奥氏体化温度对40CrNiMo钢组织和性能的影响

详细研究了奥氏体化温度对中碳调质钢40CrNiMo的淬透性、以0.7 ℃/s淬火后组织及调质处理后组织和性能的影响。研究结果显示,随着奥氏体化温度从800提高至1 000 ℃,材料的淬透性逐渐增加,尤其是当奥氏体化温度提高至950 ℃以后,淬透性增加幅度显著变大。当奥氏体化温度为800 ℃时,组织中存在相对多的铁素体,使得淬火后材料的硬度较低,但回火后具有最佳的韧性;奥氏体化温度为900 ℃时,高温回火后试样具有最高的强度,但塑性较低。随着奥氏体化温度的升高,材料的断裂机制发生明显变化,拉伸断裂均为典型韧性断裂,断口均为韧窝组成,而冲击断裂逐渐由韧窝断裂方式转变为解理或准解理断裂方式,当奥氏体化温度超过900 ℃后,断口形貌以典型河流花样为主。

Effect of austenizing temperature on microstructure and mechanical properties of 40CrNiMo steel

Effect of austenizing temperature on hardenability, microstructure of 40CrNiMo steel after quenching at a cooling rate of 0.7 ℃/s and microstructure and mechanical properties of 40CrNiMo steel after tempering was studied. Results showed that with increasing temperature from 800 to 1 000 ℃, the hardenability was increased gradually, especially when the temperature exceeded 950 ℃. When the austenitizing temperature was 800 ℃, there was some ferrite in the microstructure, resulting in lower hardness but higher toughness. When the austenitizing temperature was 900 ℃, the specimen possessed the highest strength but the ductility was lower. The fracture mechanism was also changed with increasing temperature, especially for impact specimens. All tensile specimens exhibited ductile fracture with dimples in the fracture surface. However, impact specimens changed from dimple fracture to cleavage or quasi-cleavage fracture, with more typical river pattern in the fracture surface when the austenitizing temperature exceeded 900 ℃.