析出行为进行了扫描电镜和透射电镜观察,探讨了强化机制。结论认为钼元素含量和淬火温度对AM355的强度和硬度影响较大。

In order to raise the strength and hardness of AM355 steel for the demand of aircraft material,three AM355 steel bars with different compositions were investigated,which were prepared by VIM＋ESR technique and forged into 80 mm.Mechanical properties were tested after different temperatures quenching,same cold treatment and tempering.The results indicate that,under the same w（Creq）/w（Nieq）,the AM355 steel bar with higher molybdenum content has higher strength,hardness and certain toughness.Strength and hardness of the bar after best heat treatment（1 000 ℃×1 h AC＋（-70 ℃）×8h＋450 ℃×2 h AC＋200 ℃×2 h AC） can be raised about 100 MPa in strength and HRC 5 in hardness.Details of mechanical property are as follows,Rm 1 630 MPa,ReL 1 380 MPa,A 16%,Z 59%,and impact energy 51 J,HRC 50.The types and precipitations of carbides in the AM355 bar were carried out by SEM and TEM,and strengthening mechanism was also searched.In conclusion,w（Mo） and the quenching temperature have main effect on strength and hardness.